Thermal contact conductance of molybdenum-sulphide-coated joints at low temperature

Review of prediction for thermal contact resistance

Abstract: Theoretical prediction research on thermal contact resistance is reviewed in this paper. In general, modeling or simulating the thermal contact resistance involves several aspects, including the descriptions of surface topography, the analysis of micro mechanical deformation, and the thermal models. Some key problems are proposed for accurately predicting the thermal resistance of two solid contact surfaces. We provide a perspective on further promising research, which would be beneficial to understanding mechanisms and engineering applications of the thermal contact resistance in heat transport phenomena.

Thermal Design Procedure for Micro- and Nanosatellites Pointing to Earth

Abstract: This paper proposes a thermal design procedure for micro- and nanosatellites that can be completed in one year. Two thermal design concepts keep components within their design temperature range, reducing the temperature change by using the whole structure for heat storage and reducing the temperature change of the inner structure where the most temperature-sensitive components are mounted. One- and two-nodal analysis methods are used for the former and latter concepts, respectively, to clarify the combinations of optical properties for the structures and components to keep within the design temperature range of the components. Finally, multinodal analysis is performed for detail design based on the optical properties clarified from the one- and two-nodal analyses. This thermal design procedure was applied to the Hodoyoshi-1 satellite, which is a cube about 50 cm on a side, has two inner plates and has solar cells on the body, is on a sun-synchronous orbit at an altitude of about 500 km, and is pointing to...

Control of Thermal Contact Conductance Using Interstitial Materials and Coatings

Abstract: As noted in Chapter 1, the actual solid-to-solid contact area, in most mechanical joints, is only a small fraction of the apparent area. The voids between the actual contact spots are usually occupied by some conducting substance such as air. Other interstitial materials may be deliberately introduced to control, that is, either to enhance or to lessen, the TCC: examples include foils, powders, wire screens and epoxies. To enhance the conductance the bare metal surfaces may also be coated with metals of higher thermal conductivity by electroplating or vacuum deposition. Greases and other lubricants also provide alternative means of enhancing the TCC.

Study on Thermal Contact Resistance Estimation in Planar Medium

Abstract: Thermal contact resistance(TCR) is one of the important parameters in heat transfer problems of engineering, and it is necessary to estimate the value of TCR effectively in many engineering fields. Considering the limitation of current estimation methods of TCR such as only focusing on one-dimensional thermal conduction, getting a single value of TCR merely, and the temperature measuring points only being placed in temperature gradient direction of mediums, boundary element method(BEM) and conjugate gradient method are combined to estimate the TCR in planar mediums. The value of TCR in relation to the position of contact interface line is estimated with this method, and the positions of temperature measuring points can be selected randomly because of the characteristic of BEM that there is no necessity to discrete the inner area and it is sufficient to discrete the boundary. The analysis of calculation examples base on heat transfer model of planar medium demonstrates that:this method can estimate the TCR effectively, but the ill-posedness is also existed in this method which is one of the inverse problems, and the calculation error of TCR is increased with the distance from temperature measuring points to contact interface, the estimation precision and stability can be improved after optimization with least square method.

Effect of interstitial compounds in controlling thermal contact conductance across pressed joints at cryogenic temperature and low contact pressure

Abstract: Heat transfer across pressed joint is significantly governed by thermal contact conductance which in turn depends on thermophysical properties of materials in contact, surface properties, contact pressure, working temperature and interstitials present at the interface. Application of interstitials is an effective technique to control thermal contact conductance at ambient temperature. In the present study, thermal contact conductance across joints at cryogenic temperature in presence of interstitials like silicon based conductive compound, epoxy based adhesive layer and acrylate based anaerobic sealant are explored. These interstitials have different thermophysical characteristics and retain their properties at cryogenic temperature. The joints are investigated for low contact pressure applications, for which thermal contact conductance control is difficult. Specimens are made from cryogenic compatible alloys namely Aluminium alloy AA2219, Stainless steel AISI 321 and Titanium alloy Ti6Al4V with a surface roughness of 0.9 µm. Each interstitial is applied across all six similar and dissimilar pressed joints formed between the materials and thermal characteristics are evaluated experimentally. Investigation is carried out over a temperature range of 150 K to 300 K, with a contact pressure of 140 kPa. The silicon compound enhances thermal contact conductance up to 25 times that of a bare joint while acrylate sealant enhances up to 8 times. The epoxy adhesive coating reduces thermal contact conductance by about 50%. Based on results, monograms are generated for joints based on thermal contact conductance and enhancement factor observed.

Mechanical Properties of Materials at Low Temperatures

Abstract: I N a review paper of this nature it is impossible to cover adequately all aspects of such a large subject as the mechanical properties of materials at low temperatures, and any choice of topics must inevitably leave some areas completely uncovered and others barely indicated. The selection of topics has been made on personal preference but it is hoped that this paper will convey some idea of the present position in the major branches of this subject.

Thermal contact conductance of pressed contacts at low temperatures

Abstract: The influence of variations of interface temperature in the range 50–300 K on the thermal contact conductance between aluminium and stainless steel joints was determined. Predictions were done by modeling the deformation at the interface for different values of surface finish and contact pressure over the range of interface temperatures. Both elastic and plastic deformation was considered. Experiments were carried out in a closed loop cryostat and the results were shown to compare well with the predictions. A reduction of the interface temperature resulted in a smaller value of thermal contact conductance. Interfacial pressure variation had much lower influence at the smaller value of temperatures. The role of surface roughness at the contact was also seen to be less significant at lower interface temperatures and the zone of hysteresis was smaller. A correlation was developed for estimating thermal contact conductance at joints over this temperature range. An explicit dependence of contact conductance on temperature was not seen to be necessary as long as the changes in the hardness and thermal conductivity of the material with temperature are incorporated in the correlation.

Thermal Contact Conductance of Non-Flat, Rough, Metallic Coated Metals

Abstract: Thermal contact conductance is an important consideration in such applications as thermally induced stress in supersonic and hypersonic flight vehicles, nuclear reactor cooling, electronics packaging, spacecraft thermal control, and gas turbine and internal combustion engine cooling In many instances, the highest possible thermal contact conductance is desired For this reason, soft, high conductivity, metallic coatings are sometimes applied to contacting surfaces (often metallic) to increase thermal contact conductance Two previously developed theoretical models for thermal contact conductance of metallic coated metals have been proven accurate for flat, rough surfaces However, these two theories often substantially over-predict the conductance of non-flat, rough, metallic coated metals In this investigation, a previously developed semi-empirical conductance model for flat and non-flat, rough, uncoated metals is employed in predicting the conductance of flat and non-flat, rough, metallic coated metals The more commonly cited of the previous theoretical models for flat surfaces and the semi-empirical model are compared to experimental thermal contact conductance results from a number of investigations in the literature Results for a number of metallic coating/substrate combinations on surfaces with widely varying flatness and roughness were analyzed Both models agree well with experimental results for flat, rough, metallic coated metals However, the semi-empiricalmore » model is substantially more accurate and more conservative than the theoretical model compared to the majority of experimental results for non-flat, rough, metallic coated metals« less

Thermal Contact Resistance Modeling of Non-Flat, Roughened Surfaces With Non-Metallic Coatings

Abstract: Essentially all models for prediction of thermal contact conductance or thermal contact resistance have assumed optically flat surfaces for simplification. A few thermal constriction models have been developed which incorporate uncoated, optically non-flat surfaces based on the bulk mechanical properties of the material. Investigations have also been conducted which incorporate the thermophysical properties of metallic coatings and their effective surface microhardness to predict the overall thermal contact conductance. However, these studies and subsequent models have also assumed optically flat surfaces; thus, the application of these models to optically non-flat, coated surface conditions is not feasible without modifications. The present investigation develops a thermomechanical model that combines both microscopic and macroscopic thermal resistances for non-flat, roughened, surfaces with non-metallic coatings. The thermomechanical model developed as a result of this study predicts the thermal contact resistance of several non-metallic coatings deposited on metallic aluminum substrates quite well

Thermal spreading resistance in multilayered contacts : Applications in thermal contact resistance

Abstract: Application of highly conductive coatings to contacting surfaces is a commonly employed method to enhance thermal contact conductance. In many applications it is often necessary to apply an intermediate coating such that the conductive coating may be applied to a nonadhering substrate. In these instances, it is desirable to predict the effect that the intermediate and e nal coatings have on the spreading resistance. A solution for computing the thermalspreading resistanceofa planarcircularcontactona doubly coatedsubstrateispresented.Also,a modelis developed to compute the contact conductance between a bare substrate and a coated substrate. Comparisons are made with data obtained in the literature for which no analytical model was available. Solution of the governing equations and numerical computation of the spreading resistance were obtained using computer algebra systems. Nomenclature Ac; At; Aa = area, m 2 Ain; Bin = Fourier‐Bessel coefe cients a;b = two radii with a < b, m CL = spreading correction factor e = natural log base Hc = contact microhardness, MPa hc = contact conductance, W/m 2 K J0.x/