Effect of Hydraulic Diameter on Condensation of R-134A in Flat, Extruded Aluminum Tubes

Webb, Ralph L.; Ermiş, Kemal

doi:10.1615/jenhheattransf.v8.i2.20

Cited by 55 publications

(25 citation statements)

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“…DP pred ¼ DP inlet þ DP gap þ DP outlet (8) where DP=Dz was the pressure gradient, / f was the two-phase multiplier, v was Lockhart-Martinelli parameter, ðDP=DzÞ f and ðDP=DzÞ g were the frictional pressure gradient with liquid or gas only, respectively, and DP pred , DP inlet, DP gap, and DP outlet were predicted pressure drops in the entire test section, inlet tube, condensation mini-gap, and outlet tube, respectively.…”

Section: Condensation Heatmentioning

confidence: 99%

“…Compared to conventional-sized hydrophilic channels, hydrophilic mini-channels, and microchannels have been shown to enhance condensation heat transfer [4][5][6][7][8]. Kandlikar [9] considered mini-channels to have diameters between 200 lm and 3 mm and microchannels to have diameters between 10 lm and 200 lm.…”

Section: Introductionmentioning

confidence: 99%

“…In mini-and microchannels, body forces such as gravity and buoyancy decrease in significance and surface tension increases in importance [10][11][12][13][14][15]. Condensation heat transfer coefficients typically increase with increasing mass flux and steam quality [7,8,12,13,16,17], except at low qualities [4,18].…”

Section: Introductionmentioning

confidence: 99%

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Combined Visualization and Heat Transfer Measurements for Steam Flow Condensation in Hydrophilic and Hydrophobic Mini-Gaps

Chu

Derby

2016

Journal of Heat Transfer

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Condensation enhancement was investigated for flow condensation in mini-channels. Simultaneous flow visualization and heat transfer experiments were conducted in 0.952-mm diameter mini-gaps. An open loop steam apparatus was constructed for a mass flux range of 50-100 kg/m 2 s and steam quality range of 0.2-0.8, and validated with single-phase experiments. Filmwise condensation was observed in the hydrophilic minigap; pressure drop and heat transfer coefficients were compared to the (Kim and Mudawar, 2013, "Universal Approach to Predicting Heat Transfer Coefficient for Condensing Mini/Micro-Channel Flow," Int. J. Heat Mass Transfer, 56(1-2), pp. 238-250) correlation and prediction was very good; the mean absolute error (MAE) was 20.2%. Dropwise condensation was observed in the hydrophobic mini-gap, and periodic cycles of droplet nucleation, coalescence, and departure were found at all mass fluxes. Snapshots of six typical sweeping cycles were presented, including integrated flow visualization quantitative and qualitative results combined with heat transfer coefficients. With a fixed average steam quality ( x ¼ 0.42), increasing mass flux from 50 to 75 to 100 kg/m 2 s consequently reduced average sweeping periods from 28 to 23 to 17 ms and reduced droplet departure diameters from 13.7 to 12.9 to 10.3 lm, respectively. For these cases, condensation heat transfer coefficients increased from 154,700 to 176,500 to 194,800 W/m 2 K at mass fluxes of 50, 75, and 100 kg/m 2 s, respectively. Increased mass fluxes and steam quality reduced sweeping periods and droplet departure diameters, thereby reducing liquid thickness and increasing heat transfer coefficients.

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Section: Condensation Heatmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Combined Visualization and Heat Transfer Measurements for Steam Flow Condensation in Hydrophilic and Hydrophobic Mini-Gaps

Chu

Derby

2016

Journal of Heat Transfer

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“…Macro-scale condensation has been well documented after over fifty years of study [1,2]. More recently, smaller diameter channels have been shown to offer higher heat transfer coefficients than macro channels, yet mini-and micro-scale condensation has only been explored for the last ten to fifteen years [3,4]. Despite larger heat transfer coefficients achieved by researchers at the mini-and micro-scales, few enhancements other than channel shape have been found at the mini-and micro-scale.…”

Section: Introductionmentioning

confidence: 99%

“…Condensation heat transfer coefficients increased with increasing mass flux and quality [3,4,[17][18][19][20], with a few exceptions found at lower mass fluxes [14,21]. Flow regimes affected condensation behavior; the absence of stratified flow, and the presence of annular flow at the mini-and micro-scales suggested that gravity does not play a significant role in small scale condensation [17,20,[22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

Flow condensation heat transfer enhancement in a mini-channel with hydrophobic and hydrophilic patterns

Derby

Chatterjee

Peles

et al. 2014

International Journal of Heat and Mass Transfer

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Multiphase Flow, Evaporation, and Condensation at the Microscale

Jensen

Peles

Kandlikar

2006

Advanced Micro and Nanosystems

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A review of boiling and condensation heat transfer, fluid flow, and pressure drop characteristics in mini-and microchannels is presented. Because this topic of research is relatively new, the literature is not as extensive as with conventional-sized channels. Nevertheless, flow patterns, heat-transfer coefficients (boiling and condensing), the critical heat flux condition, onset of nucleate boiling, and two-phase pressure drop data have been acquired and quantified to a limited extent. Likewise, engineering correlations and analytic/numerical approaches have been developed to predict behavior. Flow-and heat-transfer similarities and differences compared to large-scale systems have been observed, but further investigations are needed to fully assess and predict these thermohydraulic phenomena at the microscale.

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Effect of Hydraulic Diameter on Condensation of R-134A in Flat, Extruded Aluminum Tubes

Cited by 55 publications

References 0 publications

Combined Visualization and Heat Transfer Measurements for Steam Flow Condensation in Hydrophilic and Hydrophobic Mini-Gaps

Combined Visualization and Heat Transfer Measurements for Steam Flow Condensation in Hydrophilic and Hydrophobic Mini-Gaps

Flow condensation heat transfer enhancement in a mini-channel with hydrophobic and hydrophilic patterns

Multiphase Flow, Evaporation, and Condensation at the Microscale

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