Flow Boiling in Microgap Channels: Experiment, Visualization by Tamanna Alam, Poh Seng Lee, Liwen Jin

By Tamanna Alam, Poh Seng Lee, Liwen Jin

Flow Boiling in Microgap Channels: scan, Visualization and Analysis offers an updated precis of the main points of the limited to unconfined stream boiling transition standards, stream boiling warmth move and strain drop features, instability features, part movement trend and circulation regime map and the parametric examine of microgap measurement. merits of movement boiling in microgaps over microchannels also are highlighted. the target of this short is to procure a greater primary figuring out of the circulate boiling strategies, evaluate the functionality among microgap and standard microchannel warmth sinks, and review the microgap warmth sink for instabilities and hotspot mitigation.

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Extra info for Flow Boiling in Microgap Channels: Experiment, Visualization and Analysis

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In a small sized channel, the vapor growth phase is limited in the radial direction because of the hydraulic diameter as shown in Fig. 1. Only the axial direction allows vapor growth when boiling occurs. On the contrary, in microgap heat sink, the vapor generated has room to expand both spanwise and downstream instead of being forced upstream as presented in Fig. 2 which minimizes the pressure fluctuation. Further, instead of wall heat flux if inlet pressure fluctuation is plotted at a given effective heat flux as is done in Fig.

It is noted by comparing the photos in Figs. 3 that at smaller microgap heat sinks, the effect of surface roughness is less marked. Confinement and coalescence of bubbles start at even low imposed heat flux 13 W/cm2 and confined slug/ annular flow dominant the boiling behavior at this 300 lm microgap heat sink. 2 Flow Boiling Curves Surface roughness effects on boiling curves for different microgap sizes at mass flux, G = 390 kg/m2s are presented in Fig. 4. 6 lm microgap heat sinks. The local wall temperatures presented here are those measured near the exit at diode position 15.

11. The spanwise wall temperatures presented here are those measured near the exit at diode position 5, 10, 15, 20, and 25. It is noted from the figure that microgaps ranging from 100 to 360 lm maintain very uniform and low wall temperature, whereas 500 lm maintains uniform but slightly higher wall temperature. This is attributed to stable annular flow and thin film evaporative boiling over the heated surface in smaller gap. In the thin film evaporative boiling dominant region, higher boiling heat transfer is possible due to the thinner micro-layer [2–4].

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