Performance simulation of a Heat Pump Drying System using R744 as refrigerant

Summary

Convective drying requires significant amount of thermal energy in order to evaporate water from the product. In most cases this energy, present as latent heat in removed drying air, is not recovered. However, the simultaneous availability of waste heat and thermal energy demand is ideal for heat pump applications.
This case study evaluates the performance of CO2 as refrigerant in heat pump assisted drying system for grain drying. The system was designed for a thermal capacity of up to 400 kW. This allows a mobile design in order to move the heat pump system to different drying locations.
The energy demand of the drying system is decreased to 200 kWh per ton of evaporated water, which equals an energy saving potential of over 70%. Estimated investment costs indicate that the return of investment can be lower than 3 years, depending on seasonal variations and drying demand.