Measurement of Vapor Superheat in Post-Critical-Heat-Flux Boiling

A differentially-aspirated superheat probe was developed to measure vapor temperatures in post-critical-heat-flux, dispersed-flow boiling. Measurements obtained for water, at low-to-moderate pressures and mass flow rates in a tube, indicated very significant non-equilibrium, with vapor superheats of several hundred degrees (°C). Predictions of published correlations showed unsatisfactory agreement with the experimental results.

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Experimental results and interfacial lift-off model predictions of critical heat flux for flow boiling with subcooled inlet conditions – In preparation for experiments onboard the International Space Station

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2021.122241 ◽

2021 ◽

pp. 122241

Author(s):

Steven J. Darges ◽

V.S. Devahdhanush ◽

Issam Mudawar ◽

Henry K. Nahra ◽

R. Balasubramaniam ◽

...

Keyword(s):

Heat Flux ◽

International Space Station ◽

Critical Heat Flux ◽

Flow Boiling ◽

Space Station ◽

Experimental Results ◽

International Space ◽

Model Predictions ◽

Inlet Conditions ◽

Lift Off

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Flow Boiling in Microscale at High Flowrates

ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels, Volume 2 ◽

10.1115/icnmm2011-58289 ◽

2011 ◽

Cited By ~ 2

Author(s):

Ali Kos¸ar

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Critical Heat Flux ◽

Boiling Heat Transfer ◽

Flow Boiling ◽

Nucleate Boiling ◽

High Flow ◽

High Mass ◽

Flow Rates ◽

Micro Scale

Boiling heat transfer is an important heat removal mechanism for cooling applications in micro scale and finds many applications. Many studies were conducted to shed light on boiling heat transfer in microchannels. They were concentrated on saturation boiling at low mass fluxes (G<1000 kg/m2s). With the enhancement in micro pumping capabilities, flow boiling could be performed at higher mass velocities so that high cooling rates (>1000 W/cm2) could be possibly attained. Due to the increasing trend in critical heat flux and suppression of boiling instabilities with increasing mass velocity flow boiling is becoming more and more attractive at higher mass velocities, where subcooled boiling conditions are expected at high mass velocities. With the shift from low to high flow rates, a transition in both boiling heat transfer (saturated boiling heat transfer to subcooling boiling heat transfer) and critical heat flux (dryout type critical heat flux to departure from nucleate boiling critical heat flux) from one mechanism to another is likely to occur. Few experimental studies are present in the literature related to this subject. In this paper, it is aimed at addressing to the lack of information about boiling heat transfer at high flow rates and presenting experimental data and results related to boiling heat transfer and Critical Heat Flux (CHF) at high flowrates. New emerging technologies resulting in local heating such as nano-scale plasmonic applications and near field radiative energy exchange between objects could greatly benefit from boiling heat transfer at high flow rates in micro scale.

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Study of the critical heat flux condition with water and R-123 during flow boiling in microtubes. Part I: Experimental results and discussion of parametric effects

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2009.02.003 ◽

2009 ◽

Vol 52 (13-14) ◽

pp. 3235-3249 ◽

Cited By ~ 22

Author(s):

A.P. Roday ◽

M.K. Jensen

Keyword(s):

Heat Flux ◽

Critical Heat Flux ◽

Flow Boiling ◽

Experimental Results ◽

Flux Condition ◽

Parametric Effects

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Near Critical Heat Flux From Small Substrates Under Controlled Spray Cooling

Volume 1: Heat Transfer in Energy Systems; Thermophysical Properties; Heat Transfer Equipment; Heat Transfer in Electronic Equipment ◽

10.1115/ht2009-88281 ◽

2009 ◽

Cited By ~ 1

Author(s):

Sergio Escobar-Vargas ◽

Jorge E. Gonzalez ◽

Orlando Ruiz ◽

Cullen Bash ◽

Ratnesh Sharma ◽

...

Keyword(s):

Heat Flux ◽

Mass Flow Rate ◽

Critical Heat Flux ◽

Mass Flow ◽

Flow Rate ◽

Heat Dissipation ◽

High Heat ◽

Heat Fluxes ◽

Experimental Results ◽

High Heat Flux

The increasing power density on electronic components has resulted in temperature problems related to the generation of hot spots and the need to remove high heat flux in small areas. This work is aimed at the cooling of small surfaces (1 mm × 1.2 mm) by using a monodisperse spray from thermal ink jet (TIJ) atomizers. Heat fluxes near the critical heat flux (CHF) are obtained for different conditions of cooling mass flow rate, droplet deposition, and number of active droplet jets. Experimental results at quasiequilibrium show the heat flux scales to the cooling mass flow rate. It is observed that two simultaneously activated jets result in slightly smaller heat flux compared to a single jet of droplets for the same mass flow rate. Droplet momentum and spreading or splashing, as determined by a combination of Weber number and Reynolds number effect via K = We1/2Re1/4, may impact the efficiency of the delivery of the cooling mass flow. Current experimental results at K = 24.5 and K = 52.2 for the copper surface temperatures ranging 110 – 120 °C indicate there is little influence of the splashing on the heat dissipation. System heat losses are measured experimentally and compared to a numerical and analytical solution to estimate the actual heat dissipated by the droplet change of phase.

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