Numerical study of the part load operation for a reverse Brayton high-temperature heat pump

Abstract

Electrification of industrial process heat from renewable sources can contribute to the reduction of energy-related CO2 emissions. High-temperature heat pumps are one of the most important technologies to realize this electrification while reducing the electrical energy required for it. The Institute of Low-Carbon Industrial Processes of the German Aerospace Center (DLR) is developing high-temperature heat pumps (HTHP) based on reverse Brayton and Rankine cycles for heat transfer temperatures above 150 °C. The development and integration process of HTHPs for industrial processes often starts with their sizing at nominal operating conditions. Once the operational boundary conditions are defined, the individual components are sized. A large proportion of industrial heat pumps operate at a fixed point and are not optimized or designed for frequent part-load operation. This is expected to change, especially when heat pumps are required for industrial processes with part load operation. The current work presents an analysis of the part load operation of a reverse Brayton HTHP built in the laboratory of DLR and investigates its operational limits.