Performance and modeling of thermosyphon heat exchangers for solar water heaters

S. D. Dahl, Jane H Davidson

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

Determining 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 discussed in terms of modeling issues. Thermosyphon heat exchangers may operate in the developing, mixed convection regime where natural convection effects can significantly influence overall heat transfer and friction coefficients. Existing models which assume the thermal and hydraulic behaviors of thermosyphon heat exchangers are only functions of the thermosyphon and collector flow rates may not be suitable for all heat exchanger types. For example, the overall heat-transfer coefficient-area product for the two-pass, tube-in-shell heat exchanger is best expressed as a function of Reynolds, Grashof, and Prandtl numbers on the thermosyphon side of the heat exchanger. It is proposed that annual simulations of solar water heaters with thermosyphon heat exchangers use this type of relationship to characterize heat transfer in the heat exchanger.

Original languageEnglish (US)
Pages (from-to)193-200
Number of pages8
JournalJournal of Solar Energy Engineering, Transactions of the ASME
Volume119
Issue number3
DOIs
StatePublished - Aug 1997

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