In the gas industry a standard unit of measure is required. In the English system it is the standard cubic foot. In the metric, it is the standard cubic meter. This standard unit is the basis of all exchange in the gas industry. When the unit of purchase is the energy content (BTU) we achieve it by multiplying the BTU content of a standard cubic foot times the number of cubic feet delivered to the customer. So we must obtain standard cubic feet or meters.
A standard cubic foot is defined as one cubic foot of gas at a pressure and temperature agreed upon by the buyer and seller. Common standard conditions are 14.73 psia and 60° Fahrenheit. The gas passing through a meter is rarely at standard conditions. It is necessary to convert the gas in the meter from the metered conditions to standard cubic feet. The tools we have for relating volume to pressure and temperature are Equations of State or, simply, the Gas Laws.
The Gas Laws serve two purposes. They allow the conversion of a gas stream from metered conditions to standard conditions. They also provide an understanding of what the gas is doing and why. This paper will briefly present the Gas Laws and the physical properties of gas which the Gas Laws describe.
