The most basic feature of gas throttling is that the enthalpy before and after throttling remains unchanged, while the volume after throttling increases, and the molecular potential energy always increases. Therefore, the change of molecular kinetic energy, that is, the change of temperature, depends on the relationship between the decrease of flow kinetic energy and the increase of molecular potential energy. When the decrease of flow kinetic energy is equal to the increase of molecular potential energy, the molecular kinetic energy and temperature remain unchanged after gas throttling. This temperature is called the conversion temperature. When the gas temperature before throttling is less than this temperature, the temperature after throttling decreases. When the gas temperature before throttling is greater than this temperature, the gas temperature after throttling increases.
