Numerical solution and validation of a dynamic model of solar collectors working with varying fluid flow rate

A method to calculate the short-term dynamic behavior of solar collectors, working with varying fluid-flow rate, has been developed. It is based on a system of first-order partial differential equations. The method was applie d to model a large unglazed collector used for heating a public outdoor swi mming-pool in Marburg (Germany). A validation with data measured at this co llector showed good short- and long-term accuracy of the model at constant and varying how rates. Furthermore, the dynamic behavior of the detailed mo del was compared to that of several model approximations especially at vary ing flow rate. In the case of unglazed collectors a simple dynamic model, b ased on an ordinary differential equation, gives accurate results in most p ractical applications even at varying how rate. The extension of the method to flat-plate collectors is demonstrated as well. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.