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The refrigerants being used in vapor compression processes have specific thermodynamic properties, which are decisive for the performance of the compressor of the system. The Montreal and the Kyoto protocols initiated a discussion of alternative refrigerants, which lead to new requirements of the compressor. The reliability of reciprocal compressor...
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... to the low charge of refrigerant, the method can be a useful tool in investigating compressors behaviour when using alternative refrigerants for which refrigerant charge of the plant is submitted to prescriptions, hydrocarbons for example. Figure 4 shows the cycle layout and the P-h diagram. Convention compressor bench tests using load stands, generally require from 2000 hours to 4000 hours (12 to 24 weeks). ...
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The parameters required to calculate the energy efficiency of household refrigerating appliances (i.e. refrigerators, freezers and their combinations) are determined by standard measurements. According to regulations, these measurements are carried out when the appliances are new. It is known from previous studies that various technical aging mechanisms can increase electrical energy consumption by up to 36 % over a product lifespan of 18 years. In order to determine the time dependence of the energy consumption of household refrigerating appliances, repeated measurements are carried out in this work. Eleven new appliances are examined under standard measurement conditions. After just two years of operation, an additional energy consumption of up to 11 % is determined. Furthermore, 21 older appliances that had previously been measured in new condition are tested again after up to 21 years of operation. For these older appliances, an average increase of energy consumption of 28 % is found. For individual appliances, the maximum increase is 36 %. An aging model is developed on the basis of these measurement results, which may help to predict the aging-related increase of energy consumption of household refrigerating appliances. This model shows an average increase in electrical energy consumption of 27 % for an appliance age of 16 years. Supplemental performance tests of eight compressors do not show any significant aging effects related to these devices after two years of operation. Furthermore, measurements of the thermal conductivity of aged polyurethane foam test samples are carried out and an increase of its thermal conductivity of 26 % over a period of about three years is determined.
Hermetic compressors are essential components of domestic refrigerators and freezers and are usually designed to operate in ambient temperatures under 32°C. This study measures the discharge and shell temperatures of hermetic compressors at different ambient temperatures. To this end, calorimetric tests are conducted in three different hermetic compressors to define the impact of tropical ambient temperatures on the discharge and shell temperatures. Environmental temperatures of 35, and 38°C and voltages of 93, 115, and 127 V were considered during the tests. Thi results are compared to the nominal parameters at 32°C and 115V. Furthermore, to identify if the wear-out of the different components affect the discharge and shell temperatures, the three compressors were tested in the calorimeter after an accelerated life test. In all cases, the evaporation temperature was controlled at -23 °C. Results show that the discharge and shell temperatures of hermetic compressors increase with the ambient temperature. Additionally, it is evidenced that the technology of hermetic compressors strongly influences the discharge and shell temperatures.
