Feasibility Study of a Brayton-Based High Temperature Heat Pump for Waste Heat Recovery in Industrial Applications

Electrification of thermal users through heat pumps can be a promising way to enhance the exploitation of increasing renewable electrical capacity, offering significant opportunities for decarbonizing the industrial sector. For this purpose, since commercial vapor compression cycles are not readily viable to displace fossil fuel boilers employed in industrial thermal processes, interest is growing towards high temperature heat pumps (supply temperature > 160 °C) and, among them, reverse Brayton cycles. This work proposes an innovative Brayton-based open heat pump cycle applied to a relevant industrial case study, with the aim of upgrading the available waste heat to the required process temperature levels. The on-design performance analysis of the reverse Brayton cycle is conducted using the modular in-house tool WTEMP-EVO. Subsequently, a sensitivity analysis is performed on temperature levels, heat sink, and compressor isentropic efficiency. Finally, an off-design model integrating existing machinery with their characteristic curves is developed to evaluate different system operating conditions, as well as possible solutions to improve system rangeability, establishing the groundwork for the implementation of an experimental prototype. Results show that the analyzed cycle can provide heat at temperatures above 200 °C with a coefficient of performance higher than 1.5 and a temperature lift of more than 100 °C, demonstrating its potential in the industrial sector.