Papers by Keyword: Natural Refrigerant

Abstract: At present, most air conditioners in an automotive use R134a as working fluid. Due to the negative impact on the environment, i.e. global warming, the refrigerant must be replaced by environmental friendly working fluid. Hydrocarbons are natural fluids, no effect on the climate, inexpensive and readily available. The hydrocarbon mixture used in the present study is R436A, composed of R290 (propane) and R600a (isobutane) with a mass ratio of 56/44. The results show that the drop-in substitute from R134a to R436A reduced COP by 4.84, 4.74 and 4.64% for the condenser temperature of 40, 45 and 50°C, respectively. To generate COP improvement on the drop-in substitute, subcooling was carried out, and results show that the COP improvement was 4.42, 5.20 and 6.09% for the condenser temperature of 40, 45 and 50°C, respectively.

Abstract: In this paper, the performances of natural refrigerant R290/CO2 cascaded refrigeration system using R290 as high temperature cycle refrigerant and CO2 as low temperature cycle refrigerant were investigated experimentally. The test results show that both CO2 compressor and R290 compressor start up stably and present good running performance. The start-up power and start-up electric current of CO2 compressor are higher than that of R290 compressor. The COP (Coefficient of performance) of R290/CO2 cascaded system enhances with the increase of cooling water mass flow rate and the decrease of cooling water inlet temperature. The effect of CO2 refrigerant charge on the COP of cascaded system is obvious; however, the effect of R290 refrigerant charge on the COP of cascaded system is not obvious. Hence, the hermetic scroll type compressor is urgent to be developed and used in CO2 cycle for ensuring run safely and reliably, the value of cooling water mass flow rate and the cooling water inlet temperature must be selected reasonability for saving water resource and energy, as well as the charge amount must be determined by experiment for obtaining the optimum refrigerant charge.

Abstract: With the question of Ozone Depression Potential and Global Warming Potential popping out day by day, the Freon refrigerant alternative has become one of the current research contents of refrigerant. Based on the given Freon refrigerant R22, R134a and natural refrigerant CO₂, the differences of their properties were compared, and the relevant alternative refrigerants conducted an investigation. The results show that the natural refrigerant CO₂ instead of Freon refrigerant has good application prospects; it provides basic data to develop new products, which enhance the COP of air conditioner and heat pump.

Abstract: The carbon dioxide (R-744) as a natural refrigerant has been an attractive alternative refrigerant to replace HFC (hydrofluorocarbon) refrigerants currently used in air conditioning systems, due to the environmental concerns. Because new compressors with CO2 are going to be operated under the high pressure, the tribology of sliding surfaces in the compressor becomes very important. To develop new compressor, especially scroll type, the friction and wear characteristics of sliding surfaces between a fixed scroll and an orbiting scroll in the scroll compressor were investigated in this paper. The sliding tests of pin-on-disk type were carried out between scroll surfaces under various sliding speeds, normal loads, surface roughness, and refrigerant pressures. Two types of lubricants were used, namely POE (polyol ester) oil and PAG (polyalkylene glycol) oil. The friction forces, wear amounts and surface temperatures were monitored during the tests. Test results showed that the wear amounts increased with increasing normal load and rotating speed, and also decreased with decreasing surface roughness. Also, the results of the sliding tests showed that using PAG oil has an advantage over POE oil in CO2 environment. As the pressure of CO2 refrigerant became higher, the amount of wear and coefficient of friction became larger in CO2/POE mixed environment, but wear and friction remained constant in CO2/PAG mixed environment. The wear coefficients in CO2/PAG and CO2/POE mixed environment were 8.60×10-9 ㎣/N·m and 2.35×10-8 ㎣/N·m, respectively.

Abstract: The carbon dioxide (CO2) is investigated as an alternative refrigerant to replace HFC (hydro fluorocarbon) refrigerants in refrigerators and air conditioning systems due to the environmental concerns. Because new compressors with the carbon dioxide are going to be operated under the high pressure, the tribology of sliding surfaces in the compressor becomes very important. To develop new compressors, especially rotary type, the friction and wear characteristics of sliding surfaces between a vane and a roller in the rotary compressor were evaluated in this paper. Several hard coatings, such as TiN, CrN, and WC/C, were applied on vane surfaces in order to improve the tribological characteristics, and their performances were evaluated experimentally. The vane-on-disk type sliding tests were carried out under the various sliding speeds, normal loads, and carbon dioxide pressures with an exclusive high pressure wear tester. From the tests wear volume of vane surfaces applied various coatings were compared. During the tests coefficients of friction and surface temperatures were monitored. Test results showed that WC/C coatings showed good tribological properties. TiN and CrN coated vanes showed good wear resistance properties but produced high friction.

Abstract: The tribology of lubricated sliding vanes in the rotary compressor was investigated to replace the HFC refrigerants by the carbon dioxide. The carbon dioxide is a natural refrigerant and very favorable to environment. Because new compressors with the carbon dioxide are going to be operated under the high pressure, the tribology of sliding surfaces in the compressor becomes very important. To develop new compressors, especially rotary type, the friction and wear characteristics of sliding surfaces between a vane and a roller in the rotary compressor were evaluated in this paper. Several hard coatings, such as TiN, CrN, WC/C and two types of nitridings, were applied on vane surfaces in order to improve the tribological characteristics, and their performances were evaluated experimentally. The vane-on-disk type sliding tests were carried out under the various sliding speeds, normal loads, and carbon dioxide pressures with an exclusive high pressure wear tester. From the tests wear volume of vane surfaces applied various coatings were compared. During the tests coefficients of friction and surface temperatures were monitored. Test results showed that WC/C coatings showed good tribological properties. TiN and CrN coated vanes showed good wear resistance properties but produced high friction.