Contact thermal conductivity of compressible rough surfaces

1971 ◽  
Vol 20 (6) ◽  
pp. 788-790
Author(s):  
V. S. Novikov
Keyword(s):  
Thermal Conductivity ◽  
Rough Surfaces ◽  
Contact Thermal Conductivity

Thermal Conductivity in Thin Silicon Nanowires with Rough Surfaces by Molecular Dynamics Simulations

2010 ◽  
Author(s):  
Xueming Yang ◽  
Albert C. To ◽  
Jane W. Z. Lu ◽  
Andrew Y. T. Leung ◽  
Vai Pan Iu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Silicon Nanowires ◽  
Rough Surfaces ◽  
Thin Silicon ◽  
Dynamics Simulations

The Micro-Temperatures of the Peaks and Valleys of Sliding Rough Surfaces

2018 ◽  
Vol 883 ◽  
pp. 53-62 ◽  
Author(s):  
Shin Yuh Chern ◽  
Jeng Haur Horng ◽  
Cheng Han Tsai ◽  
Hung Jung Tsai
Keyword(s):  
Thermal Conductivity ◽  
Temperature Rise ◽  
Rough Surfaces ◽  
Chemical Processes ◽  
The Finite Element Method ◽  
Precision Control ◽  
Sliding Speed ◽  
Surface Failure ◽  
Contact Surfaces ◽  
Transient Thermal

The surface micro-temperature of sliding, rough bodies is an important factor affecting contact properties, such as chemical reactions of automatic injectors for medicine and chemical processes and surface failure of micro-and macro-devices. In this work, the Finite Element Method is used to analyze the micro-temperature of the peaks and valleys of multiplying asperity sliding contact surfaces. The affecting parameters include pressure, roughness, sliding speed, Peclet number, and thermal conductivity of rough surfaces. Analysis results showed that the effects of the studied parameters are different to those of peak and valley temperatures. While pressure increased, the increasing rate of the temperature rise parameter of valleys was larger than those of peaks. The temperature rise of peaks increased as roughness increased. On the contrary, the temperature rise of valleys decreased as roughness increased. Sliding speed and thermal conductivity played the most important roles in affecting the maximum micro-temperature rise. The temperature rise difference between peaks and valleys was almost proportional to thermal conductivity, and was inversely proportional to sliding speed for all cases. This transient thermal analysis enables precision control of interface micro-temperature for micro-moving devices.

Effects of thermal conductivity on the thermal contact resistance between non-conforming rough surfaces: An experimental and modeling study

2020 ◽  
Vol 171 ◽  
pp. 115037
Author(s):  
Dongmei Bi ◽  
Mei Jiang ◽  
Huanxin Chen ◽  
Shanjian Liu ◽  
Yaya Liu
Keyword(s):  
Thermal Conductivity ◽  
Contact Resistance ◽  
Thermal Contact Resistance ◽  
Rough Surfaces ◽  
Thermal Contact ◽  
Modeling Study

The Effect of Element Thermal Conductivity on Turbulent Convective Heat Transfer From Rough Surfaces

2009 ◽  
Author(s):  
Stephen T. McClain ◽  
B. Keith Hodge ◽  
Jeffrey P. Bons
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Convective Heat Transfer ◽  
Rough Surfaces ◽  
Element Model ◽  
Discrete Element ◽  
Discrete Element Model ◽  
Experimental Measurements ◽  
Fin Efficiency ◽  
Roughness Elements

The discrete-element model for flows over rough surfaces considers the heat transferred from a rough surface to be the sum of the heat convected from the flat surface and the heat convected from the individual roughness elements to the fluid. In previous discrete-element model development, heat transfer experiments were performed using metallic or high-thermal conductivity roughness elements. Many engineering applications, however, exhibit roughness with low thermal conductivities. In the present study, the discrete element model is adapted to consider the effects of finite thermal conductivity of roughness elements on turbulent convective heat transfer. Initially, the boundary-layer equations are solved while the fin equation is simultaneously integrated so that the full conjugate heat transfer problem is solved. However, a simpler approach using a fin-efficiency is also investigated. The results of the conjugate analysis and the simpler fin-efficiency analysis are compared to experimental measurements for turbulent flows over ordered cone surfaces. Possibilities for extending the fin-efficiency method to randomly-rough surfaces and the experimental measurements required are discussed.

scholarly journals An effective thermal conductivity model for fractal porous media with rough surfaces

2019 ◽  
Vol 3 (2) ◽  
pp. 149-155 ◽  
Author(s):  
Xuan Qin ◽  
Yingfang Zhou ◽  
Agus Pulung Sasmito
Keyword(s):  
Thermal Conductivity ◽  
Porous Media ◽  
Effective Thermal Conductivity ◽  
Rough Surfaces ◽  
Conductivity Model ◽  
Thermal Conductivity Model

Refinement of the thermal analysis of the gearbox taking into account the thermal conductivity of the joint

2021 ◽  
Author(s):  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Analysis ◽  
Heat Transfer Coefficient ◽  
Thermal Conductivity Coefficient ◽  
Operating Temperature ◽  
Roughness Parameter ◽  
Tightening Force ◽  
Materials Used ◽  
Contact Thermal Conductivity

The existing method for calculating the operating temperature of the gearbox housing is clarified by taking into account the thermal conductivity coefficient of the contact, the value of which depends on the materials used for the housing and frame, the finish of the supporting surfaces and their area, as well as on the tightening force of the screws that pull the housing to the frame. An example of calculating the temperature of the housing of a worm gear is given. Keywords: gearbox, heat sink, heat transfer coefficient, thermal conductivity coefficient of contact, thermal conductivity coefficient of materials, roughness parameter. [email protected]

Influences of Process Parameters of Laser Transmission Welding of Polycarbonate on Contact Thermal Conductivity

2017 ◽  
Vol 44 (12) ◽  
pp. 1202002 ◽  
Author(s):  
刘海华 Liu Haihua ◽  
姜宁 Jiang Ning ◽  
郝云 Hao Yun ◽  
王传洋 Wang Chuanyang
Keyword(s):  
Thermal Conductivity ◽  
Process Parameters ◽  
Laser Transmission Welding ◽  
Contact Thermal Conductivity

Turbulent Convection From Deterministic Roughness Distributions With Varying Thermal Conductivities

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Steven R. Mart ◽  
Stephen T. McClain ◽  
Lesley M. Wright
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Wind Tunnel ◽  
Rough Surfaces ◽  
Roughness Element ◽  
Infrared Camera ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Roughness Elements ◽  
Thermal Conductivities

Many flows of engineering interest are bounded by surfaces that exhibit roughness with thermal conductivities much lower than common metals and alloys. Depending on the local roughness element convection coefficients, the low thermal conductivities of the roughness elements may create situations where temperature changes along the heights of the elements are important and must be considered in predicting the overall surface convection coefficient. The discrete-element model (DEM) for flows over rough surfaces was recently adapted to include the effects of internal conduction along the heights of ordered roughness elements. While the adapted DEM provided encouraging agreement with the available data, more data are required to validate the model. To further investigate the effects of roughness element thermal conductivity on convective heat transfer and to acquire more experimental data for DEM validation, four wind tunnel test plates were made. The test plates were constructed using Plexiglas and Mylar film with a gold deposition layer creating a constant flux boundary condition with steady state wind tunnel measurements. The four test plates were constructed with hexagonal distributions of hemispheres or cones made of either aluminum or ABS plastic. The plates with hemispherical elements had element diameters of 9.53 mm and a spacing-to-diameter ratio of 2.099. The plates with conical elements had base element diameters of 9.53 mm and a spacing-to-base-diameter ratio of 1.574. An infrared camera was used to measure the temperature of the heated plates in the Baylor Subsonic Wind Tunnel for free stream velocities ranging from 2.5 m/s to 35 m/s (resulting in Reynolds number values ranging from 90,000 to 1,400,000 based on the distance from the knife-edge to the center of the infrared camera image) in turbulent flow. At lower Reynolds numbers, the thermal conductivity of the roughness elements is a primary factor in determining the heat transfer enhancement of roughness distributions. At the higher Reynolds numbers investigated, the hemispherical distribution, which contained more sparsely spaced elements, did not exhibit a statistically significant difference in enhancement for the different thermal conductivity elements used. The results of the study indicate that the packing density of the elements and the enhancement on the floor of the roughness distribution compete with the roughness element thermal conductivity in determining the overall convection enhancement of rough surfaces.

Turbulent Convection From Deterministic Roughness Distributions With Varying Thermal Conductivities

2011 ◽  
Author(s):  
Steven R. Mart ◽  
Stephen T. McClain ◽  
Lesley M. Wright
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Wind Tunnel ◽  
Rough Surfaces ◽  
Roughness Element ◽  
Infrared Camera ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Roughness Elements ◽  
Thermal Conductivities

Many flows of engineering interest are bounded by surfaces that exhibit roughness with thermal conductivities much lower than common metals and alloys. Depending on the local roughness element convection coefficients, the low thermal conductivities of the roughness elements may create situations where temperature changes along the heights of the elements are important and must be considered in predicting the overall surface convection coefficient. The discrete-element model (DEM) for flows over rough surfaces was recently adapted to include the effects of internal conduction along the heights of ordered roughness elements. While the adapted DEM provided encouraging agreement with the available data, more data are required to validate the model. To further investigate the effects of roughness element thermal conductivity on convective heat transfer and to acquire more experimental data for DEM validation, four wind tunnel test plates were made. The test plates were constructed using Plexiglas and Mylar film with a gold deposition layer creating a constant flux boundary condition with steady state wind tunnel measurements. The four test plates were constructed with hexagonal distributions of hemispheres or cones made of either aluminum or ABS plastic. The plates with hemispherical elements had element diameters of 9.53 mm and a spacing-to-diameter ratio of 2.099. The plates with conical elements had base element diameters of 9.53 mm and a spacing-to-base-diameter ratio of 1.574. An infrared camera was used to measure the temperature of the heated plates in the Baylor Subsonic Wind Tunnel for free stream velocities ranging from 2.5 m/s to 35 m/s (resulting in Reynolds number values ranging from 90,000 to 1,400,000 based on the distance from the knife-edge to the center of the infrared camera image) in turbulent flow. At lower Reynolds numbers, the thermal conductivity of the roughness elements is a primary factor in determining the heat transfer enhancement of roughness distributions. At the higher Reynolds numbers investigated, the hemispherical distribution, which contained more sparsely spaced elements, did not exhibit a statistically significant difference in enhancement for the different thermal conductivity elements used. The results of the study indicate that the packing density of the elements and the enhancement on the floor of the roughness distribution compete with the roughness element thermal conductivity in determining the overall convection enhancement of rough surfaces.

Experimental Study of VACNT Arrays as Thermal Interface Material

2013 ◽  
Author(s):  
Yulong Ji ◽  
Gen Li ◽  
Hongbin Ma ◽  
Yuqing Sun
Keyword(s):  
Thermal Conductivity ◽  
Chemical Vapor ◽  
Laser Flash ◽  
Thermal Interface Material ◽  
Chemical Vapor Deposition Method ◽  
Free Standing ◽  
Thermal Interface ◽  
Thermal Paste ◽  
Laser Flash Analysis ◽  
Contact Thermal Conductivity

In order to improve thermal interface material (TIM), vertically aligned carbon nanotube (VACNT) arrays were synthesized by the chemical vapor deposition method, and then transferred by dipping in hydrofluoric acid (HF acid) solution to get a free standing VACNT array. Different TIM samples with sandwiched structures were fabricated by inserting the free standing VACNT arrays between two copper plates with and without bonding materials. The laser flash analysis method was applied to measure the overall thermal conductivity of these samples. Results show that: compared with two copper plates in direct contact, thermal conductivity of samples only with VACNT arrays as TIM can be enhanced about 142%–460% depending on the thickness of VACNT arrays. Conventional TIM made up of thermal paste (TG-550 with thermal conductivity of 5 W/mK) and a thermal pad (TP-260 US with thermal conductivity of 6 W/mK) was used as a bonding material between copper plates and VACNT arrays, thermal conductivity has been shown to further improve with the highest values at 8.904 W/mK and 10.17 W/mK corresponding to the different bonding materials and different thicknesses of VACNT arrays used. Results also show that the thicker the VACNT array is when used as a TIM, the lower the overall thermal conductivity of the corresponding samples. This lower thermal conductivity caused by more defects in amorphous carbon of thicker VACNT arrays and lower density of the corresponding sandwiched samples.

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