A flat plate collector with a multi-cavity receiver as an innovative alternative in contrast to the classical design: A comparative study with experimental validation

Abstract

An innovative Flat Plate Collector (FPC) with cavity receiver is proposed in this study. This collector is investigated regarding the optical and the thermal performance, while the cavity’s geometry was optimized first. Another FPC with a typical geometry was used for evaluating the proposed system. Both collectors consist of 10 riser tubes each one. Two numerical models were set-up and several simulations were put forward regarding the two examined systems. The simulations were conducted for laminar flow conditions considering a volume flow rate of 50lt/h, which is a typical rate for such applications. The temperature range was selected to start from 10 °C up to 90 °C. The comparison in optical efficiency showed an enhancement of about 15.44%, while in thermal performance terms a remarkable difference was revealed especially in low operating temperatures, with the proposed collector to prevail. In particular, the enhancement was found to be greater than 21% for temperatures up to 60 °C. The numerical model was, also, validated using experimental results taken from literature and the maximum declination was found to be less than 7%. In addition, the numerical model results were validated for each collector using theoretical models, with the mean deviations to be less than 3% for the Darcy friction factor and 7.2% for the Heat transfer coefficient inside the flow tube. The design and the simulation of the collectors were developed in SolidWorks software.