Fire pistons

One of the most intriguing pre-modern fire-lighting techniques is the use of the fire piston. One of the simplest devices possible, it relies only on the heat generated by the adiabatic compression of air to ignite a fuel.

These tools were popular in south-east Asian cultures as an alternative to friction-based fire-lighting methods. They provide a simple and pleasing demonstration suitable for use in the teaching of basic thermodynamics or the diesel combustion engine.

Adiabatic heating occurs in the field of sonochemistry. Here, tiny bubbles formed by ultrasonic vibrations collapse in on themselves in a process known as cavitation. This creates extreme environments with temperatures around 5000 K and 1000 atm of pressure in extremely small areas and for extremely short periods of time. Meanwhile, the bulk solution remains at ambient temperatures. Highly reactive intermediates can be formed under these conditions, which greatly increase the speed of certain reactions without the need for heating.