Heat pump coefficient of conversion and power on off-nominal modes

The article considers the variation of heat pump (HP) compression parameters which define its effectiveness: power and coefficient of conversion (μ) on off-nominal modes of operation. Taking into account that the parameters of low-potential sources of heat for HP change, the demand for thermal energy also changes; study of HP operating on off-nominal modes is relevant. To analyze the operating process on partial power modes of HP, a reciprocating compressor is used. The following options are examined by authors as conditions of HP transitioning to the off-nominal mode: change in temperature of water at the condenser inlet; change in flow rate of water passing through the condenser, change in flow rate of the working medium. Based on the analysis of relationships for determining the coefficient of conversion and power consumed by HP, it is shown that these parameters change if HP transitions to off-nominal mode. The increase of temperature entering the condenser leads to decrease in μ, and with temperature decrease μ increases. Decrease in flow rate of water cooling the condenser moves the beginning point of compression of the working medium to higher moisture region and reduces the efficiency of the compressor. Working medium flow rate decrease virtually does not affect the Carnot cycle efficiency and μ decreases because of rising moisture of gas.