Performance evaluation of modified parabolic trough collector based solar water heater

• Experimentally investigated the new concept of intermittent rotation of the PTC absorption tube. • Evaluate the conventional type of absorption tube and the rotary absorption tube. • A parabolic trough is designed to tend to tilt at different angles like 10°, 20°, 30° towards north and south. • The maximum thermal efficiency of the PTC using the rotary absorption tube is 38.93 % higher than that of the conventional PTC. Parabolic trough collectors are one of the most significant solar techniques that are extensively used in commercial and demonstration applications. In this paper, we experimentally investigated the new concept of intermittent rotation of the parabolic trough collector (PTC) absorption tube and made an evaluation between the conventional type of absorption tube and the rotary absorption tube. Intermittent rotation of the absorber tube tends to enhance heat generation by contacting the lowest side of the absorber tube with direct sunlight. The rotation is only about 180°, because in the initial stage, the absorber tube began to absorb from two parts of radiation, one of which is direct sunlight and the other is reflected sunlight, although the flow rate is very low and the heat transfer fluid (HTF) flows only at the bottom surface of the absorber tube. The heat generated on the top surface of the absorber tube is idle, so we implanted a new concept of intermittent rotation of the absorber tube. A comparative investigation of the results showed that the maximum outlet temperature attained in the modified PTC was 53.1 °C and indicated a maximum increase in the average outlet temperature of 18.21 % as compared to conventional PTC. Similarly, the maximum increase in the average heat transfer rate of modified PTC was 39.14 % as compared to the conventional PTC. The above results subsequently increased the maximum thermal efficiency of the modified PTC by 38.93 % as compared to conventional PTC. Also the results indicated that the rotating the tube could potentially optimize heat absorption, enhance convective heat transfer, or mitigate issues such as stagnation.