## Chapter 2

## Fourier’s Law and Its Consequences

#### 2.1 Introduction

While studying the subject of heat transfer, one of our objectives is to calculate the rate of heat transfer. From the second law of thermodynamics, we know that there must be a temperature gradient for heat transfer to occur, i.e. heat flows from a location of high temperature to a location of low temperature. Fourier’s law gives the relation between the rate of heat flow and temperature gradient and is therefore considered to be the fundamental law of conduction.

In this chapter, we will first study Fourier’s law and the assumptions behind this law. Then, follow two important consequences of Fourier’s law; the first one being the definition of thermal conductivity—an important ...