Exploratory study on low-GWP working fluid mixtures for industrial high temperature heat pump with 200 °C supply temperature

The development of an industrial high temperature heat pump (HTHP) using a subcritical vapor-compression cycle (VCC) for process heat delivery at 200 °C faces significant challenges due to the scarcity of suitable single-component working fluids. These challenges are further compounded by safety, environmental concerns, material and lubrication oil compatibility and cost considerations. In response, this study investigates the potential of various fluid mixtures to meet these stringent criteria. Using the REFPROP and Cantera software libraries, a Python code was developed to simulate a simplified HTHP VCC with an advanced cycle architecture and assess the flammability risks of the proposed mixtures. Ten single-component fluids of two different families of compounds, hydrocarbons (HCs) and hydro(chloro)fluoroolefins (H(C)FOs), were pre-selected as promising candidates as mixture components. From these, over 460,000 binary, ternary, and quaternary mixtures were generated and evaluated for cycle performance. Although no mixture perfectly met all the predefined criteria, a binary blend of cyclopentane and R1336mzz(Z) in a mole fraction of 0.68 and 0.32, respectively, emerged as the most promising candidate. This mixture demonstrated the best balance of performance and safety under the imposed constraints and is selected for further experimental investigation and validation in a specially designed test rig.