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.

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.

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.

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.

Experimental studies on direct expansion solar thermal heat pump systems using R430A as a substitute to R134a

2021 ◽  
pp. 095440892110209
Author(s):  
M Mohanraj ◽  
I M Kartheheyan
Keyword(s):  
Global Warming ◽  
Energy Consumption ◽  
Heat Pump ◽  
Energy Performance ◽  
Solar Thermal ◽  
Coefficient Of Performance ◽  
Direct Expansion ◽  
Pump System ◽  
Discharge Temperature ◽  
Heating Capacity

The use of halogen-based refrigerants in heat pump applications is restricted because of their high global warming potential (GWP). Therefore, it is necessary to identify a low GWP substitute for heat pump applications. This article presents the energy performance of a direct expansion solar thermal heat pump system (DXSTHPS) using R430A as an environmentally friendly substitute to phase out R134a. The effects of ambient parameters on compressor discharge temperature, compressor energy consumption, condenser heating capacity and coefficient of performance (COP) of a DXSTHPS using R134a and R430A are estimated and compared. Moreover, the total equivalent global warming impacts (TEGWI) of a DXSTHPS using R134a and R430A are evaluated. The results showed that the R430A has 0.7–1.9% lower compressor energy consumption than R134a. The condenser heating capacity and COP of a DXSTHPS using R430A are higher than R134a by 4.6–8.7% and 5.1–10.2%, respectively. The compressor discharge temperature observed in a DXSTHPS using R430A is 5.8 °C higher than R134a. The lubricant physical properties are retained at higher compressor operating temperatures, ensuring compressor reliability. The DXSTHPS using R430A has 4.2–12.9% lower TEGWI due to its lower GWP with lower compressor energy consumption than R134a.

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 Enhancing Heating Performance of Low-Temperature Air Source Heat Pumps Using Compressor Casing Thermal Storage

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3269 ◽  
Author(s):  
Zhongbao Liu ◽  
Fengfei Lou ◽  
Xin Qi ◽  
Yiyao Shen
Keyword(s):  
Low Temperature ◽  
Heat Pump ◽  
Waste Heat ◽  
Thermal Storage ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Pump System ◽  
Heat Pump System ◽  
Discharge Temperature ◽  
Vapor Injection

Air source heat pumps (ASHPs) are widely recognized as energy-saving and environmentally friendly heating and air-conditioning equipment with broad applications. However, when conventional ASHPs are operated at a low ambient temperature, they suffer from problems such as high discharge temperature and low heating efficiency. To address these problems, this study designed a new type of dual evaporator combined with a compressor casing thermal storage heat pump system (DE-CCTS) on the basis of a low-temperature air source heat pump water heater with enhanced vapor injection (EVI). The proposed DE-CCTS used thermal storage phase change material (PCM), which was filled in the secondary evaporator (the thermal storage heat exchanger), to recover the waste heat of the compressor casing. Unlike that in the original system under different ambient temperatures, the suction temperature increased by 0.1–1 °C, the discharge temperature decreased by 0.1–0.5 °C, and the coefficient of performance (COP) of DE-CCTS increased by 0.85–4.72% under the proposed system. These effects were especially evident at low temperatures.

Influences of Variable Mass Flowrate of Refrigerant Blend R125/R290 on Heat Pump Performance

2015 ◽  
Author(s):  
Fang Wang ◽  
Xiaowei Fan ◽  
Zhuangyu Guo ◽  
Lu Zhang ◽  
Huiyan Zheng
Keyword(s):  
Heat Pump ◽  
Variable Mass ◽  
Coefficient Of Performance ◽  
Pinch Point ◽  
Pump System ◽  
Heat Pump System ◽  
Discharge Temperature ◽  
Mass Flowrate ◽  
The One ◽  
Compressor Power

The off-design experimental performances of heat pump system using R125/R290 (25/75, mass fraction) blend are investigated by varying the mass flowrate of refrigerant blend. The influences of variable mass flowrate upon system coefficient of performance (COP), discharge temperature, temperature glide (GT) and temperature profile in condenser are analyzed, the system performance comparisons between R125/R290 and substituted refrigerant R22 are carried out. The results show that when the blend mass flowrate increases, compressor power increases linearly, the COP linearly increases at first and then gradually decreases, and an optimum COP of 3.04 is obtained when mixture mass flowrate reaches 1.12 kg/min. The compressor discharge temperature is almost decreased linearly whereas specific mass heating capacity is increased firstly and then it has a drop. The temperature differences between refrigerant and water at the inlet and in the middle of the condenser is gradually increased while the one at the outlet is decreased gradually with a heat transfer pinch point kept in the middle of the heat exchanger. Compared with that of R22, the overall performance has proved that the new refrigerant blend could be a promising substitute for R22, which are of significance for the application of the new refrigerant blends used in heat pump system.

TECHNOLOGY REVIEW OF TWO-STAGE VAPOR COMPRESSION HEAT PUMP SYSTEM

2013 ◽  
Vol 21 (03) ◽  
pp. 1330002 ◽  
Author(s):  
KOJO ATTA AIKINS ◽  
SANG-HYEOK LEE ◽  
JONG MIN CHOI
Keyword(s):  
Heat Pump ◽  
High Efficiency ◽  
Industrial Applications ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Two Stage ◽  
Pump System ◽  
Heat Pump System ◽  
Discharge Temperature ◽  
Increasing Demand

There is increasing demand for domestic and industrial refrigeration, space heating and air conditioning. Heat pump systems offer economical alternatives for recovering heat from different sources for use in these applications. As a renewable energy technology for sustainable environment, the heat pump's high efficiency and low environmental impact have already drawn a fair amount of attention all over the world. Some of these domestic and industrial applications require very low evaporating temperatures and very high condensing temperatures which induce high compressor pressure ratios beyond the practical range for single-stage heat pump cycles. These high pressure ratios also produce low coefficient of performance (COP) values and expose the compressor to high discharge temperature, low volumetric efficiency and damage. However, this challenge can be overcome by adopting two-stage heat pump cycles. In this paper, recent works on two-stage heat pump systems for various applications are reviewed. They include two-stage cycle with intercooling, two-stage cycle with refrigerant injection and two-stage cascade cycle. Research and innovative designs of systems that make use of these two-stage cycles have been able to get heat pumps to handle applications with lower and higher temperatures, while enhancing heating capacity up to 30% and COP up to 31%.

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