FREE-CONVECTION HEAT-TRANSFER IN MULTIPLE VERTICAL CHANNELS

Free convection heat transfer in multiple parallel vertical channels with isothermal walls is considered in this paper. Systems consisting of two, three and an infinite number of channels located side by side and with aspect ratios (the ratio of channel height to its width) ranging from 5 to 20 and for Grashof numbers, based on the channel width, up to 10(5) were investigated numerically. Results show that the heat transfer in a channel is affected by its interaction with the neighboring channels, This interaction depends upon the number of participating channels; it increases with an increase of the Grashof number and decreases with an increase of the distance between the channels. Compared with a single isolated channel, the Nusselt number in the case of a two-channel system increases by up to 5% on the channel inner wall (wall closer to the other channel) and decreases by up to 5% on the channel outer wall. When an infinite number of channels is present (periodic configuration), the Nusselt number increases by up to 18%. When heat transfer only in the entrance region of the channel is considered (the first 10% of the channel total length), the interaction between the channels increases the corresponding Nusselt number by up to 38% on the channel inner wall and decreases it by up to 33% on the channel outer wall for a two-channel system and increases it by up to 48% for the periodic configuration. Correlations permitting quick determination of the Nusselt numbers for both configurations are given.