Explaining Minor Loss Calculations

1
Explaining Minor Loss Calculations

• ChE 3O4

2
Which Velocity?

• The minor loss coefficient, K, is an
  experimentally determined value
• This means that the researcher determined the
  conditions under which the K value was determined
  that includes which velocity, before or after
  the fitting, was used.
• Fortunately, in most cases, the velocity used was
  always the highest if it differed before and
  after the fitting

3
Example 1

• A fitting arrangement that includes a reducer

D1 gt D2
Q
Thus A1 gt A2
D1
D2
Q VA
Therefore, V1 lt V2
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Example 1
Q
D1
D2
5
Example 1

• Bernoulli minor loss components

In this case, V2 is greater than V1 so we use V2.
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Example 2

• A T-joint

D1 D2 D3
Q2
Thus A1 A2 A3
D2
Q1
Q VA
Q3
D3
D1
But V1 ? V2 ? V3
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Example 2

• Potential confusing case but if the diameter is
  equivalent for all three openings then
• V1 must be greater than V2 or V3 since Q1 is
  greater than Q2 or Q3 (i.e. Q1 Q2 Q3)
• So what does this mean for the Bernoulli minor
  loss terms?

8
Example 2

• Bernoulli minor loss components

T-joint, branch flow
T-joint, line flow
V2
V1
V1
V3
In this case, V1 is greater than V2 or V3.