| Abstract: |
Parabolic trough solar collectors (PTSCs) are a well-established concentrating solar thermal technology suitable for low- to medium-temperature water heating applications, ranging from domestic use to industrial process heat. This study presents a detailed experimental thermal analysis of a parabolic trough solar collector (PTSC1720) with an aperture width of 2.4 m and length of 3.0 m, designed for water heating under the climatic conditions of Indore, India (22.7°N, 75.8°E). Continuous field measurements were carried out over a 90-day period (February–April 2026), recording solar irradiance, ambient temperature, wind speed, inlet/outlet water temperature, and mass flow rate at 10-minute intervals using calibrated instruments. Thermal performance was evaluated using the ASHRAE 93-2010 testing standard combined with first-law thermodynamic analysis, determining instantaneous thermal efficiency, useful heat gain, overall heat loss coefficient, collector heat removal factor, and thermal time constant [1]. Experimental results show a peak instantaneous thermal efficiency of 68.4% at a mass flow rate of 0.030 kg/s, with average daily efficiency ranging from 52.1% to 61.7% over the testing period. Under a peak direct normal irradiance (DNI) of 945 W/m² and an ambient temperature of 36.2°C, the outlet water temperature reached a maximum of 84.6°C. A strong positive correlation (Pearson r = 0.91) was observed between DNI and useful heat gain, while wind speeds ranging from 1–12 m/s increased convective heat losses from the receiver by 12–18% compared to calm conditions. Regression analysis further showed that the selective black chrome coating reduced radiative losses to just 22% of the value obtained with conventional black paint. These findings confirm the technical viability of PTSC-based systems for efficient, cost-effective water heating in semi-arid climates such as Central India. |
