Experimental Investigation on Natural Convection Behavior Inside the Shroud of a Closed Vertical Cylindrical Vessel With Ellipsoidal Head and Development of Heat Transfer Correlation

ABSTRACT Natural convection heat transfer from a closed vertical cylindrical vessel with a shroud has been investigated experimentally. The experimental study has been performed for the large‐diameter cylindrical vessel having a diameter of 0.8 m. The steam at atmospheric pressure has been injected into the vertical cylindrical vessel. The shroud around the vessel has been used to enhance the heat transfer performance. Experiments were conducted at different steam injection rates at atmospheric pressure and saturated steam conditions. The vessel outer wall temperatures and the air temperatures in the gap between the vessel and shroud at different vertical locations were measured during experiments using thermocouples. The heat transfer coefficients, Nusselt numbers, and Rayleigh numbers at different vertical locations have been calculated. The Rayleigh number varies from 4.48 × 10 7 to 6.03 × 10 9 based on the locations from the bottom to the top section of the closed vertical cylindrical vessel with ellipsoidal head. In the steady state, similar natural convection behavior of air between the vessel and shroud has been observed for different steam injection rates, as the outer wall temperature of the vessel at various vertical locations reaches a temperature close to that of saturated steam temperature, irrespective of the steam injection rate. The heat transfer coefficient was observed to decrease slightly from the bottom to the top vertical location on the vessel. The average heat transfer coefficient was found to be ≈ 7.98 ± 1.09 W/m 2 K. The variation in air temperature, vessel temperature, Nusselt number, and Rayleigh number along the vertical locations of the vessel has been discussed. The Rayleigh number was found to increase significantly along the height of the vessel. A correlation for the Nusselt number as a function of the Rayleigh number has been developed for the closed vertical cylindrical vessel with ellipsoidal head using experimental values. The comparison between developed correlation and well‐known published correlations has been performed. The values predicted by the published correlations were found to underpredict the results, possibly due to differences in shape and geometry.