CORRELATION FOR THE CONVECTIVE HEAT TRANSFER WITHIN THE AIR IN THE CAVITY OF A COMPOUND PARABOLIC CONCENTRATING COLLECTOR
Publication Date : 01/02/2007
The heat transfer processes governing the performance of a solar compound parabolic concentrator (CPC) with evacuated receiver envelope employed for hot water generation were studied. The results showed that the convective heat transfer was dominant and that the contribution of the radiation heat transfer from the receiver tube to the overall heat transfer from the collector is insignificant. An empirical correlation of the natural convection heat transfer within the enclosed air surrounding the enveloping glass tube of the collector has been proposed. The correlation expressed in the form 0.35 0.238 1.28 Gr.Pr D H Nu yielded a linear plot of the Nu – Ra relationship over the range of Ra values 3.84 x 103 ≤ Ra ≤5.65 x 104.
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