Comparison of Analytical and Experimental Immersed, Collector-Side Heat Exchanger Results

This paper compares the results from testing four immersed heat exchangers to previous experimental data and from two of the heat exchangers tested to analytical and numerical models. These types of heat exchangers are typically used in indirect solar hot water systems between the collector subsystem and the storage subsystem. The experimental results show that the effectiveness decreases significantly at lower temperature differences between the heat exchanger inlet and a well-mixed storage tank. This not only leads to higher control system turn-off differentials but may be a major reason that measured field performance of indirect systems is sometimes less than predicted.