Performance Assessment of Blends of CO2 With Eco-Friendly Working Fluids for Heat Pump Applications

2013 ◽  
Author(s):  
Xiaowei Fan ◽  
Xianping Zhang ◽  
Xinli Wei ◽  
Fang Wang ◽  
Xiaojing Zhang
Keyword(s):  
Heat Pump ◽  
Mass Fraction ◽  
Experimental Results ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Outlet Temperature ◽  
Pump System ◽  
Heat Rejection ◽  
Working Fluids ◽  
Optimum Heat

Since pure CO2 as refrigerant has some disadvantages failing to meet requirements, binary blends of CO2 (or R744) with other eco-friendly working fluids, R290, R1270, R170, RE170 and HFC134a are proposed in this paper to be used for medium temperature heat pump systems. The eco-friendly refrigerant mixtures can reduce the heat rejection pressure as that for pure CO2, and meanwhile suppress the flammability, explosivity as that for pure HCs or RE170. Based on the pinch point of heat transfer, the numerical models of heat pump cycle using CO2-based mixture are developed. With a comprehensive consideration of heating coefficient of performance (COPh), optimum heat rejection pressure, volumetric heating capacity, discharge temperature, the binary mixture CO2/R290 is determined as the most suitable working fluid for the given heat pump application. Compared to pure CO2, the optimum heat rejection pressure of mixture for 95/5, 90/10, 85/15 and 80/20 is decreased by 0.82, 0.94, 1.06 and 1.86MPa respectively for heat sink outlet temperature of 65°C. The experimental testrig is designed and set up for the transcritical heat pump system. The experimental study with different CO2 mass fraction has been carried out, which conducts a study on the variations of heat pump performance, component’s mass fraction and working fluid charge. The experimental results validated the CO2/R290 natural mixture proposed in theory. The experimental results provide useful references on the optimization and improvement of CO2/R290 heat pump testrig.

scholarly journals Theoretical study of heat pump system using CO2/dimethylether as refrigerant

2013 ◽  
Vol 17 (5) ◽  
pp. 1261-1268 ◽  
Author(s):  
Xiao-Wei Fan ◽  
Xian-Ping Zhang ◽  
Fu-Jun Ju ◽  
Fang Wang
Keyword(s):  
Heat Pump ◽  
Mass Fraction ◽  
Coefficient Of Performance ◽  
Space Heating ◽  
Water Heater ◽  
Pump System ◽  
Heat Rejection ◽  
Volumetric Heating ◽  
Heat Pump System ◽  
Heating Capacity

Nowadays, HCFC22 is widely used in heat pump systems in China, which should be phased out in the future. Thus, eco-friendly mixture CO2/dimethylether is proposed to replace HCFC22. Compared with pure CO2 and pure dimethylether, the mixture can reduce the heat rejection pressure, and suppress the flammability and explosivity of pure dimethylether. According to the Chinese National Standards on heat pump water heater and space heating system, performances of the subcritical heat pump system are discussed and compared with those of the HCFC22 system. It can be concluded that CO2 /dimethylether mixture works efficiently as a refrigerant for heat pumps with a large heat-sink temperature rise. When mass fraction of dimethylether is increased, the heat rejection pressure is reduced. Under the nominal working condition, there is an optimal mixture mass fraction of 28/72 of CO2/dimethylether for water heater application under conventional condensation pressure, 3/97 for space heating application. For water heater application, both the heating coefficient of performance and volumetric heating capacity increase by 17.90% and 2.74%, respectively, compared with those of HCFC22 systems. For space heating application, the heating coefficient of performance increases by 8.44% while volumetric heating capacity decreases by 34.76%, compared with those of HCFC22 systems. As the superheat degree increases, both the heating coefficient of performance and volumetric heating capacity tend to decrease.

scholarly journals Binary blend of carbon dioxide and fluoro ethane as working fluid in transcritical heat pump systems

2015 ◽  
Vol 19 (4) ◽  
pp. 1317-1321
Author(s):  
Xian-Ping Zhang ◽  
Fang Wang ◽  
Xiaowei Fan ◽  
Yong-Fei Xue
Keyword(s):  
Carbon Dioxide ◽  
Heat Pump ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Binary Blend ◽  
Pump System ◽  
Heat Rejection ◽  
Volumetric Heating ◽  
Operation Conditions ◽  
Discharge Temperature

As an eco-friendly working fluid, carbon dioxide or R744 is expected to substitute for the existing working fluids used in heat pump systems. It is, however, challenged by the much higher heat rejection pressure in transcritical cycle compared with the traditional subcritical cycle using freons. There exists a worldwide tendency to utilize blend refrigerants as alternatives. Therefore, a new binary blend R744/R161 in this research is proposed in order to decrease the heat rejection pressure. Meanwhile, on mixing R744 with R161, the flammability and explosivity of R161 can be suppressed because of the extinguishing effect of R744. A transcritical thermodynamic model is developed, and then the system performances of heat pump using R744/R161 blend are investigated and compared with those of pure R744 system under the same operation conditions. The variations of heat rejection pressure, heating coefficient of performance, unit volumetric heating capacity, discharge temperature of compressor and the mass fraction of R744/R161 are researched. The results show that R744/R161 mixture can reduce the heat rejection pressure of transcritical heat pump system.

The Experimental Investigation and Theoretical Analysis on Transcritical Carbon Dioxide Heat Pump Cycle

2012 ◽  
Vol 455-456 ◽  
pp. 240-245
Author(s):  
Lu Xiang Zong ◽  
Jian Lin Liu ◽  
Xue Shi ◽  
Ying Bai Xie
Keyword(s):  
Carbon Dioxide ◽  
Experimental Investigation ◽  
Theoretical Analysis ◽  
Heat Pump ◽  
Coefficient Of Performance ◽  
Pump System ◽  
Working Fluids ◽  
Heat Pump System ◽  
Exit Temperature ◽  
Transcritical Carbon Dioxide

The (H)CFC-phase out and the fear for future problems for other synthetic working fluids, because of their known and unknown impact on the environment, have introduced a rising interest in environmentally safe natural working fluids. CO2is one of the few non-toxic and non-flammable working fluids that do not contribute to ozone depletion or global warming, if leaked to the atmosphere. Because the critical temperature of CO2is only 31.1°C, the transcritical cycle can be used to improve the coefficient of performance of the system. The experimental investigation and theoretical analysis on transcritical carbon dioxide heat pump system are carried out in this paper. It points out that there is an optimum operational pressure on transcritical carbon dioxide heat pump cycle, when the outlet temperature of gas cooler is constant, the coefficient of performance increases with increasing evaporating temperature at the same conditions, and the operational efficiency increased with decrease of gas cooler exit temperature. So in order to obtain the optimum performance, the influence of evaporating temperature, gas cooler exit temperature, and the operational pressure should be considered during the designing and operating transcritical carbon dioxide heat pump system.

Absorption Heat Pump/Refrigeration System Utilizing Ionic Liquid and Hydrofluorocarbon Refrigerants

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Sarah Kim ◽  
Yoon Jo Kim ◽  
Yogendra K. Joshi ◽  
Andrei G. Fedorov ◽  
Paul A. Kohl
Keyword(s):  
Ionic Liquid ◽  
Heat Pump ◽  
Waste Heat ◽  
Working Fluid ◽  
Coolant Temperature ◽  
Low Grade ◽  
Outlet Temperature ◽  
Refrigeration System ◽  
Pump System ◽  
Absorption Heat Pump

The ionic liquid butylmethylimidazolium hexafluorophosphate (bmim)(PF6) and five different hydrofluorocarbon refrigerants were investigated as the working fluid pairs for a waste-heat driven absorption heat pump system for possible applications in electronics thermal management. A significant amount of the energy consumed in large electronic systems is used for cooling, resulting in low grade waste heat, which can be used to drive an absorption refrigeration system if a suitable working fluids can be identified. The Redlich–Kwong-type equation of state was used to model the thermodynamic conditions and the binary mixture properties at the corresponding states. The effects of desorber and absorber temperatures, waste-heat quality, and system design on the heat pump performance were investigated. Supporting experiments using R134a/(bmim)(PF6) as the working fluid pair were performed. Desorber and absorber outlet temperatures were varied by adjusting the desorber supply power and the coolant temperature at the evaporator inlet, respectively. For an evaporator temperature of 41 °C, which is relevant to electronics cooling applications, the maximum cooling-to-total-energy input was 0.35 with the evaporator cooling capability of 36 W and the desorber outlet temperature in the range of 50 to 110 °C.

Thermoeconomic Analysis on the Performance Characteristics of a Multi-Stage Irreversible Combined Heat Pump System

2000 ◽  
Vol 122 (4) ◽  
pp. 212-216 ◽  
Author(s):  
Jincan Chen ◽  
Chih Wu
Keyword(s):  
Heat Transfer ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Power Input ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Pump System ◽  
Heat Pump System ◽  
Maximum Profit ◽  
Multi Stage

A cycle model of a multi-stage combined heat pump system, which includes the irreversibility of finite rate heat transfer across finite temperature differences and the irreversibilities inside the working fluid, is established and used to investigate the influence of these irreversibilities on the performance of the system. The profit of operating the heat pump system is taken as an objective function for optimization. The maximum profit is calculated for a given total heat transfer area or total thermal conductance of heat exchangers. The coefficient of performance, heating load, and power input at the maximum profit are determined. The distribution of the heat transfer areas or the thermal conductances of heat exchangers and the temperature ratios of the working fluids of two adjacent cycles in heat exchange processes are optimized. The results obtained here are generally significant. They are suitable for an arbitrary-stage irreversible and endo- reversible combined heat pump system. [S0195-0738(00)01104-3]

Heating Performance of Zeotropic Mixture and Temperature Glide Matching with Secondary Fluid

2011 ◽  
Vol 474-476 ◽  
pp. 1657-1660
Author(s):  
Xian Ping Zhang ◽  
Fang Wang ◽  
Huan Lin Duan ◽  
Ai Dong Chen
Keyword(s):  
Heat Transfer ◽  
Mass Fraction ◽  
Transfer Efficiency ◽  
Coefficient Of Performance ◽  
Heat Transfer Fluid ◽  
Pump System ◽  
Heat Rejection ◽  
Heat Pump System ◽  
Heating Performance ◽  
Heat Transfer Efficiency

In order to decrease the heat rejection pressure of pure CO2 refrigerating system and meanwhile have sustainable environmentally benefits for working fluild, several natural zeotropic CO2/Propane mixtures are applied to heat pump system to investigate the heating performance. The heat rejection pressure of CO2/Propane mixtures is reduced when the mass fraction of carbon dioxide is decreased. Under the given conditions, there is an optimum range of mass fraction of CO2/Propane of which the mixtures have superior heating coefficient of performance. The temperature glide characteristics of CO2/Propane mixtures at heating mode was also researched to analyze the heat transfer efficiency. Both a sufficient heat exchange area and a good working fluid’s temperature gradient matching with that of the secondary heat transfer fluid contribute to a higher heat transfer efficiency of heat exchanger.

Vortex Tube Expansion Two-Stage Transcritical CO2 Refrigeration Cycle

2012 ◽  
Vol 516-517 ◽  
pp. 1219-1223 ◽  
Author(s):  
Ying Fu Liu ◽  
Guang Ya Jin
Keyword(s):  
Mass Fraction ◽  
Vortex Tube ◽  
Coefficient Of Performance ◽  
Refrigeration Cycle ◽  
Outlet Temperature ◽  
Two Stage ◽  
Evaporation Temperature ◽  
Optimum Heat ◽  
Tube Expansion ◽  
Cold Mass

Use of vortex tube as an expansion device in transcritical CO2 cycle could reduce the throttle loss and improve the coefficient of performance. In this paper, a vortex tube expansion two-stage transcritical CO2 refrigeration cycle(VTTC) is established and compared to that of the two-stage transcritical CO2 refrigeration cycle with throttle valve(TVTC). Thermodynamic analysis results indicate that there is also an optimum heat rejection pressure for the vortex tube cycle, and the COP improvement is 2.4%~16.3% at given conditions. Decrease in evaporation temperature or increase in gas-cooler outlet temperature decrease the COP, but the COP improvement will increase. The effect of cold mass fraction on the COP is negligible, but the COP improvement will increase fast with the increase of cold mass fraction.

scholarly journals Performance evaluation of heat pump system using R744/R161 mixture refrigerant

2014 ◽  
Vol 18 (5) ◽  
pp. 1673-1677
Author(s):  
Xian-Ping Zhang ◽  
Xin-Li Wei ◽  
Xiao-Wei Fan ◽  
Fu-Jun Ju ◽  
Lei Yang
Keyword(s):  
Heat Pump ◽  
Mass Fraction ◽  
Variable Mass ◽  
Heat Pumps ◽  
Montreal Protocol ◽  
Coefficient Of Performance ◽  
Pump System ◽  
Heat Pump System ◽  
Conservation Technology ◽  
Phase Out

As an efficient and energy conservation technology, heat pumps working with R22, which are scheduled to be phased out by Montreal Protocol, are widely used in China at present. The global deteriorating ecology environment would accelerate the phase-out time of R22 in developing countries. Therefore, as a matter of urgency, an eco-friendly substitute should be investigated in order to replace R22. Under this context, and with a consideration of the environmental protection, R744/R161 mixture refrigerant is proposed. R744/R161 mixture refrigerant?s condensation pressure is reduced and its flammability and explosivity are suppressed. A thermodynamic model is developed, and under the given working conditions, the performances of subcritical heat pump system using R744/R161 mixture of variable mass fraction are discussed and compared with those of the R22 system. The optimal mass fraction of R744/R161 is given, which corresponds to a maximal heating coefficient of performance. The simulation results show that R744/R161 mixture can work as a competitive alternative to R22 in heat pump system.

Development and Experimental Study of New Working Fluids for Moderate-High-Temperature Heat Pumps

2012 ◽  
Vol 468-471 ◽  
pp. 1313-1321
Author(s):  
Shi Jie Liu ◽  
Wen Sheng Yu ◽  
Wu Chen
Keyword(s):  
High Temperature ◽  
Heat Pump ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Working Fluid ◽  
Working Fluids ◽  
Heating Efficiency ◽  
Temperature Heat ◽  
Performance Results ◽  
High Temperature Heat Pump

Some suggestions for developing new working fluids for moderate-high-temperature heat pump with excellent thermal and environmental performance were given firstly in this paper. The theoretical and experimental performance analysis of new-developed working fluids M1-M6 was carried out. The theoretical performance results showed that M1-M6 had high heating efficiency and GWP (Global Warming Potential) of M2 was less than 150. The experimental results showed that M5 had higher thermal efficiency than other two working fluids under same working condition. At the ambient temperature respectively of 30 Centigrade Degree and 40 Centigrade Degree, it took 70 and 65 minutes by the heat pump charged with M5 as working fluid to heat 100 liters of water respectively from 30 Centigrade Degree to 80 Centigrade Degree. Meanwhile the system’s COP (Coefficient of Performance) was respectively 2.9 and 3.0.

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