Boiling instability in parallel silicon microchannels at different heat flux
Boiling instability in parallel silicon microchannels at different heat flux
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DOI：
10.1016/j.ijheatmasstransfer.2004.04.012
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发表时间：
2004-08
影响因子：
5.2
通讯作者：
Huiying Wu;P. Cheng
中科院分区：
文献类型：
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作者：
Huiying Wu;P. Cheng
本文对常压下微通道内水在不同热流密度和质量流量下的沸腾不稳定模式进行了实验研究。实验中使用了8个平行的硅微通道，具有相同的梯形横截面，水力直径为186 μm，长度为30 mm。当壁面热流密度从13.5 W/cm 2增加到22.6 W/cm 2，水的时均质量流量从14.6 g/cm 2 s减少到11.2 g/cm 2 s时，微通道内出现了3种不稳定沸腾模式。这些是（1）在低热流密度和高质量通量下的液体/两相交替流动（LTAF），（2）在中等热流密度和中等质量通量下的连续两相流动（CTF），以及（3）在高热流密度和低质量通量下的液体/两相/蒸气交替流动（LTVAF）。同时，壁温，进口和出口的水的温度和压力，和瞬时质量通量的周期性振荡进行了测量。在三种不稳定沸腾模式中，LTVAF的振荡幅度最大，压力和质量流量的振荡几乎是异相的。CTF中的振荡幅度最小，压力和质量流量的振荡几乎同相。LTAF的振荡幅度介于LTVAF和CTF之间，压力和质量流量的振荡几乎是异相的。振荡周期（包括两相周期、液相周期和汽相周期）与热通量和质量通量的大小密切相关。在两相流阶段，微通道内出现了泡状流和一些特殊的两相流流型。
In this paper, a series of experiments have been carried out to study different boiling instability modes of water flowing in microchannels at various heat flux and mass flux with the outlet of the channels at atmospheric pressure. Eight parallel silicon microchannels, with an identical trapezoidal cross-section having a hydraulic diameter of 186 μm and a length of 30 mm, were used in this experiment. When the wall heat flux was increased from 13.5 to 22.6 W/cm2and the time average mass flux of water was decreased from 14.6 to 11.2 g/cm2s, three kinds of unstable boiling modes were observed in the microchannels. These were (1) the liquid/two-phase alternating flow (LTAF) at low heat flux and high mass flux, (2) the continuous two-phase flow (CTF) at medium heat flux and medium mass flux, and (3) the liquid/two-phase/vapor alternating flow (LTVAF) at high heat flux and low mass flux. Simultaneously, periodic oscillations of wall temperature, inlet and outlet water temperatures and pressures, and instantaneous mass flux were measured. Among the three unstable boiling modes, oscillation amplitudes in LTVAF were the largest with oscillations of pressures and mass flux nearly out of phase. Oscillation amplitudes in CTF were the smallest with oscillations of pressures and mass flux nearly in phase. Oscillation amplitudes in LTAF lied in between LTVAF and CTF with oscillations of pressures and mass flux nearly out of phase. Also, the oscillation period (including two-phase period, liquid period and vapor period) depends greatly on the amounts of heat flux and mass flux. Bubbly flow and some peculiar two-phase flow patterns were observed in the microchannels during two-phase flow periods.