Parametric analysis of thermodynamic and economic performance of high-temperature heat pump using CO2/acetone zeotropic mixtures: Effects of condenser pressure drop on system performance

Despite the growing industrial demand for high-temperature heat pumps (HTHPs), systematic studies that simultaneously evaluate thermodynamic performance and economic viability of CO2-based zeotropic mixtures which includes condenser pressure drop effect remain scarce. The lack of studies comparing pure refrigerants with zeotropic mixtures by accounting condenser pressure drop effects, limits the ability to make informed refrigerant selection decisions. This study presents a comprehensive thermodynamic and economic comparison between pure acetone and CO2/acetone zeotropic mixture for HTHPs. A consistent cycle configuration was applied for all fluids, and condenser sizing was iteratively determined. Thermodynamic analysis reveals that introducing CO2 improves both Coefficient of Performance (COP) and effective COP, with optimal performance observed at 8–10% CO2 mass fraction at the specified boundary conditions to achieve a lift temperature of 70K. At an evaporator outlet temperature of 140 °C, the COP peaks at 4.8 for 10% CO2, compared with 3.1 for pure acetone. Accounting for condenser pressure drop reduces pure acetone COP by 12–16%, whereas mixtures with 6–12% CO2 experience reductions below 5%. Economic analysis mirrors these trends the 8% CO2/92% acetone mixture achieves the lowest levelized cost of heat (0.055 €/kWh), shortest payback (3.02 years), and highest net present value (851.5 k€) outperforming pure acetone. Inclusion of condenser pressure drop raises pure acetone's LCOH by 13.6%, while zeotropic mixtures containing 4 – 8% CO2 remain below 5%, and mixtures with 8–12% CO2 show increases under 3%. These findings identify 8–10% CO2 balances thermodynamic efficiency and economic advantage under specified conditions.