Effect of Thermophysical Properties of Solid Walls on Turbulent Modes of Complex Heat Transfer in an Enclosure

2016 ◽  
Vol 683 ◽  
pp. 540-547
Author(s):  
Igor V. Miroshnichenko ◽  
Mikhail A. Sheremet
Keyword(s):  
Heat Transfer ◽  
Thermophysical Properties ◽  
Building Materials ◽  
Temperature Fields ◽  
Main Attention ◽  
Numerical Studies ◽  
Internal Surfaces ◽  
Complex Heat Transfer ◽  
Energy Efficient Building ◽  
Solid Walls

Two-dimensional numerical studies were performed for investigation of the effect of thermophysical properties of solid walls on turbulent <em>convective </em>– <em>radiative </em>heat transfer in an air filled square cavity. The <em>main attention was paid to the influence of </em>thermal conductivity ratio1 ≤ κ1, 2 ≤ 1000 and an emissivity of internal surfaces of the solid walls 0 £ < 1 on velocity and temperature fields. Numerical results were obtained by means of the finite difference method. The effect of the governing parameters on the average Nusselt number has been defined. The obtained results provide better technical support for development and research of energy-efficient building materials

scholarly journals Heat Treatment Technology of Porous Building Materials with Predictability of Thermophysical Properties

2018 ◽  
Vol 7 (3.2) ◽  
pp. 501
Author(s):  
Mustafa Baba Babanli ◽  
Liubov Shumska ◽  
Maryna Leshchenko
Keyword(s):  
Heat Transfer ◽  
Heat Treatment ◽  
Porous Material ◽  
Thermophysical Properties ◽  
Building Materials ◽  
Process Development ◽  
Thermal Protection ◽  
Raw Material ◽  
Technological Parameters ◽  
Treatment Technology

The work is devoted to theoretical and experimental research of thermophysical features of the creation of new porous heat insulating materials, precisely: research of thermodynamic parameters of the heating processes, swelling and drying of materials; substantiation of the choice of the raw mixture method formation and determination of the optimal energy parameters of the swelling process; development of mathematical models of material heat treatment process and methods of basic technological parameters determination; development of advanced technologies for thermal protection of buildings and power equipment. Experimentally determined dependencies of technological parameters of heat treatment of the raw material mixture in the discharge, its composition, which allows obtaining material with minimal thermal conductivity. Also, the resulting dependencies ensure to find the required mode of heat treatment for the given thermophysical properties. The experimental setup has been developed, which provided to determine the basic laws of heat transfer of porous material, on the basis of which data were obtained, which allow to carry out an estimation of heat transfer and exchange characteristics of the new dispersed porous material necessary for technological calculations. A complex mathematical model of the heat energy mode of the building was created, as well as a program for solving the equations of this model, which makes it possible to determine the basic energy characteristics.  

Heat Transfer in Friction Stir Welding—Experimental and Numerical Studies

2003 ◽  
Vol 125 (1) ◽  
pp. 138-145 ◽  
Author(s):  
Yuh J. Chao ◽  
X. Qi ◽  
W. Tang
Keyword(s):  
Heat Transfer ◽  
Friction Stir Welding ◽  
Temperature Fields ◽  
Transient Temperature ◽  
Friction Stir ◽  
Heat Flows ◽  
Numerical Studies ◽  
Weld Residual Stress ◽  
Joining Process

In the friction stir welding (FSW) process, heat is generated by friction between the tool and the workpiece. This heat flows into the workpiece as well as the tool. The amount of heat conducted into the workpiece determines the quality of the weld, residual stress and distortion of the workpiece. The amount of the heat that flows to the tool dictates the life of the tool and the capability of the tool for the joining process. In this paper, we formulate the heat transfer of the FSW process into two boundary value problems (BVP)—a steady state BVP for the tool and a transient BVP for the workpiece. To quantify the physical values of the process the temperatures in the workpiece and the tool are measured during FSW. Using the measured transient temperature fields finite element numerical analyses were performed to determine the heat flux generated from the friction to the workpiece and the tool. Detailed temperature distributions in the workpiece and the tool are presented. Discussions relative to the FSW process are then given. In particular, the results show that (1) the majority of the heat generated from the friction, i.e., about 95%, is transferred into the workpiece and only 5% flows into the tool and (2) the fraction of the rate of plastic work dissipated as heat is about 80%.

A Case Study of Hyperthermia Induced Temperature Computations in Human Sarcomas Using Discrete Vasculature and Relative Perfusion Maps

2001 ◽  
Author(s):  
Oana I. Craciunescu ◽  
Bas W. Raaymakers ◽  
Alexis N. T. J. Kotte ◽  
Shiva K. Das ◽  
Thaddeus V. Samulski ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mr Angiography ◽  
Temperature Fields ◽  
Continuum Models ◽  
Resonance Imaging ◽  
Mr Thermometry ◽  
Complex Heat Transfer ◽  
Perfusion Maps ◽  
Large Vessels

Abstract One of the most important technical aspects in clinical hyperthermia is the ability to measure and/or simulate the 3D temperature fields. Related to that, an essential part is the way in which the complex heat transfer related to vasculature is described. We report here the results of a collaboration between the hyperthermia modeling groups from the UMC Utrecht, The Netherlands, and Duke UMC, USA. Utrecht’s hyperthermia group has developed a flexible, discrete vasculature thermal model (DIVA) (Kotte et al. 1996) that describes the heat transfer related to discrete vasculature. The vasculature was imaged using MR angiography. To account for the smaller vessels that are responsible for the significant bioheat transport, relative perfusion maps measured at Duke using dynamic enhanced-magnetic resonance imaging were used. Alternatively, the VAMP program (Van Leeuwen et al. 1998) was used to artificially generate smaller vasculature. The cases with discretized vasculature were compared to continuum models where either heterogeneous isotropic perfusion, or relative perfusion maps were used. All simulations were compared to MR thermometry data. The conclusion is that for tumors crossed by or near large vessels, a combination of large vessels discretization and perfusion maps yields temperatures that match very well the MR thermometry data.

Parametric Study of a Transient Liquid Flow in a Microchannel of Square Cross-Section

2010 ◽  
Author(s):  
Guyh Dituba Ngoma ◽  
Amsini Sadiki
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Liquid Flow ◽  
Thermophysical Properties ◽  
Electric Potential ◽  
Thermal Characteristics ◽  
Temperature Fields ◽  
Transfer Coefficients ◽  
The Impact ◽  
Potential Pressure

Time-dependent laminar liquid flow and thermal characteristics in a square cross-section microchannel were numerically investigated using computational fluid dynamics code. In the numerical model developed the upper and bottom microchannel substrate properties, Joule heating caused by applying electric potential, pressure driven flow, electroosmosis, heat transfer coefficients on the microchannel bottom wall and variations in the liquid thermophysical properties were all taken into account. Liquid flow velocity distribution and temperature fields were calculated by solving both Navier-Stokes and energy equations, and electric field distribution was determined based on their electric potential. The results obtained demonstrate the impact that applied potential, pressure difference, heat transfer coefficient and microchannel dimensions have on liquid flow and thermal behaviors in a square microchannel. Finally, the results with the model developed were then compared with those of a liquid having constant thermophysical properties.

Heat Transfer between Parallel Walls: An Interferometric Investigation

1972 ◽  
Vol 14 (2) ◽  
pp. 107-127 ◽  
Author(s):  
R. G. Brooks ◽  
S. D. Probert
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Temperature Fields ◽  
Heated Wall ◽  
Thermal Boundary Conditions ◽  
Numerical Studies ◽  
Air Layers ◽  
Interferometric Investigation ◽  
The Difference

The temperature fields and the transfer of heat within vertical, inclined and horizontal air layers are examined for each of three different heat transfer regimes. Experimental evidence is offered which explains the difference between the heat transfer correlations of previous investigations in which the Nusselt modulus is based on the heat flux leaving the heated wall and those in which the Nusselt number is based upon the rate at which heat is transferred to the cooled wall. It is also shown that some of the thermal boundary conditions which have generally been assumed in numerical studies are unrealistic.

The Effect of Regulating Elements on Convective Heat Transfer along Shaped Heat Exchange Surfaces

2013 ◽  
Vol 34 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Jozef Cernecky ◽  
Jan Koniar ◽  
Zuzana Brodnianska
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Cfd Simulation ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Temperature Fields ◽  
Transfer Coefficients ◽  
Heat Transfer Intensification ◽  
Heat Transfer Coefficients ◽  
Forced Air

Abstract The paper deals with a study of the effect of regulating elements on local values of heat transfer coefficients along shaped heat exchange surfaces with forced air convection. The use of combined methods of heat transfer intensification, i.e. a combination of regulating elements with appropriately shaped heat exchange areas seems to be highly effective. The study focused on the analysis of local values of heat transfer coefficients in indicated cuts, in distances expressed as a ratio x/s for 0; 0.33; 0.66 and 1. As can be seen from our findings, in given conditions the regulating elements can increase the values of local heat transfer coefficients along shaped heat exchange surfaces. An optical method of holographic interferometry was used for the experimental research into temperature fields in the vicinity of heat exchange surfaces. The obtained values correspond very well with those of local heat transfer coefficients αx, recorded in a CFD simulation.

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