Dynamic process simulation of industrial heat pump drying of clipfish

A heat pump drying system of an industrial sized batch tunnel drier with 40 tons of clipfish was analyzed in a dynamic process simulation. The convective drying dynamics were determined experimentally and used to verify a drying model for clipfish. The drying process was simulated in a 250 kW heat pump system. The model of the heat pump drier (HPD) consisted of the major components: evaporator, compressor, condenser and expansion valve, and was investigated using R717 (Ammonia) as refrigerant. The performance of the HPD unit was compared to a hot air drying system (HAAD), using heated ambient air as drying agent. The energy consumption, respectively production costs, was calculated to 195.5 kWh ton-1 for HPD and 973.8 kWh ton-1 for HAAD. The moisture profile of the tunnel drier was well described with the used model. Energy consumption, Specific Moisture Evaporation Rate (SMER) and heat flows were determined and used to discuss process optimization.