2020 Volume 37 Issue 3 Pages 301-
In cold regions of Japan, the energy required for heating and hot water supply accounts for 81% of the energy consumption of the whole household, and this reduction can be expected to have high energy saving effect. However, in cold regions, the outside air temperature is low and the efficiency of the heat pump is reduced, so that it is not widely used and kerosene is mainly used. In this study, a thermosiphon type heat pipe using CO2 as working fluid is applied to heat recovery to prevent the efficiency from decreasing by using the underground surface heat of the underground as the heat source of the evaporator. Attempts to improve the performance of CO2 thermosiphon that can be considered when using, such as the shape of the heat pipe container, the effect of changing the temperature of the condenser and auxiliary heating to the lower part of the evaporator on the performance, and a simulation incorporating the obtained data are carried out. As a result, when the condenser temperature was set to 0°C, the maximum heat exchange amount of the condenser was obtained without a corrugated tube heater and the encapsulation rate was 45%. The maximum heat exchange in the condensation section was shown at a rate of 40%. It was confirmed that the auxiliary heater was installed to suppress the rise in wall temperature at the bottom of the evaporator. Using the heat transfer coefficient rearrangement formula obtained from the measured values, 8 smooth tubes are needed at 10 m long, 5 at 15 m long, and corrugated tubes are also 7 at 10 m and 5 at 15 m, with a COP=2.8. Achieved.
