Effects of mass transfer time relaxation parameters on condensation in a thermosyphon

Kim, Young‐Chul; Choi, Jung-Sik; Kim, Sungcho; Zhang, Kun

doi:10.1007/s12206-015-1151-5

Cited by 38 publications

(15 citation statements)

References 22 publications

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“…and are the evaporation and condensation mass-transfer time relaxation factors, respectively calculated using Equations (18) and (19). Kim et al [21] proposed that the calculation of the mass transfer time relaxation factors should be proportional to the ratio of phase densities for which a phase change is occurring:…”

Section: B Phase Change Modelmentioning

confidence: 99%

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Performance Evaluation of a Two-Phase Closed Thermosyphon Having a Converging-Diverging Pipe Body

Bliss¹,

Tarokh²

2020

Progress in Canadian Mechanical Engineering. Volume 3

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The present study focuses on improving the heat transfer performance of a two-phase closed thermosyphon (TPCT) by altering the geometry of a typical straight pipe thermosyphon body to have a converging-diverging section. The flow path of the liquid-vapor fluid mixture is augmented with this new design to induce thermal boundary layer mixing thereby enhancing the convection heat transfer within the system during operation. A multiphase numerical simulation model has been developed to simulate the fluid phase change and wall temperature distribution of a two-phase closed thermosyphon. The Lee model is used to calculate mass transfer source terms during the condensation and evaporation phase change processes and the Volume of Fluid (VOF) method is employed to track liquid-vapor interface movement during the simulations. Wall temperature distributions as well as overall thermal resistance values are compared with experimental values available in the literature in order to validate the simulation model for a straight pipe geometry. Two additional model geometries are then used for comparative study where the converging-diverging (CD) section is positioned within the adiabatic section and condenser section respectively. The numerically simulated wall temperature distribution and overall thermal resistance results indicate that the most significant impact can be made when the CD section is positioned in the adiabatic section and condenser section exhibiting reduction of 1.7% and 3.4%, respectively, in overall thermal resistance.

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Section: B Phase Change Modelmentioning

confidence: 99%

“…As discussed in their study, Fadhl et al [11] sourced these values using a steam-table as follows: where is the density of the liquid phase, is the surface tension coefficient. Temperature based properties in Equations (20)(21) and all other constant material properties for each phase are specified in…”

mentioning

confidence: 99%

Performance Evaluation of a Two-Phase Closed Thermosyphon Having a Converging-Diverging Pipe Body

Bliss¹,

Tarokh²

2020

Progress in Canadian Mechanical Engineering. Volume 3

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“…Reasons behind that are that the location of the interface between phases varies for each computational step, and physical properties at the interface are also changeable which make the numerical simulation computationally expensive. Thus, solving these problems can be achieved using VOF model by defining the motion of all phases and tracking the location of the interface accordingly [16][17][18][19][20][21][22][23][24][25][26][27][28]. In the VOF model, movement of different fluids can be tracked by solving a single set of Navier-Stocks equations for the volume fraction of each fluid throughout the computational cell [28].…”

Section: Governing Equationsmentioning

confidence: 99%

“…Results show that the heat transfer characteristics of the TPCT increase as inclination angle and input energy increase. Kim et al [21] implemented a CFD simulation to study the effect of the condensation frequency on the mass transfer rate during phase change inside a thermosiphon heat pipe. The study concluded that the condensation frequency should be considered as 0.1×(ρ l /ρ v ) to accurately simulate the mass transfer process during condensation and evaporation phenomena.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of effect of fill ratio and inclination angle on a thermosiphon heat pipe thermal performance

Alammar

Al-Dadah

Mahmoud

2016

Applied Thermal Engineering

110

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Where a licence is displayed above, please note the terms and conditions of the licence govern your use of this document. When citing, please reference the published version. Take down policy While the University of Birmingham exercises care and attention in making items available there are rare occasions when an item has been uploaded in error or has been deemed to be commercially or otherwise sensitive.

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“…A valuable numerical study of the thermosyphon was also realized by Kim [37]. He assumed a domain with identical dimensions as in Fadhl's work and the same boundary conditions, fluid properties, and simulation parameters.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of a Cooling System Using Phase Change of a Refrigerant in a Thermosyphon

Czerwiński

Wołoszyn

2021

Energies

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With the increasing trend toward the miniaturization of electronic devices, the issue of heat dissipation becomes essential. The use of phase changes in a two-phase closed thermosyphon (TPCT) enables a significant reduction in the heat generated even at high temperatures. In this paper, we propose a modification of the evaporation–condensation model implemented in ANSYS Fluent. The modification was to manipulate the value of the mass transfer time relaxation parameter for evaporation and condensation. The developed model in the form of a UDF script allowed the introduction of additional source equations, and the obtained solution is compared with the results available in the literature. The variable value of the mass transfer time relaxation parameter during condensation rc depending on the density of the liquid and vapour phase was taken into account in the calculations. However, compared to previous numerical studies, more accurate modelling of the phase change phenomenon of the medium in the thermosyphon was possible by adopting a mass transfer time relaxation parameter during evaporation re = 1. The assumption of ten-fold higher values resulted in overestimated temperature values in all sections of the thermosyphon. Hence, the coefficient re should be selected individually depending on the case under study. A too large value may cause difficulties in obtaining the convergence of solutions, which, in the case of numerical grids with many elements (especially three-dimensional), significantly increases the computation time.

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Effects of mass transfer time relaxation parameters on condensation in a thermosyphon

Cited by 38 publications

References 22 publications

Performance Evaluation of a Two-Phase Closed Thermosyphon Having a Converging-Diverging Pipe Body

Performance Evaluation of a Two-Phase Closed Thermosyphon Having a Converging-Diverging Pipe Body

Numerical investigation of effect of fill ratio and inclination angle on a thermosiphon heat pipe thermal performance

Numerical Study of a Cooling System Using Phase Change of a Refrigerant in a Thermosyphon

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