Calorific value

Calorific Value

The calorific value or heat of combustion is a measure of the energy content of a substance. It is defined as the amount of heat energy released when a known quantity of a substance is burned in the presence of oxygen. The calorific value is typically measured in units of energy per unit mass or volume, such as joules per gram (J/g), calories per gram (cal/g), or British thermal units per pound (Btu/lb).

Measurement of Calorific Value

The calorific value of a substance can be determined using a bomb calorimeter. In this process, a known quantity of the substance is burned in a high-pressure oxygen atmosphere. The heat released by the combustion is absorbed by a known mass of water, and the temperature rise of the water is measured. From this, the calorific value of the substance can be calculated.

Types of Calorific Value

There are two types of calorific value: higher calorific value (HCV) and lower calorific value (LCV). The HCV, also known as the gross calorific value (GCV), includes the heat of condensation of the water vapor produced during combustion. The LCV, also known as the net calorific value (NCV), excludes this heat of condensation.

Factors Affecting Calorific Value

The calorific value of a substance depends on its chemical composition. Substances with a high proportion of carbon and hydrogen, such as coal and natural gas, have high calorific values. Substances with a high proportion of oxygen or nitrogen, such as water or air, have low calorific values.

Applications of Calorific Value

The calorific value is an important parameter in the design and operation of power plants, heating systems, and internal combustion engines. It is also used in the calculation of the carbon footprint of a process or product.

See Also

• Energy density
• Heat of combustion
• Bomb calorimeter
• Coal
• Natural gas