Experimental investigation on flow boiling in radial expanding minichannel heat sinks applied for low flow inertia condition

摘要

It is known that bubble elongation in an expanding channel produces a forward additional pressure caused by surface tension difference on both sides, which can relieve reverse flow. This merit is expected to solve the failure of heat sink under low mass flux and high vapor quality, where inlet subcooled liquid is rejected to channels by severe flow instability. In present work, two types of circular radial expanding minichannels heat sink (REMHS) utilizing flow boiling of deionized water are proposed. The thermal performances of REMHS are inspected with visualization experiments under low flow inertia. The average mass flux ranges from 12.0 to 110.5 kg.m(-2) s(-1) and heat flux spans from 79.6 to 176.4 kW/m(2). The experimental results illustrate that flow instability is substantially relieved in REMHS with a gentle temperature fluctuation (below 1.5 K). The inlet flow status in REMHS is barely affected by the flow instability at the downstream. Besides, the wall temperatures of REMHS display a good symmetry, showing an even flow distribution among the radial expanding channel array. With a rational design of expanding channel, no heat transfer deterioration occurs in REMHS-2, heat transfer coefficient increases with x(out) and reaches 28 kW m(-2) K-1 at x(out) = 0.52. The proposed REMHS is suitable for low mass flux condition with a superior heat transfer capacity, which enlarges the applicable range of REMHS and enables more operating modes. Applications of the proposed REMHS in traditional electronic cooling, as well as newly developed information and communication technology (ICT) thermal management system become promising. (C) 2019 Elsevier Ltd. All rights reserved.