Verified Accurate Performance Simulation Model of Direct Thermosyphon Solar Energy Water Heaters

[+] Author and Article Information
P. A. Hobson

AFRC Institute of Engineering Research, Wrest Park, Bedford, MK45 HMS, U.K.

B. Norton

Solar Energy Technology Centre, School of Mechanical Engineering, Cranfield Institute of Technology, Bedford MK43 0AL, United Kingdom

J. Sol. Energy Eng 110(4), 282-292 (Nov 01, 1988) (11 pages) doi:10.1115/1.3268269 History: Received January 16, 1988; Revised June 20, 1988; Online November 11, 2009


A detailed analysis of the heat transfers and fluid flows within direct thermosyphonic solar energy water heaters has been undertaken. The collector energy equations were cast in a two-dimensional form in order that the heat transfer and thermal capacitance effects can be simulated accurately at the small flow rates encountered commonly in these buoyancy-driven systems. The use of an appropriate nonisothermal friction factor correlation when calculating energy losses in the collector’s riser pipes, produced predicted flow rates which were corroborated to within 2 percent by the values measured under steady flow conditions. For the laminar flow rates and the store configuration investigated, relaxation of the thermocline was shown to be dominated by axial conduction in the store walls. An indoor test facility, monitored and controlled by a microcomputer, enabled “real” operating conditions to be simulated. The predicted responses of the system to identical conditions showed good agreement with the corresponding experimental observations, the predicted heat delivery being within 2.8 percent of that measured.

Copyright © 1988 by ASME
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