Heat and Mass Transfer in Stored Milo. Part I. Heat Transfer Model

1992 ◽  
Vol 35 (5) ◽  
pp. 1569-1573 ◽  
Author(s):  
S. K. Abbouda ◽  
D. S. Chung ◽  
P. A. Seib ◽  
A. Song
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Heat Transfer Model ◽  
Transfer Model

scholarly journals Evolution of Temperature Field around Underground Power Cable for Static and Cyclic Heating

Energies ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 8191
Author(s):  
Shahbaz Ahmad ◽  
Zarghaam Haider Rizvi ◽  
Joan Chetam Christine Arp ◽  
Frank Wuttke ◽  
Vineet Tirth ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Weather Conditions ◽  
Nonlinear Dependence ◽  
Transfer Model ◽  
Power Cable ◽  
Cable Systems ◽  
Underground Power Cable

Power transmission covering long-distances has shifted from overhead high voltage cables to underground power cable systems due to numerous failures under severe weather conditions and electromagnetic pollution. The underground power cable systems are limited by the melting point of the insulator around the conductor, which depends on the surrounding soils’ heat transfer capacity or the thermal conductivity. In the past, numerical and theoretical studies have been conducted based on the mechanistic heat and mass transfer model. However, limited experimental evidence has been provided. Therefore, in this study, we performed a series of experiments for static and cyclic thermal loads with a cylindrical heater embedded in the sand. The results suggest thermal charging of the surrounding dry sand and natural convection within the wet sand. A comparison of heat transfer for dry, unsaturated and fully saturated sand is presented with graphs and colour maps which provide valuable information and insight of heat and mass transfer around an underground power cable. Furthermore, the measurements of thermal conductivity against density, moisture and temperature are presented showing positive nonlinear dependence.

Heat Transfer and Air Diffusion Phenomena in a Bed of Polymer Powder Using Apparent Heat Capacity Method: Application to the Rotational Molding Process

2007 ◽  
Author(s):  
M. Boutaous ◽  
E. Pe´rot ◽  
A. Maazouz ◽  
P. Bourgin ◽  
P. Chantrenne
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Flux ◽  
Phase Change ◽  
Heat And Mass Transfer ◽  
Granular Media ◽  
Transfer Model ◽  
Melting Front ◽  
Polymer Powder ◽  
Air Diffusion

The process of rotational moulding consists in manufacturing plastic parts by heating a polymer powder in a biaxial rotating mould. In order to optimise the production cycle of this process, a complete simulation model has to be used. This model should describe the phenomena of heat and mass transfer in a moving granular media with phase change, coalescence, sintering, air evacuation and crystallization during the cooling stage. This paper focus on the study of heat and mass transfer in a quiescent polymer powder during the heating stage. An experimental device has been built. It consists in an open plane static mold on which an initial thickness, e, of a polymer powder is deposited. This powder is then heated until it melts. An inverse heat conduction method is used to determine the heat flux and temperature at the interface between the mold and the powder. This interfacial heat flux is taken as a boundary condition in a numerical heat transfer model witch takes into account the heat transfer in granular media with phase change, coalescence, sintering, air bubbles evacuation and rheological behaviour of the polymer. For the numerical simulation of the heat transfer, the apparent specific heat method is used. This approach allows to solve the same energy equation for all the material phases, so one do not have to calculate the melting front evolution. This fine modelling, close to the real physical phenomena makes it possible to estimate the temperature profile and the evolution of the polymer powder characteristics (phase change, air diffusion, viscosity, evolution of the thermophysical properties of the equivalent homogeneous medium, thickness reduction, air volume fraction...). Several results are then presented, and the influence of different parameters, like the thermal contact resistance, the process initial conditions and the polymer’s rheological characteristics are studied and commented. Indeed the predictions of the temperature rises in the polymer bed, agree well with the experimental measurements.

Condensation of Zeotropic Mixtures in Horizontal Tubes: New Simplified Heat Transfer Model Based on Flow Regimes

2005 ◽  
Vol 127 (3) ◽  
pp. 221-230 ◽  
Author(s):  
D. Del Col ◽  
A. Cavallini ◽  
J. R. Thome
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Flow Pattern ◽  
Bulk Composition ◽  
Heat Transfer Model ◽  
Dew Point ◽  
Transfer Model ◽  
Transfer Resistance ◽  
Refrigerant Mixtures ◽  
Numerical Effort

The need for optimal design of heat exchangers with in-tube condensation of zeotropic refrigerant mixtures has pushed the research of predictive methods in the last years. Some procedures have been developed, based on the Colburn and Drew (1937, Trans. AIChemE 33, pp. 197–215) analysis, that require significant numerical effort and the diffusivity properties of the mixture to calculate the mass transfer resistance in the process and, hence, are rarely used for heat exchanger design. Proposing a modified version of the well-known simplified approach of Silver (1947, Trans. Inst. Chem. Eng. 25, pp. 30–42) and Bell and Ghaly (1973, AIChE Symp. Ser. 69, pp. 72–79) to include the effects of interfacial roughness and nonequilibrium effects, the present study extends the flow-pattern-based model of Thome, El Hajal, and Cavallini (2003, Int. J. Heat Mass Transfer 46, pp. 3365–3387) for condensation of pure fluids and azeotropic mixtures to zeotropic mixtures. By implementing this within the above flow-pattern-based heat transfer model, it leads to an improved method for accurately predicting local mixture heat transfer coefficients, maintaining a clear relationship between flow regime and heat transfer, and achieving both the goals of higher prediction accuracy and low calculation effort. The method has been verified for refrigerant mixtures (both halogenated and hydrocarbon) having temperature glides of 3.5–22°C, that is temperature differences between the dew point and bubble point temperatures (at a fixed pressure and bulk composition).

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