Headloss Through a Valve

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CEE 320 Fluid Mechanics Lab

Head Loss Through a Valve

April 24, 2012

Abstract

This experiment determined the relationship between the head loss through a gate valve and the degree of opening of that valve with varying flow rates. The objective of this experiment was to determine the valve loss coefficient, K, for a specific gate valve as a function of both the pipe Reynolds Number, and the degree of opening.

The relationship between the Reynolds Number and the friction factor was constant. Regardless of what the Reynolds Number was, the friction factor remained the same. This means that the valve head loss coefficient, K, only depended on the degree of opening of the gate valve. As the valve is slowly turned closed, the Major Head Loss due to friction along the pipe, decreases, and the Minor Head Loss, due to the friction through the gate valve, increases. There is a positive linear relationship between the Reynolds Number and the head loss coefficient. The slope of this linear relationship showed that as the flow rate increases, the velocity increases which means the Reynolds Number gets bigger and the head loss coefficient increases. Therefore, the higher the flow and the smaller the degree of opening of the gate valve, the greater the head loss becomes through the gate valve. Table of contents

Abstract………………………………...……………………………………………………………...i
1Introduction1
1.1Background1
1.2Theory1
1.3Objective1
2Apparatus and Supplies1
3Procedures4
4Equations4
5Experimental Results5
6Error Analysis9
7Conclusions9
8Recommendations for Further Studies10
9References10

APPENDIX

Table of Figures

Figure 21: Pressure Differential Gauge Δp.2
Figure 22: Weighing Tank with Dump Valve open.3
Figure 23: Pressure Differential Gauge between Valve Set-up3

Table 51: Constants and given values.5
Table 52: Measured Data.5
Table 53: Volumetric Flow, Velocity, Reynolds #, Head Loss Coefficient.6
Table 54: Real values of K, Major Head Loss, Minor Head Loss.6

Introduction
Background
Gate valves are frequently used when constructing and fitting pipes. They provide the capability to shut off specific lines so that repairs or renovations can be made without having to turn off the main supply lines. Although these valves are useful, they also disturb the normal flow and cause friction. Theory

The head loss coefficient, K, for a gate valve is related to the Minor Head Loss, Hlm, where Hlm=V22gK. The total head loss in the pipe is divided into two parts: the Major Head Loss, Hf, due to the pipe friction over length L, and the Minor Head Loss. Using the Bernoulli’s energy equation, the coefficient, K, can be found: K=2gΔPV2γ-fLD. Objective

The objective of this experiment was to determine the valve loss coefficient, K, for a specific gate valve as a function of both the pipe Reynolds Number, and the degree of opening. Apparatus and Supplies

* 1 Weighing Tank with Dump Valve (±0.5 lb)
* 2 Stop Watches (±0.01 sec)
* Galvanized Iron pipe 27 inches (±0.03125 in) long with a diameter of 1.61 inches (±0.0005 in) * 1 Pressure Differential Gauge (±0.05 psi)
* 1 Valve located in between the Pressure Differential Gauge on Galvanized Iron Pipe

Figure 21: Pressure Differential Gauge Δp.

Weighing Tank
Dump Valve

Figure 22: Weighing Tank with Dump Valve open.

Figure 23: Pressure Differential Gauge between Valve Set-up

Procedures
1. Measure the distance between the upstream and downstream pressure tabs. 2. Turn the handle on the gate valve to determine how many turns exist between fully-opened and fully-closed. 3. Turn on the pump and open the dump valve in the weighing tank. 4. Turn the gate valve so that it is completely open.

5. Record the Pressure Difference
6. Close the dump valve in the weighing tank.
7. Start and stop the stopwatches over a 100 lb difference and record the...
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