PERFORMANCE ENHANCEMENT OF COMPOUND PARABOLIC CONCENTRATORS USING AIR AND A LIQUID SIMULTANEOUSLY AS HEAT TRANSFER MEDIUMS.

The thermal efficiency of a Compound Parabolic Concentrator (CPC) solar collector can be enhanced by extracting the solar energy absorbed not only by the receiver but also by the reflectors and aperture cover. Much of the energy that would normally be lost from the front of the collector is used to heat air blown through the collector, which can then be utilized for space or process heating. The present analysis uses a thermal network analogy to predict the radiation, conduction, and convection heat transfer between the CPC collector components and between the collector and its surroundings. Results are presented for concentration ratios of 1. 5 and for selective and nonselective absorbers and various air and liquid flow rates.