HIGH HEAT FLUX SUBCOOLED FLOW BOILING OF METHANOL IN MICROTUBES

摘要

As the proper cooling of the electronic devices leads to significant increase in the performance, two-phase heat transfer to dielectric liquids can be of an interest especially for thermal management solutions for high power density devices with extremely high heat fluxes. In this paper, the pressure drop and critical heat flux (CHF) for subcooled flow boiling of methanol at high heat fluxes exceeding 1 kW/cm~2 is investigated. Methanol was propelled into microtubes (ID= 265 and 150 μm) at flow rates up to 40 ml/min (mass fluxes approaching 10000 kg/m~2-s), boiled in a portion of the microtube by passing DC current through the walls, and the two-phase pressure drop and CHF were measured for a range of operating parameters. The two-phase pressure drop for subcooled flow boiling was found to be significantly lower than the saturated flow boiling case, which can lead to lower pumping powers and more stability in the cooling systems. CHF was found to be increasing almost linearly with Re and inverse of inner diameter (I/ID), while for a given inner diameter, it decreases with increasing heated length.