Valves and flow control


1. What are the three phases that water can have?

2. What are the phases of the propellant in the can?

3 What is your estimate for the diameter of the hole in the stem (stem orifice or IMO) using the scale in the picture?

4. What is your estimate for the diameter of the nozzle hole?

5. If a rain drop is 1mm in diameter, how many times smaller is a 10 micron diameter droplet?

6. Why do asthma inhaler sprays use a metered dose valve?


1. Vapour, liquid and solid.

2. Vapour and liquid. The liquid phase is only possible if a liquified propellant like Butane is used. For ideal gas propellants like nitrogen it is impossible to have a liquid phase at normal ambient temperature. To learn more, search for 'critical point' for nitrogen

3. About 0.3 mm

4. About 0.4mm

5. 10 microns is 1 x 10-5 m.  1 mm is 1 x 10-3 m. So the 10 micron drop is 100 times smaller in diameter.

6. The product is a drug. It must be taken in exactly the right dose. A continuous spray aerosol would risk harmful overdoses.