Gas Fitter Practice Test

If 1 cubic foot of natural gas is 1000 Btuh, what is the ratio of total air?

1. 10

2. 15

3. 5

4. 30

The correct answer is: 30

To determine the correct ratio of total air when 1 cubic foot of natural gas is equivalent to 1000 Btuh (British thermal units per hour), it’s important to understand the stoichiometric combustion of natural gas. For efficient combustion, a specific amount of air is required to fully oxidize the fuel. Natural gas primarily consists of methane (CH4), which requires approximately 10 parts of air to 1 part of natural gas for complete combustion under ideal conditions. This is a fundamental principle in combustion engineering, reflecting the need for oxygen found in the air to react with the gas to produce carbon dioxide and water. However, considering the approximation for real-world applications, the ratio of air to natural gas can vary based on the conditions and efficiency of the system. The selected answer suggests a more refined operating ratio that accounts for variations in combustion efficiency, excess air necessary for complete combustion, and safety margins in practical scenarios. Given that the choice of 30 represents a need for higher than stoichiometric air to enhance combustion efficiency and safety, this reflects the practical consideration of ensuring that there is enough oxygen for complete combustion of the natural gas used. This makes the ratio of total air to natural gas effectively aligned with standardized practices in gas balance calculations,