Advanced high temperature heat pump configurations using low GWP refrigerants for industrial waste heat recovery: A comprehensive study

High temperature heat pumps (HTHPs) have a great potential to improve industrial processes with thermal demand through industrial waste heat recovery and revalorization. Vapor compression HTHPs are very sensitive to the cycle configuration, refrigerant, components, and operating temperatures. This study compares eight advanced cycle configurations and nine low global warming potential (GWP) refrigerants from an energetic, economic, and environmental comprehensive perspective to illustrate an optimum selection for different HTHP applications. Firstly, several single-stage and two-stage compression cycles are proposed adding different components, such as the ejector, economizer, parallel compressor, flash tank, or additional evaporators and condensers. Moreover, an internal heat exchanger (IHX) has been included in all configurations to maximize the energy performance and ensure dry compression. Secondly, HC-601, HC-600, HC-600a, HFO-1336mzz(Z), HFO-1336mzz(E), R-514A, HCFO-1233zd(E), HCFO-1224yd(Z), and HFO-1234ze(Z) are considered as alternative low GWP refrigerants to replace the hydrofluorocarbon HFC-245fa. The results indicate that a two-stage cascade becomes the most appropriate configuration for high temperature lifts (60 K and above). In contrast, single-stage cycles with economizer and parallel compression are suitable for low temperature lifts (50 K and below). HCFO-1233zd(E) and HCFO-1224yd(Z) show a trade-off between coefficient of performance (COP) and volumetric heating capacity (VHC). Advanced HTHPs configurations can save up to 68% of the equivalent CO2 emissions compared to a natural gas boiler.

Automated summary

This study compares different high temperature heat pump (HTHP) cycle configurations and low global warming potential (GWP) refrigerants, showing that two-stage cascade is suitable for high temperature lifts while single-stage cycles with economizer and parallel compression are suitable for low temperature lifts.