When you breathe, a warm air mass comes out of your mouth, with a slow flow rate and a large cross section. The state is similar to orderly laminar flow, and it will not carry too much surrounding gas. The heat conduction between the air mass and the outside world is slow, so the hands that are separated by more than ten centimeters will still be hot. When blowing with a pout, the gas has a fast flow speed and a small cross section, which is equivalent to a turbulent flow, which will "attract" the surrounding air to join, so that the overall temperature of the gas flow will drop rapidly, and the farther it blows, the more heat will be lost. If you blow near your lips, you will find it is hot at first.

But even if the warm air flow cools to room temperature, it is not enough to produce coolness. When blowing, I feel cool not because of the low temperature of the airflow, but because the flowing airflow can drive the flow of the surrounding air, promote the evaporation of sweat on the body surface, and take away the heat from the skin. The faster the gas runs, the more air it can drive, and the better the heat dissipation effect. Another explanation is that when blowing, the lip opening is small, the gas is compressed, and when it goes out, it expands, the pressure decreases and the temperature decreases.

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Other knowledge of blowing cold

Blowing to lose weight, when you lose weight by blowing, you not only exercise, but also feel full in your stomach because you have to inhale and blow constantly, which inhibits the "hunger center" of your brain and reduces your appetite. Blowing balloons to lose weight is because when blowing balloons hard, you use abdominal breathing. When you blow up a big balloon, your body temperature will rise, so it is effective in promoting fat metabolism.

Many people who insist on slimming blow into hot water bottles every day and lose weight every month. Blowing to lose weight not only exercises the body, but also makes the stomach feel full due to continuous inhalation and blowing, thus inhibiting the "hunger center" of the brain and reducing appetite.