Transcript Flow Measuring Devices

FLUID FRICTION AND
PRESSURE LOSSES
ENTC-303
Dr. Alvarado
1
Objective
• To determine experimentally the loss
coefficient K for a Venturi meter
and straight elbow at different mass
flow rates
• To compare the experimental and
theoretical pressure drop values
using the Energy equation for
different conditions
ENTC-303
Dr. Alvarado
2
What we learn from experiment
• For a given fluid and flow rate, each fitting
and length of tubing adds its characteristic
pressure drop
• Pressure drops in tubing are inversely
proportional to the diameter
• Pressure drops in tubing are directly
proportional to length
• Pressure drops in tubing are directly
proportional to the flow velocity squared (V2)
ENTC-303
Dr. Alvarado
3
Venturi Meter
• The pressure drop across a gradually
converging section, a gradual
expansion section and a rapidly
diverging diffuser with an area ratio
1:4 following the Venturi meter and a
right angled bend are to be compared.
ENTC-303
Dr. Alvarado
4
Procedure
1. Record the cross sectional area or diameter reading
for the Venturi meter at points A, B, C and H.
2. Make sure that the valves in and out of the pump
are open.
3. Turn on the water bench pump.
4. Open the flow control valve (white valve) and slowly
increase the velocity of the pump until the reading in
Siemens Flowmeter starts from 6 GPM.
Note: Do not turn on pump with the flow control
valve completely closed.
ENTC-303
Dr. Alvarado
5
Procedure
5. Once steady state flow have been reached,
record the following: Reading in Siemens
Flowmeter . Manometers height readings at A,
B, C, D, G and H .
6. Repeat step 4 for the following readings in the
Siemens Flowmeter take readings for 2, 3, 4, 5
and 6 GPM.
7. Turn off the water bench and immediately close
the flow control valve. (DO NOT TURN OFF!!)
ENTC-303
Dr. Alvarado
6
Flow
(GPM)
Diameters
Area (m2)
(mm)
A
6
B
5
C
4
D,G,
H
3
Flow (m3/s)
Ha (mm)
Hb (mm） Hc (mm） Hd (mm） Hg (mm）
Hh(mm）
2
Va
Vb
Vc
Vd
(m/s)
(m/s)
(m/s)
(m/s)
Pa-b th
Pc-d th
Pa-b real
Pc-d real
K-venturi
Pa-b real
Pb-c real
Pc-d real
Pg-h real
(Pa)
(Pa)
(Pa)
(Pa)
A-C
(Pa)
(Pa)
(Pa)
(Pa)
Average
St. Dev.