The effect of using ZrO2/Distilled water nanofluids on the thermal efficiency of an evacuated tube solar collector

One of the most widely used solar collectors is a vacuum tube solar collector. Nanofluids were used to improve the heat transfer performance of these collectors because they are characterized by high thermal conductivity. This paper studied the effect of (ZrO2/DW) nanoparticles on the thermal performance of an evacuated solar collector. The ZrO2 nanoparticles used were 60 nm in diameter with three different volume fractions of 1,3 and 5% vol nanoparticles examined at various flow rates of 46, 67, and 93 L/min. Experiments were carried out in Baghdad city of Iraq, at a longitude of 44° 14 ′ E and latitude of 33° 33 ′ N. The results showed that the volume fraction of nanoparticles 5%vol at a flow rate of 93 L/min attain the maximum useful heat gain. The values denoted that adding more nanoparticles enhanced the thermal efficiency of the evacuated solar tube. The thermal enhancement result of ETSC efficiency at a flow rate of 93 L/min is raised to 5.69% for the nanoparticles volume fraction of 5% vol, while the enhancement rate of distilled water was 4.03% for the same flow rate. Findings dedicated that temperature difference and absorbed energy increased when nanoparticles are used.