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Preliminary Analysis on the Different Heating Technologies in a Rural Area of Shandong Province, China
Available Available online online at at www.sciencedirect.com www.sciencedirect.com
ScienceDirect
Available online at www.sciencedirect.com Procedia Procedia Engineering Engineering 00 00 (2017) (2017) 000–000 000–000
ScienceDirect
www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia
Procedia Engineering 205 (2017) 1461–1468
10th International Symposium on Heating, Ventilation and Air Conditioning, ISHVAC2017, 1922 October 2017, Jinan, China
Preliminary Analysis on the Different Heating Technologies in a Rural Area of Shandong Province, China a,b,c,*, Linhua Zhanga,b,c a,b,c Xiaokai Huangaa, Huixin Fangaa, Linfang Zhangaa, Jiying Liua,b,c,* aSchool of Thermal Engineering, Shandong Jianzhu University, Jinan 250101, China School of Thermal Engineering, Shandong Jianzhu University, Jinan 250101, China Key Key Laboratory Laboratory of of Renewable Renewable Energy Energy Technologies Technologies for for Buildings, Buildings, Ministry Ministry of of Education, Education, Jinan Jinan 250101, 250101, China China cc Shandong Shandong Key Key Laboratory Laboratory of of Renewable Renewable Energy Energy Technologies Technologies for for Buildings, Buildings, Jinan Jinan 250101, 250101, China China a
bb
Abstract Abstract The The living living conditions conditions and and energy energy consumption consumption have have been been gradually gradually increased increased in in rural rural area area of of Shandong Shandong Province, Province, China. China. However, However, the the existing existing heating heating technology technology cannot cannot meet meet the the requirement requirement of of occupants’ occupants’ thermal thermal comfort. comfort. Therefore, Therefore, aa more more promising promising heating heating technology technology needs needs to to be be taken taken into into account. account. With With regard regard to to public public place place in in the the rural rural area, area, this this paper paper draws draws aa comparison comparison of of heat heat source source using using Air Air Source Source Heat Heat Pump Pump (ASHP), (ASHP), gas gas boiler boiler and and biomass biomass boiler boiler in in aspects aspects of of efficiency efficiency and and economy, economy, and and conducts conducts aa simulation simulation for for the the indoor indoor air air temperature temperature field field using using different different heating heating technologies, technologies, such such as as radiator, radiator, radiant radiant floor floor and and tuyere. tuyere. Regarding Regarding the the conventional conventional residence, residence, this this paper paper summarizes summarizes the the advantages advantages of of household household ASHP ASHP in in aspects aspects of of efficiency, efficiency, environment, environment, economy, economy, technology technology and and market. market. The The results results show show that that ASHP ASHP is is suitable suitable for for application application in in Shandong Shandong rural rural area. area. © © 2017 2017 The The Authors. Authors. Published Published by by Elsevier Elsevier Ltd. Ltd. © 2017 The Authors. Published by Elsevier Ltd. committee of the 10th International Symposium on Heating, Ventilation and Air Peer-review under responsibility of the scientific Peer-review under responsibility of the scientific committee of of the the 10th 10th International International Symposium on Heating, Ventilation and and Air Peer-review under responsibility of the scientific committee Symposium on Heating, Ventilation Conditioning. Conditioning. Air Conditioning. Keywords: Keywords: Heating; Heating; Rural Rural area; area; Air Air Source Source Heat Heat Pump Pump (ASHP); (ASHP); Computational Computational Fluid Fluid Dynamics Dynamics (CFD) (CFD)
* * Corresponding Corresponding author. author. Tel.: Tel.: +86-150-9873-6935. +86-150-9873-6935. E-mail E-mail address: address: [email protected] [email protected] 1877-7058 1877-7058 © © 2017 2017 The The Authors. Authors. Published Published by by Elsevier Elsevier Ltd. Ltd. Peer-review Peer-review under under responsibility responsibility of of the the scientific scientific committee committee of of the the 10th 10th International International Symposium Symposium on on Heating, Heating, Ventilation Ventilation and and Air Air Conditioning. Conditioning.
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Air Conditioning. 10.1016/j.proeng.2017.10.365
21462
Xiaokai Huang al. / Procedia Engineering 205 (2017) 1461–1468 Xiaokai Huang et al. /etProcedia Engineering 00 (2017) 000–000
Nomenclature D C M ��� �� ��� �� �� H F q S W Q qr B 1. Introduction
the primary energy consumption of scheme the specific heat capacity of water, 4.187��⁄�� � �� hot water output, kg inlet temperature of the unit, °C power generation efficiency power transmission efficiency conversion rate of primary energy to secondary energy thermal efficiency of heat source equivalent heat value of standard coal, 7000����⁄�� operation cost per square per hour of ASHP, Chinese yuan heating index, � ⁄�� electricity bill operation cost per hour of the boiler, Chinese yuan heat value required by system, ���� heat value of fuels, ����⁄�� or ���� ⁄ �� fuels cost, ������������⁄�� or ������� ���� ⁄ ��
In November 2016, the People's Government of Shandong Province issued documents, clearly points out that more than 70% villages will realize the use of clean heating in winter by the end of 2020. It’s urgent to choose a suitable heating way for rural areas. Concerning terminal units, radiator heating, floor heating and tuyere heating are commonly used in rural areas, and each has its advantages and disadvantages. Regarding the heat sources, Air Source Heat Pump (ASHP) hot water unit, gas boiler and biomass boiler are good clean heat sources. Li et al proved the feasibility of ASHP replace the boiler in the aspects of energy saving and environmental protection [1]. Shi et al obtained a conclusion that gas boiler has rather ad-vantages in the aspects of economy and environmental protection compared with coal-fired boiler [2]. Zhao pointed that biomass boilers is applicable in rural areas [3]. Those three heat sources have their advantages, but the current studies about the comparison of these three heat sources are few. This paper takes a nursing home in Shandong rural area as a case study draws comparison about different heating technologies mentioned above, hoping to get more promising heating ways in Shandong rural areas. 2. Methods This study should be divided into two parts including public places and conventional rural residences, but the conventional rural residence research is only carried out by the theoretical analysis because of the limit of paper content. Therefore, this paper mainly introduces the re-search methodologies for public places, and this section is separated into two sub-sections that include the terminal unit research and the heat source research. 2.1. Research methods of terminal units The different terminal units lead to the different heating effect. This paper utilizes the numerical simulation method using FLUENT software, and simulates the indoor temperature field of radiator heating room, floor heating room, tuyere heating room. Taking a nursing home in Shandong rural area as a case study, and a room on the standard floor is selected to simulate. The room window faces south, and the east and west wall are adjacent to the heating room. Outdoor heating design temperature of Jinan is selected as -7°C and the indoor design temperature of the room is 20°C. The Cartesian coordinate system is used to establish the model and the northwest corner of the house is defined as the coordinate origin. The geometry and mesh parameters of the room are shown in Table 1 and Table 2.
Xiaokai Huang et /al. / Procedia Engineering 205 (2017) 1461–1468 Xiaokai Huang et al. Procedia Engineering 00 (2017) 000–000
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Table 1. Geometric parameters of room. Room dimensions Window dimensions Terminal unit dimensions
Radiator heating room (m)
Floor heating room (m)
Tuyere heating room (m)
4× 3 × 3
4× 3 × 3
4× 3 × 3
1.2× 1.5
1.2× 1.5
1.2× 1.5
0.2× 0.5 × 0.6
4× 3
Inlet:0.24× 0.24 Outlet:0.3× 0.3
Table 2. Parameters of grid genera.
Radiator heating room (m)
Floor heating room (m)
Tuyere heating room (m)
Grid type
Unstructured grid
Structured grid
Structured grid
Main body spacing
0.10
0.05
0.05
Exterior wall spacing
0.08
0.05
0.05
Exterior windows spacing
0.05
0.05
0.05
Terminal unit spacing
0.03
0.05
0.03
The dimensions and grids of the room with different terminal units are shown in Fig 1 and Fig 2.
a
b
c
Fig. 1. Room dimensions (a) Radiator heating room; (b) Floor heating room; (c) Tuyere heating room.
a
b
c
Fig. 2. Room grids (a) Radiator heating room; (b) Floor heating room; (c) Tuyere heating room.
The model simplifications and boundary conditionings settings are listed as follows, and the specific boundary conditions parameters are shown in Table 3. • The indoor air is considered as constant, incompressible and steady flow air. The simulation of the temperature field of the radiator and floor heating room is equivalent to the numerical simulation of the temperature field of the air nature convection in cavity. Buoyancy lift of air is considered and the Boussinesq density hypothesis is used to simplify the physical model. • The pressure based solver is used. The pressure-velocity coupling option is SMPLE. The energy equation is discretized by second-order upwind.
Xiaokai Huang et al. / Procedia Engineering 205 (2017) 1461–1468 Xiaokai Huang et al. / Procedia Engineering 00 (2017) 000–000
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• In order to let these three terminal units comparable, the heat of these three terminal units supplied to the room should be same. Calculations are carried out under the premise of the indoor design temperature is 20°C and the fresh air is not considered. It is obtained that surface temperature of radiator is 53°C, surface temperature of floor radiator is 24°C, velocity of inlet is 0.66m/s and the supply air temperature is 23.5°C [4,5,6]. The calculation is not introduced because it is not the key point of this paper. Table 3. Parameters of boundary conditions Radiator heating room
Floor heating room
South wall
T=266K, h=0.54 W/m K
T=266K, h=0.54 W/m K
T=266K, h=0.54 W/m2K
South window
T=266K, h=3.7 W/m2K
T=266K, h=3.7 W/m2K
T=266K, h=3.7 W/m2K
North wall
T=289K, h=1.8 W/m K
T=289K, h=1.8 W/m K
T=289K, h=1.8 W/m2K
Ceiling
Heat insulation
Heat insulation
Heat insulation
East and west wall
Heat insulation
Heat insulation
Heat insulation
Terminal unit
T=326K
T=326K
Tair=296.5K,Vair=0.66m/s
2
2
Tuyere heating room 2
2
2.2. Research methods of heat sources The heating design parameters of the nursing home mentioned above are listed in Table 4. ASHP hot water unit, gas boiler and biomass boiler are three promising heat source ways, and this paper makes a comparison between these three ways, which are shown in Table 5. Table 4. Design parameters of building heating. Building type
Construction area (m)
Heating area (m)
Heating index (W/m2)
Heating load (Kw)
Nursing home
1100
900
100
90
Table 5. Three alternative plans. Type
model
Heat value (Kcal)
thermal efficiency (%)
Plan 1
ASHP
TRB50RD
87700
350
Plan 2
Gas boiler
CLHS0.12
100000
90
Plan 3
Biomass boiler
CLHG0.12
100000
82
Analysis of this section will be divided into two parts including energy saving analysis and economy analysis. Meanwhile, the latter consists of two parts including initial investment analysis and operating costs analysis [7]. The energy saving analysis of heat source is to compare the primary energy consumption of each scheme under the premise of satisfying the indoor heat load. The formula of calculating the primary energy consumption is as follows [8]: ��
��(��� � ���� ) 4.2(�� � ��� � �� � �� � �)
(1)
The initial investment of heat source generally includes costs of unit, boiler room construction, boiler auxiliary facilities, transportation, installation, site for fuel, etc. The installation and transportation costs are calculated at 15% of the unit costs for calculating conveniently. The heating operation cost of ASHP is the electricity bill consumed by heating, and for boiler, the heating operation cost is the fuel costs consumed by heating. The heating period is from November 15 to March 15 next year, a total of 4 month and heating for 24 hours a day. The operation cost per square per hour of ASHP can be calculated by the Equation (2) [9], and the operation cost per hour of the boiler can be calculated by the Equation (3). � � q × S ∕ (COP×1000) (2)
Xiaokai Huang et al. / Procedia Engineering 205 (2017) 1461–1468 Xiaokai Huang et al. / Procedia Engineering 00 (2017) 000–000
� � � � � � (�� � ���)
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(3)
3. Results
This part is also divided into two sections including public places and conventional rural residences, and in the following four headings, the first three are belong to the aspect of public places. 3.1. Numerical simulation results and analysis of terminal units With the conditions of the outdoor temperature of -7°C, indoor design temperature of 20°C, and the same heating capacity provided for the room of each terminal unit. Then the temperature field of room can be obtained and two faces Y=1.5 and X=2 are defined as feature planes and analysed [10,11]. Temperature field of feature planes are shown in Fig 3, Fig 4 and Fig 5, where the face Y=1.5 is on the lift, and X=2 is on the right.
a
b
Fig.3. The temperature field of radiator heating room (a) Y=1.5; (b) X=2.
a
b
Fig.4. The temperature field of floor radiator heating room (a) Y=1.5; (b) X=2.
Xiaokai Huang al. / Procedia Engineering 205 (2017) 1461–1468 Xiaokai Huang et al. /etProcedia Engineering 00 (2017) 000–000
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b
a
Fig.5. The temperature field of tuyere heating room (a) Y=1.5; (b) X=2.
• Results can be obtained from the figures above, the temperature of tuyere heating room is between 19.5°C and 21°C, and the mean temperature of it is the highest, but the temperature gradient is the biggest and the isotherms are relatively disordered because of the disturbance of the air flow. The temperature of floor radiator heating room temperature is between 19.8°C and 20.2°C, and the temperature gradient is small because of the relatively large face of the floor radiator. The temperature of radiator heating room temperature is between 19°C and 19.5°C, and the mean temperature is the lowest. • The radiator is one of the most common terminal units in the Shandong rural areas, which is installed conveniently and bought cheaply, and it is suitable for heating renovation projects. The heating radiant surface of floor heating room is large and the comfort level is high, and the low-temperature water can satisfy people’s need, which meets the concepts of energy consumption and low temperature heating. It is suitable for nursery schools and new rural communities but public place because the high floor temperature would raise dust. The temperature gradient of tuyere heating room is high and the isotherms are relatively disordered. This terminal unit is more applicable in public places with a large number of people because of its characteristics of fresh air accessible. • Combining the simulation with the characteristics of each terminal unit, the conclusion can be obtained. The way of tuyere heating is suitable for the public places with a lot of people and the way of radiator heating is available in the public place when the demand for fresh air is low. 3.2. Results of energy saving analysis ζ is defined as energy efficiency, where�ζ � �� � �� , and if plan i is more energy efficient than plan j, the formula �� � �� can be obtained, which can be simplified as ��� � ��� � ��� � ��� . The specific calculation parameters and results of each scheme are as shown in Table 6. We can clearly find that ζ� � ζ� � ζ� . Table 6. Analysis on energy saving �� �� ζ
ASHP (%)
Gas boiler (%)
Biomass boiler (%)
350
90
82
30
100
100
105
90
82
ASHP has some advantages in the aspect of energy saving, it can transform the outdoor low quality thermal energy that cannot be used directly into the high quality thermal energy, which only consumes a small amount of electricity and saves a lot of energy.
Xiaokai Huang et al. / Procedia Engineering 205 (2017) 1461–1468 Xiaokai Huang et al. / Procedia Engineering 00 (2017) 000–000
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3.3. Economy analysis The initial investment of plan 1 mainly includes the costs of ASHP unit, transportation and installation. Plan 2 mainly includes the costs of gas boiler, transportation and installation. Plan 3 mainly includes the costs of biomass boiler, transportation and installation, dust removal equipment and site for biomass fuels. The cost details are shown in Table 7. Table 7. Initial investment details ASHP (Chinese Yuan)
Gas boiler (Chinese Yuan)
Biomass boiler(Chinese Yuan)
Unit
100000
20000
23000
Transportation and installation
15000
3000
3450
Dust removal equipment
0
0
2000
Site for fuels
0
0
15000
115000
23000
43450
Total costs
The data given or calculated above have been summarized and the operation cost per year of each plan is listed as follows. ASHP spends 52704 Chinese Yuan a year; Gas boiler spends 78568 Chinese Yuan a year; Biomass boiler spends 72102 Chinese Yuan a year. The total costs can be calculated by combining the initial investment and operation cost. The total costs trend of each heat source scheme is shown in the Fig 6. The figure shows that the total costs of the ASHP is relatively high, but due to its relatively lower operating cost, ASHP becomes the most economical heat source plan 3.5 years later, and the longer years serviced, the more money saved.
Fig.6. Total costs trend of each heat source scheme.
3.4. Analysis results in conventional rural residences For the conventional rural residences, the mode of centralized heat-supply is not suitable and the decentralized heat-supply is the best choice because the house spacing is big and the population density is low. The household ASHP is the best choice for conventional rural residences in the future. The reasons are listed as follows: • The COP of ASHP is high and large amount of heat can be generated by a small amount of electricity energy consumption. • ASHP has no pollution to the environment and air energy outdoor is inexhaustible, which accords with social theme of green sustainable development.
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Xiaokai Huang et al. / Procedia Engineering 205 (2017) 1461–1468 Xiaokai Huang et al. / Procedia Engineering 00 (2017) 000–000
• Compared with the traditional heating stove, the thermal comfort of ASHP is pretty good, and it generates little odor and performs better in the temperature field of room. In comparison with domestic wall-hung gas boiler, the operation cost of ASHP is lower and the safety is better. In contrast with solar heating system, the heating effect of ASHP is stable and don’t require a large area to set solar collector heat plates. Meanwhile, contracting ASHP with the composite heating system, the former is low in price and easy to installation. • The household ASHP has been developed for many years, which is very mature at technology level. Meanwhile, the cognitive and acceptable level is relatively high. Furthermore, the production, sale, transportation, installation and after-sale process are clear and specific, and the operation is simple and convenient. 4. Conclusions • The living standard in Shandong rural areas is constantly improving, and the energy using structure tends to be urbanized, but the heat comfort level of residents required to improve. So a more appropriate heating way demands to be adopted. • The system of ASHP with tuyere is suitable for application in public places, and the system of ASHP with radiator is available in public places when the fresh air demand is low. • For conventional rural residences, the household ASHP is advantageous in the aspects of energy saving, environment friendly, economy and market. Acknowledgements This study was sponsored by Natural Science Foundation of China (NSFC, No.51176104), Natural Science Foundation of Shandong Province (ZR2016EEB08), Science and Technology Plan Project of University in Shandong Province (J16LG07), Science and Technology Development Plan in Shandong Province (2012GGX10416). Authors would like to thank graduate students for their help with the onsite data collection. References [1] S.H. Li, B.M. Dai, Y.T. Ma. Development status analysis of air source heat pump. Refrigeration technology, 2014, 34 (1): 42-48. [2] Y. Shi, J.B. Zang, A.J. Lu. Energy Saving Analysis of transforming The coal - fired boiler into gas - fired boiler. Energy saving, 2010, (2): 7677. [3] J. Zhao. Research on the Biomass granulators and the Technology of heating by Hot water boiler. Science and Technology, 2016, (30): 110111. [4] R.Y. Zhao, C.Y. Fan, D.H. Xue, Y.M. Qian. Air conditioning (fourth edition). Beijing: China construction industry press. 2008: 118-126. [5] B.J. Qian, P.W. Ren, J.F. Chang, Y.M. Ding. Concise Handbook of heat transfer. Beijing: Higher Education Press. 1983: 147,188-189. [6] X.M. Zhang, Z.P. Ren, F.M. Mei, Heat transfer (Fifth Edition). Beijing: China construction industry press. 2007: 104-120. [7] Y.B. Li, Z.Y. Zhuang. Economic Comfort Analysis of Air Source Heat Pump Waterless Heating System. Building heat ventilation and air conditioning. 2017,36 (1):45-48. [8] B. Fu, L. Liu. Energy saving analysis of air source heat pump hot water unit. Energy conservation and environmental protection, 2008, (9): 29-31. [9] F.X. Zhang, G.S. Tian, J.Y. Wei. The Feasibility analysis of air source heat pump heating in a unit of Jinan. District heating. 2015, (4): 118120. [10] B.R. Zhu, X.M. Yue. Numerical simulation of temperature field and velocity field in radiator heating room. Building heat ventilation and air conditioning, 2011, 30 (5): 92-94. [11] D.H. Zhai, J.H. Zhao, L.J. Zhang, Numerical simulation of air flow field distribution in air conditioned room. Energy-saving technology, 2013, 31(5): 420-425.
ScienceDirect
Available online at www.sciencedirect.com Procedia Procedia Engineering Engineering 00 00 (2017) (2017) 000–000 000–000
ScienceDirect
www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia
Procedia Engineering 205 (2017) 1461–1468
10th International Symposium on Heating, Ventilation and Air Conditioning, ISHVAC2017, 1922 October 2017, Jinan, China
Preliminary Analysis on the Different Heating Technologies in a Rural Area of Shandong Province, China a,b,c,*, Linhua Zhanga,b,c a,b,c Xiaokai Huangaa, Huixin Fangaa, Linfang Zhangaa, Jiying Liua,b,c,* aSchool of Thermal Engineering, Shandong Jianzhu University, Jinan 250101, China School of Thermal Engineering, Shandong Jianzhu University, Jinan 250101, China Key Key Laboratory Laboratory of of Renewable Renewable Energy Energy Technologies Technologies for for Buildings, Buildings, Ministry Ministry of of Education, Education, Jinan Jinan 250101, 250101, China China cc Shandong Shandong Key Key Laboratory Laboratory of of Renewable Renewable Energy Energy Technologies Technologies for for Buildings, Buildings, Jinan Jinan 250101, 250101, China China a
bb
Abstract Abstract The The living living conditions conditions and and energy energy consumption consumption have have been been gradually gradually increased increased in in rural rural area area of of Shandong Shandong Province, Province, China. China. However, However, the the existing existing heating heating technology technology cannot cannot meet meet the the requirement requirement of of occupants’ occupants’ thermal thermal comfort. comfort. Therefore, Therefore, aa more more promising promising heating heating technology technology needs needs to to be be taken taken into into account. account. With With regard regard to to public public place place in in the the rural rural area, area, this this paper paper draws draws aa comparison comparison of of heat heat source source using using Air Air Source Source Heat Heat Pump Pump (ASHP), (ASHP), gas gas boiler boiler and and biomass biomass boiler boiler in in aspects aspects of of efficiency efficiency and and economy, economy, and and conducts conducts aa simulation simulation for for the the indoor indoor air air temperature temperature field field using using different different heating heating technologies, technologies, such such as as radiator, radiator, radiant radiant floor floor and and tuyere. tuyere. Regarding Regarding the the conventional conventional residence, residence, this this paper paper summarizes summarizes the the advantages advantages of of household household ASHP ASHP in in aspects aspects of of efficiency, efficiency, environment, environment, economy, economy, technology technology and and market. market. The The results results show show that that ASHP ASHP is is suitable suitable for for application application in in Shandong Shandong rural rural area. area. © © 2017 2017 The The Authors. Authors. Published Published by by Elsevier Elsevier Ltd. Ltd. © 2017 The Authors. Published by Elsevier Ltd. committee of the 10th International Symposium on Heating, Ventilation and Air Peer-review under responsibility of the scientific Peer-review under responsibility of the scientific committee of of the the 10th 10th International International Symposium on Heating, Ventilation and and Air Peer-review under responsibility of the scientific committee Symposium on Heating, Ventilation Conditioning. Conditioning. Air Conditioning. Keywords: Keywords: Heating; Heating; Rural Rural area; area; Air Air Source Source Heat Heat Pump Pump (ASHP); (ASHP); Computational Computational Fluid Fluid Dynamics Dynamics (CFD) (CFD)
* * Corresponding Corresponding author. author. Tel.: Tel.: +86-150-9873-6935. +86-150-9873-6935. E-mail E-mail address: address: [email protected] [email protected] 1877-7058 1877-7058 © © 2017 2017 The The Authors. Authors. Published Published by by Elsevier Elsevier Ltd. Ltd. Peer-review Peer-review under under responsibility responsibility of of the the scientific scientific committee committee of of the the 10th 10th International International Symposium Symposium on on Heating, Heating, Ventilation Ventilation and and Air Air Conditioning. Conditioning.
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the scientific committee of the 10th International Symposium on Heating, Ventilation and Air Conditioning. 10.1016/j.proeng.2017.10.365
21462
Xiaokai Huang al. / Procedia Engineering 205 (2017) 1461–1468 Xiaokai Huang et al. /etProcedia Engineering 00 (2017) 000–000
Nomenclature D C M ��� �� ��� �� �� H F q S W Q qr B 1. Introduction
the primary energy consumption of scheme the specific heat capacity of water, 4.187��⁄�� � �� hot water output, kg inlet temperature of the unit, °C power generation efficiency power transmission efficiency conversion rate of primary energy to secondary energy thermal efficiency of heat source equivalent heat value of standard coal, 7000����⁄�� operation cost per square per hour of ASHP, Chinese yuan heating index, � ⁄�� electricity bill operation cost per hour of the boiler, Chinese yuan heat value required by system, ���� heat value of fuels, ����⁄�� or ���� ⁄ �� fuels cost, ������������⁄�� or ������� ���� ⁄ ��
In November 2016, the People's Government of Shandong Province issued documents, clearly points out that more than 70% villages will realize the use of clean heating in winter by the end of 2020. It’s urgent to choose a suitable heating way for rural areas. Concerning terminal units, radiator heating, floor heating and tuyere heating are commonly used in rural areas, and each has its advantages and disadvantages. Regarding the heat sources, Air Source Heat Pump (ASHP) hot water unit, gas boiler and biomass boiler are good clean heat sources. Li et al proved the feasibility of ASHP replace the boiler in the aspects of energy saving and environmental protection [1]. Shi et al obtained a conclusion that gas boiler has rather ad-vantages in the aspects of economy and environmental protection compared with coal-fired boiler [2]. Zhao pointed that biomass boilers is applicable in rural areas [3]. Those three heat sources have their advantages, but the current studies about the comparison of these three heat sources are few. This paper takes a nursing home in Shandong rural area as a case study draws comparison about different heating technologies mentioned above, hoping to get more promising heating ways in Shandong rural areas. 2. Methods This study should be divided into two parts including public places and conventional rural residences, but the conventional rural residence research is only carried out by the theoretical analysis because of the limit of paper content. Therefore, this paper mainly introduces the re-search methodologies for public places, and this section is separated into two sub-sections that include the terminal unit research and the heat source research. 2.1. Research methods of terminal units The different terminal units lead to the different heating effect. This paper utilizes the numerical simulation method using FLUENT software, and simulates the indoor temperature field of radiator heating room, floor heating room, tuyere heating room. Taking a nursing home in Shandong rural area as a case study, and a room on the standard floor is selected to simulate. The room window faces south, and the east and west wall are adjacent to the heating room. Outdoor heating design temperature of Jinan is selected as -7°C and the indoor design temperature of the room is 20°C. The Cartesian coordinate system is used to establish the model and the northwest corner of the house is defined as the coordinate origin. The geometry and mesh parameters of the room are shown in Table 1 and Table 2.
Xiaokai Huang et /al. / Procedia Engineering 205 (2017) 1461–1468 Xiaokai Huang et al. Procedia Engineering 00 (2017) 000–000
14633
Table 1. Geometric parameters of room. Room dimensions Window dimensions Terminal unit dimensions
Radiator heating room (m)
Floor heating room (m)
Tuyere heating room (m)
4× 3 × 3
4× 3 × 3
4× 3 × 3
1.2× 1.5
1.2× 1.5
1.2× 1.5
0.2× 0.5 × 0.6
4× 3
Inlet:0.24× 0.24 Outlet:0.3× 0.3
Table 2. Parameters of grid genera.
Radiator heating room (m)
Floor heating room (m)
Tuyere heating room (m)
Grid type
Unstructured grid
Structured grid
Structured grid
Main body spacing
0.10
0.05
0.05
Exterior wall spacing
0.08
0.05
0.05
Exterior windows spacing
0.05
0.05
0.05
Terminal unit spacing
0.03
0.05
0.03
The dimensions and grids of the room with different terminal units are shown in Fig 1 and Fig 2.
a
b
c
Fig. 1. Room dimensions (a) Radiator heating room; (b) Floor heating room; (c) Tuyere heating room.
a
b
c
Fig. 2. Room grids (a) Radiator heating room; (b) Floor heating room; (c) Tuyere heating room.
The model simplifications and boundary conditionings settings are listed as follows, and the specific boundary conditions parameters are shown in Table 3. • The indoor air is considered as constant, incompressible and steady flow air. The simulation of the temperature field of the radiator and floor heating room is equivalent to the numerical simulation of the temperature field of the air nature convection in cavity. Buoyancy lift of air is considered and the Boussinesq density hypothesis is used to simplify the physical model. • The pressure based solver is used. The pressure-velocity coupling option is SMPLE. The energy equation is discretized by second-order upwind.
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• In order to let these three terminal units comparable, the heat of these three terminal units supplied to the room should be same. Calculations are carried out under the premise of the indoor design temperature is 20°C and the fresh air is not considered. It is obtained that surface temperature of radiator is 53°C, surface temperature of floor radiator is 24°C, velocity of inlet is 0.66m/s and the supply air temperature is 23.5°C [4,5,6]. The calculation is not introduced because it is not the key point of this paper. Table 3. Parameters of boundary conditions Radiator heating room
Floor heating room
South wall
T=266K, h=0.54 W/m K
T=266K, h=0.54 W/m K
T=266K, h=0.54 W/m2K
South window
T=266K, h=3.7 W/m2K
T=266K, h=3.7 W/m2K
T=266K, h=3.7 W/m2K
North wall
T=289K, h=1.8 W/m K
T=289K, h=1.8 W/m K
T=289K, h=1.8 W/m2K
Ceiling
Heat insulation
Heat insulation
Heat insulation
East and west wall
Heat insulation
Heat insulation
Heat insulation
Terminal unit
T=326K
T=326K
Tair=296.5K,Vair=0.66m/s
2
2
Tuyere heating room 2
2
2.2. Research methods of heat sources The heating design parameters of the nursing home mentioned above are listed in Table 4. ASHP hot water unit, gas boiler and biomass boiler are three promising heat source ways, and this paper makes a comparison between these three ways, which are shown in Table 5. Table 4. Design parameters of building heating. Building type
Construction area (m)
Heating area (m)
Heating index (W/m2)
Heating load (Kw)
Nursing home
1100
900
100
90
Table 5. Three alternative plans. Type
model
Heat value (Kcal)
thermal efficiency (%)
Plan 1
ASHP
TRB50RD
87700
350
Plan 2
Gas boiler
CLHS0.12
100000
90
Plan 3
Biomass boiler
CLHG0.12
100000
82
Analysis of this section will be divided into two parts including energy saving analysis and economy analysis. Meanwhile, the latter consists of two parts including initial investment analysis and operating costs analysis [7]. The energy saving analysis of heat source is to compare the primary energy consumption of each scheme under the premise of satisfying the indoor heat load. The formula of calculating the primary energy consumption is as follows [8]: ��
��(��� � ���� ) 4.2(�� � ��� � �� � �� � �)
(1)
The initial investment of heat source generally includes costs of unit, boiler room construction, boiler auxiliary facilities, transportation, installation, site for fuel, etc. The installation and transportation costs are calculated at 15% of the unit costs for calculating conveniently. The heating operation cost of ASHP is the electricity bill consumed by heating, and for boiler, the heating operation cost is the fuel costs consumed by heating. The heating period is from November 15 to March 15 next year, a total of 4 month and heating for 24 hours a day. The operation cost per square per hour of ASHP can be calculated by the Equation (2) [9], and the operation cost per hour of the boiler can be calculated by the Equation (3). � � q × S ∕ (COP×1000) (2)
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� � � � � � (�� � ���)
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(3)
3. Results
This part is also divided into two sections including public places and conventional rural residences, and in the following four headings, the first three are belong to the aspect of public places. 3.1. Numerical simulation results and analysis of terminal units With the conditions of the outdoor temperature of -7°C, indoor design temperature of 20°C, and the same heating capacity provided for the room of each terminal unit. Then the temperature field of room can be obtained and two faces Y=1.5 and X=2 are defined as feature planes and analysed [10,11]. Temperature field of feature planes are shown in Fig 3, Fig 4 and Fig 5, where the face Y=1.5 is on the lift, and X=2 is on the right.
a
b
Fig.3. The temperature field of radiator heating room (a) Y=1.5; (b) X=2.
a
b
Fig.4. The temperature field of floor radiator heating room (a) Y=1.5; (b) X=2.
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b
a
Fig.5. The temperature field of tuyere heating room (a) Y=1.5; (b) X=2.
• Results can be obtained from the figures above, the temperature of tuyere heating room is between 19.5°C and 21°C, and the mean temperature of it is the highest, but the temperature gradient is the biggest and the isotherms are relatively disordered because of the disturbance of the air flow. The temperature of floor radiator heating room temperature is between 19.8°C and 20.2°C, and the temperature gradient is small because of the relatively large face of the floor radiator. The temperature of radiator heating room temperature is between 19°C and 19.5°C, and the mean temperature is the lowest. • The radiator is one of the most common terminal units in the Shandong rural areas, which is installed conveniently and bought cheaply, and it is suitable for heating renovation projects. The heating radiant surface of floor heating room is large and the comfort level is high, and the low-temperature water can satisfy people’s need, which meets the concepts of energy consumption and low temperature heating. It is suitable for nursery schools and new rural communities but public place because the high floor temperature would raise dust. The temperature gradient of tuyere heating room is high and the isotherms are relatively disordered. This terminal unit is more applicable in public places with a large number of people because of its characteristics of fresh air accessible. • Combining the simulation with the characteristics of each terminal unit, the conclusion can be obtained. The way of tuyere heating is suitable for the public places with a lot of people and the way of radiator heating is available in the public place when the demand for fresh air is low. 3.2. Results of energy saving analysis ζ is defined as energy efficiency, where�ζ � �� � �� , and if plan i is more energy efficient than plan j, the formula �� � �� can be obtained, which can be simplified as ��� � ��� � ��� � ��� . The specific calculation parameters and results of each scheme are as shown in Table 6. We can clearly find that ζ� � ζ� � ζ� . Table 6. Analysis on energy saving �� �� ζ
ASHP (%)
Gas boiler (%)
Biomass boiler (%)
350
90
82
30
100
100
105
90
82
ASHP has some advantages in the aspect of energy saving, it can transform the outdoor low quality thermal energy that cannot be used directly into the high quality thermal energy, which only consumes a small amount of electricity and saves a lot of energy.
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3.3. Economy analysis The initial investment of plan 1 mainly includes the costs of ASHP unit, transportation and installation. Plan 2 mainly includes the costs of gas boiler, transportation and installation. Plan 3 mainly includes the costs of biomass boiler, transportation and installation, dust removal equipment and site for biomass fuels. The cost details are shown in Table 7. Table 7. Initial investment details ASHP (Chinese Yuan)
Gas boiler (Chinese Yuan)
Biomass boiler(Chinese Yuan)
Unit
100000
20000
23000
Transportation and installation
15000
3000
3450
Dust removal equipment
0
0
2000
Site for fuels
0
0
15000
115000
23000
43450
Total costs
The data given or calculated above have been summarized and the operation cost per year of each plan is listed as follows. ASHP spends 52704 Chinese Yuan a year; Gas boiler spends 78568 Chinese Yuan a year; Biomass boiler spends 72102 Chinese Yuan a year. The total costs can be calculated by combining the initial investment and operation cost. The total costs trend of each heat source scheme is shown in the Fig 6. The figure shows that the total costs of the ASHP is relatively high, but due to its relatively lower operating cost, ASHP becomes the most economical heat source plan 3.5 years later, and the longer years serviced, the more money saved.
Fig.6. Total costs trend of each heat source scheme.
3.4. Analysis results in conventional rural residences For the conventional rural residences, the mode of centralized heat-supply is not suitable and the decentralized heat-supply is the best choice because the house spacing is big and the population density is low. The household ASHP is the best choice for conventional rural residences in the future. The reasons are listed as follows: • The COP of ASHP is high and large amount of heat can be generated by a small amount of electricity energy consumption. • ASHP has no pollution to the environment and air energy outdoor is inexhaustible, which accords with social theme of green sustainable development.
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• Compared with the traditional heating stove, the thermal comfort of ASHP is pretty good, and it generates little odor and performs better in the temperature field of room. In comparison with domestic wall-hung gas boiler, the operation cost of ASHP is lower and the safety is better. In contrast with solar heating system, the heating effect of ASHP is stable and don’t require a large area to set solar collector heat plates. Meanwhile, contracting ASHP with the composite heating system, the former is low in price and easy to installation. • The household ASHP has been developed for many years, which is very mature at technology level. Meanwhile, the cognitive and acceptable level is relatively high. Furthermore, the production, sale, transportation, installation and after-sale process are clear and specific, and the operation is simple and convenient. 4. Conclusions • The living standard in Shandong rural areas is constantly improving, and the energy using structure tends to be urbanized, but the heat comfort level of residents required to improve. So a more appropriate heating way demands to be adopted. • The system of ASHP with tuyere is suitable for application in public places, and the system of ASHP with radiator is available in public places when the fresh air demand is low. • For conventional rural residences, the household ASHP is advantageous in the aspects of energy saving, environment friendly, economy and market. Acknowledgements This study was sponsored by Natural Science Foundation of China (NSFC, No.51176104), Natural Science Foundation of Shandong Province (ZR2016EEB08), Science and Technology Plan Project of University in Shandong Province (J16LG07), Science and Technology Development Plan in Shandong Province (2012GGX10416). Authors would like to thank graduate students for their help with the onsite data collection. References [1] S.H. Li, B.M. Dai, Y.T. Ma. Development status analysis of air source heat pump. Refrigeration technology, 2014, 34 (1): 42-48. [2] Y. Shi, J.B. Zang, A.J. Lu. Energy Saving Analysis of transforming The coal - fired boiler into gas - fired boiler. Energy saving, 2010, (2): 7677. [3] J. Zhao. Research on the Biomass granulators and the Technology of heating by Hot water boiler. Science and Technology, 2016, (30): 110111. [4] R.Y. Zhao, C.Y. Fan, D.H. Xue, Y.M. Qian. Air conditioning (fourth edition). Beijing: China construction industry press. 2008: 118-126. [5] B.J. Qian, P.W. Ren, J.F. Chang, Y.M. Ding. Concise Handbook of heat transfer. Beijing: Higher Education Press. 1983: 147,188-189. [6] X.M. Zhang, Z.P. Ren, F.M. Mei, Heat transfer (Fifth Edition). Beijing: China construction industry press. 2007: 104-120. [7] Y.B. Li, Z.Y. Zhuang. Economic Comfort Analysis of Air Source Heat Pump Waterless Heating System. Building heat ventilation and air conditioning. 2017,36 (1):45-48. [8] B. Fu, L. Liu. Energy saving analysis of air source heat pump hot water unit. Energy conservation and environmental protection, 2008, (9): 29-31. [9] F.X. Zhang, G.S. Tian, J.Y. Wei. The Feasibility analysis of air source heat pump heating in a unit of Jinan. District heating. 2015, (4): 118120. [10] B.R. Zhu, X.M. Yue. Numerical simulation of temperature field and velocity field in radiator heating room. Building heat ventilation and air conditioning, 2011, 30 (5): 92-94. [11] D.H. Zhai, J.H. Zhao, L.J. Zhang, Numerical simulation of air flow field distribution in air conditioned room. Energy-saving technology, 2013, 31(5): 420-425.