Numerical study of wind effects on combined convective heat loss from an upward-facing cylindrical cavity

Abstract

Cavity receivers play a key role in the utilization of solar energy, and the convective heat losses in them can directly affect their efficiency. Yet the effect of wind on convective heat losses has not been investigated extensively. In this paper, taking an isothermal upward-facing cylindrical cavity as object, the combined convective heat loss under windy condition was studied by three-dimensional numerical model. The influences of surface temperature, cavity tilt angle, wind incident angle and wind speed were analyzed. The results were compared with those in no-windy condition. To facilitate engineering applications, empirical correlations for predicting combined convective heat loss were developed. Results show that the combined convective heat loss increases with increasing surface temperature. With the disturbance of wind, the effect of cavity tilt angle becomes complicated and is related to wind condition. For almost all of cases, as wind speed increases from zero, the combined convective heat loss is initially dropped and then increased, i.e., a minimum is observed. And the minimum is even below that in no-windy condition. The wind incident angle for maximizing combined convective heat loss is not fixed and can be affected by cavity tilt angle and wind speed.