Study On Flow And Heat Transfer Characteristics Of Single Phase In Mini-channels

MicroChannel heat exchangers are widely applied in the micro-electronics cooling for their excellent heat dissipation ability. In this thesis the flow and heat transfer characteristics of mini-channels had been investigated by using CFD(computational fluid dynamics) methods, variable fluid properties and fluid- solid conjugate heat transfer technologies on the background of miro-electronics cooling.The effect of the ratio of length to hydraulic diameter, hydraulic diameter, the aspect ratio and porous ratio on flow and heat transfer of rectangular mini-channels had been investigated by using numerical methods and experiment. The results indicated: to eliminate the entrance effects the ratio of length to hydraulic diameter should not less than 70; with the decrease of hydraulic diameter, the resistance coefficient increased and heat transfer enhanced accordingly, additionally the diameter had no effect on the transition of laminar flow to turbulence; with the increase of aspect ration, the Reynolds number of transition increased accordingly but less than 2300, at the same time flow resistance and heat transfer enhanced accordingly; with the increase of porous ratio, the flow resistance of mini-channel would not change and heat transfer of that enhanced apparently.The effect of shape, height, collocation mode and space between of roughness cell on flow and heat transfer of 2-D parallel flat mini-channel had been investigated by using CFD numerical methods with triangle and rectangle as roughness cell. The height of roughness had a important effect on flow and heat transfer of 2-D parallel flat mini-channel; the shape and collocation mode of roughness cell also had important effect on that of 2-D parallel flat mini-channel, the flow resistance of triangle was larger than that of rectangle, the heat transfer of triangle was better than that of rectangle too; with the increase of velocity, the heat transfer had been enhanced, however the entrance length of heat transfer fully developed flow had been reduced accordingly, the flow resistance would increase gradually, the transitional Reynolds number of laminar flow to turbulence became smaller and smaller, the heat transfer would enhance accordingly, besides the flow resistance had been deviated from that of traditional theory; with the increase of the ratio of height to width of roughness cell, the flow resistance increased and heat transfer enhanced accordingly; with the increase of space between of roughness cell, the flow resistance decreased and heat transfer increased correspondingly.The effect of different section shape on flow, heat transfer and heat transfer enhancement of mini-channel had been investigated by using CFD numerical methods. At the condition of same hydraulic diameter, the flow resistance of circular channel is largest and that of square channel is least; the heat transfer of rectangular channel is best and that of circular channel is worst.The experiment platform had been set up and mini-channel heat exchanger had been produced. The effect of heat power and channel material on flow and heat transfer of rectangular mini-channels had been investigated in this thesis.