Experimental, numerical and analytical investigation of a U-type evacuated tube collectors' array

Abstract

In this study an array of four commercial U-type evacuated tube collectors with mini-CPC reflectors was analyzed both experimentally and numerically. The operation of the array was examined in a range of 35–80 °C inlet temperature in Athens/Greece from 11:00 to 16:30 local hour at 2nd May using water as working medium. The data acquisition regarding the solar irradiation intensity, the inlet, the outlet and the ambient temperature was conducted every 10 min Α time-dependent computational fluid dynamic model was developed in Solidworks for validating the results while an analytical solution was, also, proposed. It was found that the simulation and the analytical results diverge 3.7% and 9.3% on average from the experimental regarding the thermal efficiency of the array while the mean divergence between them was 6.1%. The specific simulation gave us the opportunity to predict the receiver temperature as well as the thermal efficiency of each module something that the experimental process could not provide. The receiver temperature was also predicted through the analytical solution for further validation. The experiments were conducted in the National Technical University of Athens at the Applied Thermodynamics laboratory of Mechanical Engineering Department while the design of the simulated model was conducted in Solidworks.