Experimental and numerical investigation of a novel high-temperature heat pump for sensible and latent heat delivery

This paper investigates, both experimentally and numerically, the performance of a high-temperature heat pump (HTHP) prototype for steam production and thermal energy storage applications using R-1233zd(E) as a refrigerant. The main novelties of this prototype are the incorporation of an external subcooler to separate the sensible and latent heat production. Other novel points are the testing of a new variable-speed piston compressor that endures a discharge temperature of up to 160 degrees C, and the development of an advanced numerical model based on the components' specifications. In this temperature range there are very few detailed studies up-to-date. The proposed HTHP was tested experimentally in 50 different working points selected based on the compressor's limits and on the general requirements for industrial applications requiring heat at high temperatures, up to 150 degrees C. The results show that the proposed HTHP can deliver a total heat of 38.6 kW at 148.5 degrees C, within a temperature lift of 66.8 K, with an electric power consumption of 10.7 kW, and with a heating coefficient of performance (COP) of 3.6. Moreover, using the external subcooler resulted in a substantial increase in the COP, which can reach 33 % compared with similar HTHPs without a subcooler. After successfully validating the HTHP model with the experimental results, extended performance maps were developed based on more than 500 possible operating conditions covering the most common steam generation and energy storage applications. Finally, four performance correlations were obtained, with an accuracy of +/- 10 %, hereby providing a black-box model to ease the integration of such HTHPs into dynamic simulations of industrial processes.