Heat Flow through a Pipe

The heat transfer through a pipe is dependent on the thickness of the pipe and isolation layers. The thickness of the pipe and layers can be defined by the radius of layers i.e. R1, R2,..., Rn. The thermal conductivity of layers are,

2,..., . The fluid within the pipe is at temperature Tin, and the heat transfer coefficient from fluid to the wall is

in. The temperature and heat transfer coefficient for the fluid outside the pipe are Tout and

out. By using Fourier's law of conduction and Newton's law of cooling, it can be shown that for a steady state heat transfer:

where,

dQ/dt= The transferred heat per unit time 
L= Length of the pipe 
A= 2**L*R1

U which has the same unit as heat transfer coefficient is known as the overall heat transfer coefficient.