Heat Transfer Analysis Of Underground Heat And Chilled Water Distribution Systems PDF Download

This interim report presents the results of an in-depth heat transfer analysis of hot and cold piping systems intended for placement underground. The planning and implementation of field experiments to validate or invalidate the analysis given is currently underway. The analytic approach was to evaluate the use of steady-state heat transfer principles and then to extend these principles to include transient heat transfer effects due to initial cooling or heating and due to changing outdoor temperatures. Earth temperature and changes in earth temperature with season and depth were identified as being of prime importance. Extensive tables and graphs for use by engineers for estimation and decision were developed with the aid of the NBS computer facilities. Listings of the computer programs developed are included together with sample problems and solutions. The results allow quantitative estimates of heat transfer of insulated and uninsulated buried pipes that include a broad range of the variables of pipe fluid temperature, depth, pipe size, insulation thickness, types of insulation, thermal properties of soils, and the temperatures of the earth surrounding the pipes. Especially derived for this report were equations to accommodate systems of several pipes at different temperatures with variable spacing and complex relationships involving seasonal effects. This report contains the means for predicting the thermal performance of underground pipes containing chilled water, hot fluids, or a combination of hot and cold fluids. Experimental validation is needed.