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Experimental Study on the Influence of a Ventilated Window for Indoor Air Quality and Indoor Thermal Environment
Available online at www.sciencedirect.com
ScienceDirect Procedia Engineering 121 (2015) 217 – 224
9th International Symposium on Heating, Ventilation and Air Conditioning (ISHVAC) and the 3rd International Conference on Building Energy and Environment (COBEE)
Experimental Study on the Influence of a Ventilated Window for Indoor Air Quality and Indoor Thermal Environment Wufeng Jina,*, Ningning Zhanga, Junwei Hea,* a
Tianjin University of Commerce, East entrace Jinba road, Beichen district, Tianjin 300134, China
Abstract Indoor air quality has attracted more and more attention nowadays. Researches on the atmospheric haze occurred frequently in China show that the ventilated window has a great potential in improving indoor air quality. Experimental study on the effect of indoor air quality, indoor thermal environment and whole energy consumption of the test room, which are all tested under summer conditions. The results show that operating the ventilated window can filter PM 2.5 and reduce the indoor concentration of CO2; While outdoor and indoor air PM2.5 concentration are about 100-300ug/m3 and 40-130ug/m3, respectively, indoor air PM2.5 concentration will decrease 25% at most in an hour, it is suitable for running ventilated window; While outdoor air PM2.5 concentration is 300-600ug/m3 and indoor air PM2.5 concentration is less than 130ug/m3, the indoor air PM2.5 concentration will increase 90%~128%, so the ventilation window should be shut down; Operating the ventilated window one hour indoor CO2 concentration is reduced 46% at most, compared with that the ventilated window is shut down; Under summer conditions, operating the ventilated window has little influence on head-foot temperature difference and indoor thermal comfort; When a ventilated window runs 24 hours continuously, its power consumption is very low, and the overall consumption is smaller compared with the ventilated window is closed, and the energy consumption increases by 14% or so. Therefore the appropriate operation methods and time of ventilated windows need to be set to reduce energy consumption. ©2015 2015The The Authors. Published by Elsevier Ltd. © Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of ISHVACCOBEE 2015. Peer-review under responsibility of the organizing committee of ISHVAC-COBEE 2015
Keywords: Indoor air quality; Indoor thermal environment; Ventilated window; PM2.5; Energy consumption;
1. Introduction The central and eastern regions suffered serious atmospheric haze since 2013 in China, and the PM2.5 fine particulate matter (particulate matter less than 2.5 microns) (Pui et al. 2014) concentration exceeds standard badly. * Corresponding author. Tel.: +86-22-2735-8935; fax: +86-22-2735-8935. E-mail address: [email protected]
1877-7058 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of ISHVAC-COBEE 2015
doi:10.1016/j.proeng.2015.08.1058
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Wufeng Jin et al. / Procedia Engineering 121 (2015) 217 – 224
Frequent hazy weather not only affect the urban environment, but also is the health killer (Qian et al. 2008). If the concentration of PM2.5 in the air more than 100ug/m3 for a long time, the mortality risk will rise (Chueinta et al. 2008). But the haze of outdoor environment governance could take a long time. Person's life is most spend in indoors, so the indoor environment has a profound influence on people's life and work (Sundell et al. 2008). Although air conditioning system can provide a comfortable working environment, if working and living in it for a long time, people will suffer a lot of pathological reaction, such as sick building syndrome (SBS) (SAEED A. 1993). Traditional residential buildings depend on natural seepage wind or the natural ventilation of opening windows to achieve the exchange of indoor and outdoor air (Shen 2006). But with the increase of construction impermeability, there may be same indoor pollutants cannot be expulsed incompletely and achieving good phenomenon of indoor air quality (ASHRAE, 1988). Natural ventilation with a window open, the ventilation rate is not stable. In cold or hot season, it is certainly to lead to heating or cooling energy waste. Especially in the haze and pollution, it is not suitable to open the window and ventilate (Handford et al. 1992). ASHRAE standard requests residential construction should be configured mechanical ventilation system (Wei et al. 2010). The ventilated window is equipped with the mechanical supply and exhaust, without the window open to achieve that discharging the indoor foul air rapidly and supplying the outdoor fresh air into indoor after being purified, which can solve the problem of ventilating for hazy weather and improve the indoor air quality, at the same time effectively improve limitations of the small scope and single function of the exhaust fans, air purifiers and other equipment (Wei et al. 2011). 2. Methods The comprehensive laboratory of building energy is mainly divided into the test room, outdoor environmental chamber, and a new ventilation window three parts (Fig. 1-2). For a Convenient and accurate study , the all walls, floors, ceilings and doors of the test room and outdoor environmental chamber are heat preservation and insulation.
Fig. 1. The laboratory floor plan
Fig. 2. The elevation of the partition
The ventilated window (Fig.3) is installed in the partition of the test room and outdoor environmental chamber (Fig.2) . Besides the lighting and ventilation of the ordinary window, it also added to the purification for outdoor air and heat exchange with indoor exhaust air through a ventilator that is installed in the window frame and the filter mesh and graphitic layers in the ventilator (Fig.4). According to different ventilation volumes, the operation mode of the ventilated window can be divided into three grades: the low-grade, the mid-grade, and the high-grade, the performance parameters of each mode are shown in table 1.
Wufeng Jin et al. / Procedia Engineering 121 (2015) 217 – 224
219
Table 1. Performance parameters of the ventilated window Mode
Low-grade
Mid-grade
High-grade
17.46m3/h
22.65m3/h
25.54m3/h
Air changes per hour
0.64
0.83
0.93
Filter efficiency
40%
Parameters Ventilation volume
The test room is used to simulate real indoor environment, and fan-coil unit + fresh outdoor air conditioning system is installed in the test room. The outdoor environment chamber can simulate the real outdoor environment. The south windows may open to bring in outdoor air in necessary, not only make the condition of the experimental requirements more accurate, but also reduce the simulate energy consumption.
Fig. 3. The ventilated window
Fig. 4. The ventilator structure
Pollutants study of PM2.5, according to Chinese haze meteorological parameters, PM 2.5 pollution is serious, especially in the heating period. The 100ug/m3 is the average concentration among heating period for the northern city of China, 300ug/m3 is usually serious pollution concentration value, and 600ug/m3 for testing is the concentration for the most serious pollution. The outdoor environmental chamber though cigarettes burning generates flue gas that the particulate matter < 2.5μm ( the main is 0.7μm) simulates different outdoor pollutant concentration. Before the experiment is beginning, turning on the particle counter, then lighting up a moderate amount of cigarettes and running the fan to make the indoor cigarette concentration distributes uniformly and maintain the required concentration ±10ug/m3 around for experiment on the outdoor chamber and indoor test room. Setting ventilation mode to the experiment requirement, at the same time recording the concentration variation tendency of pollutants for the test room continuously. The test room is set three measuring points (Fig. 5), whose vertical height is 1.2m from the ground.
Fig. 5. The measuring points of the test room
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Wufeng Jin et al. / Procedia Engineering 121 (2015) 217 – 224
CO2 concentration test, the CO2 liberation system can liberate CO2 quantificationally. Normal person may exhale 25L CO2 per hour (Wei. 2011), the test room area is 11.4 m2 and set for 2-3 people, the liberation flow of CO2 is 1Lmin-1 that is controlled by the flow meter. Through the preliminary monitoring experiment of outdoor CO2 concentration found that variation range of outdoor CO2 concentration in the daytime was little and about 200-300ppm. Opening the south window in the outdoor environment chamber and bringing in outdoor air directly in the experiment. The initial CO2 concentration(C0) of the test room is set to 600 ppm, and the CO2 sensor of K30 is used for monitoring. There are four measuring points (Fig. 5) for CO2 concentration monitoring. The temperature of outdoor environment chamber is set to 35ć with the radiator heating, by controlling the switch to adjust the temperature. and the test room temperature is set of 26ć. Temperature measuring points are divided into 3 layers vertically : Z=0.2m, 1.2m, and 1.7m, each layer distributes 16 points uniformly. Then the distance of 0.1m, 0.2m, 0.3m, and 0.6m from the indoor ventilated window side is set. And a total of 48 temperature measurement points (Fig. 5). Measuring points connect with the computer in the monitor room and record each measuring point temperature during two hours in real time. 3. Discussion and results 3.1. The ventilated window for improvement on indoor air quality Table 2. The concentration variation of indoor PM2.5 Mode
Low-grade
Mid-grade
High-grade
Outdoor concentration
C0
Ce
ƸC
C0
Ce
ƸC
C0
Ce
ƸC
600ug/m3
——
——
——
——
——
——
39
124
218%
300ug/m3
47
70
48%
45
72
60%
41
78
90%
——
——
——
——
——
——
45
49
9%
3
100ug/m
High-grade Mid-grade Low-grade
10
20 30 Time (min) (a) Point C1
40
3
150 140 130 120 110 100 90 80 0
Concentration (ug/m )
3
Concentration (ug/m )
C0, the initial concentration. Ce,the end concentration. ƸC, the increasing concentration in one hour
50
150 140 130 120 110 100 90 80 0
High-grade Mid-grade Low-grade
10
20 30 Time (min)
40
50
(b) Point C4
Fig. 6. The PM2.5 concentration variation of points under different mode
The initial concentration of three cases (table 2) was around 40 ug/m3, and the indoor air quality level was good (HJ 633-2012, 2012). Considering the concentration of indoor PM2.5 particles is lower than outdoor generally, so defining outdoor PM2.5 concentrations base on the daily average concentration of secondary standard limit 75ug/m3 in the ambient air quality standard (GB3095-2012, 2012) of China to evaluate, and the concentration of indoor PM2.5 is evaluated in terms of the primary standard 35ug/m³ of daily average concentration. While the outdoor PM2.5 concentration was 100ug/m3, which was compared to daily average concentration of secondary limit in the ambient air quality standard exceeding 0.33 times, after operating the high-grade ventilated window an hour, indoor PM2.5 concentration was 49 ug/m3 that the indoor air quality was good and increased by 9%, which exceeded the standard level of daily average concentration limit 0.4 times only, so operating the ventilated window would not increase indoor
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Wufeng Jin et al. / Procedia Engineering 121 (2015) 217 – 224
pollution obviously. While the outdoor PM2.5 concentration was 300ug/m3, which exceeded 3 times, after operating the high-grade ventilated window an hour, indoor PM2.5 concentration increased by 90% and exceeded 1.2 times. And when the outdoor PM2.5 concentration was 600ug/m3, which exceeded 3 times, after operating the high-grade ventilated window an hour, indoor PM2.5 concentration increased by 218% and exceeded 20.5 times. The world health organization pointed out that the average concentrations of PM 2.5 levels above 25ug/m3 were harmful to the health (WHO, 2005) clearly, therefore outdoor PM 2.5 fine particles pollution was serious and indoor air quality was more than the good grade, it was not proper for operating ventilated window at the moment. Table 3. The concentration decays of different measuring points Point Mode Low-grade
C1
C3
C4
36ug/m3
——
27ug/m3
3
Mid-grade
27ug/m
——
28ug/m3
High-grade
34ug/m3
28ug/m3
29ug/m3
4000 3500 3000 2500 2000 1500 1000 500 0 0
Shut down High-grade Mid-grade Low-grade
10
20 30 40 Time (min) (a) Point C1
Concentration (ppm)
4000 3500 3000 2500 2000 1500 1000 500 0 0
50
60
Shut down High-grade Mid-grade Low-grade
10
20 30 40 Time (min) (c) Point C3
Concentration (ppm)
Concentration (ppm)
Concentration (ppm)
The experiment was taken on one day that outdoor air quality was moderate polluted which could be used as pollution source with the south window of the outdoor environment simulation chamber open. PM2.5 concentration in the chamber and indoor test room both were about 130ug/m3. It could be found that indoor PM2.5 concentration decreased about 20% after opening the ventilated window for 50mins, but the lowest concentration is 88ug/m3, which still exceeded the standard and was harmful to human health. Under the same PM2.5 concentration condition, compared with the attenuation values in 50mins on different grades, from table 3, it could be found that the higher the ventilated window working grade was, the larger supply air amount, the ventilation frequency would be, and the higher degree of indoor purification would be. Data of point C1 shown that the attenuation value on low-grade was large relatively, that’s because outdoor concentration was uncontrollable and it was only slight polluted under this condition. It can be concluded that the purification effect of PM2.5 near the supply inlet was the best and that near the return air outlet is worse.
50
60
4000 3500 3000 2500 2000 1500 1000 500 0 0
4000 3500 3000 2500 2000 1500 1000 500 0 0
Shut down High-grade Mid-grade Low-grade
10
20 30 40 50 Time (min) (b) Point C2
60
Shut down High-grade Mid-grade Low-grade
10
20 30 40 Time (min) (d) Point C4
Fig. 7. The CO2 concentration variation of points under different mode
50
60
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Wufeng Jin et al. / Procedia Engineering 121 (2015) 217 – 224
The experiment used CO2 concentration as the parameter to evaluate improvement of indoor air quality. Inner CO2 concentration was set about 600ppm which was lower than most authorities stipulation value 900 ppm (WHO, 2000; Standard A, 1989) From figure 7, it could be found that when the ventilated window was off, CO2 concentration of all test points increased gradually. The increasing rates of point C1, C2 and C4 were bigger than point C3, generally. The CO2 concentration of point C1 increased to 2700ppm in an hour, while point C2 and point C4 increased to about 2600ppm. Indoor CO2 concentration increased about 300% than initial CO2 concentration, and the indoor air quality was poor. If using PD as the criterion to evaluate indoor air quality, PD increases 10% at least (Jokl, 2000). Compared with the condition that the ventilated window was off, CO2 concentration of point C1, C2 and C4 reduced obviously. CO2 concentration reduce up to 46% under conditions with the ventilated window open for an hour. Ignoring the influence of initial CO2 concentration, indoor temperature and outdoor CO2 concentration, the more air supplied, the better improvement of indoor CO2 concentration will be. 3.2. Effect on indoor thermal environment by the ventilated window Table 4. The maximum vertical temperature difference of different plane ƸT(ć)
X=0.1m
X=0.2m
X=0.3m
X=0.6m
Mode
Stand posture
Sitting posture
Stand posture
Sitting posture
Stand posture
Sitting posture
Stand posture
Sitting posture
Shut down
1.3
0.4
0.5
0.4
0.4
0.4
0.4
0.4
Low-grade
1.2
0.8
0.5
0.4
0.6
0.3
0.4
0.4
Mid-grade
1.2
1
0.5
0.6
0.6
0.5
0.7
0.7
High-grade
0.6
0.7
0.5
0.4
0.6
0.5
0.6
0.4
ƸT, the temperature difference.
Energy consumption (kW/h)
The head-foot temperature difference of sitting posture is the temperature difference between height of 1.2m and 0.2m (ISO, 1984) while the temperature difference of stand posture is the that between height of 1.7m and 0.2m (ASHRAE, 1992). From table 4, it could be found that the head-foot temperature difference under different conditions were low, the max of them was 1.4ć, far less than 3ć, and met the comfort demand. It would have significant influence on the temperature at height of 1.2m in the area that’s 0.1m distant from the ventilated window, it was because the test points at height of 1.2m was right facing the air output of the ventilated window. The head-foot temperature difference increased with the operating grade of the ventilated window. But operating the ventilated window had little effect on the head-foot temperature difference of stand posture due to the close range between test points and the ventilated window which caused that the air flow could not reach the height of 1.7m. On the distance of 0.2m, 0.3m and 0.6m, operating the ventilation would have little effect on the vertical temperature difference. 8 7 6 5 4 3 2 1 0
5.780
Shut down
6.323
6.466
High-grade Mid-grade Mode
6.602
Low-grade
Fig. 8. The overall energy consumption of different modes
Wufeng Jin et al. / Procedia Engineering 121 (2015) 217 – 224
223
The experiment compared the energy consumption between 3 modes with the condition with the ventilated window off. Figure 8 shown that operating the ventilated window would increase the indoor cold load and electric energy to run the ventilated window. Due to the Special materials in the ventilator, when the outdoor air is supplied in, there will be simple heat exchange. Under testing condition, compared with the condition with the ventilated window off, it increased 14.2% of energy consumption (8% for air conditioning) with the ventilated window operating on the highgrade for 24hours; 11.9% on the mid-grade (6.2% for air conditioning) and 9.4% on the low-grade (4.3% for air conditioning). 4. Conclusions (1) Operating on the ventilated window can filter the outdoor air PM2.5 concentration and supply fresh air to the indoor area. When outdoor air PM2.5 concentration and indoor air PM2.5 concentration are about 100-300ug/m3 and 40-130ug/m3, respectively, indoor air PM2.5 concentration will decrease 25% at most after running the ventilated window for an hour. Thus it’s acceptable to running the ventilated window. (2) While outdoor air PM2.5 concentration is 300-600ug/m3 and indoor air PM2.5 concentration is less than 130ug/m3, the indoor air PM2.5 concentration will increase 90%~128% with the ventilated window open in an hour. It exceeds the national daily average concentration standard of 0.2-2.5 times. So it’s not appropriate to operating the ventilated window; (3) Compared with the case that the ventilated window is off, the indoor CO2 concentration may decrease up to 46% after running it. And the more air sent by the ventilated window is, the more indoor CO2 concentration will decrease. (4) Running the ventilated window only has little effect on head and foot parts of a sitting human in area that is 0.1m distant from the ventilated window. and indoor comfort satisfys the requirements. (5) The electricity consumption by the ventilated window itself is low even it worked for a whole day. Compared with the condition with the ventilated window off, it increases 14.2% of energy consumption (8% for air conditioning) with the ventilated window operating on high-grade for 24hours; 11.9% on mid-grade(6.2% for air conditioning) and 9.4% on low-grade (4.3% for air conditioning). It can be found that the whole energy consumption increasing is low, about 14%, thus it’s necessary to set the running ways and time correctly to reduce the energy consumption. Acknowledgements This study was supported by the Innovation Team of Tianjin City (TD12-5048). References [1] Y.H. Pui David, S. Chen, Z.L. Zuo, PM2.5 in China: Measurements, sources, visibility and health effects, and mitigation, Particuology. 13(2014) 1–26. [2] J. Qian, A.R. Ferro, K.R. Fowler, Estimating the resuspension rate and residence time of indoor particles, J Air Waste Manage. 58(4) 502-516. [3] W. Chueinta, P. K. Hopke, P. Paacero, Investigation of source atmospheric aerosol at urban and suburban residential areas in Thailand by positive matrix factorization. Atmos Environ, 34(2000), 3319-3329. [4] J. Sundell, Uncertainty and the environment implications for deision-making and environmental policy, Indoor Air. 14 (2004) 51-58. [5] A. SAEED, Subjective assessment of indoor air quality in office buildings, Master's Thesis, Kind Fand University, the Dhahran, 1993. [6] J. M. Shen, Strategies and measures for improving indoor air quality in China, Journal of HV&AC. 32 (2002) 34-37. [7] ASHRAE Standard 119. 1988. Air Leakage Performance for Detached Single-family Residential Buildings. American Society of Heating, Refrigerating and Air Conditioning Engineers. [8] J.W. Handford and Y.J. Huang, Residential heating and cooling loads component analysis, Lawrence Berkeley Laboratory Report, 1992. [9] J. Wei, J. Zhao, Q. Chen, Energy performance of a dual airflow window under different climates, Energ Buildings. 42 (2010) 111-122. [10] J. Wei, J. Zhao, Q. Chen, Applicability study of dual-airflow for different climatic zones, Journal of HV&AC. 41 (2011) 69-72. [11] J.S. Wei, Performance evaluation and optimazation of a dual-airflow window, Ph.D. Thesis, Harbin Institute of Technology, The Haerbin, 2011. [12] HJ 633-2012, Technical regulation on ambient air quality index (on trial). Ministry of environmental protection of the people’s republic of China, Beijing, 2012. [13] GB 3095-2012, Ambient air quality standards. Ministry of environmental protection of the people’s republic of China, Beijing, 2012. [14] World Health Organization Regional Office for Europe, Air quality guidelines. Global update 2005, World Health Organization Regional Office for Europe. Copenhagen, 2005.
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[15] World Health Organization Regional Office for Europe, Air quality guidelines for Europe. WHO Regional Office Europe, 2000. [16] Standard A, Standard 62-1989, Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. 1989. [17] M.V. Jokl, Evaluation of indoor air quality using the decibel concept based on carbon dioxide and TVOC, Build Environ. 35 (2000) 677-697. [18] International Organization for Standardization. Moderate Thermal Environments: Determination of the PMV and PPD Indices and Specification of the Conditions for Thermal Comfort. International Organization for Standardization, 1984. [19] ASHRAE, ANSI/ASHRAE Standard 55-1992, Thermal Environmental Conditions for Human Occupancy. American Society of Heating, Refrigerating and Air-Conditioning Engineers. Atlanta, 1992.
ScienceDirect Procedia Engineering 121 (2015) 217 – 224
9th International Symposium on Heating, Ventilation and Air Conditioning (ISHVAC) and the 3rd International Conference on Building Energy and Environment (COBEE)
Experimental Study on the Influence of a Ventilated Window for Indoor Air Quality and Indoor Thermal Environment Wufeng Jina,*, Ningning Zhanga, Junwei Hea,* a
Tianjin University of Commerce, East entrace Jinba road, Beichen district, Tianjin 300134, China
Abstract Indoor air quality has attracted more and more attention nowadays. Researches on the atmospheric haze occurred frequently in China show that the ventilated window has a great potential in improving indoor air quality. Experimental study on the effect of indoor air quality, indoor thermal environment and whole energy consumption of the test room, which are all tested under summer conditions. The results show that operating the ventilated window can filter PM 2.5 and reduce the indoor concentration of CO2; While outdoor and indoor air PM2.5 concentration are about 100-300ug/m3 and 40-130ug/m3, respectively, indoor air PM2.5 concentration will decrease 25% at most in an hour, it is suitable for running ventilated window; While outdoor air PM2.5 concentration is 300-600ug/m3 and indoor air PM2.5 concentration is less than 130ug/m3, the indoor air PM2.5 concentration will increase 90%~128%, so the ventilation window should be shut down; Operating the ventilated window one hour indoor CO2 concentration is reduced 46% at most, compared with that the ventilated window is shut down; Under summer conditions, operating the ventilated window has little influence on head-foot temperature difference and indoor thermal comfort; When a ventilated window runs 24 hours continuously, its power consumption is very low, and the overall consumption is smaller compared with the ventilated window is closed, and the energy consumption increases by 14% or so. Therefore the appropriate operation methods and time of ventilated windows need to be set to reduce energy consumption. ©2015 2015The The Authors. Published by Elsevier Ltd. © Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of ISHVACCOBEE 2015. Peer-review under responsibility of the organizing committee of ISHVAC-COBEE 2015
Keywords: Indoor air quality; Indoor thermal environment; Ventilated window; PM2.5; Energy consumption;
1. Introduction The central and eastern regions suffered serious atmospheric haze since 2013 in China, and the PM2.5 fine particulate matter (particulate matter less than 2.5 microns) (Pui et al. 2014) concentration exceeds standard badly. * Corresponding author. Tel.: +86-22-2735-8935; fax: +86-22-2735-8935. E-mail address: [email protected]
1877-7058 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of ISHVAC-COBEE 2015
doi:10.1016/j.proeng.2015.08.1058
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Wufeng Jin et al. / Procedia Engineering 121 (2015) 217 – 224
Frequent hazy weather not only affect the urban environment, but also is the health killer (Qian et al. 2008). If the concentration of PM2.5 in the air more than 100ug/m3 for a long time, the mortality risk will rise (Chueinta et al. 2008). But the haze of outdoor environment governance could take a long time. Person's life is most spend in indoors, so the indoor environment has a profound influence on people's life and work (Sundell et al. 2008). Although air conditioning system can provide a comfortable working environment, if working and living in it for a long time, people will suffer a lot of pathological reaction, such as sick building syndrome (SBS) (SAEED A. 1993). Traditional residential buildings depend on natural seepage wind or the natural ventilation of opening windows to achieve the exchange of indoor and outdoor air (Shen 2006). But with the increase of construction impermeability, there may be same indoor pollutants cannot be expulsed incompletely and achieving good phenomenon of indoor air quality (ASHRAE, 1988). Natural ventilation with a window open, the ventilation rate is not stable. In cold or hot season, it is certainly to lead to heating or cooling energy waste. Especially in the haze and pollution, it is not suitable to open the window and ventilate (Handford et al. 1992). ASHRAE standard requests residential construction should be configured mechanical ventilation system (Wei et al. 2010). The ventilated window is equipped with the mechanical supply and exhaust, without the window open to achieve that discharging the indoor foul air rapidly and supplying the outdoor fresh air into indoor after being purified, which can solve the problem of ventilating for hazy weather and improve the indoor air quality, at the same time effectively improve limitations of the small scope and single function of the exhaust fans, air purifiers and other equipment (Wei et al. 2011). 2. Methods The comprehensive laboratory of building energy is mainly divided into the test room, outdoor environmental chamber, and a new ventilation window three parts (Fig. 1-2). For a Convenient and accurate study , the all walls, floors, ceilings and doors of the test room and outdoor environmental chamber are heat preservation and insulation.
Fig. 1. The laboratory floor plan
Fig. 2. The elevation of the partition
The ventilated window (Fig.3) is installed in the partition of the test room and outdoor environmental chamber (Fig.2) . Besides the lighting and ventilation of the ordinary window, it also added to the purification for outdoor air and heat exchange with indoor exhaust air through a ventilator that is installed in the window frame and the filter mesh and graphitic layers in the ventilator (Fig.4). According to different ventilation volumes, the operation mode of the ventilated window can be divided into three grades: the low-grade, the mid-grade, and the high-grade, the performance parameters of each mode are shown in table 1.
Wufeng Jin et al. / Procedia Engineering 121 (2015) 217 – 224
219
Table 1. Performance parameters of the ventilated window Mode
Low-grade
Mid-grade
High-grade
17.46m3/h
22.65m3/h
25.54m3/h
Air changes per hour
0.64
0.83
0.93
Filter efficiency
40%
Parameters Ventilation volume
The test room is used to simulate real indoor environment, and fan-coil unit + fresh outdoor air conditioning system is installed in the test room. The outdoor environment chamber can simulate the real outdoor environment. The south windows may open to bring in outdoor air in necessary, not only make the condition of the experimental requirements more accurate, but also reduce the simulate energy consumption.
Fig. 3. The ventilated window
Fig. 4. The ventilator structure
Pollutants study of PM2.5, according to Chinese haze meteorological parameters, PM 2.5 pollution is serious, especially in the heating period. The 100ug/m3 is the average concentration among heating period for the northern city of China, 300ug/m3 is usually serious pollution concentration value, and 600ug/m3 for testing is the concentration for the most serious pollution. The outdoor environmental chamber though cigarettes burning generates flue gas that the particulate matter < 2.5μm ( the main is 0.7μm) simulates different outdoor pollutant concentration. Before the experiment is beginning, turning on the particle counter, then lighting up a moderate amount of cigarettes and running the fan to make the indoor cigarette concentration distributes uniformly and maintain the required concentration ±10ug/m3 around for experiment on the outdoor chamber and indoor test room. Setting ventilation mode to the experiment requirement, at the same time recording the concentration variation tendency of pollutants for the test room continuously. The test room is set three measuring points (Fig. 5), whose vertical height is 1.2m from the ground.
Fig. 5. The measuring points of the test room
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Wufeng Jin et al. / Procedia Engineering 121 (2015) 217 – 224
CO2 concentration test, the CO2 liberation system can liberate CO2 quantificationally. Normal person may exhale 25L CO2 per hour (Wei. 2011), the test room area is 11.4 m2 and set for 2-3 people, the liberation flow of CO2 is 1Lmin-1 that is controlled by the flow meter. Through the preliminary monitoring experiment of outdoor CO2 concentration found that variation range of outdoor CO2 concentration in the daytime was little and about 200-300ppm. Opening the south window in the outdoor environment chamber and bringing in outdoor air directly in the experiment. The initial CO2 concentration(C0) of the test room is set to 600 ppm, and the CO2 sensor of K30 is used for monitoring. There are four measuring points (Fig. 5) for CO2 concentration monitoring. The temperature of outdoor environment chamber is set to 35ć with the radiator heating, by controlling the switch to adjust the temperature. and the test room temperature is set of 26ć. Temperature measuring points are divided into 3 layers vertically : Z=0.2m, 1.2m, and 1.7m, each layer distributes 16 points uniformly. Then the distance of 0.1m, 0.2m, 0.3m, and 0.6m from the indoor ventilated window side is set. And a total of 48 temperature measurement points (Fig. 5). Measuring points connect with the computer in the monitor room and record each measuring point temperature during two hours in real time. 3. Discussion and results 3.1. The ventilated window for improvement on indoor air quality Table 2. The concentration variation of indoor PM2.5 Mode
Low-grade
Mid-grade
High-grade
Outdoor concentration
C0
Ce
ƸC
C0
Ce
ƸC
C0
Ce
ƸC
600ug/m3
——
——
——
——
——
——
39
124
218%
300ug/m3
47
70
48%
45
72
60%
41
78
90%
——
——
——
——
——
——
45
49
9%
3
100ug/m
High-grade Mid-grade Low-grade
10
20 30 Time (min) (a) Point C1
40
3
150 140 130 120 110 100 90 80 0
Concentration (ug/m )
3
Concentration (ug/m )
C0, the initial concentration. Ce,the end concentration. ƸC, the increasing concentration in one hour
50
150 140 130 120 110 100 90 80 0
High-grade Mid-grade Low-grade
10
20 30 Time (min)
40
50
(b) Point C4
Fig. 6. The PM2.5 concentration variation of points under different mode
The initial concentration of three cases (table 2) was around 40 ug/m3, and the indoor air quality level was good (HJ 633-2012, 2012). Considering the concentration of indoor PM2.5 particles is lower than outdoor generally, so defining outdoor PM2.5 concentrations base on the daily average concentration of secondary standard limit 75ug/m3 in the ambient air quality standard (GB3095-2012, 2012) of China to evaluate, and the concentration of indoor PM2.5 is evaluated in terms of the primary standard 35ug/m³ of daily average concentration. While the outdoor PM2.5 concentration was 100ug/m3, which was compared to daily average concentration of secondary limit in the ambient air quality standard exceeding 0.33 times, after operating the high-grade ventilated window an hour, indoor PM2.5 concentration was 49 ug/m3 that the indoor air quality was good and increased by 9%, which exceeded the standard level of daily average concentration limit 0.4 times only, so operating the ventilated window would not increase indoor
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pollution obviously. While the outdoor PM2.5 concentration was 300ug/m3, which exceeded 3 times, after operating the high-grade ventilated window an hour, indoor PM2.5 concentration increased by 90% and exceeded 1.2 times. And when the outdoor PM2.5 concentration was 600ug/m3, which exceeded 3 times, after operating the high-grade ventilated window an hour, indoor PM2.5 concentration increased by 218% and exceeded 20.5 times. The world health organization pointed out that the average concentrations of PM 2.5 levels above 25ug/m3 were harmful to the health (WHO, 2005) clearly, therefore outdoor PM 2.5 fine particles pollution was serious and indoor air quality was more than the good grade, it was not proper for operating ventilated window at the moment. Table 3. The concentration decays of different measuring points Point Mode Low-grade
C1
C3
C4
36ug/m3
——
27ug/m3
3
Mid-grade
27ug/m
——
28ug/m3
High-grade
34ug/m3
28ug/m3
29ug/m3
4000 3500 3000 2500 2000 1500 1000 500 0 0
Shut down High-grade Mid-grade Low-grade
10
20 30 40 Time (min) (a) Point C1
Concentration (ppm)
4000 3500 3000 2500 2000 1500 1000 500 0 0
50
60
Shut down High-grade Mid-grade Low-grade
10
20 30 40 Time (min) (c) Point C3
Concentration (ppm)
Concentration (ppm)
Concentration (ppm)
The experiment was taken on one day that outdoor air quality was moderate polluted which could be used as pollution source with the south window of the outdoor environment simulation chamber open. PM2.5 concentration in the chamber and indoor test room both were about 130ug/m3. It could be found that indoor PM2.5 concentration decreased about 20% after opening the ventilated window for 50mins, but the lowest concentration is 88ug/m3, which still exceeded the standard and was harmful to human health. Under the same PM2.5 concentration condition, compared with the attenuation values in 50mins on different grades, from table 3, it could be found that the higher the ventilated window working grade was, the larger supply air amount, the ventilation frequency would be, and the higher degree of indoor purification would be. Data of point C1 shown that the attenuation value on low-grade was large relatively, that’s because outdoor concentration was uncontrollable and it was only slight polluted under this condition. It can be concluded that the purification effect of PM2.5 near the supply inlet was the best and that near the return air outlet is worse.
50
60
4000 3500 3000 2500 2000 1500 1000 500 0 0
4000 3500 3000 2500 2000 1500 1000 500 0 0
Shut down High-grade Mid-grade Low-grade
10
20 30 40 50 Time (min) (b) Point C2
60
Shut down High-grade Mid-grade Low-grade
10
20 30 40 Time (min) (d) Point C4
Fig. 7. The CO2 concentration variation of points under different mode
50
60
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Wufeng Jin et al. / Procedia Engineering 121 (2015) 217 – 224
The experiment used CO2 concentration as the parameter to evaluate improvement of indoor air quality. Inner CO2 concentration was set about 600ppm which was lower than most authorities stipulation value 900 ppm (WHO, 2000; Standard A, 1989) From figure 7, it could be found that when the ventilated window was off, CO2 concentration of all test points increased gradually. The increasing rates of point C1, C2 and C4 were bigger than point C3, generally. The CO2 concentration of point C1 increased to 2700ppm in an hour, while point C2 and point C4 increased to about 2600ppm. Indoor CO2 concentration increased about 300% than initial CO2 concentration, and the indoor air quality was poor. If using PD as the criterion to evaluate indoor air quality, PD increases 10% at least (Jokl, 2000). Compared with the condition that the ventilated window was off, CO2 concentration of point C1, C2 and C4 reduced obviously. CO2 concentration reduce up to 46% under conditions with the ventilated window open for an hour. Ignoring the influence of initial CO2 concentration, indoor temperature and outdoor CO2 concentration, the more air supplied, the better improvement of indoor CO2 concentration will be. 3.2. Effect on indoor thermal environment by the ventilated window Table 4. The maximum vertical temperature difference of different plane ƸT(ć)
X=0.1m
X=0.2m
X=0.3m
X=0.6m
Mode
Stand posture
Sitting posture
Stand posture
Sitting posture
Stand posture
Sitting posture
Stand posture
Sitting posture
Shut down
1.3
0.4
0.5
0.4
0.4
0.4
0.4
0.4
Low-grade
1.2
0.8
0.5
0.4
0.6
0.3
0.4
0.4
Mid-grade
1.2
1
0.5
0.6
0.6
0.5
0.7
0.7
High-grade
0.6
0.7
0.5
0.4
0.6
0.5
0.6
0.4
ƸT, the temperature difference.
Energy consumption (kW/h)
The head-foot temperature difference of sitting posture is the temperature difference between height of 1.2m and 0.2m (ISO, 1984) while the temperature difference of stand posture is the that between height of 1.7m and 0.2m (ASHRAE, 1992). From table 4, it could be found that the head-foot temperature difference under different conditions were low, the max of them was 1.4ć, far less than 3ć, and met the comfort demand. It would have significant influence on the temperature at height of 1.2m in the area that’s 0.1m distant from the ventilated window, it was because the test points at height of 1.2m was right facing the air output of the ventilated window. The head-foot temperature difference increased with the operating grade of the ventilated window. But operating the ventilated window had little effect on the head-foot temperature difference of stand posture due to the close range between test points and the ventilated window which caused that the air flow could not reach the height of 1.7m. On the distance of 0.2m, 0.3m and 0.6m, operating the ventilation would have little effect on the vertical temperature difference. 8 7 6 5 4 3 2 1 0
5.780
Shut down
6.323
6.466
High-grade Mid-grade Mode
6.602
Low-grade
Fig. 8. The overall energy consumption of different modes
Wufeng Jin et al. / Procedia Engineering 121 (2015) 217 – 224
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The experiment compared the energy consumption between 3 modes with the condition with the ventilated window off. Figure 8 shown that operating the ventilated window would increase the indoor cold load and electric energy to run the ventilated window. Due to the Special materials in the ventilator, when the outdoor air is supplied in, there will be simple heat exchange. Under testing condition, compared with the condition with the ventilated window off, it increased 14.2% of energy consumption (8% for air conditioning) with the ventilated window operating on the highgrade for 24hours; 11.9% on the mid-grade (6.2% for air conditioning) and 9.4% on the low-grade (4.3% for air conditioning). 4. Conclusions (1) Operating on the ventilated window can filter the outdoor air PM2.5 concentration and supply fresh air to the indoor area. When outdoor air PM2.5 concentration and indoor air PM2.5 concentration are about 100-300ug/m3 and 40-130ug/m3, respectively, indoor air PM2.5 concentration will decrease 25% at most after running the ventilated window for an hour. Thus it’s acceptable to running the ventilated window. (2) While outdoor air PM2.5 concentration is 300-600ug/m3 and indoor air PM2.5 concentration is less than 130ug/m3, the indoor air PM2.5 concentration will increase 90%~128% with the ventilated window open in an hour. It exceeds the national daily average concentration standard of 0.2-2.5 times. So it’s not appropriate to operating the ventilated window; (3) Compared with the case that the ventilated window is off, the indoor CO2 concentration may decrease up to 46% after running it. And the more air sent by the ventilated window is, the more indoor CO2 concentration will decrease. (4) Running the ventilated window only has little effect on head and foot parts of a sitting human in area that is 0.1m distant from the ventilated window. and indoor comfort satisfys the requirements. (5) The electricity consumption by the ventilated window itself is low even it worked for a whole day. Compared with the condition with the ventilated window off, it increases 14.2% of energy consumption (8% for air conditioning) with the ventilated window operating on high-grade for 24hours; 11.9% on mid-grade(6.2% for air conditioning) and 9.4% on low-grade (4.3% for air conditioning). It can be found that the whole energy consumption increasing is low, about 14%, thus it’s necessary to set the running ways and time correctly to reduce the energy consumption. Acknowledgements This study was supported by the Innovation Team of Tianjin City (TD12-5048). References [1] Y.H. Pui David, S. Chen, Z.L. Zuo, PM2.5 in China: Measurements, sources, visibility and health effects, and mitigation, Particuology. 13(2014) 1–26. [2] J. Qian, A.R. Ferro, K.R. Fowler, Estimating the resuspension rate and residence time of indoor particles, J Air Waste Manage. 58(4) 502-516. [3] W. Chueinta, P. K. Hopke, P. Paacero, Investigation of source atmospheric aerosol at urban and suburban residential areas in Thailand by positive matrix factorization. Atmos Environ, 34(2000), 3319-3329. [4] J. Sundell, Uncertainty and the environment implications for deision-making and environmental policy, Indoor Air. 14 (2004) 51-58. [5] A. SAEED, Subjective assessment of indoor air quality in office buildings, Master's Thesis, Kind Fand University, the Dhahran, 1993. [6] J. M. Shen, Strategies and measures for improving indoor air quality in China, Journal of HV&AC. 32 (2002) 34-37. [7] ASHRAE Standard 119. 1988. Air Leakage Performance for Detached Single-family Residential Buildings. American Society of Heating, Refrigerating and Air Conditioning Engineers. [8] J.W. Handford and Y.J. Huang, Residential heating and cooling loads component analysis, Lawrence Berkeley Laboratory Report, 1992. [9] J. Wei, J. Zhao, Q. Chen, Energy performance of a dual airflow window under different climates, Energ Buildings. 42 (2010) 111-122. [10] J. Wei, J. Zhao, Q. Chen, Applicability study of dual-airflow for different climatic zones, Journal of HV&AC. 41 (2011) 69-72. [11] J.S. Wei, Performance evaluation and optimazation of a dual-airflow window, Ph.D. Thesis, Harbin Institute of Technology, The Haerbin, 2011. [12] HJ 633-2012, Technical regulation on ambient air quality index (on trial). Ministry of environmental protection of the people’s republic of China, Beijing, 2012. [13] GB 3095-2012, Ambient air quality standards. Ministry of environmental protection of the people’s republic of China, Beijing, 2012. [14] World Health Organization Regional Office for Europe, Air quality guidelines. Global update 2005, World Health Organization Regional Office for Europe. Copenhagen, 2005.
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[15] World Health Organization Regional Office for Europe, Air quality guidelines for Europe. WHO Regional Office Europe, 2000. [16] Standard A, Standard 62-1989, Ventilation for acceptable indoor air quality. American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc. 1989. [17] M.V. Jokl, Evaluation of indoor air quality using the decibel concept based on carbon dioxide and TVOC, Build Environ. 35 (2000) 677-697. [18] International Organization for Standardization. Moderate Thermal Environments: Determination of the PMV and PPD Indices and Specification of the Conditions for Thermal Comfort. International Organization for Standardization, 1984. [19] ASHRAE, ANSI/ASHRAE Standard 55-1992, Thermal Environmental Conditions for Human Occupancy. American Society of Heating, Refrigerating and Air-Conditioning Engineers. Atlanta, 1992.