Entropy Generation Analysis Of Heat Transfer In Microflows

Microfluidic chip is widely used to delivery, analysis, detect sample species and heat sink due to its small size, low cost, fast response and high precision. Electroosmosis and pressure are major means which could drive fluid to flow in microfluidic chip. The aim of this thesis is researching the effect of different values of flow parameters on characteristic of heat transfer in microchannel by means of theoretical analysis and numerical simulation, and major work and conclusion are as follows:Heat transfer in fully developed electroosmotic flow in a shit microchannel with taking temperature-dependent properties, Joule heating and viscous dissipation effect into consideration is investigated numerically, analyse the effect of flow parameters with different values on heat transfer. The results show that it is not necessary to consider temperature-dependent properties in majority of application, and an increasing dimensionless Joule heat parameter will deduce the effect of temperature-dependent properties on heat transfer and fluid flow. As dimensionless zeta potential or Debye-H?ckel parameter increasing, viscous dissipation will be restrained, but Joule heat will be enhanced. In general, the lager zeta potential will be, the higher dimensionless temperature ? will get.Heat and mass transfer in fully developed mixed electroosmotically and pressuredriven flow is investigated numerically by means of the second law, analyze proportion of each thermal effect in entropy generation. The results show that the dimensionless temperature ? and total entropy are lower and smaller in pressure opposed flow than those in pressure assisted flow. Local fluidic entropy is minimum value in the middle of microchannel and it will increase to maximum value at the wall. An increasing Debye-H?ckel parameter K will enlarge dimensionless ionic concentration. The effect of flow parameters on each thermal effect is pronounced, and will adjust the proportion of each thermal effect in entropy generation.Heat transfer of pressure-driven flow in shit microchannel is investigated numerically with considering viscous dissipation and the effect of zeta potential on fluidic electric resistance, analyze the effect of flow parameters with different values on heat transfer and the magnitude of streaming potential. The results show that current density balance is more precisely than current balance in analyzing microfluidic flow. Viscous dissipation will be immune to Debye-H?ckel parameter K. Electroviscous effect is the most significant at Debye-H?ckel parameter K=10, and fluidic total entropy is minimum correspondingly. An increasing electroviscous parameter ?* will deduce the velocity, streaming potential and total entropy generation in microchannel.By means of analyzing the effect of flow parameters-which could restrain the effect of Joule heat and viscous dissipation on heat transfer in microchannel-on heat transfer in microfluidic flow, and render a given microfluid to attain maximum value in heat transfer efficiency which has a direct significance on designing of microfluidic chip and heat sink for microelectronic component.