# Mechanical Engineering - Heat Transfer, Refrigeration and Air Conditioning - Discussion

Discussion Forum : Heat Transfer, Refrigeration and Air Conditioning - Section 7 (Q.No. 3)
3.
The most commonly used method for the design of duct size is the
velocity reduction method
equal friction method
static regain method
dual or double method
Explanation:
No answer description is available. Let's discuss.
Discussion:
20 comments Page 1 of 2.

WinA said:   7 years ago
Here the total frictional drop and fitting pressure drop is calculated for the ducts, and the line with the biggest pressure drop is taken. This method is the most accurate but take lots of time for calculation.

Ritzie Argota said:   8 years ago
Static regain has complicated method of calculating the size of duct. The equal friction should be considered as commonly used method in duct sizing.

Nithin John simon said:   4 years ago
Velocity, equal friction, and static regain are all commonly used methods, but the most simple one among them is velocity method only.

Tony stark said:   5 years ago
For ducts total pressure (To) = PS + PV.
Where, ps= static pressure.
Pv= velocity pressure, so answer C is right.

Bmsce said:   5 years ago
Equal friction method is the correct answer.

Static regain method is not suitable for long ducts.

Syed Khaja mohinuddin said:   9 years ago
Its a rarely used method and only for circular duct. In gulf equal friction method is used.

Shrivardhan said:   5 years ago
Equal friction method is right answer.

Reference - lesson 38 of nptel R & AC subject.

Charit said:   8 years ago
Please, clarify me. I think it's option B. Equal friction method.

Wael said:   8 years ago
The equal friction method is the most commonly used.

Anilreddy said:   5 years ago
Given answer option C is right.

Ref: R S KURMI.