Final answer:
The induced draft fan is larger than a forced draft fan due to the need for increased airflow, improved combustion, and enhanced safety. Induced draft fans deal with hot and corrosive gases, requiring a more robust system.
Step-by-step explanation:
The question is asking for reasons why an induced draft fan is larger than a forced draft fan. It is a question related to the design and function of industrial ventilation systems, typically found in the field of engineering. To operate effectively, induced draft fans must handle hotter and more corrosive gases compared to forced draft fans, as they are positioned after the combustion zone where the gases are already heated. Furthermore, induced draft fans work to pull flue gases through the system and maintain a slightly negative pressure to ensure combustion gases pass completely through the boiler or furnace, whereas forced draft fans push air into the system.
Considering the options provided, the answer which best fits the context of having a larger induced draft fan as compared to a forced draft fan would be B) Increased airflow, improved combustion, and enhanced safety. A larger fan size generally correlates with the ability to move a larger volume of air, which in turn can improve the efficiency of combustion processes and provide a margin of safety by ensuring proper evacuation of gases.