Question:
A gradually expanding duct fitted to the outlet of an exhaust fan is known as
A gradually expanding duct fitted to the outlet of an exhaust fan is known as
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Think about the specific mining ventilation term, not the general engineering word, for a duct that flares out at a mine fan's outlet.
Updated On: Jul 27, 2026
- chimney
- diffuser
- evasee
- equivalent orifice
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Verified By Collegedunia
The Correct Option is C
Solution and Explanation
Step 1: Understanding the Question:
The question asks for the specific mining ventilation term used for a duct that flares outward gradually where it is fitted onto the outlet of an exhaust or main mine fan.
Step 2: Key Formula or Approach:
In mine ventilation practice, a duct that widens gradually in cross section slows down the air as it leaves the fan. This converts some of the fast moving air's kinetic energy back into useful static pressure, so the fan pushes air through the mine more efficiently.
This particular fitting has its own name in mining terminology, separate from the general engineering word for a flaring outlet.
Step 3: Detailed Explanation:
A chimney is a vertical shaft or duct built to carry exhaust air or gases away. It says nothing about a gradually expanding shape, so option (A) is wrong.
A diffuser is the general mechanical engineering word for any duct that slows a flow by widening its area. It describes the same idea but is not the specific word mining engineers use for this fan fitting, so option (B) does not fit.
An evasee is exactly this gradually flaring outlet duct fitted on a mine fan. It lowers the air's exit velocity, cuts the exit loss, and recovers static pressure, letting the fan work more effectively.
An equivalent orifice is a mine ventilation network concept used to combine the resistance of several airways in series or parallel into one imaginary opening. It has nothing to do with the shape of a duct at a fan outlet, so option (D) is wrong.
Step 4: Final Answer:
The gradually expanding duct fitted to the outlet of an exhaust fan is called an evasee. \[ \boxed{\text{Evasee}} \]
The question asks for the specific mining ventilation term used for a duct that flares outward gradually where it is fitted onto the outlet of an exhaust or main mine fan.
Step 2: Key Formula or Approach:
In mine ventilation practice, a duct that widens gradually in cross section slows down the air as it leaves the fan. This converts some of the fast moving air's kinetic energy back into useful static pressure, so the fan pushes air through the mine more efficiently.
This particular fitting has its own name in mining terminology, separate from the general engineering word for a flaring outlet.
Step 3: Detailed Explanation:
A chimney is a vertical shaft or duct built to carry exhaust air or gases away. It says nothing about a gradually expanding shape, so option (A) is wrong.
A diffuser is the general mechanical engineering word for any duct that slows a flow by widening its area. It describes the same idea but is not the specific word mining engineers use for this fan fitting, so option (B) does not fit.
An evasee is exactly this gradually flaring outlet duct fitted on a mine fan. It lowers the air's exit velocity, cuts the exit loss, and recovers static pressure, letting the fan work more effectively.
An equivalent orifice is a mine ventilation network concept used to combine the resistance of several airways in series or parallel into one imaginary opening. It has nothing to do with the shape of a duct at a fan outlet, so option (D) is wrong.
Step 4: Final Answer:
The gradually expanding duct fitted to the outlet of an exhaust fan is called an evasee. \[ \boxed{\text{Evasee}} \]
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