Summer air conditioning: In most of the places the summer season is hot and humid. Hence, in order to provide comfortable conditions to the occupants during summer, it is required to supply cold and dry air to the occupied space. This requires systems wherein the hot and humid air can be cooled to temperatures lower than the dew point temperature, so that the water vapour in air can be removed by condensation, and the resulting cold and dehumidified air supplied to the conditioned space in required quantity for providing thermal comfort. Thus it can be seen that a typical summer air conditioning system requires a refrigeration system that reduces the temperature of the air to temperatures much lower than the surroundings. Of course, in some areas such as deserts, the summer is hot and dry. Air conditioning systems for these hot and dry climates also require cooling of air below the ambient temperatures, however, in stead of removing water vapour it may be required to add water to the air supplied to the conditioned space.