Flow Boiling in an Asymmetrically Heated Single Rectangular Microchannel

Heat transfer and fluid flow in microscale domains are found in many places such as microchannel heat sinks and microfluidic devices. In fact, microfluidic devices are the fastest growing area, and the development of these devices has greatly exceeded our ability to analyze them in detail. A two-phase microchannel heat sink is one of the best candidates for resolving this form of thermal management. Furthermore, limited pumping power capabilities in microscale devices have introduced concerns about large pressure drops in microchannel geometries. Many experimental investigations have been carried out to evaluate the pressure drop and heat transfer for in mini/microchannels. However, heat transfer and fluid flow in the microscale domain frequently display counterintuitive behavior due to the different forces dominating at micro-length scales. Therefore, experimental diagnostic techniques are essential for understanding two-phase pressure drop and flow boiling heat transfer in a microchannel. In addition, to elucidate the boiling heat transfer characteristics without interference from the flow distributor and the interactions between adjacent channels, it is necessary to study two-phase flow in a single microchannel. A modified Chisholm’s C parameter as a function of the hydraulic diameter based on measured the void fraction and frictional pressure drop for air-water flows in capillary tubes with inner diameters in the range of 1 to 4 mm was proposed (Mishima et al., 1993; Mishima & Hibiki, 1996). Two-phase flow pressure drop measurements for three refrigerants: R-134a, R-12, and R-113 were carried out (Tran et al., 2000). The experiments were performed in two round tubes (inner diameters of 2.46 and 2.92 mm) and one rectangular channel (4.06 x 1.7 mm). The measured two-phase frictional pressure drops were not accurately predicted by conventional macro-channel correlations. A new twophase frictional multiplier based on Chisholm’s B-coefficient method (Chisholm, 1973) as a function of the dimensionless physical property coefficient and the confinement number was suggested. Another modified C parameter based on the Lockhart-Martinelli two-phase multiplier was proposed with an air-water two-phase pressure drop experiments in a narrow channel 20 mm in width and 0.4 to 4 mm in height (Lee & Lee, 2001). They proposed a modified C parameter based on the Lockhart-Martinelli two-phase multiplier to take into