18.13 : Conduction, Convection and Radiation: Problem Solving

There are three methods by which heat transfer can take place: conduction, convection, and radiation. Each method has unique and interesting characteristics, but all three have two things in common: they transfer heat solely because of a temperature difference; and the greater the temperature difference, the faster the heat transfer.

In order to solve a problem related to heat transfer, first of all, the situation needs to be examined to determine the type of heat transfer involved. This could be conduction, convection, radiation, or all three of them. The second step is to identify and write down the unknown quantities in the problem. A list can be prepared of what is given or what can be inferred from the problem as stated, i.e., the known quantities, followed by solving the appropriate equation for the quantity to be determined.

For heat transfer through conduction, the following equation should be used.

For convection, the rate of heat loss depends on the temperature gradient, surface area, and heat transfer coefficient.

The following equation gives the net heat transfer rate for radiation.

Substituting the known quantities along with their units into the appropriate equation and solving it numerically gives the correct solution.