Natural convection heat transfer from a vertical circular tube sheet

Experiments were conducted to determine natural convection heat transfer coefficients (a) on a plain vertical circular plate, and (b) on a similar plate with a square array of non-conducting tubes fixed in it. The experiments were carried out using air as the heat transfer medium. The diameter of the brass plates used was 350 mm. The diameter of the bakelite tubes used was 19.2 mm. The range of Rayleigh numbers was from 1.06x108 to 1.66x108. The results show that the heat transfer coefficients in case (a) are very close to those obtained using standard correlations for vertical flat plates, whereas for case (b) the heat transfer coefficients are at least 50 percent higher than those predicted by the Churchill-Chu correlation. It is hence concluded that the disturbance to boundary layer caused by the presence of tubes enhances the heat transfer coefficient significantly. (author). 4 refs., 3 figs