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# Thermal Resistance and Thermal Conductance

## Introduction

Thermal resistance (R) and thermal conductance (C) of the materials are reciprocals of one another and can be derived from thermal conductivity (k) and the thickness of the materials. The C-Therm Trident Thermal Conductivity Instrument measures thermal conductivity and, therefore, paves the way to determine thermal resistance and thermal conductance.

In this post, we’re going to describe and explain how to get thermal resistance and thermal conductance from thermal conductivity.

## Thermal Conductivity (k-Value)

Thermal conductivity is the time rate of steady-state heat flow through a unit area of a homogeneous material induced by a unit temperature gradient in a direction perpendicular to that unit area, W/m⋅K.

Where,

L – Thickness of the specimen (m)
T – Temperature (K)
q – Heat flow rate (W/m2) Equation 1 – Thermal Conductivity

## Thermal Resistance (R-Value)

Thermal resistance is the temperature difference, at steady state, between two defined surfaces of a material or construction that induces a unit heat flow rate through a unit area, K⋅m2/W. According to this definition and Equation 1, Equation 2, therefore, can be obtained.

As indicated in Equation 2, the value of the thermal resistance can be determined by dividing the thickness with thermal conductivity of the specimen. Equation 2 – Thermal Resistance

## Thermal Conductance

Thermal conductance is the time rate of steady state heat flow through a unit area of a material or construction induced by a unit temperature difference between the body surfaces, in W/m2⋅K. C-value, hence, is the reciprocal of the R-value and can be expressed as Equation (3).

Consequently, the value of the thermal conductance can be calculated by dividing the thermal conductivity with the thickness of the specimen. Equation 3 – Thermal Conductance

## Applications

Thermal resistance and thermal conductance can be conveniently calculated from the thermal conductivity and thickness of the material. The C-Therm Trident Thermal Conductivity Platform is a flexible, rapid, non-destructive, highly sensitive and cost effective instrument that can directly measure thermal conductivity and thermal effusivity of a wide variety of samples, easing the process of determining thermal resistance and thermal conductance.

Take a look below to learn more about how to measure thermal conductivity of specific applications and materials.

## Next Step: Analyze Thermal Conductivity

There are three major methods for analyzing transient thermal conductivity:

• Transient Plane Source
• Needle Probe
• Modified Transient Plane Source

Learn which is right for your application and material in this free in-depth report.