On the Prediction of Pressure Fluctuations and Pressure Drop Caused by Confined Bubble Growth During Flow Boiling in a Rectangular Mini/Micro-Channel

doi:10.1080/01457632.2019.1670456

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On the Prediction of Pressure Fluctuations and Pressure Drop Caused by Confined Bubble Growth During Flow Boiling in a Rectangular Mini/Micro-Channel

Journal Article•DOI•

On the Prediction of Pressure Fluctuations and Pressure Drop Caused by Confined Bubble Growth During Flow Boiling in a Rectangular Mini/Micro-Channel

Shashwat Jain¹, Sateesh Gedupudi¹•Institutions (1)

Indian Institute of Technology Madras¹

29 Nov 2020-Heat Transfer Engineering (Taylor & Francis)-Vol. 41, Iss: 21, pp 1763-1783

TL;DR: In this paper, heat sinks based on flow boiling in microchannels have the potential to mitigate temperature rise in high heat flux devices such as electronic equipment. But the major challenge is the instabil...

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Abstract: Heat-sinks based on flow boiling in microchannels have the potential to mitigate temperature rise in high heat flux devices such as electronic equipment. One of the major challenges is the instabil...

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Liquid-liquid slug flow hydrodynamics and pressure drop in micro channels

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J. Jovanovic, Evgeny V. Rebrov, T.A. Nijhuis, Volker Hessel, J.C. Schouten - Show less +1 more

01 Jan 2010

TL;DR: In this article, the hydrodynamics and the pressure drop of liquid-liquid slug flow in round microcapillaries are presented, and two models are presented: the stagnant film model and the moving film model.

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Abstract: Abstract In this paper, the hydrodynamics and the pressure drop of liquid–liquid slug flow in round microcapillaries are presented. Two liquid–liquid flow systems are considered, viz. water-toluene and ethylene glycol/water-toluene. The slug lengths of the alternating continuous and dispersed phases were measured as a function of the slug velocity (0.03–0.5 m/s), the organic-to-aqueous flow ratio (0.1–4.0), and the microcapillary internal diameter (248 and 498 μm). The pressure drop is modeled as the sum of two contributions: the frictional and the interface pressure drop. Two models are presented, viz. the stagnant film model and the moving film model. Both models account for the presence of a thin liquid film between the dispersed phase slug and the capillary wall. It is found that the film velocity is of negligible influence on the pressure drop. Therefore, the stagnant film model is adequate to accurately predict the liquid–liquid slug flow pressure drop. The influence of inertia and the consequent change of the slug cap curvature are accounted for by modifying Bretherton’s curvature parameter in the interface pressure drop equation. The stagnant film model is in good agreement with experimental data with a mean relative error of less than 7%.

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20 citations

Journal Article•DOI•

Dynamic instabilities of flow boiling in micro-channels: A review

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Biao Wang, Yanwei Hu, Yurong He, N. G. Rodionov, Jiaqi Zhu - Show less +1 more

01 Jun 2022-Applied Thermal Engineering

TL;DR: In this article , a review of the literature addressing gas-liquid two-phase flow boiling dynamic instabilities in micro-channels in theoretical and experimental aspects is presented, combined with bubble dynamics, the mechanism and criteria of dynamic instability are revealed.

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12 citations

Journal Article•DOI•

Modeling of pressure drop and heat transfer for flow boiling in a mini/micro-channel of rectangular cross-section

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Shashwat Jain¹, Prasanna Jayaramu¹, Sateesh Gedupudi¹•Institutions (1)

Indian Institute of Technology Madras¹

01 Sep 2019-International Journal of Heat and Mass Transfer

TL;DR: In this paper, a one-dimensional model is proposed to estimate the pressure drop and heat transfer coefficient for flow boiling in a rectangular microchannel, taking into account the pressure fluctuations caused due to the confined bubble growth and the effect of pressure fluctuations on the heat transfer characteristics.

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12 citations

Journal Article•DOI•

Fourier series based 1-D numerical modelling of the dynamics of inclined closed loop buoyancy driven heat exchangers with conjugate effect

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Akhil Dass¹, Sateesh Gedupudi¹•Institutions (1)

Indian Institute of Technology Madras¹

01 Sep 2021-International Journal of Thermal Sciences

TL;DR: In this paper, a 1D numerical model of the dynamics of inclined closed loop buoyancy driven heat exchangers with inclusion of the wall conduction effect at the heat exchanger is presented.

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5 citations

Journal Article•DOI•

Growth of elongated vapor bubbles during flow boiling heat transfer in wavy microchannels

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Odumuyiwa A. Odumosu, Huashi Xu, Tianyou Wang, Zhizhao Che

01 Mar 2023-Applied Thermal Engineering

TL;DR: In this paper , Wang et al. studied the effect of the wavy structure of the microchannel on the growth of the vapor bubbles in the flow boiling process and quantified the effects of key dimensionless numbers on bubble growth rate and wall heat transfer, including the Weber number, the Capillary number, and Jakob number.

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2 citations

References

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Journal Article•DOI•

Patients’ Responsibilities in Medical Ethics

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Zhu Fengqing

28 Sep 2016-Philosophy study

TL;DR: It is argued that certain duties of patients counterbalance an otherwise unfair captivity of doctors as helpers and that vulnerability does not exclude obligation.

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Abstract: There has been a shift from the general presumption that “doctor knows best” to a heightened respect for patient autonomy. Medical ethics remains one-sided, however. It tends (incorrectly) to interpret patient autonomy as mere participation in decisions, rather than a willingness to take the consequences. In this respect, medical ethics remains largely paternalistic, requiring doctors to protect patients from the consequences of their decisions. This is reflected in a one-sided account of duties in medical ethics. Medical ethics may exempt patients from obligations because they are the weaker or more vulnerable party in the doctor-patient relationship. We argue that vulnerability does not exclude obligation. We also look at others ways in which patients’ responsibilities flow from general ethics: for instance, from responsibilities to others and to the self, from duties of citizens, and from the responsibilities of those who solicit advice. Finally, we argue that certain duties of patients counterbalance an otherwise unfair captivity of doctors as helpers.

...read moreread less

17,373 citations

Journal Article•DOI•

High-performance heat sinking for VLSI

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David B. Tuckerman¹, Roger Fabian W. Pease¹•Institutions (1)

Stanford University¹

01 May 1981-IEEE Electron Device Letters

TL;DR: In this paper, a water-cooled integral heat sink for silicon integrated circuits has been designed and tested at a power density of 790 W/cm2, with a maximum substrate temperature rise of 71°C above the input water temperature.

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Abstract: The problem of achieving compact, high-performance forced liquid cooling of planar integrated circuits has been investigated. The convective heat-transfer coefficient h between the substrate and the coolant was found to be the primary impediment to achieving low thermal resistance. For laminar flow in confined channels, h scales inversely with channel width, making microscopic channels desirable. The coolant viscosity determines the minimum practical channel width. The use of high-aspect ratio channels to increase surface area will, to an extent, further reduce thermal resistance. Based on these considerations, a new, very compact, water-cooled integral heat sink for silicon integrated circuits has been designed and tested. At a power density of 790 W/cm2, a maximum substrate temperature rise of 71°C above the input water temperature was measured, in good agreement with theory. By allowing such high power densities, the heat sink may greatly enhance the feasibility of ultrahigh-speed VLSI circuits.

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4,214 citations

Journal Article•

Proposed Correlation of Data for Isothermal Two-Phase, Two-Component Flow in Pipes

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R. W. Lockhart

01 Jan 1949-Chemical Engineering Progress

2,739 citations

"On the Prediction of Pressure Fluct..." refers methods in this paper

...Pressure drop in the two-phase region is calculated using the heterogeneous model developed by Lockhart and Martinelli [69]....
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...Nature of fluctuation, i.e., stable or unstable, was also quantified Nomenclature A area, m2 C Chisholm parameter C1 factor for estimation of wall superheat c2 constant CFD computational fluid dynamics D diameter, m Dh hydraulic diameter, m f Fanning friction factor freq frequency, Hz G mass flux, kg/m2s h height of the channel, m i counter for bubbles/slugs ilv latent heat of vaporization, J/kg k conductivity, W/m-K L length, m L1 nucleation site, m m liquid slug number in between the last bubble and the exit MAE mean absolute error n liquid slug number in between the first bubble n and second bubble from inlet p heated perimeter, m P pressure, Pa DP pressure drop, Pa q wall heat flux, W/m2 R critical cavity radius, m Re Reynolds number, Re ¼ (q U Dh / m) t time, s tnuc nucleation time period, s T temperature, K Dt time step, s DTsup wall superheat, Twall - Tsat, K U velocity, m/s w width of the channel, m x quality X2 Lockhart-Martinelli parameter Xm parameter, Xm ¼ lllv 0:07 1 x x 0:64 qv ql 0:36 z position of the bubble, m Greek symbols a aspect ratio, h/w b void fraction q density, kg/m3 e non-dimensional number, e ¼ rl rwallR U2ql r surface tension, N/m h contact angle, deg s time constant, s m dynamic viscosity, Pa-s ;2l two-phase frictional pressure drop multiplier Greek symbols acc acceleration base bubble base bub bubble ch channel cross cross-section d downstream end e exit heat heated in inlet l liquid lo entire mixture as liquid loc location max maximum min minimum nuc nucleation sat saturated sp single-phase sub sub-cooled sup superheat t time instant tp two-phase u upstream end v vapor vis viscous wait waiting by Wang et al. [16] based on the ratio of heat flux to mass flux (q/G)....
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...Average pressure drop in a microchannel heat sink is quantified using a separated flow model developed by Lockhart and Martinelli, based on steady-state thermodynamic equilibrium condition....
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...DPvis, sp ¼ 2 f G 2Lsub ql Dh (18) Pressure drop in the two-phase region is calculated using the heterogeneous model developed by Lockhart and Martinelli [69]....
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...The two-phase friction pressure drop multiplier U2l is based on the Lockhart-Martinelli parameter X2 and Chisholm parameter C. Table 2 lists different expressions for Chisholm parameter as a function of hydraulic diameter, mass flux, Reynolds number and quality....
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Journal Article•DOI•

Pure and Pseudo-pure Fluid Thermophysical Property Evaluation and the Open-Source Thermophysical Property Library CoolProp.

[...]

Ian H. Bell¹, Jorrit Wronski², Sylvain Quoilin¹, Vincent Lemort¹•Institutions (2)

University of Liège¹, Technical University of Denmark²

12 Feb 2014-Industrial & Engineering Chemistry Research

TL;DR: A survey of all the state-of-the-art formulations of thermophysical properties is presented, finding the most-accurate thermodynamic properties are obtained from multiparameter Helmholtz-energy-explicit-type formulations.

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Abstract: Over the last few decades, researchers have developed a number of empirical and theoretical models for the correlation and prediction of the thermophysical properties of pure fluids and mixtures treated as pseudo-pure fluids In this paper, a survey of all the state-of-the-art formulations of thermophysical properties is presented The most-accurate thermodynamic properties are obtained from multiparameter Helmholtz-energy-explicit-type formulations For the transport properties, a wider range of methods has been employed, including the extended corresponding states method All of the thermophysical property correlations described here have been implemented into CoolProp, an open-source thermophysical property library This library is written in C++, with wrappers available for the majority of programming languages and platforms of technical interest As of publication, 110 pure and pseudo-pure fluids are included in the library, as well as properties of 40 incompressible fluids and humid air The source code for the CoolProp library is included as an electronic annex

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1,472 citations

Journal Article•DOI•

Some characteristics of air-water two-phase flow in small diameter vertical tubes

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Kaichiro Mishima¹, Takashi Hibiki¹•Institutions (1)

Kyoto University¹

01 Aug 1996-International Journal of Multiphase Flow

TL;DR: In this article, the authors measured air-water flows in capillary tubes with inner diameters in the range from 1 to 4 mm and found that the boundary between flow regimes was predicted well by Mishima-Ishii's model.

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898 citations

"On the Prediction of Pressure Fluct..." refers methods in this paper

...Mishima and Hibiki [26] measured the void fraction, slug bubble velocity and frictional pressure drop for air-water two-phase flow in circular tubes with diameter ranging from 1mm to 4mm....
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...Mishima and Hibiki [26] C 1⁄4 21 1 expð 319DhÞ ð Þ be 1⁄4 1þ 1 xe xe qv ql 2 3 1...
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...Author(s) C Value Exit void fraction (be) Chisholm [72] C ¼ 5, 10, 12, 20, based on flow regimes be ¼ ð1þ 0:28 X0:71m Þ 1 Mishima and Hibiki [26] C ¼ 21 1 expð 319DhÞð Þ be ¼ 1þ 1 xexe qv ql 2 3 1 Qu and Mudawar [73] C ¼ 21 1 expð 319DhÞð Þ ð0:00418 Gþ 0:0613Þ be ¼ 1þ 1 xexe qv ql 2 3 1 Lee and Garimella [70] C ¼ 2566 G0:5466D0:8819h ð1 exp ð 319DhÞÞ be ¼ 1þ 1 xexe qv ql 2 3 1 Lee and Lee [74] C ¼ 0:06185 Re0:726lo be ¼ 1þ 1 xexe qv ql 2 3 1 David et al. [66] C ¼ 1:84 Re0:3lo þ 1:5 Relo x1:85 be ¼ 1þ 1 xexe qv ql 2 3 1 English and Kandlikar [75] C ¼ c2 1 exp 319Dhð Þð Þ c2 ¼ 5, 10, 12, 21, based on flow regimes be ¼ 1þ 1 xexe qv ql 2 3 1 Warrier et. al [71] C ¼ 38 be ¼ ð1þ 0:28 X0:71m Þ 1 Figure 10....
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