Levelized cost of heat based optimisation framework of plate heat exchangers for high temperature heat pumps: simultaneous optimisation of geometry, pinch point temperature difference and CO2/acetone mixtures composition

High-temperature heat pumps (HTHPs) delivering heat at 200 °C and above require large temperature lifts, leading to increased thermodynamic irreversibilities and greater sensitivity to heat exchanger pressure losses and pinch point temperature differences ( ∆Tpp ). While plate heat exchangers (PHEs) and zeotropic refrigerants have been widely investigated for HTHPs, previous studies have largely relied on fixed heat exchanger geometries and prescribed ∆Tpp values, overlooking the coupled effects of PHE design, pressure drop induced compressor power, refrigerant composition, and system-level economics. The novelty of this study is the comprehensive thermo-economic optimisation framework that simultaneously optimises evaporator and condenser PHE geometries, ∆Tpp , and CO₂/acetone refrigerant composition to minimise the levelized cost of heat ( LCOHΔP both ). The framework explicitly accounts for the additional compressor power required to overcome pressure losses in both heat exchangers. Four PHE geometric parameters, plate length, plate width, corrugation pitch, and corrugation height were optimised by evaluating 34,944 geometric configurations across 16 ∆Tpp values. Unlike conventional approaches, ∆Tpp was treated as a design variable, enabling simultaneous optimisation of heat exchanger geometry and operating conditions. The optimum configuration, comprising an 8% CO₂/92% acetone mixture with a ∆Tpp of 1.6 K, achieved the lowest LCOHΔP both of 0.0667 €/kWh. The results indicate that the evaporator pressure drop contributes more significantly to performance degradation than the condenser pressure drop and highlight the importance of integrated optimisation of heat exchanger design, refrigerant composition, ∆Tpp , and pressure-drop effects to minimise heat generation costs in high-temperature industrial waste heat recovery syste