A comparative thermodynamic analysis of different supercritical CO2 reverse Brayton high temperature heat pumps

• sCO 2 reverse Brayton high-temperature heat pumps are studied for industries. • Heat production temperatures up to 250 °C are examined. • Low-grade waste heat sources in the range of 50–120 °C drive the heat pump. • Internal heat exchanger increases COP by up to 8.13% and exergy efficiency by 6.54%. • Reheating and internal heat exchanger cycles improve COP by up to 15.5%. High-temperature heat pumps (HTHPs) are high-potential technologies for the decarbonization of low- and medium-temperature industrial heating processes. The conventional HTHPs can deliver heat up to 150-160 °C, while the process heat production at higher temperatures is a challenge that has attracted a lot of research in the last year. The goal of this work is to conduct a detailed investigation of different configurations of supercritical CO 2 reverse Brayton HTHPs, aiming to determine the most efficient and promising designs. This analysis investigates different process heat production from 150 °C up to 250 °C, while the HTHPs are driven by low-grade waste heat in the range of 50 –120 °C. This work is performed with developed mathematical thermodynamic models in Engineering Equation Solver, which are verified with literature data. According to the results of this analysis, the recompression is a proper solution for low heating production temperatures (mainly at 150 °C), while at higher heating production temperatures, the Reheating with an internal heat exchanger has to be selected. The application of the internal heat exchanger enhances the coefficient of performance up to 8.13% and the exergy efficiency up to 6.54%. For the typical case with source temperature at 100 °C, the average COP enhancement is found at 3.9% with internal heat exchanger, at 12.5% with Reheating with internal heat exchanger and at 15.5% with Double reheating with internal heat exchanger compared to the Simple cycle.