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A water heater using very high‐temperature storage and variable thermal contact resistance
Author(s) -
Jotshi C. K.,
Goswami D. Y.,
Klausner J. F.,
Malakar S.
Publication year - 2001
Publication title -
international journal of energy research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.808
H-Index - 95
eISSN - 1099-114X
pISSN - 0363-907X
DOI - 10.1002/er.727
Subject(s) - materials science , tube (container) , thermal , contact resistance , composite material , thermal resistance , cylinder , thermal energy storage , thermal contact conductance , metallurgy , mechanical engineering , thermodynamics , engineering , layer (electronics) , physics
This paper describes the role of thermal contact resistance in a high‐temperature sensible heat storage water heater using cast iron as a storage material. An experimental set‐up consisting of a cast iron cylinder and a stainless‐steel tube running through its centre was fabricated and tested. The experimental data were compared with a theoretical model. It was observed that the variation in thermal contact resistance between the cast‐iron blocks and the tube with temperature plays a dominant role in extracting the heat at a reasonably constant temperature. The contact resistance between two contacting surfaces was modelled as the composite of two parallel resistances: one due to the points where two surfaces contact each other and the other due to a gap between the surfaces, which is often air filled. An approximate contact resistance prediction was obtained by assuming the resistance due to the air gap modulated by a correction factor which accounts for the contacting surface area. Based on the results from the experimental set‐up and theoretical modelling, a prototype storage water heater using cast‐iron blocks as the storage material was designed, fabricated and tested. Copyright © 2001 John Wiley & Sons, Ltd.