Boiling heat transfer and critical heat flux in high-speed rotating liquid films

Mudawwar, I.; El-Masri, M. A.; Wu, Chenlong; Ausman-Mudawwar, J.R.

doi:10.1016/0017-9310(85)90230-3

Cited by 17 publications

(9 citation statements)

References 9 publications

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“…This indicates that for low ω , nucleate boiling contributes significantly (

> 50 %

, according to a comparison with the correlation of Gungor and Winterton) to the overall heat transfer rate, while for increasing ω , nucleate boiling is partially suppressed and convective evaporation dominates. The suppression of nucleate boiling due to rotation is explained by the high single phase forced convection heat transfer coefficients observed in rotor–stator cavities, which removes the local superheat required for vapor bubble nucleation, and is observed in centrifugally enhanced thin film boiling . For pure convective evaporation, h b is assumed to be determined by

h_{L} a_{r}

and

h_{G L} a_{G}

in series, as indicated in Figure .…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, intensification of boiling heat transfer focuses on increasing the convective evaporation process, mainly by increasing the turbulence in the evaporating liquid and by decreasing the distance between heating surface and vapor–liquid interface by creating a thin liquid film. Enhancement of convective evaporation is realized by passive means, such as corrugated plates and finned surfaces, and by active means, such as rotating surfaces . In passive evaporators, the convective heat transfer is largely determined by the shear stress between the vapor and liquid phases, which makes it a strong function of x G .…”

Section: Introductionmentioning

confidence: 99%

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Forced convection boiling in a stator–rotor–stator spinning disc reactor

et al. 2016

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Boiling of a pure fluid inside the rotor-stator cavities of a stator-rotor-stator spinning disc reactor (srs-SDR) is studied, as a function of rotational velocity x, average temperature driving force DT and mass flow rate / m . The average boiling heat transfer coefficient h b increases a factor 3 by increasing x up to 105 rad s 21, independently of DT and / m . The performance of the srs-SDR, in terms of h b vs. specific energy input , is similar to tubular boiling, where pressure drop provides the energy input. The srs-SDR enables operation at > 10 5 Wm 23R , yielding values of h b not practically obtainable in passive evaporators, due to prohibitively high pressure drops required. Since h b is increased independently of the superficial vapor velocity, h b is not a function of / m and the local vapor fraction. Therefore, the srs-SDR enables a higher degree of control and flexibility of the boiling process, compared to passive flow boiling. V C 2016 American Institute of Chemical Engineers AIChE J, 00: 000-000, 2016 Keywords: evaporation, spinning disc reactor, heat transfer, intensification IntroductionForced convection boiling processes are widely encountered in the (chemical) process industry, e.g., in evaporative separations, in refrigeration cycles and in withdrawing heat of highly exothermic reactions.1,2 Intensification of boiling heat transfer reduces the required heat exchange area, which reduces the capital costs and the space requirements. Moreover, it allows the application of a lower temperature driving force DT, which is thermodynamically favorable and essential in utilization of low-grade heat streams using vapor recompression. Intensification of flow boiling is realized by increasing the boiling heat transfer coefficient h b , and by efficient removal of the formed vapor phase from the heat exchanging surface.The heat transfer in forced convection boiling occurs via two parallel mechanisms, viz. nucleate boiling and convective evaporation. [3][4][5][6][7] Both mechanisms contribute to the overall value of h b . Nucleate boiling is the formation of vapor bubbles at the heat exchanging surface, due to a high local superheating of the liquid. The formation of bubbles induces convection on a microscale, which leads to high values of h b , similar to pool boiling. 1,8,9 Convective evaporation is the macroscale fluid forced convection, with evaporation occurring at the liquid-vapor interface. Typically, at a high heat flux q 00 , obtained at a high DT, and a low vapor superficial velocity v G , h b is dominated by the nucleate boiling mechanism, resulting in a high value of h b . At a high vapor velocity (at a high mass flow rate / m or a high vapor fraction x G ), nucleate boiling is suppressed due to a more effective withdrawal of the local superheat by forced convection, 10,11 resulting in lower values of h b , compared to the nucleate boiling regime. 5,6 In this convective evaporation regime, h b increases with increasing turbulence in the liquid and decreasing distance between the heat exchanging ...

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“…This indicates that for low ω , nucleate boiling contributes significantly (

> 50 %

h_{L} a_{r}

and

h_{G L} a_{G}

in series, as indicated in Figure .…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Forced convection boiling in a stator–rotor–stator spinning disc reactor

et al. 2016

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“…An often-cited study by Tuckerman and Pease [2] proved such devices could dissipate up to 790 W/cm 2 from a simulated electronic heat source using water as working fluid. Interestingly, flow boiling in micro-channels has been the subject of intense study since the mid-1970s at the Massachusetts Institute of Technology Energy Laboratory for cooling of electrodes in magnetohydrodynamic energy converters and turbine blades [3]. A fairly large number of studies of flow boiling in microchannels have been published since the mid-1990s, e.g., [4][5][6][7][8][9][10][11][12][13][14][15][16].…”

Section: Application Of Subcooled Flow Boiling For High-flux Coolingmentioning

confidence: 99%

Fluid flow and heat transfer characteristics of low temperature two-phase micro-channel heat sinks – Part 2. Subcooled boiling pressure drop and heat transfer

Lee¹,

Mudawar²

2008

International Journal of Heat and Mass Transfer

110

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“…This form of cooling was the subject of intense study since the mid 1970s at the Massachusetts Institute of Technology Energy Laboratory for cooling of electrodes in magnetohydrodynamic energy converters and turbine blades [22]. A number of subsequent studies demonstrated the enormous cooling potential of subcooled flow boiling.…”

Section: Indirect Refrigeration Cooling and Subcooled Microchannelmentioning

confidence: 99%

Low-Temperature Two-Phase Microchannel Cooling for High-Heat-Flux Thermal Management of Defense Electronics

Lee¹,

Mudawar²

2009

IEEE Trans. Comp. Packag. Technol.

138

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For a given heat sink thermal resistance and ambient temperature, the temperature of an electronic device rises fairly linearly with increasing device heat flux. This relationship is especially problematic for defense electronics, where heat dissipation is projected to exceed 1000 W cm 2 in the near future. Direct and indirect low-temperature refrigeration cooling facilitate appreciable reduction in the temperature of both coolant and device. This paper explores the benefits of cooling the device using direct and indirect refrigeration cooling systems. In the direct cooling system, a microchannel heat sink serves as an evaporator in a conventional vapor compression cycle using R134a as working fluid. In the indirect cooling system, HFE 7100 is used to cool the heat sink in a primary pumped liquid loop that rejects heat to a secondary refrigeration loop. Two drastically different flow behaviors are observed in these systems. Because of compressor performance constraints, mostly high void fraction two-phase patterns are encountered in the R134a system, dominated by saturated boiling. On the other hand, the indirect refrigeration cooling system facilitates highly subcooled boiling inside the heat sink. Both systems are shown to provide important cooling benefits, but the indirect cooling system is far more effective at dissipating high heat fluxes. Tests with this system yielded cooling heat fluxes as high as 840 W cm 2 without incurring critical heat flux (CHF). Results from both systems are combined to construct an overall map of performance trends relative to mass velocity, subcooling, pressure, and surface tension. Extreme conditions of near-saturated flow, low mass velocity, and low pressure produce "micro" behavior, where macrochannel flow pattern maps simply fail to apply, instabilities are prominent, and CHF is quite low. One the other hand, systems with high mass velocity, high subcooling, and high pressure are far more stable and yield very high CHF values; two-phase flow in these systems follows the fluid flow and heat transfer behavior as well as the flow pattern maps of macrochannels.Index Terms-Electronics cooling, high heat flux, microchannel flow, phase change. NOMENCLATUREAspect ratio of microchannel. Boiling number. Specific heat.

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Boiling heat transfer and critical heat flux in high-speed rotating liquid films

Cited by 17 publications

References 9 publications

Forced convection boiling in a stator–rotor–stator spinning disc reactor

Forced convection boiling in a stator–rotor–stator spinning disc reactor

Fluid flow and heat transfer characteristics of low temperature two-phase micro-channel heat sinks – Part 2. Subcooled boiling pressure drop and heat transfer

Low-Temperature Two-Phase Microchannel Cooling for High-Heat-Flux Thermal Management of Defense Electronics

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