Household compressor, compressor efficiency, compressor test-stand
In Switzerland the efficiency of household refrigerators has to be proved by the manufacturer to get the energy label for the devices. The efficiency is tested in the beginning of the lifetime of the fridge and each component, respectively. Especially the compressor might assumedly reach its best performance not before some hours of operation. The exact knowledge about this characteristic is quite important for the manufacturer to optimize the products. Therefore, an automated compressor test stand was designed and built to test variable speed compressors on their evolution of isentropic and volumetric efficiencies. The test stand features three electronic expansion valves to control high and low pressure, and the suction gas temperature of the compressor, automatically. If necessary, an additional heater compensates for the non-isenthalpic pressure drop through the mass flow meter at the discharge of the compressor to enable high suction gas temperatures. Also, the ambient temperature of the device under test is controlled in its separate compartment. The power consumption of the compressor is detected with and without the controller to get additional information. The testing range is 20â€¦200 W cooling capacity with pressures of the refrigerant R600a down to the corresponding evaporation temperature of -35Â°C and condensing temperatures up to 55Â°C. The test-stand is equipped with high precision sensors to ensure measurement uncertainties of volumetric and isentropic efficiencies smaller than 5% over the whole range. This paper reports the design of the test stand as well as the control of the system.