The Experimental Development of Solar Collector with Different Types of Nanofluid

<ns7:p>In the present study, the flow rate and nanofluid effects on a parabolic trough solar collector were examined experimentally in Kirkuk city climate conditions during the period from May to July. Three flow rates, 0.1, 0.2, and 0.3 l/min were utilized. The theoretical and experimental results prove that lower flow rates enhance the thermal performance significantly as they increase the fluid residence time. According to the obtained results, two nanofluids, ZnO-water and MgO-water (at 0.2 wt. %), were experimentally evaluated at the optimal flow rate of 0.1 l/min. Both nanofluids showed better results than base fluid (water). Thus, MgO exhibited a better thermal efficiency of 66.9% at 12 pm than ZnO (62.7%) and water (57.19%). Directly, MgO generated the better thermal efficiency with maximum outlet temperature of MgO was 75.08°C. This could be due to the higher thermal efficiency of MgO-water, which is attributed to its much higher thermal conductivity (48.4 W/m·K) than ZnO (29 W/m·K). The exergy efficiency was nearly the same and negligible, that is, 13.8% for MgO, owing to the thermodynamic limitations. The practical results show that MgO nanofluid at a low flow rate could be an optimal solution for the parabolic trough solar collector.</ns7:p>