Chapter 3 - Single-Phase Liquid Flow in Minichannels and Microchannels

Abstract

This chapter focuses on the friction factor and heat transfer during liquid flow in microchannels. The need for higher heat transfer performance in IC chips, cold plates, and electronic components has been driving development in this area. A detailed analysis of pressure drop in microchannel systems is presented with design equations and tables for fully developed and developing flows. The minor losses are estimated using the available information on macroscale tubes. The importance of accurately measuring channel dimensions is emphasized as it leads to significant deviations from theoretical predictions. Roughness effects on friction factor and heat transfer are analyzed and a modified Moody diagram is presented based on the constricted flow model. Structured roughness is identified as a promising enhancement technique providing heat transfer performance superior to any of the conventional enhancement techniques. Heat transfer equations for entrance region and fully developed regions are presented for H1 and H2 boundary conditions. Some of the recent work on axial conduction effects and roughness effect on heat transfer is presented. The effect of nanofluids on heat transfer is reviewed. The chapter ends with an optimization section that indicates the need for enhanced microchannels. Solved examples are presented highlighting some of the recent developments in this area.