Characterization of solar flat plate collectors

Characterization of solar collectors is based on experimental techniques next to validation of associated models. Both techniques may be adopted assuming different complexities. In this work, a general methodology to validate a collector model, with undetermined associated complexity, is presented. It serves to characterize the device by means of critical coefficients, such as the film (convection) transfer coefficient, plate absortance or emmitance. The first step consists of identifying those significant parameters that match the selected model with the experimental data, via nonlinear optimization techniques, applied to steady state conditions. Second, new correlations must be adopted, in those terms where it is necessary (i.e. film coefficient equations). Finally, the overall model must be checked in transient regime. To illustrate the technique, a tailor-made prototype flat plate solar collector has been analyzed. An intermediate complex collector model has been proposed (2D finite-difference method). Both steady and transient states were analyzed under different operating conditions. Parameter identification is based on Newton's method optimization. For parameter approximation, exponential regression functions through multivariate analysis of variance is proposed among many other alternatives. Results depicted a robustness of the overall proposed method as starting point to optimize models applied to solar collectors.