Energy consumption is still growing worldwide and due to the problems of global warming, sustainable developments become of more importance. Heat pumps are one of the technologies that can contribute to energy savings of industrial processes, for example by heat recovery from waste water streams. The focus of this research is to improve the performance of these heat pump systems.
The compression-resorption heat pump (CRHP) can be distinguished from a traditional vapor-compression heat pump (VCHP) by operating with non-azeotropic mixtures and an incomplete evaporation in the desorber. The working fluid enters the compressor as a two-phase mixture. This type of compression is known as wet compression. The efficiency of the wet compression process has significant influence on the performance of the complete heat pump system. Ammonia water mixtures are often used in this type of heat pump systems. A new mixture, NH3-H2O-CO2, has been proposed in order to increase the performance of CRHPs. However this improvement can only be reached if the compressor efficiency is not negatively influenced by the addition of CO2.
A wet compressor model operating with NH3-H2O-CO2 is developed in order to predict the efficiency of the compressor. The model indicates improvements on the isentropic efficiency of the compressor with NH3-H2O-CO2 compared to ammonia water up to 3.5 %. With the compressor model heat pump applications can be investigated by taking into account the efficiency of the compressor, predicted with the model. Especially for heating applications, improvements on the heat pump system operating with NH3-H2O-CO2 are indicated. Experimental validation of the compressor model is the next important step at this point.