A model and thermal loss evaluation of a direct-absorption solar collector under the influence of radiation

Abstract

A complete two-wavelength band radiation model of a direct-absorption solar collector (DASC) is proposed herein. The model considers not only the absorption but also the emission and scattering effects in the heat transfer fluid. In previous studies, the emission and scattering effects are generally ignored because of the complex solution of the radiative transport equation in the participant medium. This work also improves the evaluation of heat loss and analyzes the effects of fluids on the radiative heat loss of two-wavelength bands. The results show that the DASC has both advantages and drawbacks compared with the traditional surface absorption solar collector (SASC). Also, this study realizes the regression of the radiative heat loss and effective emissivity using response surface methodology (RSM) with a maximum error of 5.6%. When measurement errors of 2% were introduced into the numerical model, the maximum deviation between the calculated results and the reference values corresponding to no error still met the accuracy requirements. This work demonstrates the necessity of considering the effects of emission and scattering in the DASC photothermal conversion, and provides a robust method to evaluate the heat loss of the DASC.