thermal contact resistance.pdf

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1,1,1-TRICHLOROETHANE

T-JUNCTIONS

TACHOMETRIC FLOWMETERS

TACONITE

TAIT EQUATION

TAME

TANK COILS

TANTALUM

TARS

TAU METHOD

TAYLOR COLUMN

TAYLOR EQUATION FOR MIXTURE

VISCOSITY

TAYLOR FLOWS

TAYLOR INSTABILITY

TAYLOR NUMBER

TAYLOR SERIES

TAYLOR'S THEOREM

TAYLOR-COUETTE HEAT

EXCHANGER

TAYLOR-GRTLER VORTEX FLOWS

TAYLOR-PROUDMAN THEOREM

TDS, TOTAL DISSOLVED SOLIDS

TEMA

TEMA STANDARDS

TEMPERATURE

TEMPERATURE GRADIENT IN

EARTH'S CRUST

TEMPERATURE MEASUREMENT,

BASES

TEMPERATURE MEASUREMENT,

PRACTICE

(1)

(2)

THERMAL CONTACT RESISTANCEDOI: 10.1615/AtoZ.t.thermal_contact_resistance

When a junction is formed by pressing two similar or dissimilar metallic materials together, only a small fraction of the

nominal surface area is actually in contact because of the nonflatness and roughness of the contacting surfaces. If a heat flux

is imposed across the junction, the uniform flow of heat is generally restricted to conduction through the contact spots, as

shown in Figure 1. The limited number and size of the contact spots results in an actual contact area which is significantly

smaller than the apparent contact area. This limited contact area causes a thermal resistance, the contact resistance or thermal

contact resistance.

Figure 1. Magnified view of two materials in contact.

The presence of a fluid or solid interstitial medium between the contacting surfaces may contribute to or restrict the heat

transfer at the junction, depending upon the thermal conductivity, thickness, and hardness (in the case of a solid) of the

interstitial medium. If there is a significant temperature difference between the surfaces composing the junction, heat

exchange by radiation also may occur across the gaps between the contacting surfaces.

When a metallic junction is placed in a vacuum, conduction through the contact spots is the primary mode of heat transfer,

and the contact resistance is generally greater than when the junction is in the presence of air or other fluid. In a vacuum, the

temperature distribution in the contacting materials, with the resulting temperature difference at the junction, is shown

Figure 2 for both flat and cylindrical junctions.

Figure 2. Temperature distribution across flat and cylindrical contacting solids.

This temperature difference is used to define the contact resistance at the junction, such that:

where T1 and T2 are the temperatures of the bounding contact surfaces, S is the area across which the heat is transferred, and

ac is the heat transfer coefficient for the junction, or the thermal contact conductance. This contact conductance or joint

conductance is often reported in the literature and is defined as:

The magnitude of the contact conductance is a function of a number of parameters including the thermophysical and

mechanical properties of the materials in contact, the characteristics of the contacting surfaces, the presence of gaseous or

nongaseous interstitial media, the apparent contact pressure, the mean junction temperature, and the conditions surrounding

the junction, as noted by Fletcher (1988).

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TEMPERATURE PROFILES IN

BOUNDARY LAYER AND

SEPARATED FLOWS

TEMPERATURE SENSITIVE

COATINGS

TEMPERATURE-DEPENDENT

VISCOSITY VARIATION

TEMPERATURE-HEAT LOAD PLOT

TEMPERING

TEMPERING OF CHEMICAL

REACTION

TERMINAL SETTLING VELOCITY

TERMINAL VELOCITY

TERMINAL VELOCITY OF PARTICLE

IN GAS

TERRAIN INDUCED INSTABILITIES

TETRAFLUOROETHYLENE

TEXTURE

THEORETICAL BASIS OF

STOCHASTIC MODELS

THEORETICAL PLATE

THERMAL ANEMOMETERS

THERMAL BARRIER COATINGS

THERMAL BOUNDARY LAYER

THERMAL BUILDING DYNAMICS

THERMAL CAMERA

THERMAL CONDUCTIVITY

THERMAL CONDUCTIVITY IN

POROUS MEDIA

THERMAL CONDUCTIVITY OF

ALUMINUM NANOPOWDERS


CARBON DIOXIDE


GASES

THERMAL CONDUCTIVITY VALUES

THERMAL CONDUCTIVITY, OF AIR

THERMAL CONTACT

CONDUCTANCE

THERMAL CONTACT RESISTANCE

THERMAL DATA FOR METALS

THERMAL DIFFUSION

THERMAL DIFFUSIVITY

THERMAL EFFECTS

THERMAL EFFICIENCY

THERMAL EMISSION

THERMAL ENERGY STORAGE

THERMAL EQUILIBRIUM

THERMAL EXPANSION

THERMAL EXPANSION

COEFFICIENTS

THERMAL EXPLOSION

THERMAL FATIGUE

THERMAL FLOWMETERS

THERMAL FRONT IN A POROUS

MEDIUM

THERMAL GRAVITATION

CONVECTION

THERMAL IMAGING

THERMAL INSULATION

THERMAL MASS FLOWMETER

THERMAL MICROWAVE RADIATION

OF DISPERSE SYSTEMS ON SEA

SURFACE

In view of the significant number of parameters affecting the contact conductance or contact resistance, it has not been

possible to develop a single analytical expression for the prediction of the contact resistance at a junction between two

materials, except for cases of highly idealized single and multiple contacts. An overview of the idealized models has been

reported by Sridhar and Yovanovich (1994). An analytical expression for predicting the contact conductance of nonflat or

machined metallic surfaces in contact has been developed by Lambert and Fletcher (1995) for a wide range of metallic

materials and test conditions. Despite the availability of these models, a majority of the. contact resistance information is

determined experimentally in order to provide a measure of the thermal performance of a specific configuration or system.

Most experimental contact resistance data are obtained using a traditional cutbar, vertical column test facility in a vacuum

or ambient environment over a range of steadystate test conditions. More specialized test facilities have been developed for

use with such configurations as bolted joints, periodic or sliding contacts, concentric cylinders, and full scale or partial scale

models, while some configurations are studied by electrolytic analogue techniques. Essentially all of these experimental

facilities may be used for evaluation of metallic and nonmetallic materials in contact, or metallic and nonmetallic materials

with gaseous or nongaseous interstitial media between the contacting surfaces, over a wide range of test parameters.

The force applied to the nominal contact area of the junction provides the apparent contact pressure on the junction. The

mean junction temperature, Tm, is the average of the contacting surface temperatures. The apparent contact pressure and the

mean junction temperature, combined with the thermophysical and mechanical properties of the contacting materials and

the surface characteristics, are the primary factors in determining the magnitude of the contact resistance. High junction

loads and high temperatures result in low contact resistances, whereas light junction loads and low temperatures lead to

high contact resistances.

The surface finish, or roughness and flatness of the contacting surfaces, can significantly affect the magnitude of the contact

resistance. If the axial force on the contacting surfaces is increased, the surface roughness peaks or asperities may deform

plastically or elastically, depending upon the material properties, leading to increased contact area and decreased contact

resistance. An elevated temperature at the junction may also cause plastic and/or elastic deformation of the roughness

asperities, especially for softer materials, with an associated increase in the actual contact area and a decrease in the contact

resistance. Typical contact resistance values for Aluminum 2024T4 samples in contact at moderate test conditions in a

vacuum environment are shown in Figure 3, to demonstrate the effect of surface finish and mean junction temperature on

contact resistance [Fletcher (1991)].

Figure 3. Temperature distribution across flat and cylindrical contacting solids.

Some additional factors which may affect the contact resistance are the direction of the heat flux, surface scratches or cracks,

nonuniform loading which causes uneven contact pressure, relative motion or slipping between the surfaces, and the

presence of oxides or contaminants on the contacting surfaces.

The use of interstitial or thermal control materials for thermal enhancement or thermal isolation of metallic junctions further

effects the contact resistance. Although there are variations in material thickness and composition, the contact resistance for

representative interstitial materials is shown in Figure 4. These interstitial materials have been categorized as greases and

oils; metallic foils and screens; ceramic composites and cements; and synthetic and natural sheets [Fletcher (1972)]. While

metallic foils and greases are often used for thermal enhancement, most of the interstitial materials are generally used for

thermal isolation.



THERMAL MODULATION OF

RALEIGH-BENARD CONVECTION

THERMAL PERFORMANCE OF TUBE

BANKS

THERMAL PHENOMENA

THERMAL PROCESSING

THERMAL PUMPING

THERMAL RADIATION FROM

NONISOTHERMAL PARTICLES IN

COMBINED HEAT TRANSFER

PROBLEMS


NONISOTHERMAL SPHERICAL

PARTICLES


SPHERICAL PARTICLES TO

ABSORBING MEDIUM THROUGH

NARROW CONCENTRIC GAP

THERMAL RADIATION IN

UNWANTED FIRES

THERMAL RADIATION OF A TWO-

PHASE EXHAUST JET

THERMAL REACTORS

THERMAL REGENERATORS

THERMAL SHOCK

THERMAL STRATIFICATION

THERMAL TRANSPORT

THERMALIZATION

THERMISTORS

THERMO-CAPILLARY CONVECTION

IN ELECTRONIC DISCHARGE

MACHINING

THERMOCAPILLARY FLOW

THERMOCHEMICAL CALORIE

THERMOCLINE

THERMOCOUPLES

THERMODYNAMIC EQUILIBRIUM

THERMODYNAMIC

NONEQUILIBRIUM

THERMODYNAMIC OPTIMIZATION

THERMODYNAMIC PROBABILITY

THERMODYNAMIC PROPERTIES

THERMODYNAMIC PROPERTIES OF

AIR

THERMODYNAMIC TEMPERATURE

SCALE

THERMODYNAMIC WET BULB

TEMPERATURE

THERMODYNAMICS

THERMODYNAMICS FOR

MODELING SCALE-DEPENDENT

PLASTICITY

THERMOELECTRIC HEAT PUMPS

THERMOELECTRIC PHENOMENON

THERMOELECTRIC

REFRIGERATORS

THERMOEXCEL SURFACES

THERMOGRAPHIC CAMERAS

THERMOGRAPHY

THERMOLUMINESCENCE

THERMOMETER

THERMOMETRIC GROUPS

THERMONUCLEAR REACTORS

THERMOPHOTOVOLTAIC

APPLICATION

THERMOPHYSICAL PROPERTIES

Figure 4. Contact resistance for selected interstitial materials for thermal enhancement or thermal isolation.

Surface treatments, or coatings and films, may also be used for thermal enhancement or thermal isolation. Metallic coatings

provide modest to significant thermal enhancement, depending upon the metal used and the method of application. Ceramic

coatings provide modest to excellent thermal isolation depending upon the choice of material. Ceramic coatings may also

provide hard, corrosion resistant coatings that are not electrically conducting. Care must be taken to assure that galvanic

corrosion will not occur with the choice of materials for some applications.

References

1. Fletcher, L. S. (1972) A review of thermal control materials for metallic junctions, A1AA Journal of Spacecraft and Rockets, 9,

12, 849850. DOI: 10.2514/3.61809

2. Fletcher, L. S. (1988) Recent developments in contact conductance heal transfer. ASME Journal of Heat Transfer, 110, 4B,

10591070.

3. Fletcher, L. S. (1991) Conduction in solidsImperfect metaltometal contacts: Thermal contact resistance, Section 502.5,

Heat Transfer and Fluid Mechanics Data Books, Genium Publishing Company, Schenectady, New York.

4. Lambert, M. A. and Fletcher, L. S. (1995) Thermal Contact Conductance of Spherical Rough Metals: Theory and

Comparison to Experiment, Proceedings of the ASME/JSME Thermal Engineering Joint Conference, Maui, Hawaii, March

1924.

5. Sridhar, M. R. and Yovanovich, M. M. (1993) Critical Review of Elastic and Plastic Contact Conductance Models and

Comparison with Experiment, AIAA Paper 932776, A1AA Thermophysics Conference, Orlando, Florida, July 69.

Number of views: 39541 Article added: 2 February 2011 Article last modified: 9 February 2011 Copyright 20102015 Back to top



THERMOSORPTIVE COMPRESSOR

THERMOSYPHON

THERMOSYPHON REBOILERS

THERMOSYPHONING AIR PANEL,

TAP

THICKENERS

THICKENING

THIN CHANNEL

THIN FILM EVAPORATION

THIN FILM SUPERCONDUCTORS

THIN FLEXIBLE SHELLS

THIN LAY CHROMATOGRAPHY

THIN LIQUID FILMS

THIN VERTICAL CYLINDER

THIRD LAW OF THERMODYNAMICS

THIXOTROPIC FLUIDS

THIXOTROPY

THOMA COEFFICIENT

THOMPSON EFFECT

THOMPSON, BENJAMIN, COUNT

RUMFORD

THOMSON, WILLIAM, LORD KELVIN

THORIUM

THREE FLUIDS WITH VARIABLE

THERMOPHYSICAL PROPERTIES

THREE MILE ISLAND ACCIDENT

THREE-DIMENSIONAL COMPUTING

THREE-DIMENSIONAL MESH

REFINEMENT METHOD

THREE-DIMENSIONAL MODELING

OF ICP TORCHES

THREE-DIMENSIONAL PIV USING

INTENSITY GRADIENTS OF A TWO-

COLOR LASER BEAM

THREE-PHASE, GAS-LIQUID-LIQUID

FLOWS

TIDAL ENERGY

TIDAL POWER

TIME LAPSE PHOTOGRAPHY

TIME STRETCH PHOTOGRAPHY

TITANIUM

TOLLMEIN-SCHLICHTING WAVES

TOMOGRAPHIC IMPEDANCE

METHOD

TOMOGRAPHY

TOP FLOODING

TOP HAT PROFILE, OPTICS

TORNADOS

TORR

TORTUOSITY FACTOR

TOTAL HEAD

TOTAL HEAD LINE

TOTAL PRESSURE TUBE

TOTAL SURFACE EFFECTIVENESS

TOWERS, COOLING

TOXIC WASTES

TRACER METHODS

TRACER PARTICLES

TRAILING VORTICES

TRAJECTORY AND MOMENTUM

COHERENCE

TRAJECTORY PROBLEM, OPTICS



TRANSCENDENTAL EQUATION

TRANSCENDENTAL FUNCTIONS

TRANSFER PROCESSES IN AN

EVAPORATING DROPLET

TRANSIENT CONDUCTION

TRANSIENT HEAT TRANSFER

TRANSIENT HEAT TRANSFER IN

JACKETED VESSELS

TRANSIENT NON-DARCY

MAGNETOHYDRODYNAMIC

CONVECTION FLOW OF

MICROPOLAR FLUIDS

TRANSIENT PLUMES

TRANSIENT PROBLEMS

TRANSIENT SPRAY

TRANSITION BOILING

TRANSITION FLOW REGIME

TRANSITION FROM LAMINAR TO

TURBULENT FLOW

TRANSITION TO TURBULENT

BOUNDARY LAYER

TRANSMISSIVITY

TRANSONIC WIND TUNNELS

TRANSPIRATION COOLING

TRANSPORT APPROXIMATION

TRANSPORT DISENGAGING

HEIGHT IN FLUIDIZED BED

TRANSPORT PHENOMENA

TRANSPORT PROPERTIES OF

GASES

TRANSPORT THEOREM

TRANSVERSE ACOUSTIC

PERTURBATION

TRANSVERSE VORTEX ROLLS

TRAPEZOIDAL RULE

TRAYS, COLUMNS

TREATED SURFACES

TREVITHICK ENGINES

TRI-DRUM HEAT RECOVERY

BOILER

TRIANGULAR CAVITIES

TRIANGULAR DUCTS, FLOW AND

HEAT TRANSFER

TRIANGULAR ENCLOSURES

TRIANGULAR RELATIONSHIP IN

ANNULAR FLOW

TRIARYLMETHANE

TRIBLOCK COPOLYMERS

TRICHLOROETHYLENE

TRIGONOMETRIC FUNCTIONS

TRIGONOMETRIC POLYNOMIALS

TRIGONOMETRIC SERIES

TRIPLE INTERFACE

TRIPLE POINT

TRIPLE POSNT PRESSURE

TRIPLET STATE

TRITIUM

TROMBE WALLS

TROMBE-MICHEL WALLS

TROPOSPHERE

TRUE MASS FLOW METER

TSUNAMIS



TUBE BANKS, CONDENSATION

HEAT TRANSFER IN

TUBE BANKS, CROSSFLOW OVER

TUBE BANKS, SINGLE-PHASE HEAT

TRANSFER IN

TUBE BUNDLES

TUBE BUNDLES, TWO-PHASE

CROSSFLOW

TUBE SHEETS

TUBE-FIN EXTENDED SURFACES

TUBES

TUBES AND TUBE BANKS, BOILING

HEAT TRANSFER ON

TUBES SINGLE-PHASE HEAT

TRANSFER TO, IN CROSS-FLOW

TUBES, CONDENSATION IN

TUBES, CONDENSATION ON

OUTSIDE IN CROSSFLOW

TUBES, CROSSFLOW OVER

TUBES, GAS-LIQUID FLOW IN

TUBES, SINGLE-PHASE FLOW IN

TUBES, SINGLE-PHASE HEAT

TRANSFER IN

TUBULAR BOWL CENTRIFUGE

TUBULAR EXCHANGER

MANUFACTURERS ASSOCIATION,

TEMA

TUNGSTEN

TUNGSTEN CATHODE

TUNNEL BURNERS

TUNNEL KILN

TURBINE

TURBINE BLADE

TURBINE EFFICIENCY

TURBINE FLOWMETERS

TURBOMOLECULAR PUMP

TURBOPHORETIC VELOCITY

TURBULENCE

TURBULENCE MODELING

TURBULENCE, IN WIND TUNNELS

TURBULENCE-CHEMISTRY

INTERACTION

TURBULENT BURSTS

TURBULENT DIFFUSION

TURBULENT ENERGY DISSIPATION

TURBULENT FLOW

TURBULENT FLOW, HEAT

TRANSFER

TURBULENT FLOW, TRANSITION TO

IN TUBES

TURBULENT FREE CONVECTION

TURBULENT KINETIC ENERGY

TURBULENT MASS TRANSFER

TURBULENT MIXED CONVECTION

TURBULENT PIPE CONTRACTOR

TURBULENT SPOTS

TURBULENT WALL FLOW

TWIN FLUID ATOMIZERS

TWISTED JETS

TWISTED TAPE INSERTS

TWISTED TUBES

TWO DISKS WITH NON-COINCIDENT

PARALLEL AXES OF ROTATION



TWO-DIMENSIONAL MODEL OF

DECOHESION

TWO-DIMENSIONAL MODELING OF

LOW PRESSURE AIR PLASMA

REACTOR

TWO-FLUID MODELS

TWO-FLUX APPROXIMATION

TWO-LAYER POROUS BURNER

TWO-PHASE CRITICAL FLOW

TWO-PHASE FLOW COMBINING

TWO-PHASE FLOW CONSERVATION

EQUATIONS

TWO-PHASE FLOW DYNAMICS

TWO-PHASE FLOW IN POROUS

MEDIA

TWO-PHASE FLOW MULTIPLIER

FOR BENDS

TWO-PHASE FLOW SPLITTING

TWO-PHASE FLOWS

TWO-PHASE INSTABILITIES

TWO-PHASE STRATIFIED

TURBULENT DUCT FLOW

TWO-PHASE THERMAL-CONTROL

TWO-PHASE THERMOSYPHON

TWO-PHASE TURBULENT JETS

TWO-STROKE CYCLE

TYN AND CALUS METHOD

TYPICAL GLASS FOAMS

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