A semi-empirical model for assessing the effects of berms on the heat loss from partially buried heat storage tanks

摘要

Complete analysis of the heat flow from buried seasonal thermal storage tanks is exceedingly complex. In order to provide designers with a usable and rational basis upon which an initial design choice with respect to berming can be made, a semi-empirical model has been developed to describe the heat flows in the soil regime surrounding large, cylindrical, partially buried seasonal heat storage tanks having soil bermed against the above grade portion of the tank wall. The model assumes steady state conditions, and that the soil has homogeneous and isotropic thermal properties. A berm-factor expression (which indicates the increase in tank heat loss rate occurring when an in-ground tank is repositioned at a higher level and bermed) is developed analytically using a simplified heat flow model. The simplification of the two-dimensional heat flow field is described in detail. The model is calibrated, using data obtained in previous studies by the author using a numerical simulation, for several berm configurations, insulation widths and soil conductivities. The predictions obtained using the calibrated model are found to be in good agreement with the predictions obtained using numerical and empirical approaches. The results appear to provide convenient and reasonably accurate design aids for predicting the heat loss characteristics of bermed seasonal heat storage tanks, and as well to be applicable with little error to most non-circular tanks normally encountered. The results may be particularly useful for activities involving numerical simulation, economic analysis, and optimization of systems incorporating thermal storages.