Numerical Analysis on Thermal Performance of the U-shaped Vacuum Tube Solar Collector

According to the basic principles of thermal transmission, the energy balance equations and efficiency expression of U-shaped vacuum tube solar collector are established. The thermal performance is evaluated by means of Matlab programming for changing inlet flow velocity, structure dimensions, solar irradiation and ambient temperature. Numerical analysis results present that slower incoming flow rate, smaller U-tube diameter, higher solar irradiation or bigger U-tube length can lead to higher outlet temperature. Where as faster incoming flow rate, bigger U-tube diameter, higher solar irradiance or higher ambient temperature can result in higher thermal efficiency. Compared with other factors, appropriate incoming flow rate and U-tube diameter are play an even greater role in improving hermal performance and optimizing structure.