Vapour compression refrigeration is used in almost 80 % of the refrigeration industries in the world for refrigeration, heating, ventilating and air conditioning. The high-grade energy consumption of these devices is very high and the working substance creates environmental problems due to environmental unfriendly refrigerants such as chloroflurocarbons, hydrochloroflurocarbons and hydroflurocarbons. Heating, ventilating, air conditioning and refrigeration industries are searching for ways to increase performance, durability of equipments and energy efficiency in a sustainable way while reducing the cost of manufacturing. With the present refrigerants, environmental problems such as ozone layer depletion, global warming potential, green house gases and carbon emission are increasing day by day. In this paper, the popular refrigerant is thoroughly studied experimentally and recommendations are given for alternatives such as carbon dioxide, ammonia and hydrocarbons and new artificially created fluid, HydroFluoro-Olefin 1234yf by DuPont and Honeywell which exhibit good thermo-physical and environmental properties and will be commercialized in the near future.
An experimental performance study on vapour compression refrigeration system with R134a and drop in substitute R152a with aluminium microchannel condenser was carried out for condensation temperature of 48°C while evaporation temperature varied from -10 to 15°C. Refrigerant charge of R152a was reduced by 40% over R134a with the microchannel condenser. Performance parameters like work input to the compressor, coefficient of performance, refrigerating capacity, condenser capacity and the product of the overall heat transfer coefficient & surface area of the condenser are plotted and results are discussed.
A jet pump or an ejector uses primary fluid flow as motive fluid to entrained secondary fluid. In this paper, the main intention is to find suction flow rate, primary flow rate, secondary flow rate, loss factors and ejector efficiency for an applied pressure. The values of the different loss factors estimated are primary nozzle loss factor (Kp)=0.06, suction loss factor (Ks)=0.04-0.1, mixing loss factor (Km)=0.07-0.1 and diffuser loss factor (Kd)=0.0289. It is found that with the increase in pressure across the ejector, efficiency increases with increase in flow ratio and decrease in pressure ratio.
Versatile vapor compression refrigeration system is designed, developed and fabricated such that desired condensing and evaporating temperatures can be obtained by providing different electronic controls for superheating, subcooling, fan speed, air heaters and water heaters to use alternative refrigerants to R134a such as R1234ze, R152a, R600a, R290 and R290/R600a (50/50%) with conventional and minichannel condenser. All the refrigerant are tested for condensing temperature ranging from 40 °C to 55 °C while evaporating temperature changes from -10 °C to 15 °C for both condensers. The total exergy loss for main system components such as compressor, condenser, expansion valve and evaporator are calculated. It is found that condenser represented maximum exergy loss in all refrigerants for conventional and minichannel condenser. The total exergy loss is more for conventional condenser than minichannel condenser for all refrigerants while R1234ze represented minimum exergy loss. Exergy efficiency for minichannel condenser is more than conventional condenser for R1234ze over other refrigerants at all condensing and evaporating temperatures. The condensation temperature reduced by 3 °C with the minichannel condenser over conventional condenser resulted into increase in coefficient of performance (COP) by 10% to 15% for different evaporating temperatures. Thus, it is concluded that R1234ze is direct drop-in substitute to R134a as compared to R152a, R600a, R290 and R290/R600a (50/50%) considering exergy loss, exergy efficiency and COP with minichannel condenser over conventional condenser.
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