Investigation On Flow And Heat Transfer Characteristics In A Micro-Channel Heat Sink

As miniaturization, reduction in products weight, high power have become the latest trend in electronic products development, traditional design methods and manufacturing technology fail to meet today's demands. Of the currently available coolers for electronic products with a high heat flux, microchannel heat sinks have been proved to be able to provide the best heat transfer performance and are one of the most promising coolers. As the MEMS technology developemt, various heat sinks have been desigied and investigated.In this paper, four styles of heat sink were designed and investigated, each of their channel form is trapezium, rectangle, staggered arrangement fins and manifold microchannel (MMC) heat sink, thereinto staggered arrangement fins heat sink is a new structure. Their flow and heat transfer characteristics are thoroughly studied by experimental methods, and de-ionized water and surfactant aqueous solution are used as working fluids.Pre-experimental-study of flow and heat transfer characteristics of rectangle and staggered arrangement fins heat sinks, influence of viscous dissipation was reviewed. The experimental results indicate that the viscous dissipation don't influence the flow and heat transfer characteristics due to microchannels are relative short and flow velocity is slow.It's indicated by experimental study that drag reduction effects aren't obvious at low Reynolds number whichever MMC and TMC by adding little surfactants, on the contrary heat transfer performance is reduced, this is related with absoption characteristic of surfactants.By comparison of four heat sinks'performance, it's found that friction factor and pump power of staggered arrangement heat sink are larger at same Reynolds number due to its particular form, the difference of heating film surface temperature of MMC is smaller, but its heat resistance is larger because its soleplate is thicker, the difference of heating film surface temperature of triangle microchannel heat sink is larger and performance of heat transfer is worse.The results showed that the experimental values of the friction factor of the de-ionized water in a microchannel don't agree well with those calculated using the theoretical laminar formula chichever isothermal water or non-isothermal water. The break transformation of laminar flow to turbulent flow dosn't appeared when Reynolds number is 1400 in trapezium heat sink, and friction factor of isothermal water and non-isothermal water has biggish difference which is that friction factor of non-isothermal water in rectangle heat sink is smaller than in trapezium. It's considered that friction factor and transformation of flow pattern is related with channel roughness by analysis.The results indicated that Nusselt number is influenced by heat flux. Experimental values of trapzium microchannel heat sink are compared with those calculated using a fitting equation given in the paper, and that rectangle micro-channel heat sink agree well with empirical equation given by Stephan. Performance of rectangle microchannel heat sink is better than trapzium microchannel heat sink.Whichsoever heatsink, it couldn't enhance performance of heat sink just by increase Reynolds number or pump power, but to roundly consider all factors such as form, material and working substance.