Experimental Investigation of Natural Circulating Solar Energy System Including a Parabolic Trough Solar Collector

Abstract The most common natural flow water heating systems are in one-ended inclined pipes today. This study aims to investigate the natural circulation solar energy system experimentally with a parabolic trough solar collector. For this purpose, a natural circulation solar energy system including a parabolic trough solar collector that follows the sun in one dimension on the N–S axis in the outdoor environment has been established. Experiments were conducted on different dates. The radiation values coming into the opening of the moving collector were calculated. With the soltrace program, it has been found that 56% of this radiation can reach the vacuum tube glass pipe in the focus of the collector. In addition, the Rayleigh number was calculated for each experiment for the section of the glass tube close to the tank inlet, and it was monitored whether there was natural circulation throughout the experiment. As a result, the average Rayleigh number in the experiments conducted on February13, March 31, April 24, May 23, June 9, and July 6 was 1.4E + 06, 7.6E + 05, 7.8E + 04, 2.2E + 04, 3.1E + 05, respectively. and calculated as 2.8E + 05. In the experiments on May 23 and April 24, when the cooling system was open, it was observed that the Rayleigh number constantly dropped below the critical value. In other experiments, the situation is the opposite, and the natural flow is continuous.