scholarly journals Heat and Mass Transfer of the Droplet Vacuum Freezing Process Based on the Diffusion-controlled Evaporation and Phase Transition Mechanism

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Zhijun Zhang ◽  
Jingxin Gao ◽  
Shiwei Zhang
Keyword(s):  
Phase Transition ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Freezing Process ◽  
Transition Mechanism ◽  
Diffusion Controlled ◽  
Vacuum Freezing

scholarly journals Heat and Mass Transfer of Droplet Vacuum Freezing Process Based on Dynamic Mesh

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Lili Zhao ◽  
Yuekai Zhang ◽  
Zhijun Zhang ◽  
Xun Li ◽  
Wenhui Zhang
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Droplet Diameter ◽  
Dynamic Mesh ◽  
Freezing Process ◽  
Freezing Time ◽  
Droplet Temperature ◽  
Obvious Effect ◽  
Initial Droplet ◽  
Vacuum Freezing

A numerical simulation using dynamic mesh method by COMSOL has been developed to model heat and mass transfer during vacuum freezing by evaporation of a single droplet. The initial droplet diameter, initial droplet temperature, and vacuum chamber pressure effect are studied. The surface and center temperature curve was predicted to show the effect. The mass transfer rate and radius displacement were also calculated. The results show the dynamic mesh shows well the freezing process with the radius reduction of droplet. The initial droplet diameter, initial droplet temperature, and vacuum pressure have obvious effect on freezing process. The total freezing time is about 200 s, 300 s, and 400 s for droplet diameter 7.5 mm, 10.5 mm, and 12.5 mm, respectively. The vacuum pressure less than 200 Pa is enough for the less time to freezing the droplet, that is, the key point in freezing time. The initial droplet temperature has obvious effect on freezing but little effect on freezing temperature.

Numerical Study on Microwave Dehydro-Freezing of Fish Tissues

2011 ◽  
Author(s):  
Yuichiro Oku ◽  
Hirofumi Tanigawa ◽  
Takaharu Tsuruta
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Numerical Study ◽  
Fish Tissue ◽  
Cell System ◽  
Moisture Distribution ◽  
Freezing Process ◽  
Tissue Cell ◽  
Frozen Fish ◽  
Fundamental Equations

In this study, a numerical simulation on the freezing process is carried out to evaluate the effects of pre-dehydration on the quality of frozen fish tissue. We use a simulation model which contains a muscle fiber to express the microscale heat and mass transfer phenomena inside the tissue cell system. Fundamental equations on heat and mass transfer are formulated in a two-dimensional coordinate system. The governing equations include phase-change terms. In order to take account of the characteristic moisture distribution produced by the microwave room-temperature drying, initial moisture distributions are given in this calculation. The numerical results indicate that the control of the water content by the pre-dehydration can shorten the freezing time. It is found that the cell shrinkage ratio is larger than that of the result using uniform distribution. As an increase of pre-dehydration, the central cell significantly shrinks but the surface-layer cell doesn’t shrink so much due to the large cooling rate.

Modeling heat and mass transfer during vacuum freezing of puree droplet

2013 ◽  
Vol 36 (4) ◽  
pp. 1319-1326 ◽  
Author(s):  
C. Cogné ◽  
P.U. Nguyen ◽  
J.L. Lanoisellé ◽  
E. Van Hecke ◽  
D. Clausse
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Vacuum Freezing

scholarly journals Numerical Modelling of Tailings Dam Thermal-Seepage Regime Considering Phase Transitions

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Aniskin Nikolay Alekseevich ◽  
Antonov Anton Sergeevich
Keyword(s):  
Phase Transition ◽  
Mass Transfer ◽  
Liquid Phase ◽  
Heat And Mass Transfer ◽  
Variational Formulation ◽  
Tailings Dam ◽  
Real Situation ◽  
Dam Foundation ◽  
Liquid Phase Transition ◽  
Calculation Results

Statement of the Problem. The article describes the problem of combined thermal-seepage regime for earth dams and those operated in the permafrost conditions. This problem can be solved using the finite elements method based on the local variational formulation. Results. A thermal-seepage regime numerical model has been developed for the “dam-foundation” system in terms of the tailings dam. The effect of heat-and-mass transfer and liquid phase transition in soil interstices on the dam state is estimated. The study with subsequent consideration of these factors has been undertaken. Conclusions. The results of studying the temperature-filtration conditions of the structure based on the factors of heat-and-mass transfer and liquid phase transition have shown that the calculation results comply with the field data. Ignoring these factors or one of them distorts the real situation of the dam thermal-seepage conditions.

scholarly journals Parameter Sensitivity of the Microdroplet Vacuum Freezing Process

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Zhijun Zhang ◽  
Yuekai Zhang ◽  
Lili Zhao ◽  
Wenhui Zhang ◽  
Shuangshuang Zhao
Keyword(s):  
Thermal Conductivity ◽  
Mass Transfer ◽  
Transfer Coefficient ◽  
Mass Transfer Coefficient ◽  
Initial Temperature ◽  
Parameter Sensitivity ◽  
Chamber Pressure ◽  
Freezing Process ◽  
Cooling Stage ◽  
Vacuum Freezing

The vacuum freezing process of microdroplets (<100 μm in diameter) is studied by dynamic mesh method. The mass transfer coefficient was studied using the results of related papers that considered droplet diameters exceeding 1 mm. The diameter, initial temperature, and vacuum chamber pressure effects are also discussed. To estimate parameter sensitivity, the effects of material density, specific heat, and thermal conductivity in 20% scope, as well as latent evaporation/sublimation in 5%, were simulated. The results show that the mass transfer coefficientKis essentially different between microdroplets (<100 μm) and macrodroplet (>1 mm). Pressure and droplet diameter have an effect on cooling and freezing stages, but initial temperature only affects the cooling stage. The thermal conductivity coefficientklaffected the cooling stage, whereaskiaffected the freezing stage. Heat capacityClaffected the cooling stage, butCihas virtually no effect on all stages. The actual latent heat of freezingΔHwas also affected. Higher density corresponds to lower cooling rate in the cooling stage.

scholarly journals Mathematical model of the liquefied methane phase transition in the cryogenic tank of a vehicle

2020 ◽  
Vol 243 ◽  
pp. 337
Author(s):  
Otari Didmanidze ◽  
Alexander Afanasev ◽  
Ramil Khakimov
Keyword(s):  
Phase Transition ◽  
Mass Transfer ◽  
Natural Gas ◽  
Heat And Mass Transfer ◽  
Liquefied Natural Gas ◽  
Closed Volume ◽  
Two Phase ◽  
Cryogenic Tank ◽  
Cartesian Coordinate ◽  
Control Volumes

In order to increase the efficiency of using vehicles (VEH) in mining and quarrying conditions, it is necessary to improve the components of gas equipment (cryogenic tank, gas nozzles, fuel supply cryogenic tubes, etc.) for supplying liquefied natural gas to the engine, as well as storage of liquid methane in a cryogenic tank with a long service life. For this, it is necessary to consider the process of heat and mass transfer of liquefied natural gas in a two-phase liquid-gas medium, taking into account the phase transition in the closed volume of the cryogenic tank under consideration. The article presents a model of unsteady heat and mass transfer of a two-phase liquefied methane medium in a developed two-tank cryogenic tank using a Cartesian coordinate system with fractional control volumes in space. The experimental data confirm the efficiency of using a cryogenic tank on the VEH platform, in which the run on liquefied methane compared to standard fuels is tripled, the shelf life of liquefied gas in the proposed cryogenic tank is 2-2.5 times longer than in the standard one.

Heat and Mass Transfer in Low-Temperature Insulation in Moisture Conditions

2015 ◽  
Vol 725-726 ◽  
pp. 21-25
Author(s):  
Vyacheslav Polonnikov ◽  
Artem Habibulin
Keyword(s):  
Phase Transition ◽  
Numerical Simulation ◽  
Mass Transfer ◽  
Low Temperature ◽  
Heat And Mass Transfer ◽  
Outer Contour ◽  
Moisture Migration ◽  
Heat Leakage ◽  
Moisture Conditions

The results of numerical simulation of heat and mass transfer in a low-temperature insulation in conditions of insulation freezing, a moisture migration to the front of phase transition and a condensation forming on an outer contour of interaction were obtained. Values of heat leakage were established.

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