15 May 2023

Presentation No 1133 – Exploration of Heat-Driven Ejector High-Temperature Heat Pumps – 14th IEA Heat Pump Conference, Chicago, USA

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Heat-driven ejector heat pumps use a supersonic ejector as a thermo-compressor to replace the mechanical
compressor. Supersonic ejectors have many advantages in high-temperature heat pump (HTHP) applications,
including high operating temperature tolerance, no need for lubrication, low maintenance, and low cost. The
coefficient of performance of ejector HTHPs could be improved by selecting binary fluids with unique
thermodynamic properties. Although supersonic ejectors have been widely used in refrigeration systems, their
application in spaces and water heating is limited. This study explores the theoretical potential of ejector
HTHPs with a sink temperature of 100°C–130°Cand a lift temperature of 10°C–30°C. Ejector HTHPs were
evaluated with single-fluid ejectors (SFEs) and binary-fluid ejectors (BFEs). A comprehensive, geometry-free
theoretical model of BFEs was developed to predict the theoretical maximum entrainment ratios. HFE7500
and R718 (water) were selected as working fluids for SFEs and BFEs. SFEs operating with R718 provided a
higher coefficient of performance of ejector HTHPs than SFEs operating with HFE7500 and BFEs. This study
preliminarily demonstrates the technical potential of ejector HTHP applications in recovering moderate-temperature heat sources.