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Comments on ‘a simplified theory for a matrix solar collector’
Author(s) -
Suggett G. J.
Publication year - 1984
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.4440080403
Subject(s) - mathematics , thermal conduction , matrix (chemical analysis) , thermodynamics , function (biology) , mathematical analysis , physics , materials science , evolutionary biology , biology , composite material
A critical analysis is given of Singh and Bansal's paper (1983) ‘A simplified theory for a matrix solar collector'. The following points are demonstrated: 1 Singh and Bansal use the equation of heat conduction to model an experimental system in which transfer of heat by conduction plays very little part. They make no attempt to show that the true radiative transfer equations can be approximated by a conduction equation. 2 The units and dimensions of the equations are internally self‐inconsistent. 3 Correcting the equations to make them dimensionally consistent, and using the data given by Singh and Bansal, their calculations cannot be replicated. The values for outlet temperature are in the region 4°C rather than the 12°C claimed by Singh and Bansal. 4 Some of the data values quoted by Singh and Bansal are wrong (in terms of their stated objective of using values corresponding to the experimental system of Chau and Henderson) and others appear to have been assigned in an extremely arbitrary fashion. One crucial parameter (the absorptivity of the matrix material) is not even mentioned in Singh and Bansal's analysis. 5 Using the correct values for those parameters referring to the experimental system, and including the effect of absorptivity, the theory can be made to give results of the same order of magnitude as the experimental results. However, the variation of the outlet temperature as a function of the experimental parameters is very different to that obtained from Chau and Henderson's computer simulations. Indeed, Singh and Bansal appear not to have noticed that their solution possesses a singularity, so that for certain values of the parameters, an infinite outlet temperature can be obtained. This would appear to invalidate their model as a serious analysis of the matrix air heater.