High temperature heat pumps – An evaluation of the mutual influence between system and control design
High temperature heat pumps are essential in reaching the decarbonisation targets of the process industry, but there still exist several gaps before widescale application can be reached. One of them relates to increasing the supply temperatures, while achieving acceptable system performances and ensuring system reliability. To this end, combined design and control is key. The goal of this study is to investigate the mutual influence between the system and control design for a water-ammonia prototype applied in the 160 – 200 °C supply temperature range. Hence, this work develops a dynamic simulation model for the prototype and uses the model to evaluate the system’s behaviour under varying conditions. A sensitivity analysis on the sizing of the heat exchangers found a stronger sensitivity of the coefficient-of-performance (COP) on sizing the condenser when compared to the evaporator heat exchanger. Moreover, an evaluation on changing the control settings of the compressor, expansion valve and circulation pump at the heat source is performed. Results point out that changing both the control strategy and its control parameters are important key elements to take into account when optimising the design of high temperature heat pumps.