Recuperative heat pump cycle concept for high-temperature glide process heating applications

Decarbonising industrial process heat remains challenging for conventional heat pumps, as high discharge pressures and limited temperature-profile matching degrade efficiency. This study introduces and evaluates a new family of recuperative heat pump (RHP) cycles that reposition internal recuperative heat exchangers (RHXs) using Pinch Analysis principles to superheat the suction gas while easing gas-cooler pinch constraints. A modular Python framework (supported by REFPROP v10 for thermophysical properties, and SciPy for optimisation within the cycle) was developed to simulate a baseline standard heat pump (SHP) and three recuperative heat pump cycle variants (RHP1, RHP2, RHP3) using 20 natural and low-GWP refrigerants for a spray-dryer case study (air heating from 15 °C to 200 °C, large heat sink temperature glide over 150 K). Simulated steady-state thermodynamic performance was evaluated in terms of coefficient of performance (COP), reduction in maximum cycle pressure (P max ), volumetric heating capacity, and three integrative metrics: mean temperature difference over all gas coolers, entropic temperature lift, and specific lift energy. Results show that internal recuperation can substantially lower P max with minimal COP penalty. Depending on refrigerant selection and RHX configuration, COP gains up to about 14% and P max reductions of up to around 80% were achieved relative to the SHP baseline. For example, butane (R600) required 8800 kPa in a SHP cycle (transcritical) compared to 3850 kPa for a RHP cycle. The best overall performers are R1234ze(Z), dimethyl ether (DME), and R600. Alignment of the gas-cooler pinch point emerged as a practical diagnostic for optimal RHX placement. The findings outline actionable design insights for high-temperature glide heating applications and motivate targeted experimental validation.