Mantle heat exchangers for horizontal tank thermosyphon solar water heaters

This paper describes the characteristics of horizontal mantle heat exchange rs for application in thermosyphon solar water heaters. A new correlation f or hear transfer in horizontal mantle heat exchangers with bottom entry and exit ports was used to predict the overall heat transfer and stratificatio n conditions in horizontal tanks with mantle heat exchangers. The model of a mantle heat exchanger tank was combined with the thermosyphon solar colle ctor loop model in TRNSYS to develop a model of a thermosyphon solar water heater with collector loop heat exchanger. Predictions of stratification co nditions in a horizontal mantle tank are compared with transient charging r ests in a laboratory test rig. Predictions of daily energy gain in solar pr eheaters and in systems with in-tank auxiliary boosters are compared with e xtensive outdoor measurements and the model is found to give reliable resul ts for both daily and long-term performance analysis. (C) 2000 Elsevier Sci ence Ltd. All rights reserved.