Definition:
Heat is the thermal energy that in transit from one body to another due to a temperature difference between them.
The heat only passes spontaneously from the warmest body to the coldest.
Heat Transfer Processes
Heat transfer is the passage of thermal energy from one body to another, or from one part to another in the same body.
Heat transfer can occur in three different processes:
• Driving;
• Irradiation or radiation;
• Convection.
Units of Measure of heat
In the International System (SI) of units the amount of heat is measured in Joule (J). However, in the refrigeration field, other units are used, such as Calorie (cal) and Quilocaloria (kcal) that have Joule equivalence. In English-speaking countries it is very common to use the unit BTU (British Thermal Unit).
The relations of equivalence between the main units of measurement of heat are:
1 kcal = 3,968 BTU = 4.1858 J
