×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

# Could somebody explain the differen

 Forum Search FAQs Links MVPs

## Could somebody explain the differen

(OP)
Could somebody explain the difference between a flow coefficient and a coefficient of discharge please?
Replies continue below

### RE: Could somebody explain the differen

If we are using the same terminoligy, then the flow coefficient is usually used to specify the capcity of a valve in the following equation,

Q = Cv*sqrt(dP*62.4/rho)

where,

Q = volumetric flow, gpm
Cv = flow coefficient, gpm/sqrt(psi)
dP = pressure drop through valve
62.4 = reference water density
rho = actual water density
sqrt = mathematical symbol for square root

The coefficient of discharge, or discharge coefficient, is typically used as a linear multiplier of flow area to represent minor losses and friction losses:

Q = Cd*A*sqrt(2*dP/rho)

where,

Q = volumetric flow
Cd = discharge coeffient
A = actual flow area
dP = pressure drop
rho = fluid density

Often times the discarge coefficient is applied when a tank or pipe system is blowing down to represent the non-ideal behavior of the blowdown.  However, the discharge coefficient can also be related to friction and minor losses by,

Cd =  = 1/sqrt(1+fL/D+K)

where,

f = friction factor
L = pipe length
D = pipe diameter
K = sum of minor losses

### RE: Could somebody explain the differen

A good reference for fluid flow formulas like these is Crane's TP-410, available at www.cranevalve.com.  There's also a software version; I have not used that so I can't vouch for it.

JN

#### Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

#### Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

#### Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!