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.