Experimental Study of the Compressor in a R410a Heat Pump Water Heater System

Nowadays, energy saving is a worldwide task under the pressure of the global energy crisis. Heat pump water heaters (HPWH) are more efficient than traditional boilers and electric heaters and therefore attack more and more attentions. As a key componet, the compressor plays an important role in the HPWH system. To valuate the performance of a HPWH system, the compressor should be studied in details. In this paper, an experimental bench for the R410a HPWH with a variable speed compressor was developed. Subsequently, the volumetric efficiencies and the isentropic efficiencies of the compressor, whose frequency varied from 40Hz to 120Hz under different experimental conditions, were studied with the experimental bench. The experimental results indicted that the values of the volumetric efficiency varied from 0.60 to 0.80 and the values of the isentropic efficiency varied from 0.65 to 0.90. A new model was proposed in this paper to calculate the volumetric efficiencies and the isentropic efficiencies of the compressor under different working conditions and then was tested with the experimental data. For the calculation of the volumetric efficiencies, the average absolute deviation was 3.901% and the maximum deviation was 8.344%. For the calculation of the isentropic efficiencies, the average absolute deviation and the maximum deviation were 3.065% and -7.871%, respectively. It can be concluded that the compressor can work well under all the HPWH conditions and the new model can also work well in the calculation of the compressor performance.