Boundary Condition Effect on Two-Phase Fluid Flow and Heat Transfer inside 3-D Microchannels

Two-phase Taylor flows play a vital role in dissipating heat effectively for the proper functioning of electronic systems. In the present study, the thermal performance of liquid-liquid Taylor flow was carried out in a 3D microchannel with uniform wall heat flux boundary for five different cases: uniform heat flux on the four walls, three walls, two opposite walls, single wall, and two adjacent walls, and the aspect ratio of microchannel was varied in the range of 0.2-5. The length of the microchannel was 4 mm, height and width were 0.1 mm each for a square microchannel. For varying aspect ratios of the microchannel, the height and width of the microchannel were taken in the range of 0.06-0.3 mm to keep the hydraulic diameter constant. Dodecane and water were the working fluids in the study and assumed to be Newtonian, incompressible, immiscible, and the properties of fluids were assumed to be independent of temperature. The pressure distribution in the microchannel was investigated under five thermal boundary cases and the aspect ratio effect on pressure drop was also discussed. Results showed Nusselt number of two-phase flow with four-wall heat flux increases up to 280% compared to liquid-only flow and it has been validated with standard heat transfer correlation available in the literature. A higher heat transfer rate (Nu=10.41) was recorded in the opposite walls boundary condition and the heat transfer rate (Nu=7.81) was minimum when the adjacent walls were subjected to uniform heat flux. The effect of microchannel aspect ratio on Taylor flow heat transfer under thermal boundary conditions was also analyzed.