Saturated vapor pressure

                                                        Saturated vapor pressure

When the liquid in the airtight space limited evaporation, liquid molecules through liquid level into the space above, become a vapor molecules. Due to the vapor molecules in disorders of thermal motion, they collide with each other, and collision and vessel wall and liquid level, and the collision of liquid level, some molecules are attracted by the liquid molecules, and back to become liquid molecules in the liquid. Began to evaporate, the number of molecules into space than returns the number of molecules in the liquid, with the evaporation of the continued, space density increasing of vapor molecules, and returns the number of molecules of the fluid is also increasing. When the number of molecules per unit time into space and return equals the number of molecules in the liquid, the evaporation and condensation is in dynamic equilibrium state, although the evaporation and condensation is still on, but the density of vapor molecules in space no longer increases, the state is called a saturated state. In under the saturation state of liquid called saturated liquid, the steam is called saturated steam or dry saturated steam.
The dynamic balance is based on a certain temperature and pressure conditions, and this kind of circumstance temperature and pressure were independent of each other state parameter. If temperature or pressure changed, the balance will be destroyed, after a period of time, will appear in the new dynamic balance under the condition of saturation state. For different refrigerant, under the same saturation pressure, its saturation temperature also each are not identical.