Experimental Study of Forced Convection Heat Transfer of Water in a Short Microduct at a Turbulent Reynolds Number

Abstract

The present study deals with experimental investigation of cooling of machining tools, by water flowing through a microduct at the tip of the tool. The average diameter of the microduct is 200 µm and the flow takes place at a turbulent Reynolds number. The outer wall temperature of the tool and the temperature of water at inlet and exit have been measured. The convective heat transfer coefficient is calculated at different wall temperatures and mass flux. The experimental results show that the average Nusselt numbers in the short microduct are higher than those predicted by conventional correlations for large-diameter ducts. This enhancement may be attributed to the micro size of the duct, entry effects, transition from laminar to turbulent flow at the microduct entrance, suspended microscopic particles in coolant water, and Prandtl number estimation based on the mean fluid temperature. A correlation has been proposed to compute convective heat transfer during turbulent flow through a short microduct of a particular geometry for a range of Reynolds and Prandtl numbers.