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Combined convection in an annulus applied to a thermal storage problem
Author(s) -
Zenen S. R.,
Collins M. W.,
Simonson J. R.
Publication year - 1985
Publication title -
international journal for numerical methods in engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.421
H-Index - 168
eISSN - 1097-0207
pISSN - 0029-5981
DOI - 10.1002/nme.1620210409
Subject(s) - mechanics , annulus (botany) , laminar flow , forced convection , natural convection , thermodynamics , combined forced and natural convection , reynolds number , heat transfer , thermal , materials science , mathematics , physics , turbulence , composite material
In a solar energy application involving thermal storage, one of the heat transfer situations is that of combined convection in vertical annuli for rather complex wall thermal boundary conditions. Predictive data of a high order of reliability are needed for incorporation within the suite of programs treating the whole problem. The program reported here treats the complete equations for combined free and forced convection in a vertical annulus. It allows for viscosity and density variation with temperature, and a variable heat flux or temperature at the walls. It was developed from a similar program for circular tubes. Comparisons are made with published data for velocity profiles and heat transfer performance. These are good, and show the step‐wise energy balance method is necessary and valid. The strategy of generation of the required data is explained, together with sample output. These data are themselves analysed computationally; the performance equations agree with original predictions typically to within ± 11 per cent, with a standard deviation of around 2 per cent. The working fluid is water with 37 per cent ethylene glycol. Upward heated and downward cooled flows give aided combined convection. For the given design, laminar flow is predicted for the Reynolds number range 1800–2200.