# LAB 7: MINOR HEAD LOSSES IN PIPE FLOW

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LAB 7: MINOR HEAD LOSSES IN PIPE FLOW

7.1. Objective This lab considers the minor head loss associated with changes in the flow pattern. The corresponding minor loss coefficient will be determined.

7.2. Theory of Experiment Minor head losses occur in piping systems because of changes in the fluid`s flow pattern. This occurs in flow through valves or fittings such as expansions, contractions, and bends. An energy loss occurs at the point where the valve or fitting is located. For a piping system with a large amount of valves and fittings, the sum of these minor head losses can be significant. Therefore, it is important to have a method for determining these head losses. Minor head loss, hL-m, can be expressed as

ℎ�-� = � [ �2 2� ]

where: hL-m = head loss due to changes in flow pattern (minor loss), (ft, m, etc) k = minor head loss coefficient, (dimensionless) g = acceleration due to gravity (ft/s2 , m/s2 , etc) V = average velocity of the fluid in motion (ft/s, m/s, etc)

The minor head loss coefficient, k, is varied for each type of valve or fitting. If the minor loss coefficient is previously known for a certain type of valve or fitting, the minor loss can be readily determined using Equation 7.1. However, if it is not known, it can be determined using the Energy equation:

�1 � + �1 + �1 2 2� + ℎ� = �2 � + �2 + �2 2 2� + ℎ� + ∑ℎ� (7.2)

where: p = pressure at the respective location (psf, N/m2 , etc) � =

specific weight of the fluid (lb/ft3 , N/m3 , etc) � = elevation above the datum at the respective location (ft, m, etc) V =

average velocity of the fluid in motion at the respective location (ft/s, m/s, etc) g = acceleration due to gravity (ft/s2 , m/s2 , etc) hp = energy added by a pump or pump head (ft, m, etc)

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