Contact heat exchange in conjunction with metal surfaces which have deviations in form or waviness

2015 ◽  
Vol 5 (4) ◽  
pp. 234-241
Author(s):  
Ерин ◽  
Oleg Erin ◽  
Кондратенко ◽  
Irina Kondratenko ◽  
Попов ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Metal Surfaces ◽  
Calculated Data ◽  
Contact Thermal Resistance ◽  
Contact Heat ◽  
Mechanical Loads ◽  
Physical Experiments ◽  
Contact Heat Exchange ◽  
Constituent Elements

In the design of thermally stressed units in the sectors of mechanical engineering, aviation, aerospace, energetics it is often necessary to have information about the formation of the contact thermal resistance resulting from the discrete nature of parts metal surfaces contacting. While passing through the section zones of heat flows the temperature gradient increases, thus reducing the heat transfer capability of the contact junction and leads to thermal expansion of the constituent elements of the systems, relative shifts and warpages. The process of heat transfer through the zone of contact between metal surfaces having deviation of shapes in the form of nonflatness or waviness under conditions suitable to small mechanical loads is considered. The model of formation of the contact thermal resistance (CTR), in case of double contraction of the heat flow of channel and contact mаcrospots, caused by nonflatness or waviness, and then to microspots caused by roughness. Subject to the provisions of the theory of mechanical contacting of solids theoretical curves is derived describing the contact thermal resistance for compounds with surfaces having microdeviation or waviness operating in the regime of small mechanical loads. The results of physical experiments give satisfactory agreement with the calculated data. It was established that the presence of nonflatness or waviness on the contact surfaces increases CTR significantly as compared with rough surfaces. Increase of CTR is explained by the increase of wave height or equivalent nonflatness

scholarly journals The inverse coefficient problem of heat transfer in layered nanostructures

2017 ◽  
Vol 20 (3) ◽  
pp. 213-219
Author(s):  
K. K. Abgarian ◽  
R. G. Noskov ◽  
D. L. Reviznikov
Keyword(s):  
Heat Transfer ◽  
Inverse Problem ◽  
Thermal Resistance ◽  
Transfer Problem ◽  
Dominant Role ◽  
Rapid Development ◽  
Problem Solution ◽  
Microwave Range ◽  
Contact Thermal Resistance ◽  
Resistance Coefficients

The rapid development of electronics leads to the creation and use of electronic components of small dimensions, including nanoelements of complex, layered structure. The search for effective methods for cooling electronic systems dictates the need for the development of methods for the numerical analysis of heat transfer in nanostructures. A characteristic feature of energy transfer in such systems is the dominant role of contact thermal resistance at interlayer interfaces. Since the contact resistance depends on a number of factors associated with the technology of heterostructures manufacturing, it is of great importance to determine the corresponding coefficients from the results of temperature measurements.The purpose of this paper is to evaluate the possibility of reconstructing the thermal resistance coefficients at the interfaces between layers by solving the inverse problem of heat transfer.The complex of algorithms includes two major blocks — a block for solving the direct heat transfer problem in a layered nanostructure and an optimization block for solving the inverse problem. The direct problem was formulated in an algebraic (finite difference) form under the assumption of a constant temperature within each layer, which is due to the small thickness of the layers. The inverse problem was solved in the extreme formulation, the optimization was carried out using zero-order methods that do not require the calculation of the derivatives of the optimized function. As a basic optimization algorithm, the Nelder—Mead method was used in combination with random restarts to search for a global minimum.The results of the identification of the contact thermal resistance coefficients obtained in the framework of a quasi-real experiment are presented. The accuracy of the identification problem solution is estimated as a function of the number of layers in the heterostructure and the «measurements» error.The obtained results are planned to be used in the new technique of multiscale modeling of thermal regimes of the electronic component base of the microwave range, when identifying the coefficients of thermal conductivity of heterostructure.

Questions of thermoregulation in heatstressed composite systems with mesh screens

10.12737/1780 ◽  
2013 ◽  
Vol 3 (3) ◽  
pp. 156-160
Author(s):  
Ерин ◽  
Oleg Erin ◽  
Попов ◽  
Viktor Popov ◽  
Кондратенко ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Metal Surfaces ◽  
Thermal Conditions ◽  
Metal Wire ◽  
Contact Thermal Resistance ◽  
Composite Systems ◽  
Intensive Development

In connection with the intensive development of new areas of technology, where heat-stressed systems are widely represented, there is urgent need of directed thermoregulation. To control the thermal conditions in composite systems it is required, in particular, to create connections with good insulation. The problem of increasing contact thermal resistance between the metal surfaces by introducing of mesh screens made of metal wire into the zone section is examined on condition the application of small loads not exceeding 1 MPa.

scholarly journals Model of Complex Heat Transfer in the Package of Rectangular Steel Sections

2020 ◽  
Vol 10 (24) ◽  
pp. 9044
Author(s):  
Rafał Wyczółkowski ◽  
Marek Gała ◽  
Vazgen Bagdasaryan
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Thermal Resistance ◽  
Heat Radiation ◽  
Low Carbon ◽  
Contact Heat ◽  
Total Thermal Resistance ◽  
Model Calculations ◽  
Complex Heat Transfer ◽  
Steel Sections

During heat treatment of rectangular steel sections, a heated charge in the form of regularly arranged packages is placed in a furnace. The article presents a model of a complex heat transfer in such a package using the thermo-electric analogy. The model considers the following types of heat transfer: conduction in section walls, conduction and natural convection within gas, heat radiation between the walls of a section, as well as contact conduction between the adjacent sections. The results of our own experimental research were used for calculations of heat resistance applying to natural convection and contact conduction. We assumed that the material of sections was low-carbon steel and the gas was air. The result of the calculations of the presented model is total thermal resistance Rto. The calculations were performed for the temperature range 20–700 °C for four geometrical cases. Due to the variability of conditions for contact heat conduction, we assumed that total thermal resistance for a given charge is contained within a value range between Rto-min and Rto-max. We established that the value of Rto depends significantly on the section’s geometry. The larger the section sizes, the greater the changes of Rto. The minimal and maximal values of Rto for all packages were 0.0051 (m2·K)/W and 0.0238 (m2·K)/W, respectively. The correctness of model calculations was verified with the use of experimental data.

Growth and translation of a liquid-vapour compound drop in a second liquid. Part 2. Heat transfer

1989 ◽  
Vol 209 ◽  
pp. 639-660 ◽  
Author(s):  
S. T. Vuong ◽  
S. S. Sadhal
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Finite Difference Methods ◽  
Time History ◽  
Immiscible Liquid ◽  
Transport Processes ◽  
Contact Heat ◽  
Contact Heat Exchange ◽  
History Of ◽  
Single Compound

The present work is a comprehensive theoretical study of the heat transfer associated with a 3-singlet compound drop that is growing because of change of phase. The geometry is the same as in Part 1, i.e. a vapour bubble partially surrounded by its own liquid in another immiscible liquid. The attempt here is to gain fundamental understanding of the transport processes that take place in connection with direct-contact heat exchange. The fluid dynamics associated with its growth and translation is treated in Part 1. Here, that flow field solution is used to obtain the temperature field and hence the evaporation rate. The energy equation for the system consisting of a single compound drop is solved numerically by finite-difference methods. The results give the complete time history of evaporation of the drop. In addition, useful quantities such as the Nusselt number are given and compared with existing experimental data. Most of the results have good agreement with experimental data.

Direct Contact Heat Exchange Interfacial Phenomena for Liquid Metal Reactors: Part II — Void Fraction

2002 ◽  
Author(s):  
S. Abdulla ◽  
X. Liu ◽  
M. H. Anderson ◽  
R. Bonazza ◽  
M. L. Corradini ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Liquid Metal ◽  
Void Fraction ◽  
Direct Contact ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Test Facility ◽  
Contact Heat ◽  
Contact Heat Exchange

One concept being considered for steam generation in innovative nuclear reactor applications, involves water coming into direct contact with a circulating molten metal. The vigorous agitation of the two fluids, the direct liquid-liquid contact and the consequent large interfacial area can give rise to large heat transfer coefficients and rapid steam generation. For an optimum design of such direct contact heat exchange and vaporization systems, detailed knowledge is necessary of the various flow regimes, interfacial transport phenomena, heat transfer and operational stability. In order to investigate the interfacial transport phenomena, heat transfer and operational stability of direct liquid-liquid contact, a series of experiments are being performed in a 1-d test facility at Argonne National Laboratory and a 2-d experimental facility at UW-Madison. Each of the experimental facilities primarily consist of a liquid-metal melt chamber, heated test section (10cm diameter tube for 1-d facility and 10cm × 50cm rectangle for 2-d facility), water injection system and steam suppression tank. This paper is part II which, primarily addresses results and analysis of a set of preliminary experiments and void fraction measurements conducted in the 2-d facility at UW-Madison, part I deals with the heat transfer in the 1-d test facility at Argonne National Laboratory. A real-time high energy X-ray imaging system was developed and utilized to visualize the multiphase flow and measure line-average local void fractions, time-dependent void fraction distribution as well as estimates of the vapor bubble sizes and velocities. These measurements allowed us to determine the volumetric heat transfer coefficient and gain insight into the local heat transfer mechanisms. In this study, the images were captured at frame rates of 100 fps with spatial resolution of about 7mm with a full-field view of a 15cm square and five different positions along the test section height. The full-field average void fraction increases rapidly to about 15% in these preliminary tests, with the apparent boiling length of less than 20cm. The volumetric heat transfer coefficient between the liquid metal and water are compared to the CRIEPI data, the only prior data for direct contact heat exchange for these liquid metal/water systems.

scholarly journals FUNDAMENTALLY NEW APPROACHES TO SOLVING THERMOPHYSICAL PROBLEMS IN THE FIELD OF NANOELECTRONICS

2021 ◽  
Author(s):  
Vladimir Khvesyuk ◽  
Aleksandr Barinov ◽  
B. Liu ◽  
W. Qiao
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Solid State ◽  
Thermal Resistance ◽  
Effective Thermal Conductivity ◽  
Contact Thermal Resistance ◽  
New Approaches ◽  
Rough Boundaries

The paper discusses current problems related to the heat transfer in solid-state nanostructures: the influence of real rough boundaries on the effective thermal conductivity and contact thermal resistance

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