Gas meters must be designed to measure temperature, pressure and heating value of gaseous fuels flowing through the gas meters. Many gas meters measure just the volume of gas flow through the gas meter. Gas volume does not take into account the quality of the gas, and the amount of heat available when burned. By gas quality measurement, the utility customers are billed according to the heat available in the gas. The quality of the gas is measured and adjust the gas price for in each billing cycle. Gas quality is known by several names as the gas calorific value, gas heating value, or gas thermal value.

Many types of gas fuels are available such as LPG, CNG, LNG, and various types of biogases. All of these gases do not have same heating value or thermal energy. The customer is to be billed based on the quality of gas. The calorific value of natural gas can be obtained using a process gas chromatograph, which measures the amount of each constituent of the gas, namely: methane, ethane, carbon dioxide, water, etc.

Measurement of Gas Heating Value using Gas Calorimeter

The heating value of a material is measured using the following system: The sample of natural gas is passed through a wet gas meter for measuring and humidifying before being burned. The air for combustion is also humidified before combustion. The air and natural gas are then mixed in the Calorimeter and burned. The exhaust gas is passed through a cooling spiral in the calorimeter and cooled to ambient temperature. The heat produced during combustion is passed completely into the coolant. The water formed during combustion is also condensed and measured.

Measurement of Gas Heating Value using Volume based Gas Meter

Additionally, by using volume based gas flow meters, to convert from gas volume data to gas thermal energy, the pressure and temperature of the gas must be taken into consideration. Pressure is generally not a problem, the meter is simply installed immediately downstream of a pressure regulator and is calibrated to read accurately at that pressure. Pressure compensation then occurs in the utility’s billing system. Varying temperature cannot be handled as easily, but some meters are designed with built-in temperature compensation to keep them reasonably accurate over their designed temperature range, and others are corrected for temperature electronically.