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Experimental investigation of phase change materials for insulation of residential buildings
Sustainable Cities and Society 36 (2018) 42–58
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Experimental investigation of phase change materials for insulation of residential buildings
MARK
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Mushtaq I. Hasana, , Hadi O. Basherb, Ahmed O. Shdhanb a b
Mechanical Engineering Department, College of Engineering, Thi-Qar University, Iraq Mechanical Engineering Department, College of Engineering, Wasit University, Iraq
A R T I C L E I N F O
A B S T R A C T
Keywords: Electric consumption cost Cooling load Phase change material PCM Thermal insulation
In this paper, an experimental study has been conducted for using PCM as thermal insulation materials by its incorporating with layers of the walls and the ceiling. The effect of PCM and its role in improvement of thermal performance and thermal comfort is experimentally studied. Two room’s models have been built, the first model is a standard room for comparison and the second model is an experimental room for testing. Wasit university in Kut city, (32.5° N) latitude, was the place of the building models and testing of PCM. The type of PCM which was used in this experiment is paraffin wax with a melting point (44 °C). Many cases were studied according to the thickness of the PCM and according to the orientation (North wall, South wall, East wall, West wall, and ceiling). Results obtained showed a reduction in indoor temperature of the zone and the reduction in cooling load and as a result saving in electricity consumption with using PCM as insulation materials.
1. Introduction The apportionment of thermal mass inside buildings is the consequence of constitutional and architectural resolutions and can highly affect how the building interacts to internal heat gains, solar radiation or changes in outdoor conditions. Lightweight components interact readily to changes in interior gains and solar radiation. The conventional approaches employ enormous components to temperate temperature inconstancy. Thermo-physical properties of the construction materials will have a direct effect on energy consumption of the building. Within a negative solar purpose, the heat capacity of the internal wall layer is governing. This approach it applicable in sites that have an efficacious daily temperature variance, else that, heavy weight building can give rise to problems of excrescent thermal mass and cost. The nature of Iraq’s climate can be described in two basic seasons, hot dry and long summer, and cold short winter. The difference of daily range temperature is limited and causes the assemblage of heat in the building layers. The consumption of electrical demand is increasing, especially in hot regions due to using the cooling system where the consumption of electric energy in the building sector in Iraq reach about 38% of the total energy which is produced, where in 2020 it will be built more than six million building unit and this will increase in electric demand. The phase change materials and its using in the building material considers one of methods to improve the thermal properties of the
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Corresponding author. E-mail address: [email protected] (M.I. Hasan).
http://dx.doi.org/10.1016/j.scs.2017.10.009 Received 4 April 2017; Received in revised form 1 October 2017; Accepted 8 October 2017 Available online 12 October 2017 2210-6707/ © 2017 Elsevier Ltd. All rights reserved.
construction material where integrate these PCM with layers of the building material play important role in shifting the cooling load especially in peak load and Contributes to reducing cooling load. In this research, we will study experimentally integrate the PCM with layers of local construction material in Kut city in Iraq. In the field of using the PCM as insulation materials and it’s incorporating with building materials there are many experimental and numerical studies were conducted. Halford and Boehm (2007) conducted simulation of using encapsulated PCM to shift cooling load. They used encapsulated PCM in ceiling and walls and incorporated the PCM with construction materials like concrete and gypsum wallboard. They used TRANSYS program software to simulate. By comparting their results with other cases without PCM, they found 11–25% reduction in peak load compared with the case without PCM. Muruganantham (2010) conducted experimental and numerical studying about using BIOPCM in envelope building, ceiling and the walls. He used energy plus program in simulation. the layers of the wall were, from outside to inside, sliding door, insulation, BIOPCM and gypsum board as well as wood frame at two sides. BIOPCM was as small block. He made sheds contain door and window and conducted comparison between these sheds. The dimensions of the shed were (4.876 m length, 3.657 m width and 2.436 m height). He used wood frame to install BIOPCM. The melting range of the PCM was (27–31 °C). He found that maximum energy saving about 30%, and maximum cost saving was 30%. Al-Hadithi (2011) studied
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Nomenclature
Q RT Tr Tm U X
Amb,T Ambient air temperature (°C) A Surface area (m2) CLTDc Correction of cooling load temperature difference (°C) CLTD Cooling load temperature difference (°C) C.L.R Cooling load reduction (%) C.LwithPCM Cooling load of the room with PCM (W) C.LwithoutPCM Cooling load of the room without PCM (W) DR daily range of outdoor (°C) Fi Inside film resistance for envelop internal wall (W m−2 K−1) Fo Outside film resistance for envelop internal wall (W m−2 K−1) f Ventilation factor K Color correction factor LM Latitude and month correction factor
Transfer during walls or ceiling (W) Total Thermal Resistance (m2 K W−1) Indoor temperature of room (°C) Outdoor design temperature (°C) Overall heat transfer coefficient (W m−2 K−1) Layer thickness (m)
Greek symbols ΔTr λ
Indoor temperature difference (°C) Thermal conductivity (W m−1 K−1)
Abbreviations BIOPCM Bio phase change material Exp Experimental PCM Phase change material
insulation material in many weathers. He used model one -dimensional transient heat equation and used the Crank-Nicolson scheme to solve this equation. He used TMY3 data for creating weather data. He found the optimizing location of the PCM in layers of building is important and depended on thermal resistance of the layers between the PCM and outside boundary. He compared his results with cases without PCM and he found reducing in the cooling load from the wall by 19.7% and from the roof by 8.1% and reducing in heating load from walls by 6% and from roof by 6.4%. Monteiro da Silva and Almeida (2013) conducted simulation for using of gypsum plasterboards with micro-encapsulated PCM and macro-encapsulated PCM in family house has area 91 m2. They used software energy plus 7.2 for simulation. The melting range of the PCM (paraffin) was (23–26 °C) and PCM (salt hydrate) was (22 °C–28 °C). The simulation was conducted in the coolest and hottest days. They integrated the PCM with the ceiling and the walls and they used three types of construction materials: concrete wall, single hollow brick and double hollow brick. They concluded that the reduction in the heating needs by 16% in coolest day and reduction in the cooling needs about 28% in hottest day and reduced 16% in the annual energy needs. Also, they found that increasing the indoor temperature by 0.7 °C in coolest day and decreasing the indoor temperature by 1.4 °C in hottest day. Mushtaq, Ahmed, and Hasanain (2013) investigated experimentally and numerically the using of the PCM in the ceiling with cooling system to cool PCM. They used two rooms with and without PCM, dimensions of the rooms were (1.8 m*1.8 m*2.44 m). The layers of the roof, from bottom to top, without PCM were (concrete 12 cm and brick mixture + mortar 10 cm) and with PCM were (concrete 12 cm, light structure panel of aluminum with PCM 2.5 cm and brick mixture
numerical method of the effect of using PCM on heat transfer in the wall. He mixed paraffin wax (25%) with concrete (75%) to create treat wall. Layers of the wall were, from external to internal, cement 5 mm, and treat wall 20 mm, brick 300 mm and gypsum 20 mm. The treated wall was west wall. He compared between treat wall and no treat wall and his results showed that treat wall reduced heat transfer by 66%. Zalewski, Joulin, Lassue, Dutil, and Rousse (2011) studied experimentally integrating phase change material in small scale composite trombe solar wall. They used the PCM in the buildings for heating purposes where the PCM works as storage material. The PCM was mixed from hydrated salats (chliarolithe (CaCl2·6H2O) + potassium chlorides (KCl) + additives) and the melting temperature of the PCM was 27 °C. They inserted the PCM in the wall as a brick-shaped package. They replaced the PCM instant of the slab concrete in solar wall. They concluded that use the PCM was faster than the concrete slab and the interaction was 2.5 times with the knowledge that the PCM mass less than mass of concrete slab by six times. Also, they concluded that efficiency of solar wall with use the PCM was 30%. Madhumathi and Sundarraja (2012) proved experimentally of using the PCM with traditional construction materials in hot climatic zones to reduce the cooling load and air room temperature. They used organic phase change materials of Polyethylene type with melting point (25 °C and 31 °C) where it is used in hollow brick. They built models, each model was 0.020317 m3. They concluded that the using of the PCM improved thermal comfort and reduce in entering heat into room by 33.33%. Zwanzig (2012) evaluated numerically incorporating of the PCM with building material in the field of reducing of the heating load and the cooling load. He used PCM composite wallboard in the walls and the roof. He tested using PCM as
Fig. 1. Rooms Model.
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2.2. Experiment room
+ mortar 10 cm). The melting range of the PCM was (36.7–37 °C). They noted that reduction in heat transfer was about 46.71%. In literature that reviewed the PCM is usually used in the field of heating and cooling system to reduce thermal loads and it incorporated with construction materials like plaster or gypsum or concrete and it usually it was in the form of capsules. In this work, the PCM was used as an insulation layer with the aluminum frame and without capsules without merging with construction materials. The energy storage capacity of phase change materials is utilized to perform the cooling load reduction.
The experimental room is a room that has been equipped with phase change material as a thermal insulation material. The construction material of experimental room is the same for that of the standard room in addition to the PCM layer. The PCM placed in the internal side of the walls and ceiling in the frame of aluminum where the PCM has been proven between two layers of aluminum of thickness (0.7 mm). The addition layer is the aluminum frame where it consists of two layers of aluminum with thickness of (0.7 mm) for each one, as shown in Fig. 3. The aluminum frame is attached to the internal surface of the wall (cement layer) and its thickness is depended on the thickness of the PCM inside it. In addition to that, one of the layers of the aluminum frame has been used in the ceiling and supported from bottom where the PCM was placed between the ceiling direct and one of the layers of aluminum frame. The thermal conductivity of the aluminum was (221 W m−1 K−1) (Republic of Iraq Ministry, 2012).
2. Problem description Two identical rooms were built with dimensions (1.5 m*1.5 m*1 m), as shown in Fig. 1. The first is a standard room, and the second is experiment room. The rooms consist of domestic construction materials, according to the construction specifications in Iraq. The walls consist of two layers, from outside to inside which are the following on, first layer from bricks with 12 cm thickness, the second layer from cement mortar with 1 cm thickness. The ceiling was from sandwich panel with 5 cm thickness and the floor was from direct ground.
3. Mathematical formulation In this section, the used equations that used to calculate the cooling load will be mathematically presented. Conduction Resistance (R):
R= 2.1. Standard room
x λ
(1)
Total Thermal Resistance (RT): Standard room is a room which set up for comparison, its walls consists of the two major layers, as shown in Fig. 2, from outside to inside, the first layer is a local brick with dimensions (24 cm*7 cm*12 cm) and with thermal conductivity (0.54 W m−1 K−1) (Republic of Iraq Ministry, 2012), the second layer is a cement mortar with 1 cm thickness and with thermal conductivity (0.99 W m−1 K−1) (Republic of Iraq Ministry, 2012). The ceiling consists of sandwich panel “rigid polyisocyanurate foam core with external and internal sheet in steel” with 5 cm thickness and with thermal conductivity (0.034–0.038 W m−1 K−1) (Anonymous, 2017a). The floor was from direct ground.
RT =
1 x x x 1 + 1 + 2 + …+ n + Fi k1 k2 kn Fo
(2)
Where: – RT: Total Thermal Resistance in (m2 K W−1) Fi: Inside film resistance for enveloping internal wall and equal (9.26 W m−2 K−1) (Judi, 1996). Fo: Outside film resistance for enveloping external wall and equal (22.7 W m−2 K−1) (Judi, 1996). x1: Thickness of first layer for wall in (m). xn: Thickness of last layer for wall in (m). λ1: Thermal Conductivity of first layer for wall in (W m−1 K−1) Fig. 2. Standard Room.
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Fig. 3. Experimental Room.
λn: Thermal Conductivity of last layer for wall in (W m−1 K−1) Overall heat transfer coefficient (U):
U=
1 RT
Tm: Outdoor design temperature which refed to (amb, T) and equal Tm = (To − DR/2) DR: Daily range of outdoor -For Ceilings: –
(3)
CLTDc = [(CLTD + LM )*K + (25.5 − Tr ) + (Tm − 29.4)]*f
Where: – U: Overall heat transfer coefficient (W m−2 K−1).
Where: – f: Ventilation factor between second ceiling and italics ceiling (f = 1.0 for no fan ventilation, f = 0.75 for mechanical ventilation) CLTD: Cooling load temperature difference for ceiling (°C) which can be taken from special table (Republic of Iraq Ministry, 2012) depended upon ceiling construction.
3.1. Cooling load There are three ways for the heat transfer between objects in nature: conduction, convection and radiation. Heat Gain of Zone: Heat gain defined as the rate of heat transfer into zone during certain time period which equal to the cooling load. One of the main source caused heat gain is the building structure where the cooling load through building exterior structure can be calculated by using the (CLTD) method (ASHRAE, 1981) Q = U A CLTDc
3.2. Cooling load reduction (%) The reduction in cooling load which is caused by using PCM as insulation materials is calculated as follow:
(4)
C. L. R =
Where: – Q: Amount of heat transfer during walls or ceiling in (W) U: Overall heat transfer coefficient of wall or ceiling in (W m−2 K−1) A: Surface area in (m2) CLTDc: Correction cooling load temperature difference (°C) and calculated by equations: – -For Walls: –
CLTDc = [(CLTD + LM )*K + (25.5 − Tr ) + (Tm − 29.4)]
(6)
C . L withPCM − C . L withoutPCM *% C . L withoutPCM
(7)
Where: – C.LwithPCM: Cooling load of room with PCM in (W). C.LwithoutPCM: Cooling load of room without PCM (W). 4. Properties of the phase change materials (PCM) The phase change materials are thermal storage materials and it is used as a thermal insulation material due to its property in thermal storage and to curb the heat. The PCMs have many applications or uses in buildings, including the field of integrated the heating and cooling systems, as well as the field of heating and cooling together. It is also used in air conditioning and in the ceiling panels of thermally activated and incorporated into building materials (Subramanian, 2011). The PCM is usually used in the field of heating and cooling system to reduce thermal loads and integrated with construction materials as plaster, gypsum or concrete and it is usually in the form of capsules (Flz
(5)
Where: – CLTD: Cooling load temperature difference for walls (°C) which can be taken from special tables (Republic of Iraq Ministry, 2012) depended upon wall construction. LM: Latitude and month correction factor for wall K: Color correction factor (Dark = 1, med = 0.83, light = 0.65) Tr: Indoor temperature of room (°C) Table 1 Properties of the PCM (paraffin wax) (Hasan, 2017; The Ministry of Science, 2017). material
Paraffin wax
density (kg m−3)
Specific heat (kJ kg−1 K−1)
solid
liquid
solid
liquid
830
783
2.44
2.53
Melting point (°C)
Latent heat (kJ kg−1)
Thermal Conductivity (W m−1 K−1)
44
174.12
0.13
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were compared with the standard room at the same experimental time.
Karlsruhe Gmbh, 2009). In this paper, the energy storage capabilities of PCM are utilized since the PCM was used as insulation layer for residential building which is inside aluminum frame attached to the room inside walls and ceiling. The main role of PCM is to shift the maximum cooling load by absorbing heat during melting in peak hours and as a result reducing the heat crossing the wall toward inside the room, and then this heat is released during solidification process in night hours. The used PCM is a paraffin wax with white color. The cost of paraffin wax was (2.44 $ kg−1) i.e. (2.9 $ L−1) from local market and the thermal physical properties of the PCM were presented in Table 1.
5.1.3.2. South wall only with 2 cm thickness of PCM. The South wall was insulated by using PCM with 2 cm thickness and the area of PCM was (1 m*1.5 m). The PCM was poured in the aluminum frame after melting process by using gas heater. The probationary period was from (21-Sep2016) at 12 a.m. to (22-Sep-2016) at 12 a.m. The results were compared with the standard room at the same experimental time. 5.1.3.3. North wall only with 2 cm thickness of PCM. The North wall was insulated by using PCM with 2 cm thickness and the area of PCM was (1 m*1.5 m). The PCM was poured in the aluminum frame after melting process by using gas heater. The probationary period was from (31-Aug2016) at 12 a.m. to (1-Sep-2016) at 12 a.m. The results were compared with the standard room at the same experimental time.
5. Experimental work 5.1. Cases of conducted experimental tests Several of tests were performed on the PCM and their use as a thermal insulation and with several thicknesses where it was combined with the walls and ceiling, as follows:
5.1.3.4. East wall only with 2 cm thickness of PCM. The East wall was insulated by using PCM with 2 cm thickness and the area of PCM was (1 m*1.5 m). The PCM was poured in the aluminum frame after melting process by using gas heater. The probationary period was from (24-Sep2016) at 12 a.m. to (25-Sep-2016) at 12 a.m. The results were compared with the standard room at the same experimental time.
5.1.1. All walls with PCM with 1 cm thickness In this case, all walls of experimental room were insulated by paraffin wax with 1 cm thickness. As maintained before the using of PCM inside aluminum frame with area equal to the wall area. First the paraffin wax is melted by gas heater and then poured the molten paraffin wax in the aluminum frame as shown in Figs. 4–6. The test was performed in the period from (16-Aug-2016) at 12 a.m. to (17-Aug2016) at 12 a.m. The date for experimental and standard rooms was recorded at the same time.
5.2. Measurement instrument 5.2.1. Temperature data logger 5.2.1.1. Lab jack. Lab Jack model (U3-LV) data logger was used to record the temperature in this study. This device has 16-channels with the increment, as shown in Fig. 8(a and b). The channels were distributed by wires in all walls and installed inside walls to measure the temperature. The ambient temperature and internal, external temperature of all the walls were recorded by this device. The data logger was connected to computer with the help of special software, as shown in Fig. 9. The temperature value was stored and recorded by this software for both rooms and at the same time in interval time 10 min for 24 h to all experimental cases.
5.1.2. Ceiling with PCM with 1 cm thickness The ceiling was insulated by using PCM with 1 cm thickness, as shown in Fig. 7 and with area of PCM was (1.5 m*1.5 m). The PCM was poured in the aluminum frame after melting process by using gas heater. The probationary period was from (8-Sep-2016) at 12 a.m. to (9-Sep-2016) at 12 a.m. The results were compared with the standard room at the same experimental time.
5.2.1.2. Thermistors. Thermistors silicon from kind (LM35) were used to measure the temperature which are read by the lab jack data logger, as shown in Fig. 10, by well settling the thermistors on the safeguard surface to diminish the contact resistance. The used thermistors are (LM35) which a high accuracy and it not subject to oxidation.
5.1.3. Individual walls with 2 cm thickness of PCM In this case, the different walls were tested individually by insulating them by 2 cm layer of paraffin wax. 5.1.3.1. West wall only with 2 cm thickness of PCM. The West wall was insulated by using PCM with 2 cm thickness and the area of PCM was (1 m*1.5 nm). The PCM was poured in the aluminum frame after melting process by using gas heater. The probationary period was from (22-Aug-2016) at 12 a.m. to (23-Aug-2016) at 12 a.m. The results
5.3. The temperature recording The sensor of temperature kind (LM 35 DZ) was used to record the Fig. 4. Melting process by gas heater.
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Fig. 5. PCM poured process in aluminum frame.
due to its melting in day hours and absorbing the heat and lead to maintain the temperature of the room at low values. While at night hours, it can be observed that the indoor temperature of room in a case of using PCM as insulation material becomes higher than that for similar room without PCM which is due to discharge effects, since the PCM start discharging heat through solidification process at night time. Also, it can be seen from this figure that there is a fluctuation in temperature of the room for two cases with and without PCM due to the effect of the outside temperature fluctuation. The difference between room indoor temperature with PCM and without was 2.18 °C at 6 p.m. Fig. 13 indicates the variation of internal surface temperature of all walls for two cases with and without PCM for experimental results. For the room with PCM, all walls are coated with PCM (paraffin wax) with 1 cm thickness where the PCM placed in the internal surface of all walls. In this figure, it can be seen that the internal surface temperature of all walls with PCM is decreased at day hours as a result of the insulation role of the PCM where the curb and absorbed heat and converting the PCM to liquid state and thus reduced the entry of heat to the inner surface of the all walls and thus reduced heat that enter into the zone. As concerning in night hours, it can be seen that the internal surface temperature of all walls with PCM be close to the case without PCM because the internal surface walls were rejected heat in discharging process and were return to solid state.
temperature. Putting two sensor wires in every wall face in the two rooms, one in internal wall face and another one in external wall face, and it are installed in the middle of the wall to measure the average wall face temperature. One sensor was installed in outside the rooms to measure ambient air temperature. Also, one sensor in every room in the middle of the room is installed to measure indoor air temperature of the room. In every ceiling of the two rooms, two sensors have been installed, one in inside ceiling and another one in outside ceiling, to measure the ceiling temperature. Fig. 11 shows the locations of temperature sensors used. 6. Results and discussion The following findings are the results of a feasibility study of the use of phase change materials as thermal insulation materials for cooling load reduction in summer. The results were taken in August and September in the city of Kut- Iraq at the same time for both the rooms with and without PCM. Many cases were conducted with many thicknesses and orientations. 6.1. Indoor temperature and internal surface temperature 6.1.1. All walls with PCM with 1 cm thickness Fig. 12 shows the variation of room indoor temperature for two cases with and without PCM for experimental results. For the room with PCM, all walls are coated with PCM (paraffin wax). From this figure, it can be seen that the indoor temperature of the room with PCM is lower than the indoor temperature of room without PCM all day hours due to the insulation effect of PCM which reduces the heat gain to the room,
6.1.2. Ceiling with PCM with 1 cm thickness Fig. 14 shows the variation of room indoor temperature for two cases with and without PCM for experimental results. For the room with PCM the only ceiling is coated with PCM (paraffin wax). From this figure, it can be seen that the indoor temperature of the room with PCM Fig. 6. All walls insulated with 1 cm thickness of PCM.
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Fig. 7. Insulation ceiling by the PCM with 1 cm thickness.
North, and East wall respectively. For the room with PCM the West, South, North and East wall individual are coated with PCM (paraffin wax). From these figures, it can be seen that the indoor temperature of room with PCM is lower than the indoor temperature of room without PCM all day hours due to the insulation effect of PCM which reduces the heat gain to the room, due to its melting in day hours and absorbing the heat and lead to maintain the temperature of the room at low values. While at night hours, it can be observed that the indoor temperature of room in a case of using PCM as insulation material becomes higher than that for similar room without PCM which is due to discharge effects, since the PCM start discharging heat through solidification process in night time. Also, it can be seen from these figures that there is a fluctuation in temperature of the room for two cases with and without PCM due to the effect of the outside temperature fluctuation. The difference between the indoor temperature room with PCM and without for all cases and for individual walls was presented in Table 2. Figs. 20–23 indicate the variation of internal surface temperature for two cases with and without PCM and for experimental results for the West, South, North, East wall respectively. For the room with PCM the West, South, North and East wall individual are coated with PCM (paraffin wax) with 2 cm thickness where the PCM placed in the internal surface. In these figures, it can be seen that the internal surface temperature for with PCM is decreased at day hours as a result of the insulation role of the PCM where the curb and absorbed heat and converting the PCM to liquid state and thus reduced the entry of heat to the inner surface of the all walls and thus reduced heat that enter into the zone. As concerning in night hours, it can be seen that the internal surface temperature of all individual walls for with PCM be close to the case without PCM because the internal surface walls were rejected heat
is lower than the indoor temperature of room without PCM all day hours due to the insulation effect of PCM which reduce the heat gain to the room, due to its melting in day hours and absorbing the heat and lead to maintain the temperature of the room at low values. While at night hours, it can be observed that the indoor temperature of room in a case of using PCM as insulation material becomes higher than that for similar room without PCM which is due to discharge effects, since the PCM start discharging heat through solidification process at night time. Also, it can be seen from this figure that there is a fluctuation in temperature of the room for two cases with and without PCM due to the effect of the outside temperature fluctuation. The difference between room indoor temperature with PCM and without was 1.9 °C at 6 p.m. Fig. 15 indicates the variation of internal surface temperature of the ceiling only for two cases with and without PCM for experimental results. For the room with PCM, the only ceiling is coated with PCM (paraffin wax) with 1 cm thickness where the PCM placed in the internal surface of the ceiling. In this figure, the internal surface temperature of the ceiling for with PCM is decreased at day hours as a result of the insulation role of the PCM where the curb and absorbed heat and converting the PCM to liquid state and thus reduced the entry of heat to the inner surface of the ceiling and thus reduced heat that enter into the zone. As concerning in night hours, it can be that the internal surface temperature of ceiling for with PCM be close to the case without PCM because the internal surface walls were rejected heat in discharging process and were return to solid state.
6.1.3. Individual all walls with PCM with 2 cm thickness Figs. 16–19 show the variation of room indoor temperature for two cases with and without PCM for experimental results for West, South,
Fig. 8. (a and b) Lab jack and lab jack with increment.
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Fig. 9. Window of lab jack software program.
Fig. 10. Thermistors kind (LM35).
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Fig. 11. Locations of sensor (LM 35) in walls, indoor room, outdoor room and roof.
Temperature(ºC).
Amb,T
Tr with pcm
Tr without pcm
49 47 45 43 41 39 37 35 33 31 29 27 25
TIME (hours) 50
Fig. 12. Indoor temperature of rooms with and without PCM using 1 cm of PCM at all walls and outside temperature (16-Aug-2016).
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Temperature.(ºC)
Tiw North wall with pcm
Tiw South wall with pcm
Tiw East wall with pcm
Tiw West wall with pcm
Tiw West wall without pcm
Tiw South wall without pcm
Tiw East wall without pcm
Tiw North wall without pcm
Amb,T
Fig. 13. Internal surface temperature of all walls with and without PCM using 1 cm of PCM (16-Aug-2016).
52 50 48 46 44 42 40 38 36 34 32 30
TIME (hours) Fig. 14. Indoor temperature of rooms with and without PCM using 1 cm of PCM at ceiling only (8-Sep-2016).
Fig. 15. Internal surface temperature of ceiling only with and without PCM using 1 cm of PCM (8-Sep-2016).
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Fig. 16. Indoor temperature of rooms with and without PCM using 2 cm of PCM at West wall (22-Aug-2016).
Fig. 17. Indoor temperature of the rooms with and without PCM using 2 cm of PCM at south wall (21-Sep-2016).
Fig. 18. Indoor temperature of rooms with and without PCM using 2 cm of PCM at North wall (31-Aug-2016).
walls together. Also when using 2 cm thickness the south wall give maximum reduction in temperature followed by west wall.
in discharging process and were return to solid state. 6.1.4. Indoor temperature reduction The difference of the indoor temperature between rooms with PCM and rooms without PCM for all cases is shown in Table 2. Which show that, when using 1 cm thickness the temperature reduction in case of using PCM with ceiling only is comparable with case of using PCM in all
6.2. Cooling load 6.2.1. All walls with PCM with 1 cm thickness Cooling load of the rooms with and without PCM is presented in 52
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Fig. 19. Indoor temperature of rooms with and without PCM using 2 cm of PCM at East wall (24-Sep-2016).
Table 2 Difference of the indoor temperature between rooms with PCM and rooms without PCM for all cases. case
Thickness of PCM
TIME
ΔTr (Tr without PCM-Tr with PCM)
Date
All wall Ceiling South wall West wall North wall East wall
1 cm 1 cm 2 cm 2 cm 2 cm 2 cm
6 6 6 6 6 6
2.18 °C 1.9 °C 3.32 °C 2.2 °C 1.5 °C 1.2 °C
16-Aug-2016 8-Sep-2016 21-Sep-2016 22-Aug-2016 31-Aug-2016 24-Sep-2016
p.m. p.m. p.m. p.m. p.m. p.m.
Fig. 20. Internal surface temperature of West wall with and without PCM using 2 cm of PCM (22-Aug-2016).
Fig. 21. Internal surface temperature of South wall with and without PCM using 2 cm of PCM (21-Sep-2016).
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Fig. 22. Internal surface temperature of North wall with and without PCM using 2 cm of PCM (31-Aug-2016).
Fig. 23. Internal surface temperature of East wall with and without PCM using 2 cm of PCM (24-Sep-2016).
Fig. 24. Cooling load of rooms with and without PCM using 1 cm of PCM at all walls (16-Aug2016).
reduction in cooling load is 20.9% at peak hour. As concerning in night hours, the cooling load is increased due to discharging process where the PCM rejected the heat inside the room.
Fig. 24 for the room with PCM, all walls are coated with PCM (paraffin wax). In this figure, it can be seen that cooling load is reduced at day time which means that the reduction of cooling load is takes place in time which the PCM works and absorbs heat enters to the zone, 54
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Fig. 25. Cooling load of rooms with and without PCM using 1 cm of PCM at ceiling only (8-Sep2016).
Fig. 26. Cooling load of rooms with and without PCM using 2 cm of PCM at West wall (22-Aug2016).
Fig. 27. Cooling load of rooms with and without PCM using 2 cm of PCM at South wall (21-Sep2016).
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Fig. 28. Cooling load of rooms with and without PCM using 2 cm of PCM at North wall (31-Aug2016).
Fig. 29. Cooling load of rooms with and without PCM using 2 cm of PCM at East wall (24-Sep2016).
6.2.3. Individual walls with PCM with 2 cm thickness Cooling load of the rooms with and without PCM for the West, South, North, East wall are presented in Figs. 26–29 respectively. For the room with PCM the West, South, North, East wall Individual are coated with PCM (paraffin wax). In these figures, it can be seen that cooling load is reduced at day time which means that the reduction of cooling load is takes place in time which the PCM works and absorbs heat enters to the zone, percentage of reduction in cooling load for all cases and for the individual wall are presented in Table 3. As concerning in night hours, the cooling load is increased due to discharging process where the PCM rejected the heat inside the room. Increasing the effect of the PCM with increase the thickness this because increasing the heat capacity of PCM, also effect of the PCM is appeared at evening due to time lag of heat.
Table 3 Percentage of the cooling load reduction for rooms with and without PCM for all studied cases. case
Thickness of PCM
TIME
% Reduction of C-L
Date
All wall Ceiling South wall West wall North wall East wall
1 cm 1 cm 2 cm 2 cm 2 cm 2 cm
6 p.m. 6 p.m. 6 p.m. 12 p.m. 12 p.m. 12 p.m.
20.9% 6.83% 19.95% 14.36% 7% 11.52%
16-Aug-2016 8-Sep-2016 21-Sep-2016 22-Aug-2016 31-Aug-2016 24-Sep-2016
6.2.2. Ceiling with PCM with 1 cm thickness Cooling load of the rooms with and without PCM is presented in Fig. 25 for the room with PCM, the only ceiling is coated with PCM (paraffin wax). In this figure, it can be seen that cooling load is reduced at day time which means that the reduction of cooling load is takes place in time which the PCM works and absorbs heat enters to the zone, reduction in cooling load is 6.83% at peak hour. As concerning in night hours, the cooling load is increased due to discharging process where the PCM rejected the heat inside the room.
6.2.4. Percentage of cooling load reduction Fig. 30 shows the variation of percentage of cooling load reduction as a result of using PCM for different studied cases compared with cooling load for standard room. It is important to mention that the tests for different cases of PCM were carried out at different times due to preparation requirements. Table 3 summarizes the value of maximum reduction percentages for different cases. 56
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1 cm All Walls
2 cm West Wall
1 cm Ceiling
2 cm North Wall
2cm East Wall
2 cm South Wall
Fig. 30. Percentage of cooling load reduction (Aug–Sep).
40%
Cooling Load ReducƟon %
20% 0% -20% -40% -60% -80% -100% 12:00 AM
6:00 AM
12:00 PM
6:00 PM
12:00 AM
Time (Hours) ■ Using the PCM as thermal insulation materials in buildings contributed to improvement of thermal comfort. ■ Using the PCM lead to reduce the indoor temperature of zone and reducing the cooling load. ■ Reduction in the indoor temperature of the zone by using PCM and according to cases was 2.18 °C with 1 cm thickness of PCM for all walls, 1.9 °C with 1 cm thickness of PCM for ceiling, 3.32 °C with 2 cm thickness of PCM for South wall, 2.2 °C with 2 cm thickness of PCM for West wall, 1.5 °C with 2 cm thickness of PCM for North wall, 1.2 °C with 2 cm thickness of PCM for East wall. ■ Insulating the South wall lead to higher reduction in the indoor temperature. ■ Percentage of the cooling load reduction of the zone by using PCM and according to cases and for peak hour in day was 20.9% with 1 cm thickness of PCM for all walls, 6.83% with 1 cm thickness of PCM for ceiling, 19.95% with 2 cm thickness of PCM for South wall, 14.36% with 2 cm thickness of PCM for West wall, 7% with 2 cm thickness of PCM for North wall, 11.7% with 2 cm thickness of PCM for East wall. ■ The best case in cooling load reduction of the zone for peak hour was 1 cm thickness of PCM for all wall 20.9%. ■ Using PCM as insulation materials leads to saving of electricity consumption. ■ The saving in electricity cost was (1.35 Dollar/Day m3) with 1 cm thickness of PCM for all walls, (0.88 Dollar/Day m3) with 1 cm thickness of PCM for ceiling, (1.19 Dollar/Day m3) with 2 cm thickness of PCM for South wall, (1.21 Dollar/Day m3) with 2 cm thickness of PCM for West wall, (1.08 Dollar/Day m3) with 2 cm thickness of PCM for North wall, (0.58 Dollar/Day m3) with 2 cm thickness of PCM for East wall. ■ Maximum saving in electricity cost of zone was (1.35 Dollar/ Day m3) when using 1 cm thickness of PCM for all walls.
Table 4 Saving in electricity cost. case
Thickness of PCM
reduction of cooling load (kW m−3)
Saving in electricity cost Dollar/Day m3
All wall Ceiling South wall West wall North wall East wall
1 cm 1 cm 2 cm 2 cm 2 cm 2 cm
2.114 1.38 1.86 1.9 1.68 0.905
1.35 0.88 1.19 1.21 1.08 0.58
From Fig. 30 and Table 3 it can be concluded that insulating all wall with 1 cm give higher reduction in cooling load since it reduces the cooling load by 20.9% compared with standard room due to its direct impact on cooling load. Also, insulating the ceiling cause minimum reduction in cooling load compared with other cases.
6.3. Electric consumption cost Electric consumption cost was calculated at peck hour for all cases of using the PCM (paraffin wax) as insulation material. It has been using the usual default price in Iraq that is 30 Dinar per kWh “The price of electrical energy consumption in Iraq, According to The Pricing of The Ministry of Electricity” (Anonymous, 2017b). Saving in electricity cost (Dinar per day) = reduction of cooling load (kW)*30 (Dinar per kWh)*24 (h per day) Where: 24 (h per day) Operating period reduction of cooling load = cooling load PCM − cooling load of room with PCM wall.
of
room
without
Where: 1 $ = 1126 Dinar Table 4 below indicates the saving of electricity cost for experimental room for peak hour with dimensions (1.5 m*1.5 m*1 m) which indicate that for large building using of PCM as insulation materials can save considerable amounts of money.
References ASHRAE, The American Society of Heating, Refrigerating and Air Conditioning Engineers (1981). Thermal environmental conditions for human occupancy. USA: ASHRAE 55-81. Al-Hadithi, M. B. (2011). Use of phase change material in residential walls to reduce cooling load. Anbar Journal for Engineering Science, 4, 72–74. https://www.bcoms.com/products/roofandwall/sandwichpanels. http://www.moelc.gov.iq/i. Flz Karlsruhe Gmbh (2009). Latent heat storage in building. Hermann-Von-Helmholtz-Platz: German Federal Ministry of Economics and Technology: BINE Themen Info. Halford, C. K., & Boehm, R. F. (2007). Modeling of phase change material peak load shifting. Energy and Buildings, 39 Elsevier Article, 298–297. Hasan, M. I. (2017). Improving the cooling performance of electrical distribution transformer using transformer oil – Based MEPCM suspension. Engineering Science and
7. Conclusions The using of phase change materials as thermal insulation materials has been studied experimentally. From the results which are obtained can be made the following conclusions: – 57
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231. Republic of Iraq Ministry of Construction and Housing Technical Department of the draft Iraqi Blogs, Blog Iraqi for cooling, 2012. Subramanian, E. (2011). Integrating phase change materials in building materials experimentation, characterization and numerical simulation. The Graduate School of Clemson University p. 1073. The Ministry of Science and Technology of Iraq\office of materials research\oils and improvers Department. Zalewski, L., Joulin, A., Lassue, S., Dutil, Y., & Rousse, D. (2011). Experimental study of small-scale solar wall integrating phase change material. Université d'Artois. Zwanzig, S. D. (2012). Numerical simulation of phase change material composite wallboard in a multi-layered building envelope. University of Louisville.
Technology An International Journal, 20, 502–510. Judi, K. A., Dr. (1996). Principles of air conditioning and refrigeration. The University of Basra The second edition engineering. Madhumathi, A. A., & Sundarraja, B. M. C. (2012). Experimental study of passive cooling of building façade using phase change materials to increase thermal comfort in buildings in hot humid areas. International Journal of Energy and Environment, 3, 739. Monteiro da Silva, S., & Almeida, M. (2013). Using PCM to improve building’s thermal performance. 2nd international conference on sustainable energy storage (pp. 182–186). Muruganantham, K. (2010). Application of phase change material in buildings field data vs. EnergyPlus simulation. Arizona State University. Mushtaq, T. H., Ahmed, Q. M., & Hasanain, M. H. (2013). Experimental and numerical study of thermal performance of a building roof including phase change material (PCM) for thermal management. Global Advanced Research Journal of Engineering, 2,
58
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Sustainable Cities and Society journal homepage: www.elsevier.com/locate/scs
Experimental investigation of phase change materials for insulation of residential buildings
MARK
⁎
Mushtaq I. Hasana, , Hadi O. Basherb, Ahmed O. Shdhanb a b
Mechanical Engineering Department, College of Engineering, Thi-Qar University, Iraq Mechanical Engineering Department, College of Engineering, Wasit University, Iraq
A R T I C L E I N F O
A B S T R A C T
Keywords: Electric consumption cost Cooling load Phase change material PCM Thermal insulation
In this paper, an experimental study has been conducted for using PCM as thermal insulation materials by its incorporating with layers of the walls and the ceiling. The effect of PCM and its role in improvement of thermal performance and thermal comfort is experimentally studied. Two room’s models have been built, the first model is a standard room for comparison and the second model is an experimental room for testing. Wasit university in Kut city, (32.5° N) latitude, was the place of the building models and testing of PCM. The type of PCM which was used in this experiment is paraffin wax with a melting point (44 °C). Many cases were studied according to the thickness of the PCM and according to the orientation (North wall, South wall, East wall, West wall, and ceiling). Results obtained showed a reduction in indoor temperature of the zone and the reduction in cooling load and as a result saving in electricity consumption with using PCM as insulation materials.
1. Introduction The apportionment of thermal mass inside buildings is the consequence of constitutional and architectural resolutions and can highly affect how the building interacts to internal heat gains, solar radiation or changes in outdoor conditions. Lightweight components interact readily to changes in interior gains and solar radiation. The conventional approaches employ enormous components to temperate temperature inconstancy. Thermo-physical properties of the construction materials will have a direct effect on energy consumption of the building. Within a negative solar purpose, the heat capacity of the internal wall layer is governing. This approach it applicable in sites that have an efficacious daily temperature variance, else that, heavy weight building can give rise to problems of excrescent thermal mass and cost. The nature of Iraq’s climate can be described in two basic seasons, hot dry and long summer, and cold short winter. The difference of daily range temperature is limited and causes the assemblage of heat in the building layers. The consumption of electrical demand is increasing, especially in hot regions due to using the cooling system where the consumption of electric energy in the building sector in Iraq reach about 38% of the total energy which is produced, where in 2020 it will be built more than six million building unit and this will increase in electric demand. The phase change materials and its using in the building material considers one of methods to improve the thermal properties of the
⁎
Corresponding author. E-mail address: [email protected] (M.I. Hasan).
http://dx.doi.org/10.1016/j.scs.2017.10.009 Received 4 April 2017; Received in revised form 1 October 2017; Accepted 8 October 2017 Available online 12 October 2017 2210-6707/ © 2017 Elsevier Ltd. All rights reserved.
construction material where integrate these PCM with layers of the building material play important role in shifting the cooling load especially in peak load and Contributes to reducing cooling load. In this research, we will study experimentally integrate the PCM with layers of local construction material in Kut city in Iraq. In the field of using the PCM as insulation materials and it’s incorporating with building materials there are many experimental and numerical studies were conducted. Halford and Boehm (2007) conducted simulation of using encapsulated PCM to shift cooling load. They used encapsulated PCM in ceiling and walls and incorporated the PCM with construction materials like concrete and gypsum wallboard. They used TRANSYS program software to simulate. By comparting their results with other cases without PCM, they found 11–25% reduction in peak load compared with the case without PCM. Muruganantham (2010) conducted experimental and numerical studying about using BIOPCM in envelope building, ceiling and the walls. He used energy plus program in simulation. the layers of the wall were, from outside to inside, sliding door, insulation, BIOPCM and gypsum board as well as wood frame at two sides. BIOPCM was as small block. He made sheds contain door and window and conducted comparison between these sheds. The dimensions of the shed were (4.876 m length, 3.657 m width and 2.436 m height). He used wood frame to install BIOPCM. The melting range of the PCM was (27–31 °C). He found that maximum energy saving about 30%, and maximum cost saving was 30%. Al-Hadithi (2011) studied
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Nomenclature
Q RT Tr Tm U X
Amb,T Ambient air temperature (°C) A Surface area (m2) CLTDc Correction of cooling load temperature difference (°C) CLTD Cooling load temperature difference (°C) C.L.R Cooling load reduction (%) C.LwithPCM Cooling load of the room with PCM (W) C.LwithoutPCM Cooling load of the room without PCM (W) DR daily range of outdoor (°C) Fi Inside film resistance for envelop internal wall (W m−2 K−1) Fo Outside film resistance for envelop internal wall (W m−2 K−1) f Ventilation factor K Color correction factor LM Latitude and month correction factor
Transfer during walls or ceiling (W) Total Thermal Resistance (m2 K W−1) Indoor temperature of room (°C) Outdoor design temperature (°C) Overall heat transfer coefficient (W m−2 K−1) Layer thickness (m)
Greek symbols ΔTr λ
Indoor temperature difference (°C) Thermal conductivity (W m−1 K−1)
Abbreviations BIOPCM Bio phase change material Exp Experimental PCM Phase change material
insulation material in many weathers. He used model one -dimensional transient heat equation and used the Crank-Nicolson scheme to solve this equation. He used TMY3 data for creating weather data. He found the optimizing location of the PCM in layers of building is important and depended on thermal resistance of the layers between the PCM and outside boundary. He compared his results with cases without PCM and he found reducing in the cooling load from the wall by 19.7% and from the roof by 8.1% and reducing in heating load from walls by 6% and from roof by 6.4%. Monteiro da Silva and Almeida (2013) conducted simulation for using of gypsum plasterboards with micro-encapsulated PCM and macro-encapsulated PCM in family house has area 91 m2. They used software energy plus 7.2 for simulation. The melting range of the PCM (paraffin) was (23–26 °C) and PCM (salt hydrate) was (22 °C–28 °C). The simulation was conducted in the coolest and hottest days. They integrated the PCM with the ceiling and the walls and they used three types of construction materials: concrete wall, single hollow brick and double hollow brick. They concluded that the reduction in the heating needs by 16% in coolest day and reduction in the cooling needs about 28% in hottest day and reduced 16% in the annual energy needs. Also, they found that increasing the indoor temperature by 0.7 °C in coolest day and decreasing the indoor temperature by 1.4 °C in hottest day. Mushtaq, Ahmed, and Hasanain (2013) investigated experimentally and numerically the using of the PCM in the ceiling with cooling system to cool PCM. They used two rooms with and without PCM, dimensions of the rooms were (1.8 m*1.8 m*2.44 m). The layers of the roof, from bottom to top, without PCM were (concrete 12 cm and brick mixture + mortar 10 cm) and with PCM were (concrete 12 cm, light structure panel of aluminum with PCM 2.5 cm and brick mixture
numerical method of the effect of using PCM on heat transfer in the wall. He mixed paraffin wax (25%) with concrete (75%) to create treat wall. Layers of the wall were, from external to internal, cement 5 mm, and treat wall 20 mm, brick 300 mm and gypsum 20 mm. The treated wall was west wall. He compared between treat wall and no treat wall and his results showed that treat wall reduced heat transfer by 66%. Zalewski, Joulin, Lassue, Dutil, and Rousse (2011) studied experimentally integrating phase change material in small scale composite trombe solar wall. They used the PCM in the buildings for heating purposes where the PCM works as storage material. The PCM was mixed from hydrated salats (chliarolithe (CaCl2·6H2O) + potassium chlorides (KCl) + additives) and the melting temperature of the PCM was 27 °C. They inserted the PCM in the wall as a brick-shaped package. They replaced the PCM instant of the slab concrete in solar wall. They concluded that use the PCM was faster than the concrete slab and the interaction was 2.5 times with the knowledge that the PCM mass less than mass of concrete slab by six times. Also, they concluded that efficiency of solar wall with use the PCM was 30%. Madhumathi and Sundarraja (2012) proved experimentally of using the PCM with traditional construction materials in hot climatic zones to reduce the cooling load and air room temperature. They used organic phase change materials of Polyethylene type with melting point (25 °C and 31 °C) where it is used in hollow brick. They built models, each model was 0.020317 m3. They concluded that the using of the PCM improved thermal comfort and reduce in entering heat into room by 33.33%. Zwanzig (2012) evaluated numerically incorporating of the PCM with building material in the field of reducing of the heating load and the cooling load. He used PCM composite wallboard in the walls and the roof. He tested using PCM as
Fig. 1. Rooms Model.
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2.2. Experiment room
+ mortar 10 cm). The melting range of the PCM was (36.7–37 °C). They noted that reduction in heat transfer was about 46.71%. In literature that reviewed the PCM is usually used in the field of heating and cooling system to reduce thermal loads and it incorporated with construction materials like plaster or gypsum or concrete and it usually it was in the form of capsules. In this work, the PCM was used as an insulation layer with the aluminum frame and without capsules without merging with construction materials. The energy storage capacity of phase change materials is utilized to perform the cooling load reduction.
The experimental room is a room that has been equipped with phase change material as a thermal insulation material. The construction material of experimental room is the same for that of the standard room in addition to the PCM layer. The PCM placed in the internal side of the walls and ceiling in the frame of aluminum where the PCM has been proven between two layers of aluminum of thickness (0.7 mm). The addition layer is the aluminum frame where it consists of two layers of aluminum with thickness of (0.7 mm) for each one, as shown in Fig. 3. The aluminum frame is attached to the internal surface of the wall (cement layer) and its thickness is depended on the thickness of the PCM inside it. In addition to that, one of the layers of the aluminum frame has been used in the ceiling and supported from bottom where the PCM was placed between the ceiling direct and one of the layers of aluminum frame. The thermal conductivity of the aluminum was (221 W m−1 K−1) (Republic of Iraq Ministry, 2012).
2. Problem description Two identical rooms were built with dimensions (1.5 m*1.5 m*1 m), as shown in Fig. 1. The first is a standard room, and the second is experiment room. The rooms consist of domestic construction materials, according to the construction specifications in Iraq. The walls consist of two layers, from outside to inside which are the following on, first layer from bricks with 12 cm thickness, the second layer from cement mortar with 1 cm thickness. The ceiling was from sandwich panel with 5 cm thickness and the floor was from direct ground.
3. Mathematical formulation In this section, the used equations that used to calculate the cooling load will be mathematically presented. Conduction Resistance (R):
R= 2.1. Standard room
x λ
(1)
Total Thermal Resistance (RT): Standard room is a room which set up for comparison, its walls consists of the two major layers, as shown in Fig. 2, from outside to inside, the first layer is a local brick with dimensions (24 cm*7 cm*12 cm) and with thermal conductivity (0.54 W m−1 K−1) (Republic of Iraq Ministry, 2012), the second layer is a cement mortar with 1 cm thickness and with thermal conductivity (0.99 W m−1 K−1) (Republic of Iraq Ministry, 2012). The ceiling consists of sandwich panel “rigid polyisocyanurate foam core with external and internal sheet in steel” with 5 cm thickness and with thermal conductivity (0.034–0.038 W m−1 K−1) (Anonymous, 2017a). The floor was from direct ground.
RT =
1 x x x 1 + 1 + 2 + …+ n + Fi k1 k2 kn Fo
(2)
Where: – RT: Total Thermal Resistance in (m2 K W−1) Fi: Inside film resistance for enveloping internal wall and equal (9.26 W m−2 K−1) (Judi, 1996). Fo: Outside film resistance for enveloping external wall and equal (22.7 W m−2 K−1) (Judi, 1996). x1: Thickness of first layer for wall in (m). xn: Thickness of last layer for wall in (m). λ1: Thermal Conductivity of first layer for wall in (W m−1 K−1) Fig. 2. Standard Room.
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Fig. 3. Experimental Room.
λn: Thermal Conductivity of last layer for wall in (W m−1 K−1) Overall heat transfer coefficient (U):
U=
1 RT
Tm: Outdoor design temperature which refed to (amb, T) and equal Tm = (To − DR/2) DR: Daily range of outdoor -For Ceilings: –
(3)
CLTDc = [(CLTD + LM )*K + (25.5 − Tr ) + (Tm − 29.4)]*f
Where: – U: Overall heat transfer coefficient (W m−2 K−1).
Where: – f: Ventilation factor between second ceiling and italics ceiling (f = 1.0 for no fan ventilation, f = 0.75 for mechanical ventilation) CLTD: Cooling load temperature difference for ceiling (°C) which can be taken from special table (Republic of Iraq Ministry, 2012) depended upon ceiling construction.
3.1. Cooling load There are three ways for the heat transfer between objects in nature: conduction, convection and radiation. Heat Gain of Zone: Heat gain defined as the rate of heat transfer into zone during certain time period which equal to the cooling load. One of the main source caused heat gain is the building structure where the cooling load through building exterior structure can be calculated by using the (CLTD) method (ASHRAE, 1981) Q = U A CLTDc
3.2. Cooling load reduction (%) The reduction in cooling load which is caused by using PCM as insulation materials is calculated as follow:
(4)
C. L. R =
Where: – Q: Amount of heat transfer during walls or ceiling in (W) U: Overall heat transfer coefficient of wall or ceiling in (W m−2 K−1) A: Surface area in (m2) CLTDc: Correction cooling load temperature difference (°C) and calculated by equations: – -For Walls: –
CLTDc = [(CLTD + LM )*K + (25.5 − Tr ) + (Tm − 29.4)]
(6)
C . L withPCM − C . L withoutPCM *% C . L withoutPCM
(7)
Where: – C.LwithPCM: Cooling load of room with PCM in (W). C.LwithoutPCM: Cooling load of room without PCM (W). 4. Properties of the phase change materials (PCM) The phase change materials are thermal storage materials and it is used as a thermal insulation material due to its property in thermal storage and to curb the heat. The PCMs have many applications or uses in buildings, including the field of integrated the heating and cooling systems, as well as the field of heating and cooling together. It is also used in air conditioning and in the ceiling panels of thermally activated and incorporated into building materials (Subramanian, 2011). The PCM is usually used in the field of heating and cooling system to reduce thermal loads and integrated with construction materials as plaster, gypsum or concrete and it is usually in the form of capsules (Flz
(5)
Where: – CLTD: Cooling load temperature difference for walls (°C) which can be taken from special tables (Republic of Iraq Ministry, 2012) depended upon wall construction. LM: Latitude and month correction factor for wall K: Color correction factor (Dark = 1, med = 0.83, light = 0.65) Tr: Indoor temperature of room (°C) Table 1 Properties of the PCM (paraffin wax) (Hasan, 2017; The Ministry of Science, 2017). material
Paraffin wax
density (kg m−3)
Specific heat (kJ kg−1 K−1)
solid
liquid
solid
liquid
830
783
2.44
2.53
Melting point (°C)
Latent heat (kJ kg−1)
Thermal Conductivity (W m−1 K−1)
44
174.12
0.13
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were compared with the standard room at the same experimental time.
Karlsruhe Gmbh, 2009). In this paper, the energy storage capabilities of PCM are utilized since the PCM was used as insulation layer for residential building which is inside aluminum frame attached to the room inside walls and ceiling. The main role of PCM is to shift the maximum cooling load by absorbing heat during melting in peak hours and as a result reducing the heat crossing the wall toward inside the room, and then this heat is released during solidification process in night hours. The used PCM is a paraffin wax with white color. The cost of paraffin wax was (2.44 $ kg−1) i.e. (2.9 $ L−1) from local market and the thermal physical properties of the PCM were presented in Table 1.
5.1.3.2. South wall only with 2 cm thickness of PCM. The South wall was insulated by using PCM with 2 cm thickness and the area of PCM was (1 m*1.5 m). The PCM was poured in the aluminum frame after melting process by using gas heater. The probationary period was from (21-Sep2016) at 12 a.m. to (22-Sep-2016) at 12 a.m. The results were compared with the standard room at the same experimental time. 5.1.3.3. North wall only with 2 cm thickness of PCM. The North wall was insulated by using PCM with 2 cm thickness and the area of PCM was (1 m*1.5 m). The PCM was poured in the aluminum frame after melting process by using gas heater. The probationary period was from (31-Aug2016) at 12 a.m. to (1-Sep-2016) at 12 a.m. The results were compared with the standard room at the same experimental time.
5. Experimental work 5.1. Cases of conducted experimental tests Several of tests were performed on the PCM and their use as a thermal insulation and with several thicknesses where it was combined with the walls and ceiling, as follows:
5.1.3.4. East wall only with 2 cm thickness of PCM. The East wall was insulated by using PCM with 2 cm thickness and the area of PCM was (1 m*1.5 m). The PCM was poured in the aluminum frame after melting process by using gas heater. The probationary period was from (24-Sep2016) at 12 a.m. to (25-Sep-2016) at 12 a.m. The results were compared with the standard room at the same experimental time.
5.1.1. All walls with PCM with 1 cm thickness In this case, all walls of experimental room were insulated by paraffin wax with 1 cm thickness. As maintained before the using of PCM inside aluminum frame with area equal to the wall area. First the paraffin wax is melted by gas heater and then poured the molten paraffin wax in the aluminum frame as shown in Figs. 4–6. The test was performed in the period from (16-Aug-2016) at 12 a.m. to (17-Aug2016) at 12 a.m. The date for experimental and standard rooms was recorded at the same time.
5.2. Measurement instrument 5.2.1. Temperature data logger 5.2.1.1. Lab jack. Lab Jack model (U3-LV) data logger was used to record the temperature in this study. This device has 16-channels with the increment, as shown in Fig. 8(a and b). The channels were distributed by wires in all walls and installed inside walls to measure the temperature. The ambient temperature and internal, external temperature of all the walls were recorded by this device. The data logger was connected to computer with the help of special software, as shown in Fig. 9. The temperature value was stored and recorded by this software for both rooms and at the same time in interval time 10 min for 24 h to all experimental cases.
5.1.2. Ceiling with PCM with 1 cm thickness The ceiling was insulated by using PCM with 1 cm thickness, as shown in Fig. 7 and with area of PCM was (1.5 m*1.5 m). The PCM was poured in the aluminum frame after melting process by using gas heater. The probationary period was from (8-Sep-2016) at 12 a.m. to (9-Sep-2016) at 12 a.m. The results were compared with the standard room at the same experimental time.
5.2.1.2. Thermistors. Thermistors silicon from kind (LM35) were used to measure the temperature which are read by the lab jack data logger, as shown in Fig. 10, by well settling the thermistors on the safeguard surface to diminish the contact resistance. The used thermistors are (LM35) which a high accuracy and it not subject to oxidation.
5.1.3. Individual walls with 2 cm thickness of PCM In this case, the different walls were tested individually by insulating them by 2 cm layer of paraffin wax. 5.1.3.1. West wall only with 2 cm thickness of PCM. The West wall was insulated by using PCM with 2 cm thickness and the area of PCM was (1 m*1.5 nm). The PCM was poured in the aluminum frame after melting process by using gas heater. The probationary period was from (22-Aug-2016) at 12 a.m. to (23-Aug-2016) at 12 a.m. The results
5.3. The temperature recording The sensor of temperature kind (LM 35 DZ) was used to record the Fig. 4. Melting process by gas heater.
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Fig. 5. PCM poured process in aluminum frame.
due to its melting in day hours and absorbing the heat and lead to maintain the temperature of the room at low values. While at night hours, it can be observed that the indoor temperature of room in a case of using PCM as insulation material becomes higher than that for similar room without PCM which is due to discharge effects, since the PCM start discharging heat through solidification process at night time. Also, it can be seen from this figure that there is a fluctuation in temperature of the room for two cases with and without PCM due to the effect of the outside temperature fluctuation. The difference between room indoor temperature with PCM and without was 2.18 °C at 6 p.m. Fig. 13 indicates the variation of internal surface temperature of all walls for two cases with and without PCM for experimental results. For the room with PCM, all walls are coated with PCM (paraffin wax) with 1 cm thickness where the PCM placed in the internal surface of all walls. In this figure, it can be seen that the internal surface temperature of all walls with PCM is decreased at day hours as a result of the insulation role of the PCM where the curb and absorbed heat and converting the PCM to liquid state and thus reduced the entry of heat to the inner surface of the all walls and thus reduced heat that enter into the zone. As concerning in night hours, it can be seen that the internal surface temperature of all walls with PCM be close to the case without PCM because the internal surface walls were rejected heat in discharging process and were return to solid state.
temperature. Putting two sensor wires in every wall face in the two rooms, one in internal wall face and another one in external wall face, and it are installed in the middle of the wall to measure the average wall face temperature. One sensor was installed in outside the rooms to measure ambient air temperature. Also, one sensor in every room in the middle of the room is installed to measure indoor air temperature of the room. In every ceiling of the two rooms, two sensors have been installed, one in inside ceiling and another one in outside ceiling, to measure the ceiling temperature. Fig. 11 shows the locations of temperature sensors used. 6. Results and discussion The following findings are the results of a feasibility study of the use of phase change materials as thermal insulation materials for cooling load reduction in summer. The results were taken in August and September in the city of Kut- Iraq at the same time for both the rooms with and without PCM. Many cases were conducted with many thicknesses and orientations. 6.1. Indoor temperature and internal surface temperature 6.1.1. All walls with PCM with 1 cm thickness Fig. 12 shows the variation of room indoor temperature for two cases with and without PCM for experimental results. For the room with PCM, all walls are coated with PCM (paraffin wax). From this figure, it can be seen that the indoor temperature of the room with PCM is lower than the indoor temperature of room without PCM all day hours due to the insulation effect of PCM which reduces the heat gain to the room,
6.1.2. Ceiling with PCM with 1 cm thickness Fig. 14 shows the variation of room indoor temperature for two cases with and without PCM for experimental results. For the room with PCM the only ceiling is coated with PCM (paraffin wax). From this figure, it can be seen that the indoor temperature of the room with PCM Fig. 6. All walls insulated with 1 cm thickness of PCM.
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Fig. 7. Insulation ceiling by the PCM with 1 cm thickness.
North, and East wall respectively. For the room with PCM the West, South, North and East wall individual are coated with PCM (paraffin wax). From these figures, it can be seen that the indoor temperature of room with PCM is lower than the indoor temperature of room without PCM all day hours due to the insulation effect of PCM which reduces the heat gain to the room, due to its melting in day hours and absorbing the heat and lead to maintain the temperature of the room at low values. While at night hours, it can be observed that the indoor temperature of room in a case of using PCM as insulation material becomes higher than that for similar room without PCM which is due to discharge effects, since the PCM start discharging heat through solidification process in night time. Also, it can be seen from these figures that there is a fluctuation in temperature of the room for two cases with and without PCM due to the effect of the outside temperature fluctuation. The difference between the indoor temperature room with PCM and without for all cases and for individual walls was presented in Table 2. Figs. 20–23 indicate the variation of internal surface temperature for two cases with and without PCM and for experimental results for the West, South, North, East wall respectively. For the room with PCM the West, South, North and East wall individual are coated with PCM (paraffin wax) with 2 cm thickness where the PCM placed in the internal surface. In these figures, it can be seen that the internal surface temperature for with PCM is decreased at day hours as a result of the insulation role of the PCM where the curb and absorbed heat and converting the PCM to liquid state and thus reduced the entry of heat to the inner surface of the all walls and thus reduced heat that enter into the zone. As concerning in night hours, it can be seen that the internal surface temperature of all individual walls for with PCM be close to the case without PCM because the internal surface walls were rejected heat
is lower than the indoor temperature of room without PCM all day hours due to the insulation effect of PCM which reduce the heat gain to the room, due to its melting in day hours and absorbing the heat and lead to maintain the temperature of the room at low values. While at night hours, it can be observed that the indoor temperature of room in a case of using PCM as insulation material becomes higher than that for similar room without PCM which is due to discharge effects, since the PCM start discharging heat through solidification process at night time. Also, it can be seen from this figure that there is a fluctuation in temperature of the room for two cases with and without PCM due to the effect of the outside temperature fluctuation. The difference between room indoor temperature with PCM and without was 1.9 °C at 6 p.m. Fig. 15 indicates the variation of internal surface temperature of the ceiling only for two cases with and without PCM for experimental results. For the room with PCM, the only ceiling is coated with PCM (paraffin wax) with 1 cm thickness where the PCM placed in the internal surface of the ceiling. In this figure, the internal surface temperature of the ceiling for with PCM is decreased at day hours as a result of the insulation role of the PCM where the curb and absorbed heat and converting the PCM to liquid state and thus reduced the entry of heat to the inner surface of the ceiling and thus reduced heat that enter into the zone. As concerning in night hours, it can be that the internal surface temperature of ceiling for with PCM be close to the case without PCM because the internal surface walls were rejected heat in discharging process and were return to solid state.
6.1.3. Individual all walls with PCM with 2 cm thickness Figs. 16–19 show the variation of room indoor temperature for two cases with and without PCM for experimental results for West, South,
Fig. 8. (a and b) Lab jack and lab jack with increment.
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Fig. 9. Window of lab jack software program.
Fig. 10. Thermistors kind (LM35).
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Fig. 11. Locations of sensor (LM 35) in walls, indoor room, outdoor room and roof.
Temperature(ºC).
Amb,T
Tr with pcm
Tr without pcm
49 47 45 43 41 39 37 35 33 31 29 27 25
TIME (hours) 50
Fig. 12. Indoor temperature of rooms with and without PCM using 1 cm of PCM at all walls and outside temperature (16-Aug-2016).
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Temperature.(ºC)
Tiw North wall with pcm
Tiw South wall with pcm
Tiw East wall with pcm
Tiw West wall with pcm
Tiw West wall without pcm
Tiw South wall without pcm
Tiw East wall without pcm
Tiw North wall without pcm
Amb,T
Fig. 13. Internal surface temperature of all walls with and without PCM using 1 cm of PCM (16-Aug-2016).
52 50 48 46 44 42 40 38 36 34 32 30
TIME (hours) Fig. 14. Indoor temperature of rooms with and without PCM using 1 cm of PCM at ceiling only (8-Sep-2016).
Fig. 15. Internal surface temperature of ceiling only with and without PCM using 1 cm of PCM (8-Sep-2016).
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Fig. 16. Indoor temperature of rooms with and without PCM using 2 cm of PCM at West wall (22-Aug-2016).
Fig. 17. Indoor temperature of the rooms with and without PCM using 2 cm of PCM at south wall (21-Sep-2016).
Fig. 18. Indoor temperature of rooms with and without PCM using 2 cm of PCM at North wall (31-Aug-2016).
walls together. Also when using 2 cm thickness the south wall give maximum reduction in temperature followed by west wall.
in discharging process and were return to solid state. 6.1.4. Indoor temperature reduction The difference of the indoor temperature between rooms with PCM and rooms without PCM for all cases is shown in Table 2. Which show that, when using 1 cm thickness the temperature reduction in case of using PCM with ceiling only is comparable with case of using PCM in all
6.2. Cooling load 6.2.1. All walls with PCM with 1 cm thickness Cooling load of the rooms with and without PCM is presented in 52
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Fig. 19. Indoor temperature of rooms with and without PCM using 2 cm of PCM at East wall (24-Sep-2016).
Table 2 Difference of the indoor temperature between rooms with PCM and rooms without PCM for all cases. case
Thickness of PCM
TIME
ΔTr (Tr without PCM-Tr with PCM)
Date
All wall Ceiling South wall West wall North wall East wall
1 cm 1 cm 2 cm 2 cm 2 cm 2 cm
6 6 6 6 6 6
2.18 °C 1.9 °C 3.32 °C 2.2 °C 1.5 °C 1.2 °C
16-Aug-2016 8-Sep-2016 21-Sep-2016 22-Aug-2016 31-Aug-2016 24-Sep-2016
p.m. p.m. p.m. p.m. p.m. p.m.
Fig. 20. Internal surface temperature of West wall with and without PCM using 2 cm of PCM (22-Aug-2016).
Fig. 21. Internal surface temperature of South wall with and without PCM using 2 cm of PCM (21-Sep-2016).
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Fig. 22. Internal surface temperature of North wall with and without PCM using 2 cm of PCM (31-Aug-2016).
Fig. 23. Internal surface temperature of East wall with and without PCM using 2 cm of PCM (24-Sep-2016).
Fig. 24. Cooling load of rooms with and without PCM using 1 cm of PCM at all walls (16-Aug2016).
reduction in cooling load is 20.9% at peak hour. As concerning in night hours, the cooling load is increased due to discharging process where the PCM rejected the heat inside the room.
Fig. 24 for the room with PCM, all walls are coated with PCM (paraffin wax). In this figure, it can be seen that cooling load is reduced at day time which means that the reduction of cooling load is takes place in time which the PCM works and absorbs heat enters to the zone, 54
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Fig. 25. Cooling load of rooms with and without PCM using 1 cm of PCM at ceiling only (8-Sep2016).
Fig. 26. Cooling load of rooms with and without PCM using 2 cm of PCM at West wall (22-Aug2016).
Fig. 27. Cooling load of rooms with and without PCM using 2 cm of PCM at South wall (21-Sep2016).
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Fig. 28. Cooling load of rooms with and without PCM using 2 cm of PCM at North wall (31-Aug2016).
Fig. 29. Cooling load of rooms with and without PCM using 2 cm of PCM at East wall (24-Sep2016).
6.2.3. Individual walls with PCM with 2 cm thickness Cooling load of the rooms with and without PCM for the West, South, North, East wall are presented in Figs. 26–29 respectively. For the room with PCM the West, South, North, East wall Individual are coated with PCM (paraffin wax). In these figures, it can be seen that cooling load is reduced at day time which means that the reduction of cooling load is takes place in time which the PCM works and absorbs heat enters to the zone, percentage of reduction in cooling load for all cases and for the individual wall are presented in Table 3. As concerning in night hours, the cooling load is increased due to discharging process where the PCM rejected the heat inside the room. Increasing the effect of the PCM with increase the thickness this because increasing the heat capacity of PCM, also effect of the PCM is appeared at evening due to time lag of heat.
Table 3 Percentage of the cooling load reduction for rooms with and without PCM for all studied cases. case
Thickness of PCM
TIME
% Reduction of C-L
Date
All wall Ceiling South wall West wall North wall East wall
1 cm 1 cm 2 cm 2 cm 2 cm 2 cm
6 p.m. 6 p.m. 6 p.m. 12 p.m. 12 p.m. 12 p.m.
20.9% 6.83% 19.95% 14.36% 7% 11.52%
16-Aug-2016 8-Sep-2016 21-Sep-2016 22-Aug-2016 31-Aug-2016 24-Sep-2016
6.2.2. Ceiling with PCM with 1 cm thickness Cooling load of the rooms with and without PCM is presented in Fig. 25 for the room with PCM, the only ceiling is coated with PCM (paraffin wax). In this figure, it can be seen that cooling load is reduced at day time which means that the reduction of cooling load is takes place in time which the PCM works and absorbs heat enters to the zone, reduction in cooling load is 6.83% at peak hour. As concerning in night hours, the cooling load is increased due to discharging process where the PCM rejected the heat inside the room.
6.2.4. Percentage of cooling load reduction Fig. 30 shows the variation of percentage of cooling load reduction as a result of using PCM for different studied cases compared with cooling load for standard room. It is important to mention that the tests for different cases of PCM were carried out at different times due to preparation requirements. Table 3 summarizes the value of maximum reduction percentages for different cases. 56
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1 cm All Walls
2 cm West Wall
1 cm Ceiling
2 cm North Wall
2cm East Wall
2 cm South Wall
Fig. 30. Percentage of cooling load reduction (Aug–Sep).
40%
Cooling Load ReducƟon %
20% 0% -20% -40% -60% -80% -100% 12:00 AM
6:00 AM
12:00 PM
6:00 PM
12:00 AM
Time (Hours) ■ Using the PCM as thermal insulation materials in buildings contributed to improvement of thermal comfort. ■ Using the PCM lead to reduce the indoor temperature of zone and reducing the cooling load. ■ Reduction in the indoor temperature of the zone by using PCM and according to cases was 2.18 °C with 1 cm thickness of PCM for all walls, 1.9 °C with 1 cm thickness of PCM for ceiling, 3.32 °C with 2 cm thickness of PCM for South wall, 2.2 °C with 2 cm thickness of PCM for West wall, 1.5 °C with 2 cm thickness of PCM for North wall, 1.2 °C with 2 cm thickness of PCM for East wall. ■ Insulating the South wall lead to higher reduction in the indoor temperature. ■ Percentage of the cooling load reduction of the zone by using PCM and according to cases and for peak hour in day was 20.9% with 1 cm thickness of PCM for all walls, 6.83% with 1 cm thickness of PCM for ceiling, 19.95% with 2 cm thickness of PCM for South wall, 14.36% with 2 cm thickness of PCM for West wall, 7% with 2 cm thickness of PCM for North wall, 11.7% with 2 cm thickness of PCM for East wall. ■ The best case in cooling load reduction of the zone for peak hour was 1 cm thickness of PCM for all wall 20.9%. ■ Using PCM as insulation materials leads to saving of electricity consumption. ■ The saving in electricity cost was (1.35 Dollar/Day m3) with 1 cm thickness of PCM for all walls, (0.88 Dollar/Day m3) with 1 cm thickness of PCM for ceiling, (1.19 Dollar/Day m3) with 2 cm thickness of PCM for South wall, (1.21 Dollar/Day m3) with 2 cm thickness of PCM for West wall, (1.08 Dollar/Day m3) with 2 cm thickness of PCM for North wall, (0.58 Dollar/Day m3) with 2 cm thickness of PCM for East wall. ■ Maximum saving in electricity cost of zone was (1.35 Dollar/ Day m3) when using 1 cm thickness of PCM for all walls.
Table 4 Saving in electricity cost. case
Thickness of PCM
reduction of cooling load (kW m−3)
Saving in electricity cost Dollar/Day m3
All wall Ceiling South wall West wall North wall East wall
1 cm 1 cm 2 cm 2 cm 2 cm 2 cm
2.114 1.38 1.86 1.9 1.68 0.905
1.35 0.88 1.19 1.21 1.08 0.58
From Fig. 30 and Table 3 it can be concluded that insulating all wall with 1 cm give higher reduction in cooling load since it reduces the cooling load by 20.9% compared with standard room due to its direct impact on cooling load. Also, insulating the ceiling cause minimum reduction in cooling load compared with other cases.
6.3. Electric consumption cost Electric consumption cost was calculated at peck hour for all cases of using the PCM (paraffin wax) as insulation material. It has been using the usual default price in Iraq that is 30 Dinar per kWh “The price of electrical energy consumption in Iraq, According to The Pricing of The Ministry of Electricity” (Anonymous, 2017b). Saving in electricity cost (Dinar per day) = reduction of cooling load (kW)*30 (Dinar per kWh)*24 (h per day) Where: 24 (h per day) Operating period reduction of cooling load = cooling load PCM − cooling load of room with PCM wall.
of
room
without
Where: 1 $ = 1126 Dinar Table 4 below indicates the saving of electricity cost for experimental room for peak hour with dimensions (1.5 m*1.5 m*1 m) which indicate that for large building using of PCM as insulation materials can save considerable amounts of money.
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