Flow Resistance And Heat Transfer Characteristics In Micro-cylinder-groups And Numerical Simulation

Owing to the advance of micro electronic technology,the thermal load of equipment and component have increased dramatically,however traditional cooling technique is insufficient to the development of contemporary industry technology.Micro-Cylinder-Groups as one kind of microchannel construction,which can increase the heat transfer areas,what's more,the boundary layer destroyed efficiently because of the turbulent flow,and the heat transfer ability advanced obviously.The paper set up an experimental system of micro-cylinder-groups,through experimental and simulation investigate on flow resistance,heat transfer characteristics and subcooled boiling characteristics associated with the forced of working fluid through micro-cylinder-groups.The experimental investigation on flow resistance characteristics of micro-cylinder-groups for de-ionized water found that the pressure drop between inlet and outlet increase with the flow volume of working fluid,and the higher micro-cylinder-groups will produce greater pressure drop.When Re < 150,the friction factor decreased with the increase of Reynolds number rapidly,when Re > 450 the friction factor is close to constant.The existing conventional scale correlations do not accurately predict the friction factor for micro-cylinder-groups.Heat transfer characteristics about the micro-cylinder-groups have been experimentally investigated the temperature of plates wall decreased with the decrease of fluid flow volume,experimental Nusselt number increased with the increase of Reynolds number,and the relationship between Nu and Re is a linear relation.When Re < 100,influence by wall effect and conjugate heat transfer effect the Nusselt number is very small,increase height of cylinder and heating loads have small influence on Nusselt number.The existing conventional scale correlations do not accurately predict the Nusselt number for micro-cylinder-groups,an linear fitting equation about Nu and Re is also gotten based on the experimental data.An experimental research on heat transfer characteristics of subcooled boiling,the result show that the outlet temperature at low subcooling region does not change with the decreased of flux,the wall temperature increases quickly the bubbles adhere to the surface of wall and cylinder,the outlet temperature of working fluid remain unchanged.At high subcooling region,the wall temperature increases slowly,firstly the outlet temperature of working fluid increases after it remain unchanged.Under the same heating loads,cylinder height does has little influence the outlet temperature of working fluid at low subcooling region.By means of numerical simulation research the influence on flow resistance and heat transfer characteristics in micro-cylinder-groups by height of cylinder,transverse distance of cylinder,the arrangement of cylinder and cross section shape of cylinder,.The results show that increase height and transverse distance of cylinder,staggered array and the ellipse cross section shape can improve heat transfer capacity of micro-cylinder-groups,the result of numerical simulation fit to the experimental results.