Natural convection heat transfer from a horizontal hollow cylinder with internal longitudinal fins

Three dimensional numerical simulations have been carried out by solving the continuity, momentum and the energy equations to predict the flow and the temperature field around an internally finned horizontal cylinder in natural convection. The fin height, fin spacing or the fin number and the length of the cylinder were varied at different Ra to predict the heat loss from the finned cylinder and interesting findings were obtained. The heat loss from a short cylinder (L/D < 1) can be maximum for certain height of the fin and certain fin number after which the heat loss can reduce if the fin height increases or the fin spacing decreases in the laminar range of Ra to within 107. When the length of the cylinder increases (L/D > 1) the maximum point of heat loss vanishes for all heights of the fins and fin spacing. A table has been generated to show the optimum configuration of fin height, fin number where maximum heat loss can take place. The average Nu of the finned cylinder was seen to be decreasing with H/D, L/D and increasing with Ra. From the enormous numerical simulations that has been done in the present study a general correlation for the Nu as a function of L/D, H/D, fin number, N and Ra has been developed to within an accuracy of ±6% which can be beneficial to the industry and practical designers.