Performance Evaluation of Two Azeotropic Refrigerant Mixtures of HFC-134a With R-290 (Propane) and R-600a (Isobutane)

1994 ◽  
Vol 116 (2) ◽  
pp. 148-154 ◽  
Author(s):  
M. S. Kim ◽  
W. J. Mulroy ◽  
D. A. Didion
Keyword(s):  
Performance Evaluation ◽  
Heat Pumps ◽  
System Capacity ◽  
Coefficient Of Performance ◽  
Mass Percentage ◽  
Air Conditioners ◽  
Refrigerant Mixtures ◽  
Hfc 134A ◽  
Environmentally Safe ◽  
R 134A

The reduction in chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC) production and the scheduled phase-out of these ozone-depleting refrigerants require the development and determination of environmentally safe refrigerants for use in heat pumps, water chillers, air conditioners, and refrigerators. This paper presents a performance evaluation of a generic heat pump with two azeotropic refrigerant mixtures of HFC-134a (1,1,1,2-tetrafluoroethane) with R-290 (propane) and R-600a (isobutane); R-290/134a (45/55 by mass percentage) and R-134a/600a (80/20 by mass percentage). The performance characteristics of the azeotropes were compared with pure CFC-12, HFC-134a, HCFC-22, and R-290 at the high temperature cooling and heating conditions including those using liquid-line/suction-line heat exchange. The coefficient of performance of R-290/134a is lower than that of HCFC-22 and R-290, and R-134a/600a shows higher coefficient of performance than CFC-12 and HFC-134a. The capacity for R-290/134a is higher than that for HCFC-22 and R-290, and R-134a/600a exhibits higher system capacity than CFC-12 and HFC-134a. Experimental results show that the discharge temperatures of the studied azeotropic mixtures are lower than those of the pure refrigerants, CFC-12 and HCFC-22.

Latent Heat Effects in Thermoelectric Air Conditioners and Heat Pumps Equipped With a Heat Exchanger

1996 ◽  
Vol 118 (3) ◽  
pp. 221-228 ◽  
Author(s):  
K. Chen ◽  
S. Suphasith
Keyword(s):  
Heat Exchanger ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Fluid Temperature ◽  
Transfer Coefficients ◽  
Air Conditioners ◽  
Cold Fluid ◽  
Heat Effects ◽  
The Difference ◽  
Air Conditioning Systems

The effects of moisture on the performance of thermoelectric air conditioning systems and heat pumps equipped with a heat exchanger were studied. Coefficients of performance and fluid temperature variations were calculated for heat capacity ratios from 1 to 10 and relative humidities ranging from 0 to 100 percent at the cold fluid inlet. Only the energy effects of the water condensation are considered as it is assumed that the heat transfer coefficients are those of a dry heat exchanger. It was found that different flow arrangements and the energy associated with condensation on the cold fluid side have no strong effects on the variation of the hot fluid temperature. The coefficient of performance decreases and the cold fluid exit temperature increases when condensation occurs. When the moisture content at the cold fluid inlet increases most of the cases studied show a decrease in the difference between the optimum and uniform current results. The difference among different flow arrangements also becomes smaller as more water vapor condenses in the cold flow.

Capacity Control for Refrigeration and Air-Conditioning Systems: A Comparative Study

2000 ◽  
Vol 123 (1) ◽  
pp. 92-99 ◽  
Author(s):  
Mohammad Yaqub ◽  
Syed M. Zubair
Keyword(s):  
Comparative Study ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Finite Size ◽  
Cooling Capacity ◽  
System Capacity ◽  
Coefficient Of Performance ◽  
Capacity Control ◽  
Hfc 134A

The capacity control of a vapor-compression refrigeration system is investigated for three different capacity control schemes. In a hot-gas by-pass control scheme, the refrigerant is by-passed from the compressor and injected back into the suction line to decrease the cooling capacity, whereas in cylinder-unloading scheme, one or more cylinders are unloaded to decrease the refrigerant mass flow rate in the system, which decreases the cooling capacity. However, in suction gas throttling, the suction gas throttled at the inlet of the compressor, decreases the refrigerant mass flow rate, and hence a corresponding decrease in the system capacity. These schemes are investigated for HFC-134a by considering finite size of the components that are used in the refrigeration systems. The models consider the finite-temperature difference in the heat exchangers, thus allowing the variations in the condenser and evaporator temperatures with respect to capacity and external fluid inlet temperatures. A comparative study is performed among these schemes in terms of the system coefficient of performance (COP), the operating temperatures, and percentage of refrigerant mass fraction as a function of the percentage of full-load system capacity.

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