Design and off-design performance of a high temperature heat pump with ejector

We are aiming to develop a high temperature heat pump using R1233zde as refrigerant by using an ejector as work recovery measure instead of an expansion valve. Based on the design condition at 50°C source and 130°C sink temperature and about 70kW heating capacity, we show that the ejector efficiency can remain within acceptable limits even under deviating operating conditions by using a variable bypass instead of a rigid ejector geometry. The ejector efficiency can thus be kept high from about 30% in the design condition over a wide operating range. The COP increase compared to a conventional refrigeration circuit is approx. 30% in the design condition.