Performance Analysis of a Pancake Absorber-Helical Heat Exchanger for a Solar Concentrator

Abstract

This paper presents an analysis of the performance of a pancake absorber with a helical heat exchanger for use with point focus solar concentrating collectors. The principal difference between this type of absorber and most other concentrating solar collector absorbers is that the intensity of concentrated radiation monotonically increases from the inlet to the outlet of the heat exchanger tube. A performance expression for this absorber type and radiation distribution is derived and used to calculate thermal performance for several different absorber designs. Thermal performance for these designs is then calculated using a performance analysis based on the simplifying assumption that the heat exchanger tube is uniformly irradiated and the two performances are compared. The comparison indicates that the different radiation distribution assumptions lead to different absorber design choices. In particular, the simplifying assumption overstates thermal losses for increases in absorber size.