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Simulation Of A Air Liquid Combined Heat Exchanger
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Procedia Engineering
Procedia Engineering 00 (2011) 000–000 Procedia Engineering 15 (2011) 4052 – 4057 www.elsevier.com/locate/procedia
Advanced in Control Engineering and Information Science
Simulation of a air liquid combined heat exchanger Yin Liu, * , Guanghui Zhoua and Jing Mab a
Zhongyuan University of Technology, 41 Zhongyuan Middle Road, Zhengzhou 450007, China b Henan University of Technology, Lianhua Road, Zhengzhou 450001, China
Abstract Air liquid composite heat exchanger can implement refrigerant combined heat exchange synchronization with liquid and air heat source. This article has established steady state mathematical model of the heat exchanger, and simulation the solar air double heat sources combined heat pump performance with the air liquid combined heat exchanger. Results show that the performance of the solar-air double heat sources composite heat pump is improved significantly by single air source heat pump in heating under various conditions. When the outdoor air temperature is about 1.5℃, the dual heat-source heat pump heating capacity and COP can reach single air-source heat pump. When the outdoor temperature is -15℃, dual heat-source heat pump heating capacity and COP are further increases, heating capacity increase nearly 40%, COP increase nearly 30%.
© 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of [CEIS 2011] Keywords: Simulation; Combined; Heat exchanger; Performance
1. Introduction With the development of heat pump technology, solar thermal technology into air-source heat pump technology has attracted the attention of many scholars. However, these studies have focused on compressor cascade switch or two heat sources using technology [1-4], two heat sources and heat transfer of refrigerant synchronization studies also rarely. This design of composite heat pump system with solarair double heat source[5] using gas-liquid compound heat exchangers[6] as the outdoor heat exchanger, solar water heating can be achieved with two air source temperatures of different heat sources in the same
*
E-mail address: [email protected]
1877-7058 © 2011 Published by Elsevier Ltd. doi:10.1016/j.proeng.2011.08.760
4053
Yin LiuY.etLiu al. // Procedia Procedia Engineering Engineering 00 15 (2011) (2011) 000–000 4052 – 4057
2
complex synchronized with the refrigerant in the evaporator of heat, to improve the efficiency of heat pumps. Dual source composite key parts of the heat exchanger for heat pump system as a whole have significant impact on performance of heat pump system. So for the study and establishment of mathematical model of heat exchangers in heat pump system as a whole plays a vital role in the study. This article builds double-source composite heat exchanger mathematical model and simulation study on its performance. 2. Dual heat exchanger model compound 2.1. Model conditions Modeling heat exchanger models are divided into three parts: air convection, solar hot water side convective heat and heat convection in refrigerants R22 side. This three-part of the heat there is the following relationship: Air flow for heat and solar hot water side flow heat equal refrigerant R22 lateral flow of heat On compound heat exchangers with double heat sources establish a lumped parameter model of steadystate, two sources-the solar hot water and air to the heat of refrigerant R22 and calculation of heat transfer coefficient of each separately. To ensure the model of precision and simplicity, this article made the following assumptions [7]: (1) Refrigerant R22 and side are in a State of countercurrent air side and solar hot water. (2) Pipe flow of refrigerant R22 in one-dimensional homogeneous axial flow, radial temperature consistency. (3) for radial heat transfer in one-dimension heat transfer of evaporator, regardless of axial heat transfer, wall heat resistance and heat capacity of metallic materials. (4) Ignore resistance loss in the evaporator. (5) Saturation pressure and temperature of the refrigerant R22 and saturated liquid pressure and temperature are the same. (6) Refrigerant R22 in a uniform flow in piping system movement, which is perpendicular to the flow direction of the movement of points on the section of physical parameters and status. (7) Solar water heating for uniform flow in piping system movement, which is perpendicular to the flow direction of the movement of points on the section of physical parameters and status. (8) the flow of air in the tube for uniform one dimensional flow, wind speed and pressure points on the section of the same, that is, the effect of heat evenly. (9) Liquid refrigerant R22 in the road uniform. (10) System without heat leakage. Mathematical model of the air side 2.2. Mathematical model of air-side Enthalpy difference calculated by the air side flow and heat transfer equation: Qa ,1 = ξ ma ( ha ,in − ha ,out )
(1)
ha ,in = C pTa ,in
(2)
ha ,out = C pTa ,out
(3)
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Yin Liu/ et al. / Procedia Engineering 15 (2011) 4052 – 4057 Y. Liu Procedia Engineering 00 (2011) 000–000
3
Where: ξ is the wet air coefficient. Qa ,2 = α a Aa ,out (ta , m - tr , m )
(4)
Air-side heat transfer coefficient using the experimental Hideo buried bridge formula [8]: α a = 18U a0.578
(5)
Ua =
ε=
uy
(6)
ε
( s1 − d o )( s f − δ f )
ta , m =
s1s f
ta ,in + ta ,out 2
(7) (8)
Where: αa is air-side heat transfer coefficient; Ua is air flow channel in the flow; Uy is air face velocity; ε is net surface area of air flow over; s1 is air flow perpendicular to the direction of the finned tube light tube spacing; sf is finned tube fin spacing; δf is finned tube fin thickness; do is finned tube light tube diameter. Tr,m in the equation for refrigerant R22 qualitative temperature average, average temperature of the area is composed of two phase and thermal area evaluated according to respective phase length-weighted average, two phase region average temperature of vaporization temperature, two-phase area and super heater area length according enthalpy value partition, the calculation are as follows:
cl , SH =
hr ,out − hr ,2
hr ,out − hr ,in
cl ,TP = 1 − cl , SH tr , SH , m =
tr ,out + tr ,2 2
tr ,m = cl , SH ⋅ tr , SH ,rm + cl ,TP ⋅ tr ,in
(9) (10) (11) (12)
2.3. Mathematical model of the solar hot water side Solar hot water flow and heat enthalpy difference calculation equation: Qy ,1 = m y (hy ,in − hy ,out )
(13)
hy ,in = c p ⋅ Ty ,in
(14)
hy ,out = C p ⋅ Ty ,out
(15)
Lateral flow calculation of solar hot water heat temperature difference equation: Qy ,2 = α y Ay ,out (t y ,m − t y ,m )
(16)
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Yin LiuY.etLiu al. // Procedia Procedia Engineering Engineering 00 15 (2011) (2011) 000–000 4052 – 4057
4
Side tube, solar hot water and heat transfer of refrigerant R22 for single-phase heat, heat transfer coefficients using standard Dittus-Boeler in turbulent pipe flow heat transfer coefficient [9]: 0.8
⎛ρ v d ⎞ λ α y = 0.023 ⎜ y y y ,in ⎟ ⋅ Pry0.4 ⋅ y ⎜ μ ⎟ d y ,in y ⎝ ⎠ t y ,m =
t y ,in − t y ,out 2
(17) (18)
In formula (1) - (19), Q is heat transfer, h is enthalpy; m is flow; d is diameter; C is specific heat; T and t are temperature; A is surface area; ρ is density; υ is kinematic viscosity; μ is dynamic viscosity; Pr is Prandtl number; λ is thermal conductivity; subscript a, y and r are air side, solar hot water side and refrigerant side respectively; 1 and 2 are enthalpy difference and temperature calculations respectively; in, out and m are import, export and average state, respectively; SH and TP are overheated zone and twophase region respectively; p is constant pressure. 2.4. Refrigerant side of the mathematical model Qe ,r = Qy + Qa
(19)
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Yin Liu/et al. / Procedia Engineering 15 (2011) 4052 – 4057 Y. Liu Procedia Engineering 00 (2011) 000–000
5
Where: Qe,r is total refrigerant R22 side heat; Qy is total solar hot water side of the heat; Qa is air side total heat transfer. 3. Simulation conditions To double-source composite heat pump system for simulation, in order to study heating performance of heat exchanger and its effect on the overall performance of heat pump system. Other parts are made of double-source composite heat pump system steady model, set in the heat exchanger from overheating of 5 ℃. Solar hot water flow for 0.2m3/h, the temperature is higher than the ambient air temperature 5 ℃. According to the GB/T 7725-2004 of the room air conditioner standards, selected three simulation conditions, where the outdoor environment temperature of heat exchanger (that is air heat source temperature) -7℃, 2℃ and -5℃ working for better research at low temperature of heat exchanger performance, select a group of outdoor ambient temperature -10℃ cryogenic conditions. 4. Results and analysis Fig. 2 is the different conditions of two heat pump heating performance curve. It can see from Fig. 2, double solar assisted hot water solar air-source heat pump in heating under various conditions to a single air-source heat pump system in cities have increased, and dual heat source heat pump hot water heating with solar energy traffic increases. When the outdoor air temperature of about 1.5℃, dual heat source heat pump heating can achieve a single air source heat pumps rated heating conditions (outdoor air temperature is 7℃) heat. When the outdoor temperature is -15℃, dual heat source heat pump heating capacity is increase near 40% of a single air source heat pump. Fig. 3 is a COP under different conditions two heat pump system performance curve. You can see from Fig. 3, double solar assisted hot water solar air-source heat pump in COP under various conditions to a single air-source heat pump systems have improved, and COP with dual heat source heat pump solar hot water flow increases and increases. When the outdoor air temperature of about 1.5℃, double COP can reach single heat source heat pump air heat pump rated heating condition COP. Dual heat source heat pump COP is increase near 30% of a single air source heat pump. 3.2
3000 2800 2600
single air two heat source
3.0 2.8 2.6
2200
2.4
2000
COP
Heating capacity (W)
2400
1800 1600
2.2 2.0
1400
1.8
1200
1.6
1000 800 -16 -14 -12 -10
Single air Two heat source
-8
-6
-4
-2
0
2
4
6
8
Air temperature (℃)
Fig. 2. Heating capacity curve in different working conditions
1.4 -16 -14 -12 -10
-8
-6
-4
-2
0
2
4
6
8
Air temperature (℃)
Fig. 3. COP in different heating conditions
5. Conclusion In solar air double heat source composite heat pump system, a air liquid combined heat exchanger is core part, the mathematical model of compound heat exchanger is foundation for simulation of the solar-
Yin LiuY.etLiu al. // Procedia Procedia Engineering Engineering 00 15 (2011) (2011) 000–000 4052 – 4057
6
air double heat source heat pump system, for fast simulation of system performance under different conditions, implementation and experimental research of complementary. Acknowledgements This work was supported by the Ministry of Science and Technology of Henan Province (072102240013, 082300460150 and 092102310188), the Open Research Foundation of the Western Architectural Science & Technology State Key Laboratory of China (10KF10) and Young Key Teacher Foundation of Zhongyuan University of Technology. References [1] Chai Q.H., Ma G.Y., State of knowledge and current challenges in the ASHP developed for the cold areas, Energy Engineering, 2002, (5)，25-31. [2] Tian CH. Q., Shi W. X., Research On Two-Stage Compression Variablefrequency Air Source Heat Pump In Cold Regions, Acta Energiae Solaris Sinica, 2004, 25(3), 388-393. [3] Tian Ch. Q., Shao Sh. Q., Shi W. X., Inverter Air Source Heat Pump, Fluid Machinery, 2005, 33(9), 67-71. [4] Wang H. B., Hu Y. F., Direct expansion solar assisted heat pump heating system Study, Coal Enginee, 2007, 11, 103-105. [5] Zhou G. H., Liu Y., Fin-bushing three-medium compound heat exchanger, 200720091299.1. [6] Zhou G. H., Liu Y., Dong X. J., Solar energy-geothermal energy double-heat source composite heat pump. 200710054878.3. [7] Ding G. L., Zhang C. L., Simulation and optimization of refrigeration and air conditioning equipment, Peking: Science Press, 2001. [8] Yu J. Z., Principle and design heat exchanger, Beijing: Aeronautics and Astronautics Press, 2006. [9] Yang Sh. M., Heat transfer, Peking: Higher Education Press, 1987.
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Procedia Engineering
Procedia Engineering 00 (2011) 000–000 Procedia Engineering 15 (2011) 4052 – 4057 www.elsevier.com/locate/procedia
Advanced in Control Engineering and Information Science
Simulation of a air liquid combined heat exchanger Yin Liu, * , Guanghui Zhoua and Jing Mab a
Zhongyuan University of Technology, 41 Zhongyuan Middle Road, Zhengzhou 450007, China b Henan University of Technology, Lianhua Road, Zhengzhou 450001, China
Abstract Air liquid composite heat exchanger can implement refrigerant combined heat exchange synchronization with liquid and air heat source. This article has established steady state mathematical model of the heat exchanger, and simulation the solar air double heat sources combined heat pump performance with the air liquid combined heat exchanger. Results show that the performance of the solar-air double heat sources composite heat pump is improved significantly by single air source heat pump in heating under various conditions. When the outdoor air temperature is about 1.5℃, the dual heat-source heat pump heating capacity and COP can reach single air-source heat pump. When the outdoor temperature is -15℃, dual heat-source heat pump heating capacity and COP are further increases, heating capacity increase nearly 40%, COP increase nearly 30%.
© 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of [CEIS 2011] Keywords: Simulation; Combined; Heat exchanger; Performance
1. Introduction With the development of heat pump technology, solar thermal technology into air-source heat pump technology has attracted the attention of many scholars. However, these studies have focused on compressor cascade switch or two heat sources using technology [1-4], two heat sources and heat transfer of refrigerant synchronization studies also rarely. This design of composite heat pump system with solarair double heat source[5] using gas-liquid compound heat exchangers[6] as the outdoor heat exchanger, solar water heating can be achieved with two air source temperatures of different heat sources in the same
*
E-mail address: [email protected]
1877-7058 © 2011 Published by Elsevier Ltd. doi:10.1016/j.proeng.2011.08.760
4053
Yin LiuY.etLiu al. // Procedia Procedia Engineering Engineering 00 15 (2011) (2011) 000–000 4052 – 4057
2
complex synchronized with the refrigerant in the evaporator of heat, to improve the efficiency of heat pumps. Dual source composite key parts of the heat exchanger for heat pump system as a whole have significant impact on performance of heat pump system. So for the study and establishment of mathematical model of heat exchangers in heat pump system as a whole plays a vital role in the study. This article builds double-source composite heat exchanger mathematical model and simulation study on its performance. 2. Dual heat exchanger model compound 2.1. Model conditions Modeling heat exchanger models are divided into three parts: air convection, solar hot water side convective heat and heat convection in refrigerants R22 side. This three-part of the heat there is the following relationship: Air flow for heat and solar hot water side flow heat equal refrigerant R22 lateral flow of heat On compound heat exchangers with double heat sources establish a lumped parameter model of steadystate, two sources-the solar hot water and air to the heat of refrigerant R22 and calculation of heat transfer coefficient of each separately. To ensure the model of precision and simplicity, this article made the following assumptions [7]: (1) Refrigerant R22 and side are in a State of countercurrent air side and solar hot water. (2) Pipe flow of refrigerant R22 in one-dimensional homogeneous axial flow, radial temperature consistency. (3) for radial heat transfer in one-dimension heat transfer of evaporator, regardless of axial heat transfer, wall heat resistance and heat capacity of metallic materials. (4) Ignore resistance loss in the evaporator. (5) Saturation pressure and temperature of the refrigerant R22 and saturated liquid pressure and temperature are the same. (6) Refrigerant R22 in a uniform flow in piping system movement, which is perpendicular to the flow direction of the movement of points on the section of physical parameters and status. (7) Solar water heating for uniform flow in piping system movement, which is perpendicular to the flow direction of the movement of points on the section of physical parameters and status. (8) the flow of air in the tube for uniform one dimensional flow, wind speed and pressure points on the section of the same, that is, the effect of heat evenly. (9) Liquid refrigerant R22 in the road uniform. (10) System without heat leakage. Mathematical model of the air side 2.2. Mathematical model of air-side Enthalpy difference calculated by the air side flow and heat transfer equation: Qa ,1 = ξ ma ( ha ,in − ha ,out )
(1)
ha ,in = C pTa ,in
(2)
ha ,out = C pTa ,out
(3)
4054
Yin Liu/ et al. / Procedia Engineering 15 (2011) 4052 – 4057 Y. Liu Procedia Engineering 00 (2011) 000–000
3
Where: ξ is the wet air coefficient. Qa ,2 = α a Aa ,out (ta , m - tr , m )
(4)
Air-side heat transfer coefficient using the experimental Hideo buried bridge formula [8]: α a = 18U a0.578
(5)
Ua =
ε=
uy
(6)
ε
( s1 − d o )( s f − δ f )
ta , m =
s1s f
ta ,in + ta ,out 2
(7) (8)
Where: αa is air-side heat transfer coefficient; Ua is air flow channel in the flow; Uy is air face velocity; ε is net surface area of air flow over; s1 is air flow perpendicular to the direction of the finned tube light tube spacing; sf is finned tube fin spacing; δf is finned tube fin thickness; do is finned tube light tube diameter. Tr,m in the equation for refrigerant R22 qualitative temperature average, average temperature of the area is composed of two phase and thermal area evaluated according to respective phase length-weighted average, two phase region average temperature of vaporization temperature, two-phase area and super heater area length according enthalpy value partition, the calculation are as follows:
cl , SH =
hr ,out − hr ,2
hr ,out − hr ,in
cl ,TP = 1 − cl , SH tr , SH , m =
tr ,out + tr ,2 2
tr ,m = cl , SH ⋅ tr , SH ,rm + cl ,TP ⋅ tr ,in
(9) (10) (11) (12)
2.3. Mathematical model of the solar hot water side Solar hot water flow and heat enthalpy difference calculation equation: Qy ,1 = m y (hy ,in − hy ,out )
(13)
hy ,in = c p ⋅ Ty ,in
(14)
hy ,out = C p ⋅ Ty ,out
(15)
Lateral flow calculation of solar hot water heat temperature difference equation: Qy ,2 = α y Ay ,out (t y ,m − t y ,m )
(16)
4055
Yin LiuY.etLiu al. // Procedia Procedia Engineering Engineering 00 15 (2011) (2011) 000–000 4052 – 4057
4
Side tube, solar hot water and heat transfer of refrigerant R22 for single-phase heat, heat transfer coefficients using standard Dittus-Boeler in turbulent pipe flow heat transfer coefficient [9]: 0.8
⎛ρ v d ⎞ λ α y = 0.023 ⎜ y y y ,in ⎟ ⋅ Pry0.4 ⋅ y ⎜ μ ⎟ d y ,in y ⎝ ⎠ t y ,m =
t y ,in − t y ,out 2
(17) (18)
In formula (1) - (19), Q is heat transfer, h is enthalpy; m is flow; d is diameter; C is specific heat; T and t are temperature; A is surface area; ρ is density; υ is kinematic viscosity; μ is dynamic viscosity; Pr is Prandtl number; λ is thermal conductivity; subscript a, y and r are air side, solar hot water side and refrigerant side respectively; 1 and 2 are enthalpy difference and temperature calculations respectively; in, out and m are import, export and average state, respectively; SH and TP are overheated zone and twophase region respectively; p is constant pressure. 2.4. Refrigerant side of the mathematical model Qe ,r = Qy + Qa
(19)
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Yin Liu/et al. / Procedia Engineering 15 (2011) 4052 – 4057 Y. Liu Procedia Engineering 00 (2011) 000–000
5
Where: Qe,r is total refrigerant R22 side heat; Qy is total solar hot water side of the heat; Qa is air side total heat transfer. 3. Simulation conditions To double-source composite heat pump system for simulation, in order to study heating performance of heat exchanger and its effect on the overall performance of heat pump system. Other parts are made of double-source composite heat pump system steady model, set in the heat exchanger from overheating of 5 ℃. Solar hot water flow for 0.2m3/h, the temperature is higher than the ambient air temperature 5 ℃. According to the GB/T 7725-2004 of the room air conditioner standards, selected three simulation conditions, where the outdoor environment temperature of heat exchanger (that is air heat source temperature) -7℃, 2℃ and -5℃ working for better research at low temperature of heat exchanger performance, select a group of outdoor ambient temperature -10℃ cryogenic conditions. 4. Results and analysis Fig. 2 is the different conditions of two heat pump heating performance curve. It can see from Fig. 2, double solar assisted hot water solar air-source heat pump in heating under various conditions to a single air-source heat pump system in cities have increased, and dual heat source heat pump hot water heating with solar energy traffic increases. When the outdoor air temperature of about 1.5℃, dual heat source heat pump heating can achieve a single air source heat pumps rated heating conditions (outdoor air temperature is 7℃) heat. When the outdoor temperature is -15℃, dual heat source heat pump heating capacity is increase near 40% of a single air source heat pump. Fig. 3 is a COP under different conditions two heat pump system performance curve. You can see from Fig. 3, double solar assisted hot water solar air-source heat pump in COP under various conditions to a single air-source heat pump systems have improved, and COP with dual heat source heat pump solar hot water flow increases and increases. When the outdoor air temperature of about 1.5℃, double COP can reach single heat source heat pump air heat pump rated heating condition COP. Dual heat source heat pump COP is increase near 30% of a single air source heat pump. 3.2
3000 2800 2600
single air two heat source
3.0 2.8 2.6
2200
2.4
2000
COP
Heating capacity (W)
2400
1800 1600
2.2 2.0
1400
1.8
1200
1.6
1000 800 -16 -14 -12 -10
Single air Two heat source
-8
-6
-4
-2
0
2
4
6
8
Air temperature (℃)
Fig. 2. Heating capacity curve in different working conditions
1.4 -16 -14 -12 -10
-8
-6
-4
-2
0
2
4
6
8
Air temperature (℃)
Fig. 3. COP in different heating conditions
5. Conclusion In solar air double heat source composite heat pump system, a air liquid combined heat exchanger is core part, the mathematical model of compound heat exchanger is foundation for simulation of the solar-
Yin LiuY.etLiu al. // Procedia Procedia Engineering Engineering 00 15 (2011) (2011) 000–000 4052 – 4057
6
air double heat source heat pump system, for fast simulation of system performance under different conditions, implementation and experimental research of complementary. Acknowledgements This work was supported by the Ministry of Science and Technology of Henan Province (072102240013, 082300460150 and 092102310188), the Open Research Foundation of the Western Architectural Science & Technology State Key Laboratory of China (10KF10) and Young Key Teacher Foundation of Zhongyuan University of Technology. References [1] Chai Q.H., Ma G.Y., State of knowledge and current challenges in the ASHP developed for the cold areas, Energy Engineering, 2002, (5)，25-31. [2] Tian CH. Q., Shi W. X., Research On Two-Stage Compression Variablefrequency Air Source Heat Pump In Cold Regions, Acta Energiae Solaris Sinica, 2004, 25(3), 388-393. [3] Tian Ch. Q., Shao Sh. Q., Shi W. X., Inverter Air Source Heat Pump, Fluid Machinery, 2005, 33(9), 67-71. [4] Wang H. B., Hu Y. F., Direct expansion solar assisted heat pump heating system Study, Coal Enginee, 2007, 11, 103-105. [5] Zhou G. H., Liu Y., Fin-bushing three-medium compound heat exchanger, 200720091299.1. [6] Zhou G. H., Liu Y., Dong X. J., Solar energy-geothermal energy double-heat source composite heat pump. 200710054878.3. [7] Ding G. L., Zhang C. L., Simulation and optimization of refrigeration and air conditioning equipment, Peking: Science Press, 2001. [8] Yu J. Z., Principle and design heat exchanger, Beijing: Aeronautics and Astronautics Press, 2006. [9] Yang Sh. M., Heat transfer, Peking: Higher Education Press, 1987.
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