Assessment of the thermal performance of an evacuated tube solar collector with and without solar reflective curtain by using nano-fluid

In this paper, the improvement of vacuum solar collector efficiency is studied by two methods. The first method is to place a solar reflective curtain in front of the solar vacuum collector that operates on the solar panel system. This curtain increases the amount of reflection of solar radiation back to the vacuum collector. The curtain automatically follows the sun’s rays, and the reflectors’ movement depends on the nanofluid’s temperature. The second method uses the ZrO2 nanofluid with a diameter of 60 nm with distilled water. The experiment used three volume concentrations, 1,3 and 5% by volume, with three flow rates of 30,50, and 60 L/m, respectively. The results showed an improvement of the thermal properties of the solar vacuum collector when using the solar reflective curtain and nano-liquid by 10.76%, while the amount of progress without using the solar reflective curtain was 5. 51%.