Determination of the performance of indirect solar heating systems that use thermosyphon heat exchangers requires knowledge of how thermosyphon flow rate and heat exchanger performance vary with operating conditions. In this paper, measured performance of a two-pass, tube-in-shell, double-wall heat exchanger is presented and discussed in terms of modeling issues. The inadequacy of using a simple temperature difference to predict thermosyphon flow rate is illustrated. Accuracy of prediction of thermosyphon flow rate from a pressure balance on the water loop depends on the accuracy of assumed temperature distributions in the heat exchanger and tank. For a given collector flow rate, heat exchanger performance depends on natural convection heat transfer coefficient and temperature of the antifreeze fluid and is not uniquely determined by thermosyphon flow rate. Models based on the assumption that for a given collector flow rate, overall heat transfer coefficient-area product or effectiveness of the heat exchanger are determined by thermosyphon flow rate may produce erroneous predictions of system performance.
|Number of pages
|Published - Dec 1 1996
|Proceedings of the 1996 International Solar Energy Conference - San Antonio, TX, USA
Duration: Mar 31 1996 → Apr 3 1996
|Proceedings of the 1996 International Solar Energy Conference
|San Antonio, TX, USA
|3/31/96 → 4/3/96