Models for unitary air conditioners and heat pumps typically have difficulties in providing accurate predictions for the following situations: 1) charge modeling over a large range of charge levels, 2) two-phase refrigerant entering fixed-orifice expansion devices, 3) two-phase refrigerant entering compressors, and 4) non-uniform refrigerant mass flow allocation among evaporator circuits at low...

Refrigeration oil and other materials used with refrigerant for refrigerators or air conditioners should have thermal and chemical stability to maintain the system reliability. Some kinds of synthetic oil are used for alternative refrigerant, HFC’s and hydrolysis, material compatibility, and low-temperature extraction of contaminant or sludge are important subjects. Much more numbers and times ...

More than one year has passed since refrigerant for refrigerator was changed from CFC12 to HFC134a. Long term reliability of refrigerator in HFC134a refrigerant system is mainly dependent on lubrication of moving parts of compressor and clogging of capillary tube. To maintain better practical reliability in components in compressor such as refrigeration lubricant,metallic materials and motor in...

Fin-tube heat exchangers are widely used in air-conditioners and heat pumps, which are constructed with a lot of tubes. Refrigerant circuit of heat exchanger with numerous pipe can be constructed by many methods. Refrigerant circuit design is usually determined designer’s experience and case by case test without guides. The number of path affects largely on heat exchanger performance. In this p...

  A refrigeration cycle is a chain of various pieces of equipment including compressors, condensers, evaporators, and expansion devices each of which takes on a particular thermodynamic process duty in the cycle that eventually results in the production of the required refrigeration. The results of optimized mixed refrigerant cycles (MRCs) in Part I show that the configuration of MRC is an eff...

CFD was applied to evaluate the performance of both existing and improved designs for refrigerant distributors. In general, it is better to utilize a spherical base as compared with other shapes and to locate the orifice close to distributor base. These changes tend to improve the robustness of the distributor in terms of providing even flow and phase distribution in different outlet branches w...

refrigerants that are used in refrigeration systems, cause environmental difficulties such as depletion of ozone layer and greenhouse effect. thus, we must find substitutes for such refrigerants, in this paper, the effect of refrigerant on the thermodynamics performance of refrigeration cycles are studied. to do this, a refrigerator that has designed for r12, is simulated. results show that pur...

Knowledge of the solubility characteristics of an oiVrefrigerant mixture is important when analyzing the lubrication system behavior in refrigerant compressors since the solubility significantly affects the viscosity of the mixture. For an operating compressor, the lubricant is a mixture of oil and refrigerant and the viscosity of the mixture is a strong function of the refrigerant concentratio...

There is no single perfect refrigerant for diverse air conditioning, refrigeration, and industrial applications. The predominant halocarbons (CFCs, HCFCs, and HFCs) combine excellent efficiency and safety with acceptable costs. However, they contribute to ozone depletion potential (ODP) and/or global warming potential (GWP). The Montreal Protocol has eliminated ODP by requiring replacement of C...