Development of a cascaded R-717 / R-601 heat pump for heat supply above 160 °C – integration of industrial waste heat
High-temperature heat pumps are a key technology for the defossilization of industrial processes. The decision to deploy a heat pump is primarily dependent on the required temperature lift, which significantly influences the coefficient of performance (COP) of the system. With the increasing need for efficient solutions, advanced heat pump cycle architectures and the effective utilization of waste heat are becoming more important. This study presents the development of a cascaded high-temperature heat pump using R-717 (ammonia) as refrigerant in the low-temperature stage and R-601 (pentane) in the high-temperature stage, with the intention of providing heat above 160 °C with a temperature lift of up to 170 K. The architecture incorporates a threestage compression cycle with oil-injected screw compressors. The system is investigated using a numerical model. The various components were modelled based on the manufacturer's specifications and then validated using corresponding measurement data. The study examines the effects of integrating waste heat from industrial processes at a temperature level above the regular heat source temperature as well as the opportunities and challenges arising from the use of oil-cooled screw compressors.