AIR VELOCITY IN VENTILATION DUCT
Objective
Study of Pitot Tubes and measurements of air velocity in a ventilation duct with the help of Pitot Tube and U-Tube Manometer.
Apparatus used:
Pitot Tube, Inclined U-Tube Manometer, Flexible Rubber Tubes, Ventilation Duct etc.
Description Pitot Static Tube: It is an instrument which uses the principle of pressure exerted by flowing air and is suitable for measurements of high velocity. It is not capable of measuring average velocity directly but measures the velocity at a given point in the airway/duct.
Isometric View of the Ventilation Duct
Start the motor to allow the fan to attain the constant 300 rpm.
⇇
Top View of the Centrifugal fan
Trial 1
Wind Direction
Isometric View of the Ventilation Duct
The knob is being rotated
The Motor reading = 300 rpm
Calculating the angle of inclination of inclined U-Tube Manometer.
Front View of the Inclined U-Tube Manometer
Isometric View of the Ventilation Duct
Top View of the Inclined U-Tube Manometer
↑
tan θ = h/l
θ = tan-1(h/l)
θ = (θ1+θ2+θ3)/3 = 7.74°
| Point No | Length(l)(cm) | Height(h)(cm) | Angle(θ°) |
Connect flexible rubber tube of manometer to Pitot Tube fixed at point 1 of ventilation duct.
Note:1.The Pitot Tube should be fixed at point 1 in the ventilation duct tightly.2.Connect one flexible rubber tube of manometer with Total Head of Pitot Tube to take the reading of static pressure.3.Remove rubber tube from Total Head and connect that with Static Head of Pitot Tube to take the reading of total pressure.4.Now, connect one flexible rubber tube of manometer with Total Head and another with Static Head of Pitot Tube to take the reading of velocity pressure.
Isometric View of the Ventilation Duct
Top View of the inclined U-Tube Manometer
Point 1
Total Head
Pitot Tube
Static Head
First flexible rubber tube is connected to the Static Head
Second flexible rubber tube is connected to the Total Head
Both flexible rubber tubes are connected to the Static Head and Total Head
Front View of the inclined U-tube Manometer
Observations:
Variables in calculation θ :Angle of inclination of the manometer tube = 7.74°ρ :Specific gravity of the manometer liquid = 0.789
g :Acceleration due to gravity = 9.8 ms-2
q :Density of air = 1.2 kg/m3
Ls1 :Length of static head at point 1
Lt1 :Length of total head at point 1
Lv1 :Length of velocity head at point 1
| Static Head(cm) | Total Head(cm) | Velocity Head(cm) | |||||||
| No | LeftLimbReading | RightLimbReading | Difference(Ls1) | LeftLimbReading | RightLimbReading | Difference(Lt1) | LeftLimbReading | RightLimbReading | Difference(Lv1) |
| 1 | |||||||||
✔
✘
✔
✘
✔
✘
✔
✘
Connect flexible rubber tube of manometer to Pitot Tube fixed at point 2 of ventilation duct.
Top View of the inclined U-Tube Manometer
Point 2
Observations:
Variables in calculation θ :Angle of inclination of the manometer tube = 7.74°ρ :Specific gravity of the manometer liquid = 0.789
g :Acceleration due to gravity = 9.8 ms-2
q :Density of air = 1.2 kg/m3
V1 :Velocity of air at point 1 = m/s
Ls2 :Length of Static Head at point 2
Lt2 :Length of Total Head at point 2
Lv2 :Length of Velocity Head at point 2
| Static Head(cm) | Total Head(cm) | Velocity Head(cm) | |||||||
| No | LeftLimbReading | RightLimbReading | Difference(Ls2) | LeftLimbReading | RightLimbReading | Difference(Lt2) | LeftLimbReading | RightLimbReading | Difference(Lv2) |
| 2 | |||||||||
✔
✘
✔
✘
✔
✘
✔
✘
✔
✘
Start the motor to allow the fan to attain the constant 400 rpm.
⇇
Trial 2
Top View of the Centrifugal fan
Wind Direction
Isometric View of the Ventilation Duct
The knob is being rotated
The Motor reading = 400 rpm
Connect flexible rubber tube of manometer to Pitot Tube fixed at point 1 of ventilation duct.
Note:1.The Pitot Tube should be fixed at point 1 in the ventilation duct tightly.2.Connect one flexible rubber tube of manometer with Total Head of Pitot Tube to take the reading of static pressure.3.Remove rubber tube from Total Head and connect that with Static Head of Pitot Tube to take the reading of total pressure.4.Now, connect one flexible rubber tube of manometer with Total Head and another with Static Head of Pitot Tube to take the reading of velocity pressure.
Isometric View of the Ventilation Duct
Top View of the inclined U-Tube Manometer
Point 1
Total Head
Pitot Tube
Static Head
First flexible rubber tube is connected to the Static Head
Second flexible rubber tube is connected to the Total Head
Both flexible rubber tubes are connected to the Static Head and Total Head
Front View of the inclined U-tube Manometer
Observations:
Variables in calculation θ :Angle of inclination of the manometer tube = 7.74°ρ :Specific gravity of the manometer liquid = 0.789
g :Acceleration due to gravity = 9.8 ms-2
q :Density of air = 1.2 kg/m3
Ls1 :Length of Static Head at point 1
Lt1 :Length of Total Head at point 1
Lv1 :Length of Velocity Head at point 1
| Static Head(cm) | Total Head(cm) | Velocity Head(cm) | |||||||
| No | LeftLimbReading | RightLimbReading | Difference(Ls1) | LeftLimbReading | RightLimbReading | Difference(Lt1) | LeftLimbReading | RightLimbReading | Difference(Lv1) |
| 1 | |||||||||
✔
✘
✔
✘
✔
✘
✔
✘
Connect flexible rubber tube of manometer to Pitot Tube fixed at point 2 of ventilation duct.
Top View of the inclined U-Tube Manometer
Point 2
Observations:
Variables in calculation θ :Angle of inclination of the manometer tube = 7.74°ρ :Specific gravity of the manometer liquid = 0.789
g :Acceleration due to gravity = 9.8 ms-2
V1 :Velocity of air at point 1 = m/s
q :Density of air = 1.2 kg/m3
Ls2 :Length of Static Head at point 2
Lt2 :Length of Total Head at point 2
Lv2 :Length of Velocity Head at point 2
| Static Head(cm) | Total Head(cm) | Velocity Head(cm) | |||||||
| No | LeftLimbReading | RightLimbReading | Difference(Ls2) | LeftLimbReading | RightLimbReading | Difference(Lt2) | LeftLimbReading | RightLimbReading | Difference(Lv2) |
| 2 | |||||||||
✔
✘
✔
✘
✔
✘
✔
✘
✔
✘
Result:
