# The Ultimate Guide to Thermal Conductivity: Calculator, Definitions, and Application

February 8, 2024

The Thermal Conductivity Calculator is designed to compute the thermal conductivity of materials or determine the heat flux through objects based on Fourier’s law. This guide offers a clear explanation of thermal conductivity, demonstrates how to apply the heat flux formula accurately, and discusses the units of thermal conductivity in detail.

## What Is Thermal Conductivity?

Thermal Conductivity is defined as how well a material can conduct heat, a characteristic intrinsic to the material itself, unaffected by external factors or the mass of the object. This property is directly related to the amount of heat energy conveyed and the distance over which this heat is transferred, while being inversely related to the difference in temperature throughout the material.

The most common example looked at within educational institutions is a wall with insulation. So consider a wall with insulation. If it only allows a minimal amount of heat to pass through, its thermal conductivity is considered to be low.

## Fourier’s Law Definition

Fourier’s Law, states that the rate at which heat is transferred through a material is proportional to the negative gradient of the temperature and the area through which the heat is being transferred. In simpler terms, it means that heat moves from regions of higher temperature to regions of lower temperature, and the amount of heat transferred per unit of time is directly related to how quickly the temperature changes in space (temperature gradient) and the size of the area over which the heat transfer occurs.

## Heat Flux Definiton

Heat flux refers to the amount of heat energy that moves through a specific area every second. It is used within Fourier’s Law and is usually combined as seen below.

## Heat Flux and Fourier’s Law

According to Fourier’s law, heat flux is defined as:

q = –λT/Δx)

Where:

• q – Heat Flux, measured in (W/m²)
• Δx – Thickness of the object (or the distance the heat has to travel) in (m)
• ΔT – The temperature difference across the object in (K)
• λ – The Thermal Conductivity of the material (W/mK)

The negative sign expresses the direction of heat transfer. Due to heat always flowing from a warm area to a cold area, the direction of heat transfer is always opposite to the temperature gradient.

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