Abstract
Drying is an energy intensive thermal process. The specific energy consumption in industrial systems is
normally higher than 0.8 kWh/kg of evaporated water and the thermal energy demand in most drying
systems is provided through burning of fossil fuels. The potential of using R744 (CO2) as working media
in a heat pump drier was investigated for a drying process at 45°C, 60°C and 70°C. The trans-critical
temperature glide of CO2 reduces the large temperature differences during re-heating of the drying air.
The obtained Coefficients of Performance were between 3.4 and 4.3 resulting in specific energy
consumption in the range of 0.24 to 0.27 kWh/kg of evaporated water for the different drying processes.
The simulations confirm that heat pump assisted drying has the potential to reduce the energy demand
by around 70% in general and shows the feasibility of applying heat pump drying also at drying
conditions up to 70°C.
normally higher than 0.8 kWh/kg of evaporated water and the thermal energy demand in most drying
systems is provided through burning of fossil fuels. The potential of using R744 (CO2) as working media
in a heat pump drier was investigated for a drying process at 45°C, 60°C and 70°C. The trans-critical
temperature glide of CO2 reduces the large temperature differences during re-heating of the drying air.
The obtained Coefficients of Performance were between 3.4 and 4.3 resulting in specific energy
consumption in the range of 0.24 to 0.27 kWh/kg of evaporated water for the different drying processes.
The simulations confirm that heat pump assisted drying has the potential to reduce the energy demand
by around 70% in general and shows the feasibility of applying heat pump drying also at drying
conditions up to 70°C.
