Generating application design data for solar air heating systems

This paper consists of two parts. The first part provides a graphical method of determining, under different operating conditions, the design data for a system using air heaters of known characteristics, i.e. of known η vs ( Δt_m I) curves for different flow rates. The interdependent operating parameters are the inlet and outlet fluid temperatures and the fluid flow rate. The unknown third parameter, when two others are fixed, is determined by the application of a design procedure outlined in the first part of the paper. The fluid rate per unit area is usually specified when presenting an air heater performance curve. However, while maintaining the same fluid flow rate per unit area, different curves are obtained for air heaters of different dimensions. Explicit importance to this fact does not seem to have been given in the literature so far. A methodology, by which performance curves obtained from a certain air heater of specific dimensions can be suitably modified so as to predict the performance of similar heaters having different dimensions, constitutes the second part of the paper.