G2 Gas Fitter Practice Exam

In firetube boilers, where are the flue gases located?

1. Inside the Tubes

2. Outside the Tubes

3. In the Water Reservoir

4. In the Boiler Shell

The correct answer is: Inside the Tubes

In firetube boilers, the flue gases are located inside the tubes. This design is fundamental to how firetube boilers operate. In this configuration, hot gases produced from the combustion process flow through the tubes, which are submerged in water. The heat from these gases is transferred to the surrounding water, which is then turned into steam or heated for other applications. This setup allows for efficient heat transfer since the larger surface area of the tubes in contact with water maximizes the heat exchange process. As the combustion gases pass through the tubes, they cool down while simultaneously heating the water around them, demonstrating an effective use of the principles of thermodynamics for energy efficiency in heating systems. Other locations such as the water reservoir or boiler shell do not correctly represent where the flue gases move in the context of firetube boilers; the water reservoir is where water is stored, while the shell would typically enclose the pressing components rather than serve as a passage for flue gases.