L.7 - Flow Measurement

Question 1

List seven flow measurement systems:

Answer 1

1) Head type flowmeters
2) Variable area flowmeter (rotameter)
3) Turbine flowmeter
4) Vortex shedding flowmeter
5) Magnetic flowmeter
6) Coriolis flowmeter
7) Ultrasonic flowmeter

Question 2

List some Head Type flowmeters:

Answer 2

1) Orifice Plate
2) Venturi
3) Pitot tube

Question 3

List some Ultrasonic flowmeters:

Answer 3

1) Transit time
2) Doppler

Question 4

List the different factors that affect the selection of a flowmeter, w/ examples.

Answer 4

1. Hardware factors
   - accuracy
   - size
   - cost
2. Application factors
   - material compatibility
   - flow rates
3. Installation and maintenance factors
   - installation complexity
   - maintenace requirements

Question 5

Define Flow:

Answer 5

rate at which a fluid (liquid or gas) moves through a conduit

Question 6

When is flow considered laminar?

Answer 6

when Reynolds number is less than 2000

Question 7

When is flow considered turbulent?

Answer 7

when Reynolds number is greater than 4000

Question 8

What is the region between laminar and turbulent flow called?

Answer 8

transitional flow region

Question 9

How do head type flowmeters work?

Answer 9

by inserting a restriction in flow path and measuring resulting differential pressure

Question 10

What are orifice plate requirements?

Answer 10

1) turbulent flow
2) straight pipe runs
3) maintain sharp edge

Question 11

What are some adv. and disadv. of an orifice plate?

Answer 11

Adv.:
1) inexpensive
2) simple to install
3) no moving parts

Disadv.:
1) straight pipe runs
2) constant pressure loss
3) not ideal for viscous fluids (gets plugged up) (using eccentric or segmental can help)

Question 12

How do Orifice Plates and Venturi flowmeters work?

Answer 12

fluid passes through a restricted cross-sectional area causing an increase in fluid velocity and a decrease in static pressure

Question 13

What are some adv. and disadv. for venturi flowmeter?

Answer 13

Adv.:
- constant pressure loss not as large as orifice plate

Disadv.:
- more expensive
- longer axial length

Question 14

What are some adv. and disadv. for pitot tube?

Answer 14

Adv.:
- negligible pressure loss
- economical

Disadv.:
- not extremely accurate
- delta p is very small

Question 15

List some applications for pitot tube:

Answer 15

• measure airspeed (planes)
• HVAC systems
• formula one cars

Question 16

What are some adv. and disadv. for a rotameter?

Answer 16

Adv.:
- direct indication of flow
- low cost
- low pressure drop
- no power required

Disadv.:
- must be mounted vertically
- easily breaks
- fluid must be clean
- sensitive to fluid density

Question 17

What are some adv. and disadv. for turbine flowmeter?

Answer 17

Adv.:
- high accuracy
- repeatable measurement

Disadv.:
- high cost
- moving parts
- not good for low flow

Question 18

What is an application example for turbine flowmeters?

Answer 18

oil & has blending

Question 19

What are some adv. and disadv. for vortex shedding flowmeter?

Answer 19

Adv.:
- no moving parts
- good accuracy

Disadv.:
- not suitable for dirty, abrasive fluids
- not suitable for laminar flow
- midrange, expensive

Question 20

What are some adv. and disadv. for magnetic flowmeter?

Answer 20

Adv.:
- no restriction of flow
- very accurate

Disadv.:
- only works for conductive fluids

Question 21

What are some adv. and disadv. for coriolis flowmeter?

Answer 21

Adv.:
- highest accuracy

Disadv.:
- not good for slurries
- expensive

Question 22

What are some adv. and disadv. for ultrasonic flowmeters?

Answer 22

Adv.:
- simple construction
- easy to install
- can handle corrosive fluid

Disadv.:
- disturbed by electrical noise easily
- build up on pipe wall affects the reading