Abstract
Optimum utilization of heat by thermal storage is one of the solutions to improve efficiency and to save energy for various heat pump systems. Beverage vending machine controls the temperature of the beverages by thermal energy exchanged with the refrigerant of the compression type heat pump. Further improvement of the heating-energy is demanded, because it accounts for as much as 60% of the total power consumption. In this research, in order to save power of the beverage vending machines with CO2 heat pump, we clarified some design guidelines of two types of a latent heat thermal storage tank. 1st thermal storage tank used for a heating room has two heat transfer surfaces; it stores CO2 heat during the heat pump running, and then releases it into the heating room during the heat pump stopping. For 1st thermal storage tank, it is found that thermal conductivity enhancement in the thermal storage side is effective, and that heat transfer enhancement into the air side is necessary. 2nd thermal storage tank used for heating and evaporating the CO2 before compression has only one heat transfer surface; it stores heat of CO2 flowing after the heating room, and then releases it into CO2 for evaporation before compressor. For 2nd thermal storage, we showed some contribution of each parameter in thermal storage tank.
