Fabrication Of Cross-Connected Microchannel Porous Mesh Plate(CCMPMP) For Enhancing Heat Transfer

Nowadays, micro electronic components are developing toward micromation, high-power and high level of integration. The contradiction between high density heat flux and small heat dissipation space are becoming increasingly critical, which raise higher requirement for enhanced heat transfer technology. Enhanced heat transfer structures should meet the demands of high heat transfer performance and low pressure drop, and their manufacturing process shoud be as simple, efficient and cheap as possible. Therefore, a new enhanced heat transfer structure, namely cross-connected microchannel porous mesh plate(CCMPMP) is fabricated by traditional milling. CCMPMP has both structures of microchannel and regular pores. The main research contents are summarized as follows:(1) Fabrication of CCMPMP by millingCCMPMP is fabricated by up milling. The principle of milling microchannel is analysed. Then, some microchannel parameters, such as microchannel depth H_c, microchannel width W_c and microchannel interval W_s, are investigated experimentally. Finally, mechanical properties of CCMPMP, such as tensile, compressive and bending property, are investigated theoretically. Results show CCMPMP is successfully fabricated by milling, and two sets of perpendicular microchannels on both sides of metal plate intersect each other so as to form lots of meshes.(2) Burrs formation and control during fabricating CCMPMP by millingThe burr formation mechanism in fabricating CCMPMP is studied. And then the influences of radial depth of cut ae, cutting speed v, feed speed vf and mesh size on the burr formation are investigated experimentally so as to control and decrease the burr length. Results show that when every tooth exits some tear burrs occur on both top sides of the microchannel as the result of material tearing off the workpiece rather than shearing. When a_e is equal to or slightly larger than H_a/2, flake-like burrs are formed.When ae is much larger than H_a/2, curl-like burrs occur. The length of curl-like burrs can be decreased by increasing v and vf and decreasing the mesh size.(3) Cutting force model of milling microchannelCutting force model is established when the cutting thickness ac and the machined microchannel depth t is unchanged. The influences of the major and minor cutting edge and the side deformation of chip on the cutting force are investigated theoretically. Then, Cutting force of a single tooth in milling microchannel can be obtained based on the principle of up milling. Finally, Cutting force model of milling microchannel is established according to the distribution of all the teeth participating in cutting simultaneously. It can be concluded that cutting force in cutting microchannel arise from the major and minor cutting edge and the side deformation of chip, and cutting force in milling microchannel is composed of cutting forces of all the teeth participating in cutting simultaneously.(4) FEM simulation of milling microchannelFEM simulations of cutting and milling microchannel are carried out by using the commercial software DEFORM 3D. Then, some simulation results, such as the stress distribution, plastic deformation, metal flow velocity distribution and cutting force, are analysed and compared with cutting and milling boss, respectively. The results show cutting force in cutting microchannel increases with t, ac, and the cutting width aw, decreases with the rake angleγ0, and is little influenced by the cutting speed v. while, cutting force in milling microchannel increases with the radial depths of cut ae. Because the side deformation of chip is constrained, large stress occures on the the side face of the machined microchannel.(5) Enhanced heat transfer performance of CCMPMPSome porous properties of CCMPMP, such as porosity and specific surface area, are theoretically calculated, and the influences of W_s, H_c and W_c are discussed. Pressure drop and heat transfer performance are measured by using self-made testing systems. Finally, the influences of volume flowrate qV, porosity and specific surface area on pressure drop and heat transfer performance are investigated experimentally, and the optimum CCMPMP are obtained on the basis of the experimental results. Results show Pressure dropΔP and heat transfer coefficient per unit volume KV and per unit area KA become larger after packing heat exchanger with CCMPMP. High porosity favors high pressure drop and high porosity and large total surface area per unit volume is favorable for good heat transfer performance.