Performance evaluation of high-temperature heat pump systems for hot water and steam generation in food processing

A large amount of fossil fuels is consumed for hot water and steam generation in food processes such as smoking, scalding, drying, pasteurization, sterilization, cleaning, and cooking, which currently rises both economic- and environmental concerns. At the same time, there is a considerable number of low-grade waste heat available, often from associated cooling processes. High-temperature heat pumps (HTHPs) are considered as a promising solution for steam boilers replacement and waste heat recovery owing to their high energy efficiency and sustainability. In the present study, the performance of three heat pump systems - a trans-critical CO2 heat pump system, a cascade propane-butane heat pump system and an ammonia-water absorption-compression heat pump (ACHP) system, for hot water and steam production in food processing is evaluated based on different application scenarios. In all the scenarios and temperature lift levels, the ACHP exhibits the best thermal performance with moderate pressure levels and low-pressure ratios. When applying the ACHP for both the cleaning and cooking processes, the achievable energy saving rate can reach 79%. Further, the optimal HTHP system architectures for different application scenarios are discussed.