Thermal communication behavior
A coefficient is the conduction of thermal communication, a building that reflects the thermal conductivity, or ability to conduct heat, between two groups in a communication. Resistance to this property is called thermal contact strength.
Explanation
1: Heat flow between two lights in communication and temperature circulation.
When two strong bodies come in contact, such as A and B in Figure 1, heat flows from the warmer body to the colder body. From experience, the temperature profile of both bodies varies, to a large extent, as can be seen in the figure. The temperature drop is monitored at the interface between the two surfaces in communication. This phenomenon is said to be the result of thermal communication stress between the communication surfaces.
According to Fourier's law, the flow of heat between the bodies is found by the relationship:\
where the heat flows, the thermal conductivity, the cross-sectional range, and the temperature gradient are in the direction of flow.
From an energy conservation perspective, the heat flow between the two groups in communication, bodies A and B, can be found:
(2).
One might argue that the heat flow is directly related to the thermal conductivity of the groups in contact, and, the field of communication, and the opposite of thermal communication, which, as it was previously mentioned, is a trade-off of the thermal conduction coefficient,.
Weight
Most values tested by a test against thermal contact fall between 0.000005 and 0.0005 m2 K / W (the corresponding range of thermal contact behavior is 200,000 to 2000 W / m2 K). To determine whether or not the thermal contact strength is significant, the thermal stability ratings of the layers are compared with standard values against thermal contact. Thermal contact strength is important and may affect good heat conductors such as metals but may be neglected for poor heat conductors such as insulators. Thermal contact behavior is an important feature in a number of applications, largely due to the fact that many physical systems contain a mechanical combination of two materials. There are some areas where communication behavior is important
• Electronics
o Electronic package
o Heat sinking
of Branagan
• Industry
o Nuclear reactor cooling
o Gas turbine cooling
o Indoor combustion engines
o Heat exchangers
o Thermal insulation
• Fly
o Hypersonic flying vehicles
o Thermal management for space vehicles
• Residential / Construction Science
o Performance of construction envelopes
Factors influencing communication behavior
2: Increase the interface between two contact surfaces. The quality of the finish adds to the ambiguity of the argument.
Thermal communication behavior is a complex phenomenon, influenced by many factors. Experience shows that the most important are:
Contact pressure
For thermal transport between two contact groups, such as particles in a granular medium, the contact pressure is the major factor influencing overall communication behavior. As the pressure of communication grows, the real space for communication increases, and the behavior of communication increases (the stress of communication decreases). [6]
As communication stress is the most important factor, most studies, corrections, and mathematical models for measuring communication behavior are performed as a function of this factor.
The thermal contact strength of some sandwich products made by rolling under high temperatures is sometimes neglected because the reduction in thermal conductivity between them is very small.
Interdepartmental materials
Main article: interdepartmental defect
There is no very smooth surface, and surface imperfections are visible under a microscope. As a result, when two groups are pressed together, communication occurs only in a finite number of points, separated by relatively large gaps, as shown in Figs. 2. Since the actual contact area is reduced, there is another effect for heat flow. there. The gases/liquids that fill these gaps can have a significant effect on the overall heat flow across the interface. The thermal conductivity of the interstitial material and its weight, studied by reference to Knudsen number, are the two properties that govern its influence on communication behavior,
Without interstitial materials, as in a vacuum, the tension in the communication will be much greater, as there is control through flow through the close contact points.
Rough surface, waviness, and flatness
It can identify one surface that has undergone special finishing work with three main properties: roughness, waviness, and false finish. These include roughness and brittleness, with roughness often expressed in terms of RMS value, and surface fracture commonly characterized by Df. The effect of surface structures on thermal conductivity at an interface similar to the concept against electrical communication, also known as ECR, involves limited transport by communication phones rather than electricity.
Surface deformations
When the two groups come into contact, surface deformation can occur on both bodies. This deformation can be plastic or elastic, depending on the properties of the material and the contact pressure. When a surface undergoes a plastic change, the contact rate is reduced, as the deformation causes the actual contact area to increase [7] [8]
Surface cleanliness
The presence of dust, acid, etc. grains, can affect the mode of communication.
Measurement of thermal contact behavior
Going back to Formula 2, it may be difficult, even impossible, to calculate thermal conductivity, due to the difficulty of measuring the contact area, (Result of surface properties, as explained earlier). Because of this, test behavior/conflict is usually detected by testing, using standard equipment. [9]
The results of such tests are usually published in Engineering literature, in journals such as the Journal of Heat Transfer, the International Journal of Heat and Mass Transfer, etc. Unfortunately, there is no centralized database of communication behavior coefficients, a situation that sometimes causes companies to use outdated, inappropriate data, or not takes communication into consideration. between.
cocoa (Information Behavior Assessor), a project set up to solve this problem and a centralized database of communication behavior data and a computer program that uses it, was launched in 2006.
Thermal boundary transfer
While finished thermal contact behavior is due to interface gaps, surface waviness, and surface roughness, etc., even finished behavior even at near-interface is also suitable. This direction, called thermal boundary conduction, is due to the differences in electrical properties and vibration between the communication materials. This behavior is typically much higher than thermal contact behavior but will be important in nanoscale material systems.
References
1. ^ Holman, J. P. (1997). Heat transfer, 8th edition. McGraw-Hill.
2. ^ Çengel. Introduction to Thermodynamics and Heat Transfer.
3. ^ Fletcher, L. S. (November 1988). "Recent developments in communication heat transfer". Heat Transfer Journal. 110 (4b): 1059–1070. Bibcode: 1988ATJHT.110.1059F. DOI: 10.1115 / 1.3250610.
4. ^ Madhusudana, C. V .; Ling, F. F. (1995). Thermal communication behavior. Springer.
5. ^ Lambert, M. A .; Fletcher, L. S. (November 1997). "Thermal contact behavior of spherical coarse metals". Heat Transfer Journal. 119 (4): 684–690. DOI: 10.1115 / 1.2824172.
6. ^ Jump up to: a b Gan, Y; Hernandez, F; et al. (2014). Fusion Science and Technology. 66 (1): 83–90. arXiv: 1406.4199. DOI: 10.13182 / FST13-727.
7. ^ Williamson, M .; Majumdar, A. (November 1992). "Effect of surface deformations on contact behavior". Heat Transfer Journal. 114 (4): 802–810. DOI: 10.1115 / 1.2911886.
8. ^ Department of Heat Transfer (November 1970). "Behavior in solids - stable state, incomplete metal-to-metal surface contact". General Electric Inc.
9. ^ ASTM D 5470 - 06 General Test Method for Thermal Transfer Buildings of Electrical Thermal Insulation Materials
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