Two dimensional mathematical model of evacuated tubular solar collector

Rahman, Faizur (1981) Two dimensional mathematical model of evacuated tubular solar collector. Masters thesis, King Fahd University of Petroleum and Minerals.

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Presently available performance models of evacuated tubular solar collectors use HWB model to determine useful energy gain. Themain shortcoming of HWB model is that it is basically one-dimensional and is based on lumped formulation. The errors associated with using this model are compounded by the fact that the model is not conservative but gives results that are too high. A comprehensive literature search indicated that evacuated tubular solar collectors have not yet been analysed considering two dimensional effects in the absorber plate. It is believed that the two dimensional analysis will enable a more accurate evaluation to be made of the collector performance. In this thesis, a parametric analysis of evacuated tubular solar collector is presented developing two dimensional performance model. The collector uses a thin flat plate spanning its diameter as its absorbing surface. Collectors of this type are being commercially produced by Corning Glass Works, N. Y. In the analysis of the plate assuming the temperature gradient to be negligible along the plate thickness reduces the problem to a two dimensional one. For the fluid inside the tube, radial variation of temperature is neglected. Energy balances are made on collector plate and tube each considered as a separate unit and two differential equations are obtained. The solution to the differential equations gives the temperature distributions of the plate and fluid. The heat loss model developed allows for wide flexibility in ambient temperature, collector temperature, fluid flow rate, etc. The model includes optical effects also. Two-dimensional temperature distribution has been illustrated by isotherms. Performance curves obtained from two-dimensional model have been compared with that of HWB model. It as found that HWB model over-estimates performance by less than 1 percent at higher flow rates and about 3.5 percent at low flow rates. Plate thickness has negligible effect on collector performance. Increase in tube spacing or length increases fluid outlet temperature and decreases efficiency, but it is more efficient to increase fluid outlet temperature by increasing length rather than water tube spacing.

Item Type: Thesis (Masters) February 1981 Completion Chemical Engineering College Of Engineering Sciences > Chemical Engineering Dept Rahman, Faizur Al-Zakri, Abdullah S. Said, A. S. and Abdel-Rahman, H. H. 9871 KFUPM ePrints Admin 22 Jun 2008 16:51 25 Apr 2011 09:30

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