Enhancement on two phase flow boiling via expanding micro channel heat sinks

Abstract

It is proposed that the heat transfer method of two phase flow boiling is one of the most suitable solutions for solving the high heat flux in small spaces. And 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. In order to utilize two phase flow effectively and stably, a kind of radial expanding micro heat sink (REMHS) has been designed for the flow boiling process. The thermal performances of REMHS are inspected with visualization experiments under low flow inertia. The average mass flux ranges from 12.0~110.5 kg·m^-2s^-1 and heat flux spans from 79.6~176.4 kW/m². 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. And the heat transfer coefficient increases with xout and reaches 28 kW·m^-2K^-1 at x_out=0.52, which proves that the design and proposal of this expanding micro channel heat sink is a effective method to stabilize the flow instability and make full use of the heat transfer capacity of two phase flow boiling.