Liquid-liquid phase separation heat transfer in advanced micro structure

Wei, Xing; Plawsky, Joel L.; Woodcock, Corey; Yu, Xueli; Ullmann, Amos; Brauner, Neima; Peles, Yoav

doi:10.1016/j.ijheatmasstransfer.2018.08.090

Cited by 15 publications

(8 citation statements)

References 26 publications

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“…By substituting the above-derived dimensionless values in Equations ( 4), (13), and ( 15), the two-dimensional Cahn-Hilliard and the heat conduction equations are obtained. Three dimensionless numbers are derived from the above equations.…”

Section: Model Developmentmentioning

confidence: 99%

“…[1,8,9] Commonly, for the formation of anisotropic morphology through inducing a temperature gradient, quench is administered via one or two sides of the medium to induce a gradient in the cooling rate. [8,[10][11][12][13][14] This gradient leads to anisotropic morphology formation, the degree of which is determined by many factors, including the depth and rate of the quench. [9,[15][16][17][18][19][20] When a low molecular weight and high boiling point solvent is mixed with a polymer at a high temperature, thermodynamic instability serves as the basis for the TIPS process.…”

Section: Introductionmentioning

confidence: 99%

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Morphology formation during the nonisothermal thermally‐induced phase separation (TIPS) process

Ranjbarrad

Chan

2023

Can J Chem Eng

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In high‐viscosity polymer solutions and blends, temperature variations during the quench process of the thermally‐induced phase separation (TIPS) influence the dynamics and thermodynamics of phase separation. Hence, this study aims to investigate the impact of temperature variations on the morphology formation during the TIPS process. First, the influence of temporal temperature variations on phase separation is investigated by coupling a transient heat conduction model and the Cahn–Hilliard equation, and the results are compared with the isothermal phase separation process. Next, the morphology formation during phase separation is inspected by applying quench from two opposite sides of the sample to the same and different temperatures through coupling the Fourier heat transfer equation and the Cahn–Hilliard equation. The influence of the enthalpy of demixing on the morphology formation and the competition between the heat and mass transfer is also evaluated. It is confirmed that temporal variations of temperature alone have a significant impact on the morphology formation during the TIPS process. In addition, quenching the system to the same and different temperatures both leads to anisotropic morphology formation, which is affected by the quench rate, quench temperature, solution viscosity, and enthalpy of demixing. Upon applying different quench temperatures from opposite sides, two different types of morphologies and droplet sizes were formed as a result of the difference in the cooling rates between the two sides. Employing the enthalpy of demixing during phase separation induced a shallow quench effect on the deep quench side due to the fact that the heat moved toward the lowest temperature in the system, which led to the formation of a distinctive structure.

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Section: Model Developmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Morphology formation during the nonisothermal thermally‐induced phase separation (TIPS) process

Ranjbarrad

Chan

2023

Can J Chem Eng

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“…During the TIPS process, the quality of the solvent decreases through an instantaneous quench in systems with an upper critical solution temperature (UCST) or an immediate jump in temperature in systems with a lower critical solution temperature (LCST) [ 4 , 9 , 10 , 11 , 12 , 13 , 14 ]. In systems with an UCST, a low-molecular-weight high boiling point solvent is initially mixed with a polymer at an elevated temperature to form a homogenous mixture [ 15 , 16 , 17 , 18 ]. The temperature drops suddenly to induce phase separation by bringing the system into the two-phase region of the phase diagram where the system phase separates into polymer-rich and polymer lean phases [ 1 , 7 , 19 , 20 , 21 ].…”

Section: Introductionmentioning

confidence: 99%

“…Producing anisotropic morphologies is one of the most prominent features of the TIPS process [ 36 , 37 , 38 , 39 , 40 , 41 ]. An electrical field, a temperature gradient, a shear flow, a chemical reaction, or a concentration gradient can all be employed to create anisotropy [ 2 , 17 , 18 , 42 , 43 , 44 ]. A deep understanding of the impact of these techniques to induce anisotropy leads to in-depth knowledge of the fabrication of functional polymeric materials with desired morphologies, and mechanical, optical, and thermal properties [ 2 , 6 , 45 , 46 , 47 , 48 ].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Conductive Heat Transfer on the Morphology Formation in Polymer Solutions Undergoing Thermally Induced Phase Separation

Ranjbarrad

Chan

2022

Polymers

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Owing to the fact that heat transfer during the thermally induced phase separation process is limited, a quench rate is inevitably entailed, which leads to the existence of temporal and spatial variations in temperature. Hence, it is of great importance to take into account the nonisothermality during the phase separation process, especially in high viscosity polymer solutions. In this study, the influence of conductive heat transfer on the morphology formation during the thermally induced phase separation process was investigated theoretically in terms of quench depth, boundary conditions, and enthalpy of demixing to elucidate the interaction between temperature and concentration through incorporating the nonlinear Cahn-Hilliard equation and the Fourier heat transfer equation in two dimensions. The Flory-Huggins free energy theory for the thermodynamics of phase separation, slow mode theory, and Rouse law for polymer diffusion without entanglements were taken into account in the model development. The simulation results indicated a strong interaction between heat transfer and phase separation, which impacted the morphology formation significantly. Results confirmed that quench depth had an indispensable impact on phase separation in terms of higher characteristic frequency by increasing the driving force for heat transfer. Applying quench from various boundaries led to a difference in the quench rate due to the high viscosity of the polymer solution. This led to a gradation in pore size and anisotropic morphology formation. The degree and direction of anisotropy depended on quench depth and rate, quench time, heat conduction rate inside the solution, solution viscosity, temperature evolution, and the enthalpy of demixing. It was also verified that the influence of enthalpy of demixing on phase separation could not be neglected as it increased the solution temperature and led to phase separation being accomplished at a higher temperature than the initial quench temperature.

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“…For instance, Xing et al [30] proved that the Nusselt number increases about 100% when the coolant in microchannels changes from water to an aqueous triethylamine solution. Moreover, the surface temperature of the heater can be kept below 80 °C at a heat flux of 500 W/cm 2 and a pressure drop of 35 kPa when the piranha pin fins were set in the microchannels by Xing et al [31]. Even so, the temperature fluctuation inside electronic devices is inevitable, owing to the variation of heat flux in different areas or/and overtime in the same area.…”

Section: Introductionmentioning

confidence: 99%

Microscopic Exploration of Liquid-liquid Phase Separation Mechanism in LCST Solutions

Ding¹,

Feng²,

Yuan³

et al. 2022

ES Energy Environ.

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A partially miscible solution with a lower critical solution temperature (LCST) is a potential coolant for microchannel heat sinks to meet the multi-goals of high cooling performance, low-pressure drop and stable operation. However, it is a great challenge to fundamentally understand the liquid-liquid phase separation mechanism, and to harvest benefits from it for evaluating the cooling performance and regulating the flow pattern of the LCST solutions in microchannels. Here, we observed and explained the liquid-liquid phase separation behaviors of 2-Butoxyethanol/water solutions with various mass fractions (ωp) and heating rates, consisting of spinodal decomposition or nucleation, droplet growth (diffusion-driven), and droplet coalescence (convectiondriven, stage Ⅰ and stage Ⅱ). The results proved that the separated molecular cluster is covered with a layer of water molecules, causing the mass fraction of 2-Butoxyethanol in the separated liquid to be 65.4% instead of 100%. To keep a mist or droplet flow pattern in microchannels, some efforts must be made to reduce the droplet diameter and suppress the droplet coalescence in stage Ⅱ. Although the solutions with better cooling performance have been determined at ωp=27.4%~35%, future works should focus on whether the liquid-liquid phase separation ends at the droplet growth stage or coalescence stage.

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Liquid-liquid phase separation heat transfer in advanced micro structure

Cited by 15 publications

References 26 publications

Morphology formation during the nonisothermal thermally‐induced phase separation (TIPS) process

Morphology formation during the nonisothermal thermally‐induced phase separation (TIPS) process

The Effect of Conductive Heat Transfer on the Morphology Formation in Polymer Solutions Undergoing Thermally Induced Phase Separation

Microscopic Exploration of Liquid-liquid Phase Separation Mechanism in LCST Solutions

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