Psychrometry is the science dealing with the physical laws of air – water mixtures.
When designing an air conditioning system, the temperature and moisture content of the air to be conditioned, and the same properties of the air needed to produce the desired air conditioning effect, must be known. Once these properties are known, the air conditioning task can be determined. This analysis can be performed using the psychrometric chart. The psychrometric chart graphically displays several physical properties of air over a broad range of conditions. Knowing the relationship of these air properties aids the task of air conditioning system design and analysis.