Abstract
Flow and heat transfer characteristics of heat transfer fluid in vertical coaxial double tube type ground heat exchanger were investigated numerically. Heat transfer characteristics are influenced with the flow directions which are center-in and annulus-in. Ground temperature profile also affects on the heat transfer characteristics. In the case of constant ground temperature, heat transfer rate of the center-in condition was greater than the annulus-in condition. On the other hand, the heat transfer rate becomes lower for the condition of variable ground temperature profile of which the temperature of surface is lower than that of deep area. This degradation was more remarkable for the center-in condition and the difference between the flow directions became smaller. Detail of the heat transfer characteristic is also discussed.
