Investigations Of The Flow And Heat Transfer Characteristics In Printed Circuit Heat Exchanger

Fins and particles are two extensive used way to enhance heat transfer in heat exchangers. Aperiodic boundary condition is used to study the affect of the geometric construction on flow and heattransfer. An Eulerian model is used to investigate the flow and heat transfer characteristics of solid-liquid two phase flow in two dimensional wavy channels. The results and conclusions are describedbriefly as follows:(1) The characteristics of flow and heat transfer in two dimensional sinusoidal wavy channels havebeen investigated using Fluent periodic boundary condition. Effects of Reynolds numberRe (50Re1000) and geometric structure parameter (0.25-0.5、0.5-1) on the flow andheat transfer characteristics have been studyed. With the increasing of Re number, the flowcharacteristics of probe point were turn from steady flow to unsteady flow with certain oscillationfrequency. Friction factor f and Nu number both increased with the increasing of waveness.When the Re number tend to1000, Friction factor f and Nu number increased with theincreasing of spacing ratio. The performance factorsG=(Nu/Nu)/(f/f)1/300are used toevaluate the heat transfer in different wavy channel.(2) Flow and heat transfer in three dimensional sinusoidal wavy channels with rectangular section hasbeen investigated. Effects of Reynolds number(100Re800) and geometric structureparameter(0.1250.5、0.51.25、=0.151.0) on the flow and heat transfer havebeen studied. With the increasing of Re number, the flow characteristics of probe point werechanger from steady to unsteady.There are two kind of unsteady state, one is with certainoscillation frequency and another is without frequency. The simulation result showed that thewaveness, spacing ratio and aspect ratio have an effect on Friction factor f andNu number. The performance factorsG=(Nu/Nu)/(f/f1/300)are used to evaluate the heattransfer in different wavy channel.(3) The flow and heat transfer characteristic of solid-liquid two phase flow has been investigated withEulerian multiphase model when Reynolds number vary from100to1000. The effect of particlevolume fraction (p1%15%) and particle diameter (d15μm) on heat transferaugmentation were analysised. The results showed that adding particle of d1μm to the liquidcan enhance heat transfer. The performance factors G and Nu number both increased with theincreasing of volume fraction (p1%15%).