Optimal Design of an Industrial Steam Heat Pump for the Paper Drying Process
Steam, owing to its rapid and stable heat transfer characteristics through latent heat, is widely used in various drying industries such as food, biomass, chemical, laundry, and pulp and paper. As the electrification of industrial steam generation replaces fossil fuels like coal and natural gas, steam heat pumps have gained attention as a key technology for realizing low-carbon and high-efficiency steam production. By utilizing lowgrade waste heat from manufacturing processes to regenerate high-temperature steam, steam heat pumps offer higher efficiency and lower carbon emissions compared to conventional boilers. For practical application, however, detailed quantification of waste-heat conditions, including temperature and mass flow rate, is essential to design appropriate system capacity and operating conditions. In this study, the paper-drying process was analyzed using factory energy management system (F-EMS) data, and performance sweeps were conducted by varying the evaporator air-side approach temperature (?T). The results indicated optimal ?T* values ranging from 15 to 25 ?, achieving the highest cost efficiency at a steam production rate of 1.34 kg/s and power consumption of 1.26 MW. When comparing two integration strategies-direct supply to the main header (Scenario 1) and intermediate-pressure supply (Scenario 2)-the latter showed an annual economic advantage of approximately 1.47 MUSD. The system employed a low-GWP, zero-ODP refrigerant R1233zd(E), which enables 2-phase heat exchange above 130 ?. This study demonstrates the feasibility and economic benefits of industrial steam heat pumps utilizing waste heat, contributing to the advancement of electrification in thermal process industries.