Measurement of wetted area fraction in subcooled pool boiling of water using infrared thermography

Kim, Hyungdae; Park, Youngjae; Buongiorno, Jacopo

doi:10.1016/j.nucengdes.2013.07.002

Cited by 43 publications

(13 citation statements)

References 15 publications

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“…It is known that at heat fluxes close to CHF dry spots are continuously forming on the boiling surface and getting rewetted by the surrounding liquid 6 8 25 33 34 35 . As also indicated by our infrared visualization of the boiling substrate, the boiling crisis is characterized by one or more of these localized dry spots spreading irreversibly and enveloping the entire heated surface in a continuous vapour layer.…”

Section: Resultsmentioning

confidence: 99%

Critical heat flux maxima during boiling crisis on textured surfaces

2015

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Enhancing the critical heat flux (CHF) of industrial boilers by surface texturing can lead to substantial energy savings and global reduction in greenhouse gas emissions, but fundamentally this phenomenon is not well understood. Prior studies on boiling crisis indicate that CHF monotonically increases with increasing texture density. Here we report on the existence of maxima in CHF enhancement at intermediate texture density using measurements on parametrically designed plain and nano-textured micropillar surfaces. Using high-speed optical and infrared imaging, we study the dynamics of dry spot heating and rewetting phenomena and reveal that the dry spot heating timescale is of the same order as that of the gravity and liquid imbibition-induced dry spot rewetting timescale. Based on these insights, we develop a coupled thermal-hydraulic model that relates CHF enhancement to rewetting of a hot dry spot on the boiling surface, thereby revealing the mechanism governing the hitherto unknown CHF enhancement maxima.

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Section: Resultsmentioning

confidence: 99%

Critical heat flux maxima during boiling crisis on textured surfaces

2015

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“…This is somewhat higher than observed in this study (~82%) and may be due to our use of a highly wetting liquid or a more conductive silicon substrate (ksi~ 120W/m-K). Recently, Kim et al [38] measured the wetted fraction using their DEPIcT technique and also observed irreversible dry spots at CHF using water at a variety of subcoolings. The wetted fraction at saturation reached as low as 50% at CHF, which was much lower than the current results.…”

Section: Discussionmentioning

confidence: 99%

Observations of the Critical Heat Flux Process During Pool Boiling of FC-72

Jung

Kim

2014

Journal of Heat Transfer

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Experimental work was undertaken to itivestigate the process by which pool-boiling critical heat flux (CHF) occurs using an IR camera to measure the local temperature and heat transfer coefficients on a heated silicon surface. The wetted area fraction (WF), the contact line length density (CLD), the frequency between dryout events, the lifetime of the dry patches, the speed of the advancing and receding contact lines, the dty patch size distribution on the surface, and the heat transfer from the liquid-covered areas were measured throughout the boiling curve. Quantitative analysis of this data at high heat flux and transition through CHF revealed that the boiling curve can simply be obtained by weighting the heat flux from the liquid-covered areas by WF. CHF mechanisms proposed in the literature were evaluated against the observations.

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“…These include the work by Kim et al . 31 and Jung et al . 32 using IR thermometry to visualize the liquid-solid interface and measure contact line length, density, and speed.…”

Section: Discussionmentioning

confidence: 92%

Increasing Boiling Heat Transfer using Low Conductivity Materials

Rahman

Pollack

McCarthy

2015

Sci Rep

143

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We report the counterintuitive mechanism of increasing boiling heat transfer by incorporating low-conductivity materials at the interface between the surface and fluid. By embedding an array of non-conductive lines into a high-conductivity substrate, in-plane variations in the local surface temperature are created. During boiling the surface temperature varies spatially across the substrate, alternating between high and low values, and promotes the organization of distinct liquid and vapor flows. By systematically tuning the peak-to-peak wavelength of this spatial temperature variation, a resonance-like effect is seen at a value equal to the capillary length of the fluid. Replacing ~18% of the surface with a non-conductive epoxy results in a greater than 5x increase in heat transfer rate at a given superheat temperature. This drastic and counterintuitive increase is shown to be due to optimized bubble dynamics, where ordered pathways allow for efficient removal of vapor and the return of replenishing liquid. The use of engineered thermal gradients represents a potentially disruptive approach to create high-efficiency and high-heat-flux boiling surfaces which are naturally insensitive to fouling and degradation as compared to other approaches.

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Measurement of wetted area fraction in subcooled pool boiling of water using infrared thermography

Cited by 43 publications

References 15 publications

Critical heat flux maxima during boiling crisis on textured surfaces

Critical heat flux maxima during boiling crisis on textured surfaces

Observations of the Critical Heat Flux Process During Pool Boiling of FC-72

Increasing Boiling Heat Transfer using Low Conductivity Materials

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