Air Flow in a Duct

Objective:

 To demonstrate the change in air flow inside a duct by changing the distance of the fan from the duct.

Outcome:

Students will understand that shifting the fan away from the opening of the duct will decrease air flow inside the duct. This will help students understand the dynamics of mechanical and natural ventilation positioning and design the spaces mindfully.

Requirements:

Blow dryer, digital anemometer, plier (to hold the blow dryer), 1 m long flexible cylindrical duct, a table, a support structure to align the duct with the blow dryer (packaging box of duct pipe or piles of books can be used in line to level the duct).

Prerequisites:

A conceptual knowledge of 

1. Air properties and flow
2. ducting

Procedure:

Step 1: Clamp the blow dryer in the plier.

Step 2: Place the plier on the table such that the blow dryer is erect. (As shown in the reference image below)

Step 3: Place the duct in line with the air stream coming out from the blow dryer with the help of a support structure. 

Step 4: Initially, place the blow dryer at the mouth of the duct.

Step 5: Place the anemometer at the other end of the duct and note down the air flow reading in the anemometer in m/sec.

Step 6: In the second case, place the blow dryer 10 cm away from the mouth of the duct.

Step 7: Measure the air flow in m/sec at the other end of the duct.

Step 8: Compare both the values and see which one is greater.

Table:

Air Flow Rate (m/sec) in Case 1	Air Flow Rate (m/sec) in Case 2

References: