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.

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.

Sustainability Study on GCHP Heating System in Severe Cold Area of China

2013 ◽  
Vol 411-414 ◽  
pp. 3084-3087
Author(s):  
Shu Zhang ◽  
Mao Yu Zheng
Keyword(s):  
Heat Pump ◽  
Thermal Load ◽  
Heating System ◽  
Coefficient Of Performance ◽  
Heating Effect ◽  
Pump System ◽  
Heat Pump System ◽  
Heating Performance ◽  
Long Time ◽  
Cold Area

In this paper, the mathematical models of a GCHP system and a Ground-couple heat pump system with air-soil thermal storage (GCHPASTS) were developed, and the 20-year performances of the two systems were simulated in severe cold area of china, respectively. The results show that the soil temperature declines gradually during the operation of a GCHP system, which leads to the decrease of the coefficient of performance (COP) and the heating effect of the heat pump year after year. On the contrary, the balance of ground thermal load can be realized during the operation of a GCHPASTS system, and the heating performance of heat pump is stable and efficient for long time. So, it can be proved that a GCHP system cant be used for heating alone, while a GCHPASTS system is feasibility.

Analysis of Single-Phase Convective Heat Transfer and System COP at Higher Power Levels in Thermoelectric-Based Hydronic Cooling and Heating Device

2009 ◽  
Author(s):  
Michael J. Kazmierczak ◽  
Abhishek Gupta
Keyword(s):  
Heat Transfer ◽  
Heat Pump ◽  
Flow Rate ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
System Component ◽  
Pump System ◽  
Heat Pump System ◽  
Higher Power ◽  
Te Modules

Experiments were performed on a heat exchanger equipped with multiple thermoelectric (TE) modules. The TE-HX serves as the basic system component in a simple hydronic modular Peltier heat pump system designed to provide chilled or hot water for domestic use (or supplementary building climate control) of small residences [1]. The present work focuses on the detailed convection analysis inside the TE-HX component when 10 thermoelectric modules are utilized. The local heat transfer coefficient at different points along the channel are measured at steady-state, first, when a continuous heater is installed and then when replaced with 10 TE modules. The experimental heat transfer coefficients obtained are compared with available empirical correlations for “transition” (3000 < ReDh < 7000) turbulent flow inside the channel with fair-to-good results. Next, the resulting coefficient-of-performance of the TE heat pump system is measured with its value depending both on system input power and water flow rate. Testing showed that performance degradation, i.e. reduced COPs, occurred when operated at higher power levels but remains satisfactory for up to 688 Watts with higher flow rate.

Heating Performance Investigations on Two Applications of a Solar Assisted Air Source Heat Pump System

2011 ◽  
Vol 374-377 ◽  
pp. 284-287 ◽  
Author(s):  
Yu Wang ◽  
Yu Wen You ◽  
Zhi Gang Zhang
Keyword(s):  
Heat Pump ◽  
Solar Collector ◽  
Coefficient Of Performance ◽  
Experimental Investigations ◽  
Pump System ◽  
Heat Pump System ◽  
Heating Performance ◽  
Air Source Heat Pump

A solar assisted air source heat pump (SAASHP) system is proposed to improve heating performance of air source heat pump (ASHP).The proposed system has been applied in two buildings, a series of experimental investigations were conducted in the both applications, it indicated that the SAASHP system gets better heating performance than ASHP system, the coefficient of performance (COP) gets 10% and 65% increase respectively in two applications. It is also concluded that the ratio of solar collector area to construction area significantly affects the improvement of heating performance in SAASHP system. This work may promote further research and more applications of SAASHP system.

Theoretical and Experimental Study on the Falling-Film Evaporator Applied to Mechanical Vapor Compression

2013 ◽  
Vol 753-755 ◽  
pp. 2667-2673 ◽  
Author(s):  
Wei Ke Pang ◽  
Lu Wei Yang ◽  
Zhen Tao Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Pump ◽  
High Efficiency ◽  
Film Flow ◽  
Falling Film ◽  
Vapor Compression ◽  
Pump System ◽  
Heat Pump System ◽  
Film Evaporator ◽  
Heat Transfer Efficiency

Based on a heat pump system of mechanical vapor recompression (MVR) designed and manufactured independently, the heat transfer performance of falling-film evaporator was measured by a combination way of theory analysis and experiment proving as the heat pump operated in practice. After the result of theoretical calculation is worked out, the start thickness and entrance velocity of the liquid film are established by adjusting the flux of raw solution. The result shows there is an optimization that the film thickness at the bottom of the tubes amounts to that of boundary layer of velocity. Additionally, it is a process of falling-film flow with heat and mass transfer between the start and end of falling-film. The last thickness of the falling film is about 0.21~0.44mm. The thickness of falling film when the falling-film flowed and heat exchange was over is compared with each other, and the effect of heat resistance on heat transfer is discussed also. It is showed that an optimal thickness is formed during the process of falling-film flow and evaporation, and disadvantages come up when it is not formed. The falling-film evaporator propelled by the MVR heat pump with low compression ratio carries through a process of strong and high-efficiency heat transfer with phase transition. It is because the states of produced vapor both before compressed and after compressed are saturated. Its heat-transfer coefficient may be as high as 1990 W/ (m2·K). The start and end thickness of falling film become great while the evaporation pressure goes up. It leads to the drop of the heat-transfer efficiency, so there is an optimization to the system in all probability.

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]

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.

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 An Experimental Study on External Ventilation to the Heating Performance of Household Air Source Heat Pump

2021 ◽  
Vol 9 ◽  
Author(s):  
Hang Zou ◽  
Zhanqiang Liu ◽  
Enshen Long
Keyword(s):  
Heat Pump ◽  
Great Influence ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Pump System ◽  
Heat Pump System ◽  
Heating Performance ◽  
Air Source Heat Pump ◽  
Ventilation Condition ◽  
Ventilation Conditions

The external ventilation conditions have a great influence on the heating performance of the air source heat pump (ASHP) systems. The outdoor units of residential household air source heat pumps are often installed in narrow spaces such as balconies. The ventilation conditions of the outdoor unit will influent the heating performance of the air source heat pump. It is necessary to study the effect of the outdoor unit ventilation conditions on the heating performance of residential household heat pumps. This paper experimentally studied the heating performances of an air source heat pump system with the outdoor unit mounted in a balcony in different external ventilation conditions. The results indicate that the ventilation conditions for the outdoor units have a significant effect on the heating performance of the system. When the inlet of the outdoor unit was close to the sliding door and completely blocked, the ventilation environment was the worst and the coefficient of performance (COP) was the lowest. In addition, the unfavorable ventilation environment could result in a reduction of the COP by 26.2%. When the inlet of the outdoor unit was partially blocked, the heating performance could be improved and the COP was also slightly improved. The great heating performance was obtained under the cross-ventilation condition. This paper can guide the design of the installation position of the household air source heat pump outdoor units in actual engineering.

Sign in / Sign up

Export Citation Format

Share Document