How do vacuum cleaners REALLY work?

A video discussing the deeper science behind how vacuum cleaner technology works. It’s intended to be watched linearly and more than once. There are chapters to help with referencing and subsequent rewatches below. Leave a comment if you need anything clarifying.

The key takeaway message from this video is that the removal of dirt from carpets is influenced by three factors. Firstly, is the active aerodynamic properties associated with the motor and cleaner head—namely suction and airspeed. Secondly is the properties of the dirt particles, namely their shape, size, and mass. And thirdly, the properties of the carpet the dirt is trapped in, including how to manipulate it to maximise the airspeed embedded particles experience and to prevent particle netting in the flow.

The aerodynamic drag force applied to particles is dominated by the airspeed. This is controlled exclusively by the suction pressure in the flow. It is not controlled by the total airflow. Significant leakage air that increases airflow into the cleaner head actually reduces suction pressure and cleaning performance. Large motor air powers provide the means to sustain high suction pressures, even with large leakage airflows. Good cleaner head design agitates pile by flexing to release netted dirt and helps maximise airspeed at depth to improve dirt removal efficiency. Cleaning reduces dirt levels in carpets but never fully removes it all. The dirt is then separated from the air inside the machine using ever more effective and efficient means, and cleaner air is expelled.

Look out for content on the internet suggesting higher airflow rather than suction pressure is important for dirt removal from carpets. This lack of understanding of science is often manifested in irrelevant measurements of the total airflow entering the machine from the open hose, or measurements of suction pressure at the open hose, rather than actual careful measurements of comparative dirt removal profiles. An example of such nonsense can be found here    • Most Important Part of a Vacuum Poll Answer  . From this lecture, you should have an understanding why such videos are sources of nonsense and misinformation. Examples of classic sales deceptions discussed in the myths section can be found here    • Riccar Tandem Air 20th Anniversary Vacuum ...  .

Chapters:
0:00 Introduction
0:29 Basic Principle of a Vacuum Cleaner
0:56 Airspeed is King
1:45 Effect of a Cleaner Head
2:59 Importance of Suction
4:06 Types of Dirt
5:03 The Air Circuit of a Vacuum Cleaner
7:06 Relationship Between Suction, Airflow, and Air Resistance
7:55 Motor Power and Air Watts
9:02 Why Large Airflows Are Bad
12:02 Avoiding Leaks
13:22 Too Much Suction
15:13 Alleviating Clamping
16:26 Above Floor Cleaning
17:32 Influence of Carpet Backing
18:44 Dirt at Depth
20:51 Benefits of Carpet Agitation
22:52 Dirt Removal from Carpets is Stochastic
23:58 Accurately Measuring Cleaning Performance
26:15 Influence of Carpet Type
27:15 The Art of Cleaner Head Design
28:01 Best Cleaning Practice
30:03 Filtration
30:23 Mechanical separation
31:32 Inertial separation
33:21 First-stage cyclone
34:30 Pre-motor mechanical filtration
35:16 Post-motor HEPA filtration
37:22 Non-cyclonic inertial separator
40:06 The rotating disc separator
42:05 End
42:23 Debunking common myths
42:36 Myth 1: More airflow means better cleaning
43:44 Myth 2: Hose suction measurements are relevant
44:48 Myth 3: Airflow measurements are relevant
46:03 Myth 4: High airflow, low suction machines are better
47:50 Myth 5: It’s acceptable to use only sand to measure performance
48:35 Myth 6: Aggressive agitation is better
50:29 Myth 7: Sand in rug tests are meaningful
52:41 Myth 8: Sand at the base of a carpet causes damage
53:28 Myth 9: Sucking a tube shows cleaning capability
54:16 Myth 10: Big mess tests illustrate cleaning performance
15:40 Myth 11: Open gates and low power to avoid clamping reduces cleaning performance