This paper discusses the use of a cool tube as an air-to-earth heat exchanger that is used to reduce the HVAC requirements of a building. The cooling effect of the cool tube was analytically investigated, considering sensible and latent heat. The thermal characteristics of a cool tube are evaluated in Part 1 of this paper, taking into account only sensible heat. A method to utilize a wet cool tube was proposed for effective use.

In order to determine the condition of the tube surface, the thermal and hygric behavior of cool tubes was analyzed using a model that considers simultaneous heat and moisture transfer in the ground. In regions with a climate such as that of Osaka, Japan, the tube surface is found to be practically wet throughout the year.

Units: SI