G0610101 Experiment on Heat Transfer Control by Changing Contact Thermal Resistance

2014 ◽  
Vol 2014 (0) ◽  
pp. _G0610101--_G0610101-
Author(s):  
Shigeki HIRASAWA ◽  
Syota FUJIMOTO ◽  
Tatsuya NAKAMU ◽  
Tsuyoshi KAWANAMI ◽  
Katsuaki SHIRAI
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Contact Thermal Resistance

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.

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 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

scholarly journals HEAT EXCHANGE IN THE AREA OF SURFACE CONTACT WITH SHAPE DEVIATIONS

2021 ◽  
Vol 4 (4) ◽  
pp. 64-69
Author(s):  
Viktor Popov ◽  
Olga Dornyak ◽  
Andrei Latinin ◽  
Elena Lushnikova
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Thermal Resistance ◽  
Transfer Process ◽  
Thermal Model ◽  
Composite System ◽  
Rough Surfaces ◽  
Heat Transfer Process ◽  
Contact Thermal Resistance ◽  
Contact Surfaces

The article discusses a thermal model of the heat transfer process in a composite system with contacting metal surfaces with macrodeviations in the form of bulges. It is shown that the previously developed methods for calculating contact thermal resistances are suitable only for contact pairs with flat-rough surfaces. For the considered contact pairs, when deriving analytical dependences, it is necessary to take into account the effect of equivalent non-flatness, the presence of which significantly increases the contact thermal resistance, which requires taking into account the influence of deviations in the shape of the contact surfaces in the process of designing heat-stressed systems.

Experimental Measurements of the Flow and Heat Transfer of a Square Jet Impinging on an Array of Square Pin Fins

2002 ◽  
Author(s):  
Johnny S. Issa ◽  
Alfonso Ortega
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Flow Behavior ◽  
Jet Impingement ◽  
Tip Clearance ◽  
Heat Sinks ◽  
Clearance Ratio ◽  
Cross Sectional ◽  
Pressure Loss Coefficient ◽  
Air Jet

An experimental investigation was conducted to explore the flow behavior, pressure drop, and heat transfer due to free air jet impingement on square in-line pin fin heat sinks (PFHS) mounted on a plane horizontal surface. A parametrically consistent set of aluminum heat sinks with fixed base dimension of 25 × 25 mm was used, with pin heights varying between 12.5 mm and 22.5 mm, and fin thickness between 1.5 mm and 2.5 mm. A 6:1 contracting nozzle having a square outlet cross sectional area of 25 × 25 mm was used to blow air at ambient temperature on the top of the heat sinks with velocities varying from 2 to 20 m/s. The ratio of the gap between the jet exit and the pin tips to the pin height, the so-called tip clearance ratio, was varied from 0 (no tip clearance) to 1. The stagnation pressure recovered at the center of the heat sink was higher for tall pins than short pins. The pressure loss coefficient showed a little dependence on Re, increased with increasing pin density, and pin diameter, and decreased with increasing pin height and clearance ratio. The overall base-to-ambient thermal resistance decreased with increasing Re number, pin density and pin diameter. Surprisingly, the dependence of the thermal resistance on the pin height and clearance ratio was shown to be mild at low Re, and to vanish at high Re number.

Combined Microstructure and Heat Transfer Modeling of Carbon Nanotube Thermal Interface Materials1

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Sridhar Sadasivam ◽  
Stephen L. Hodson ◽  
Matthew R. Maschmann ◽  
Timothy S. Fisher
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Finite Volume ◽  
Pressure Dependence ◽  
Matrix Material ◽  
Three Dimensional ◽  
Coarse Grain ◽  
Total Thermal Resistance ◽  
Thermal Interface ◽  
Cnt Arrays

A microstructure-sensitive thermomechanical simulation framework is developed to predict the mechanical and heat transfer properties of vertically aligned CNT (VACNT) arrays used as thermal interface materials (TIMs). The model addresses the gap between atomistic thermal transport simulations of individual CNTs (carbon nanotubes) and experimental measurements of thermal resistance of CNT arrays at mesoscopic length scales. Energy minimization is performed using a bead–spring coarse-grain model to obtain the microstructure of the CNT array as a function of the applied load. The microstructures obtained from the coarse-grain simulations are used as inputs to a finite volume solver that solves one-dimensional and three-dimensional Fourier heat conduction in the CNTs and filler matrix, respectively. Predictions from the finite volume solver are fitted to experimental data on the total thermal resistance of CNT arrays to obtain an individual CNT thermal conductivity of 12 W m−1 K−1 and CNT–substrate contact conductance of 7 × 107 W m−2 K−1. The results also indicate that the thermal resistance of the CNT array shows a weak dependence on the CNT–CNT contact resistance. Embedding the CNT array in wax is found to reduce the total thermal resistance of the array by almost 50%, and the pressure dependence of thermal resistance nearly vanishes when a matrix material is introduced. Detailed microstructural information such as the topology of CNT–substrate contacts and the pressure dependence of CNT–opposing substrate contact area are also reported.

Heat Transfer Analysis and Energy-Saving Methods of the Exterior Windows in the Northern Area

2014 ◽  
Vol 881-883 ◽  
pp. 1233-1236
Author(s):  
Zhong Hua Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Energy Saving ◽  
Outdoor Environment ◽  
Heat Transfer Analysis ◽  
Radiation Heat ◽  
Mathematical Formula ◽  
Factors Affecting ◽  
Northern Area ◽  
Indoor And Outdoor

In this paper, ways of heat transfer through windows and doors between the indoor and outdoor environment in the northern area are summarized. And every heat transfer way is described by mathematical formula. On this basis, methods to improve the energy saving performance of exterior windows are put forward according to factors affecting heat transfer through windows. The first method is increasing solar radiation heat, and then reducing heat loss by infiltration, and increasing the thermal resistance as much as possible. Ideal form of energy-saving window is proposed based on compared windows with different material and thermal resistance.

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