An ingenious fluidic capacitor for complete suppression of thermal fluctuations in two-phase microchannel heat sinks. (January 2020)

• Record Type: Journal Article
• Authors: Ghosh, Durga Prasad; Sharma, Deepak; Kumar, Anurag; Saha, Sandip Kumar; Raj, Rishi
• Is Part Of: International communications in heat and mass transfer. Volume 110(2020:Jan.)
• Publication Date: 2020-01
• Subjects: Flow boiling -- Instabilities -- Microchannel -- Pulse-dampener -- Nanostructure; CAD Computer Aided Design -- CHF Critical Heat Flux -- CNC Computer Numerical Control -- HTC Heat Transfer Coefficients -- NSM Nanostructured Microchannel -- OF Oblique Fin -- OMM Open Microchannel with Manifold -- ONB Onset of Nucleate Boiling -- PPF Piranha Pin Fin -- PTFE Polytetrafluoroethylene -- PWB Printed Wire Boards -- PWM Plain Wall Microchannel -- RC Reentrant Cavity -- SEM Scanning Electron Microscope -- Si Silicon -- SiNW Silicon Nanowires; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Heat -- Transmission; Mass transfer; Periodicals; 621.4022
• DOI: 10.1016/j.icheatmasstransfer.2019.104347
• Languages: English
• ISSNs: 0735-1933

Abstract

Abstract: Rapid bubble growth within the confinement of microchannels leads to undesired flow oscillations. The flow regime cycles between single-phase, bubbly/slug, backflow, dryout, and rewetting regimes. The large difference between the heat transfer coefficient (HTC) in these regimes induces significant thermal fluctuations (≈ ± 5 ° C) and the overall HTC is low. The intensity of backflow and the time-span of dryout increases with heat flux. As a result, a gradual deterioration in HTC followed by a premature CHF is encountered. Here we introduce an ingenious pulse-dampener for complete mitigation of two-phase thermofluidic fluctuations in microchannel heat sinks. An inflatable latex bladder in the outlet manifold acts as a fluidic capacitor to accommodate the excess vapor. Such on-demand vapor removal weakens backflow to avoid extended dryout. In sharp contrast to the heat sinks without pulse-dampener, a relatively high and monotonically increasing HTC without any thermal fluctuations is observed in experiments with pulse-dampener. A maximum HTC of ≈270 kW/m 2 . K at a heat flux of ≈2 MW/m 2 was observed with a nanostructured microchannel heat sink. The monotonically increasing HTC suggests that the true potential of this pulse-dampener-based heat sink design is much larger than the maximum heat flux of ≈2 MW/m 2 tested in our work. Highlights: Fabricated an ingenious two-phase pulse-dampener using an inflatable latex bladder Pulse-dampener is incorporated at the outlet manifold of a microchannel heat sink. Pulse-dampener acts as a fluidic capacitor to facilitate on-demand vapor venting. Improved vapor removal weakens backflow to avoid extended dryout of microchannels. Quenching due to continuous high-frequency rewetting reduces thermal fluctuations. Relatively high and monotonically rising heat transfer coefficient up to 2 MW/m 2