On the Problem of Heat Transfer in a Phase-Change Slab Initially Not at the Critical Temperature

1987 ◽  
Vol 109 (1) ◽  
pp. 5-9 ◽  
Author(s):  
L. N. Gutman
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Transfer Problem ◽  
Maximum Error ◽  
Additional Time ◽  
Total Phase ◽  
Slab Temperature ◽  
Indirect Evaluation ◽  
Time Required ◽  
Perturbation Problems

A one-dimensional heat transfer problem in the phase-change slab, one side of which is isothermal while the other is insulated, is considered. Both cases—fusion and solidification—are treated. Slab temperature at the intitial moment is assumed constant and not critical. The main goal of this paper is to find the additional time required for a total phase change, compared with the case of the critical initial temperature. By analogy with perturbation problems in hydrodynamics, an appropriate solution is constructed consisting of an inner and an outer solution. The evaluation of the maximum error of the integral heat balance equation of the slab is treated as an indirect evaluation of the accuracy of the solution obtained. This evaluation shows that the solution can provide sufficient accuracy only in cases in which at least one of the three nondimensional parameters of the problem is small.

scholarly journals Effect of Inclined Magnetic Field on the Entropy Generation in an Annulus Filled with NEPCM Suspension

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Seyyed Masoud Seyyedi ◽  
M. Hashemi-Tilehnoee ◽  
M. Sharifpur
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Phase Change ◽  
Entropy Generation ◽  
Phase Change Materials ◽  
Transfer Problem ◽  
Mass Conservation ◽  
Melting Process ◽  
Industrial Applications ◽  
Inclined Magnetic Field

The encapsulation technique of phase change materials in the nanodimension is an innovative approach to improve the heat transfer capability and solve the issues of corrosion during the melting process. This new type of nanoparticle is suspended in base fluids call NEPCMs, nanoencapsulated phase change materials. The goal of this work is to analyze the impacts of pertinent parameters on the free convection and entropy generation in an elliptical-shaped enclosure filled with NEPCMs by considering the effect of an inclined magnetic field. To reach the goal, the governing equations (energy, momentum, and mass conservation) are solved numerically by CVFEM. Currently, to overcome the low heat transfer problem of phase change material, the NEPCM suspension is used for industrial applications. Validation of results shows that they are acceptable. The results reveal that the values of N u ave descend with ascending Ha while N gen has a maximum at Ha = 16 . Also, the value of N T , MF increases with ascending Ha . The values of N u ave and N gen depend on nondimensional fusion temperature where good performance is seen in the range of 0.35 < θ f < 0.6 . Also, Nu ave increases 19.9% and ECOP increases 28.8% whereas N gen descends 6.9% when ϕ ascends from 0 to 0.06 at θ f = 0.5 . Nu ave decreases 4.95% while N gen increases by 8.65% when Ste increases from 0.2 to 0.7 at θ f = 0.35 .

Seepage Monitoring of an Embankment Dam Based on Hydro-Thermal Coupled Analysis

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Chung R. Song ◽  
Tewodros Y. Yosef
Keyword(s):  
Heat Transfer ◽  
Fiber Optic ◽  
Computer Code ◽  
Fiber Optic Sensors ◽  
Coupled Analysis ◽  
Distributed Temperature Sensing ◽  
Embankment Dam ◽  
Additional Time ◽  
Time Required ◽  
Continuous Temperature

Distributed temperature sensing (DTS)-based fiber optic sensors are widely used for monitoring spatially continuous temperature distribution in structures. In this research, hydro-thermal (H-T) coupled analysis is used to monitor seepage conditions in an embankment dam. Variably saturated two-dimensional heat transport (VS2DHI), a computer code developed by the U.S. Geological Survey, was used for this coupled analysis. From the coupled analysis, the temperature profile for a dam with an artificially generated crack clearly showed the location of the crack. In addition, it turned out that the temperature change in the dam took much longer than the seepage time due to the additional time required for heat transfer. The study shows that temperature variation in the dam is comparable to the seepage condition with time delay for heat transfer. This study also shows the possibility that temperature data may serve as a tool to diagnose prior seepage conditions and past incidents of a dam.

Phase Change Around Insulated Buried Pipes: Quasi-Steady Method

1981 ◽  
Vol 103 (3) ◽  
pp. 201-207 ◽  
Author(s):  
V. J. Lunardini
Keyword(s):  
Heat Transfer ◽  
Thermal Properties ◽  
Phase Change ◽  
Transfer Problem ◽  
Approximate Solutions ◽  
Burial Depth ◽  
Field Phase ◽  
Buried Pipes ◽  
Pipe Surface ◽  
Insulation Thickness

The heat transfer problem for cylinders embedded in a medium with variable thermal properties cannot be solved exactly if phase change occurs. Approximate solutions have been found using the quasi-steady method. The temperature field, phase change location, and pipe surface heat transfer can be estimated using graphs presented for parametric ranges of temperature, thermal properties, burial depth, and insulation thickness. The accuracy of the graphs increases as the Stefan number decreases and they should be of particular value for insulated hot pipes or refrigerated gas lines.

scholarly journals Numerical analysis on thermal characteristics and ice melting efficiency for microwave deicing vehicle

2016 ◽  
Vol 30 (13) ◽  
pp. 1650203 ◽  
Author(s):  
Can Wang ◽  
Bo Yang ◽  
Gangfeng Tan ◽  
Xuexun Guo ◽  
Li Zhou ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Moving Boundary ◽  
Transfer Problem ◽  
Energy Generation ◽  
Heating Process ◽  
Ice Melting ◽  
Ambient Conditions ◽  
One Dimensional ◽  
Temperature Distributions

In the high latitudes, the icy patches on the road are frequently generated and have a wide distribution, which are difficult to remove and obviously affect the normal usage of the highways, bridges and airport runways. Physical deicing, such as microwave (MW) deicing, help the ice melt completely through heating mode and then the ice layer can be swept away. Though it is no pollution and no damage to the ground, the low efficiency hinders the development of MW deicing vehicle equipped without sufficient speed. In this work, the standard evaluation of deicing is put forward firstly. The intensive MW deicing is simplified to ice melting process characterized by one-dimensional slab with uniform volumetric energy generation, which results in phase transformation and interface motion between ice and water. The heating process is split into the superposition of three parts — non-heterogeneous heating for ground without phase change, heat transfer with phase change and the heat convection between top surface of ice layer and flow air. Based on the transient heat conduction theory, a mathematical model, combining electromagnetic and two-phase thermal conduction, is proposed in this work, which is able to reveal the relationship between the deicing efficiency and ambient conditions, as well as energy generation and material parameters. Using finite difference time-domain, this comprehensive model is developed to solve the moving boundary heat transfer problem in a one-dimensional structured gird. As a result, the stimulation shows the longitudinal temperature distributions in all circumstances and quantitative validation is obtained by comparing simulated temperature distributions under different conditions. In view of the best economy and fast deicing, these analytic solutions referring to the complex influence factors of deicing efficiency demonstrate the optimal matching for the new deicing design.

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