Headloss in Pipe Fittings 6
Florida Institute of Technology
CVE 3033 Lab 11
Lab #11: Headloss in Pipe Fittings
OBJECTIVE
To determine the head loss associated with flow of water through standard fittings used in plumbing installation.
INTRODUCTION
Method: Measure the differential head between tappings on fittings and test valves.
Minor Losses
The losses that occur in a pipeline due to bends, elbows, joints, valves, etc. are sometimes called minor losses. This is a misnomer because in many cases these losses are more important than the losses due to pipe friction, considered in the preceding section. For all minor losses in turbulent flow (Re>4000), the head loss varies as the square of the velocity. Thus a convenient method of expressing the minor losses in flow is by means of a loss coefficient (K). Values of the loss coefficient (K) for typical situations and fittings is found in standard books.
Head loss in a pipe fitting is proportional to the velocity head of the fluid flowing through the fitting:
(Head loss in a pipe fitting is proportional to the velocity head of the fluid flowing through the fitting).
Where K is the fitting “loss factor”, u is the mean velocity of water through the pipe in m/s and g is the acceleration due to gravity in m/s.
Note:
A flow control valve is a pipe fitting which has an adjustable “K” factor.
The minimum value foe “K” and the relationship between stem movement and “K” factor are important in selection a valve for an application.
For a short pipe system, with a relatively large number of bends and fittings, minor losses can easily exceed major losses. In designs, minor losses are usually estimated from tables using coefficients.
APPARATUS
The experiment uses the C6-MKII-10 Fluid Friction Apparatus. Water is fed in from the hydraulic bench via the barbed connector, it flows through the network of pipes and fittings, and is fed back into the volumetric tank via the exit tube.
Short samples of each size test pipe are provided loose so that the students can measure the exact diameter and determine the nature of the internal finish. The ratio of the diameter of the pipe to the distance of the pressure tappings from the ends of each pipe has been selected to minimize end and entry effects.
The C6-50 Data Logging Accessory consists of a turbine type flow meter, two pressure sensors with quick release connectors and a signal conditioning and interface console.
The unit is powered by a separate power supply unit and is connected to the computer via a USA socket at the rear. Two LED’s on the front panel illuminate when the unit is powered and active.
The apparatus must be set up in accordance with the installation sheet supplied.
Flow rates through the apparatus may be adjusted by operation of the control valve on the hydraulics bench.
The flow path through the pipe friction network is controlled using the system of isolating valves. By opening and closing these valves as appropriate it is possible to select flow through any combination of pipes.
The head loss due to pipe fittings is measured by taking pressure readings at different tapping points on the 2 sides of the fittings.
Each pressure point on the apparatus is fitted with a self-sealing connection. To connect a test probe to a pressure point, simply push the tip of the test probe into the pressure point until it latches.
To disconnect a test probe from a pressure point, press the metal clip of the side of the pressure point to release the test probe. Both test probe and pressure point will seal to prevent loss of water.
PROCEDURE
Check the tank in hydraulic bench to be sure it is fitted with water for at least 75% of its volume.
Connect the transparent tube from the C6-MKII-10 apparatus to the outlet of hydraulic bench so that it can provide water for the apparatus.
Plug in the hydraulic bench.
Open/Close the appropriate valves on the apparatus to allow water flow through the desired fittings.
Start the pump and open the valve on the hydraulic bench to provide the apparatus with water.
Set the flow rate to a high discharge so that most of the bubbles in the pipes go away because they cause errors.
Start from a minimum flow rate and increase it 9 times, so that you would have 10 trials (10 different flow rates) for each pipe.
Read the head loss due to pipe fitting (between the two tappings) from the computer software.
Measure the volumetric flow rate for each trial. For small flow rates use the measuring cylinder.
Use the computer software to get the flow rate in lit/s. Don’t forget to convert it to cubic meter per sec for the purpose of calculations.
Measure the inside diameter of the pipe that is carrying the fitting. Samples of each pipe are provided for measurements with a Vernier Caliper.
The following fittings and valves will be tested.
Sudden Contraction
Sudden Enlargement
Ball Valve (Full and Part)
90º Short radius Bend
90º T Junction
90º Mitre
Trials
Fitting Type
Time(s)
Flow Rate
(m3/s)
Pipe Diameter A (m)
Pipe Diameter B (m)
Velocity
(m/s)
Velocity Head (m)
Head Loss (m)
Fitting Factor
Kexperimental
Kreal
Comments
Equation/Parameter Description
1
Sudden Contraction
2
Sudden Contraction
3
Sudden Contraction
1
Sudden Enlargement
2
Sudden Enlargement
3
Sudden Enlargement
1
90° T Junction
2
90° T Junction
3
90° T Junction
1
90° Mitre
2
90° Mitre
3
90° Mitre
1
90° Short Radius Bend
Flowrate was measured directly
2
90° Short Radius Bend
3
90° Short Radius Bend
1
Ball Valve Completely Open
2
Ball Valve Completely Open
3
Ball Valve Completely Open
1
Ball Valve Partially Open
2
Ball Valve Partially Open
3
Ball Valve Partially Open
Comments
Small Q: Vol. = 5L
Data Sheet: Lab 11 Name: _______________________
Notes: ___________________________________________________________________________________
Data Sheet: Lab 11 Name: _______________________
Notes: ___________________________________________________________________________________
Fall 2021