The Parr Oxygen Bomb Combustion Calorimeter is a commercial example
of a bomb calorimeter. It can be used to measure the chemical
potential energy in food by burning the food inside a strong,
sealed container and measuring the temperature rise of the surrounding
water in a carefully isolated thermal chamber.
The sample of food (a couple grams) is placed inside the steel "bomb" container, which is then filled with pure oxygen (O2). This "bomb" is immersed in a water chamber surrounded by an insulated (non-conducting) shell. A sensitive electronic thermometer is used to measure the temperature of the water.
Two wires pass through the shell to the inside of the "bomb." When an electric current heats the small igniter, the sample burns rapidly. The combustion process releases chemical potential energy of the food in the form of heat. Since the food is in a pure oxygen environment, it burns completely. The heat is transferred to the water bath, causing a temperature rise that is measured by the thermometer. Because the water bath is well insulated, the energy can't escape, and the rise in the water's temperature can be used to calculate the energy that was trapped in the food sample before it was burned.