Characterization of convective heat transfer in channels of small cross section using digital interferometry

Forced convection in channels of small cross sectional dimensions has been recommended as an effective heat removal method for electronic components and packages. Many of the experimental results reported in the literature on the heat transfer performance of small-cross section channels are of contradicting nature, even though some generally agreeing results are also found. One of the probable reasons for the deviations, as suggested by investigators, is the intrusive nature of measurement techniques, which interferes with the flow field. Hence a non intrusive measurement technique is preferable for temperature measurement in small channels. The present work is aimed at developing an interferometric method for convective heat transfer measurement in a liquid medium flowing through channels of small cross sectional dimensions, with hydraulic diameters ranging from 12 to 3 mm and characterizing the nature of fluid flow and heat transfer in these channels. Mach–Zehnder interferometric arrangement is used to obtain the temperature distributions in water flowing through the channels, which are further analyzed digitally to obtain the local heat transfer coefficients and Nusselt numbers. The results are compared and contrasted with classical results for channel flow and heat transfer, and attempt has been made to interpret the variations and deviations observed. The experimental study has been performed under different fluid velocities in the laminar flow regime, and under various wall heat fluxes corresponding to the heat dissipation range expected in microelectronic devices. Parametric variations for the heat transfer performance have been obtained and correlated using the experimental results.