Numerical Study Of Convective Heat Transfer In The Dimpled Channel

Present thesis applies numerical simulation to study flow and heat transfer in rectangular channel with a dimpled surface.In the past of twenty years, people have increased heat transfer of channel with the rough channel wall, for instance, rib, groove, cavity, protrude, dimple and so on. Many researchers, in particular, is interesting in the channel with the array of dimples on a wall. A great deal of experimental data, measured on the rectangular dimpled channel, are given to illustrate enhancement of the overall heat transfer rate is about 1.5~3.5 times of smooth surface value. The improvements in surface heat transfer augmentation produced by arrays of dimples are useful in a variety of practical applications, including electronics cooling, heat exchangers, macro- and micro-scale passages, bio-medical devices, and combustion chamber liners.Present thesis, in the first, built up the physical model of the rectangular channel with the arrays of dimples on the bottom surface, on the basis of actual flow and heat transfer in the channel, brought forward the hypothesizes and built up the math model. In the math model turbulent model was employed, and algorithm was applied to resolve the pressure-velocity coupling. This model was checked up by the experimental data.Present thesis simulated the flow and heat transfer of the big scale rectangular channel with a dimpled surface. Numerical data indicate: While the liquid stream the dimple, the fluid flow separated from the edge of the dimple, formerly boundary layer were broke, the lengthways vortex, transverse vortex and the secondary flow produce in the dimple, these vortexes and the secondary flows will influence the fluid in the channel. In the condition of difference Reynolds numbers, the vortexes produce and vanish in the difference frequency, accordingly, the flow and heat transfer periodically change in the dimpled channel, the quantity of the local heat transfer is lowest in the both sides of the upstream halves of the dimples.The numerical investigation was conduced to analyze the flow field and heat transfer characteristics in the narrow-channel with a dimpled surface. Computation results indicate: (1) the narrow-channel with the dimples can also augment the magnitude of heat transfer, and also increases the pressure drops in the channel. (2) The secondary flow and vortexes are also produced in the dimple, but the influence of these in the channel is small. (3) The heat transfer performance of the narrow-channel with a dimpled surface is under influence of Reynolds number, aspect ratio, dimple depth, dimple density, dimple print diameter. By the numerical investigation, thesis investigated flow and heat transfer in rectangular dimpled channel and narrow-channel with a dimple surface, discussed these factors that affect on the flow and heat transfer of the dimpled channel and the condition of these influences. These works will provide for farther investigation on the dimpled channel.