Experimental Investigation and Comparison Between an Integrated Compound Parabolic Domestic Solar Water Heater with and Without an Air Gap Introduced at the Arms of the CPC

Abstract

The introduction of a concentrator in a domestic solar water heating system is not yet commercialized but research studies have been carried out and model validation done with symmetrical and asymmetrical type of reflectors. With concentrating collectors it becomes imperative to track the sun. Now the method of tracking to be adopted and the number of adjustments required depends upon the collection efficiency and its application. However for households, systems operating at the lower temperature range the optical system best suited are the compound parabolic concentrator. The advantage is that it has large acceptance angle and therefore requires only occasional tracking. The model studied is batch type heater, as the receiver serves the dual purpose of absorber and storage tank, unlike conventional design which consist of a large number of smaller diameter tubes and separate storage tank. The concentrator i.e. the reflector in this case, is supported on a wooden cradle which comprises the two parabolas of the compound parabolic concentrator. In the present work experimental studies have been carried out and mean collector efficiency computed on model with an air gap introduced in the side walls (arms of the CPC) and performance compared with the model without an air gap. This work is built on a model but without the air gap. Results have shown that there is 37.7% percentage increase in collector collection efficiency with air gap.