Vaporization as a Cooling Agent.
—The evaporation of water has a distinct value aside from humidifying the air, in that the cooling effect is in direct proportion to the added moisture. In the process of evaporation the heat necessary to change the water into vapor is taken from the surrounding air and the temperature is thus materially lowered.
In practical air-conditioning apparatus, of the evaporative or spray types, the process consists of drawing the outside air into a chamber filled with falling water that is broken up into drops like rain or spray. In passing, every particle of the air comes into contact with the water drops; the almost invisible particles of dust adhere to the water and are carried away leaving the air washed clean. In addition to freeing the air from dust, the intimate mixture of the air permits of a ready absorption of the water, which is taken up to any per cent. of saturation. After leaving the spray chamber, the moisture-laden air passes through an eliminator in which any unabsorbed moisture is extracted. It is possible for air to become not only completely saturated with water under the conditions encountered in a humidifying plant, but in addition, the movement of the air may carry along unabsorbed particles that are precipitated directly after leaving the spray chamber. For this reason the air is passed through an eliminator.
The eliminator is composed of a series of irregular sheet-metal surfaces so arranged that the air is required to abruptly change its direction several times in its passage of a short distance. The impact of the air against the surfaces and the centrifugal force exerted by the sudden changes of direction throw out the excess moisture and any remaining suspended matter the air may contain.
The saturated air from the eliminator passes through a heater where the temperature is raised to that of the rooms. In the rise of temperature the air which is saturated is rendered capable of absorbing more moisture, and hence has been dehumidified. The rise of temperature and the corresponding decrease in relative humidity is intended to be such as to leave in the finished air the desired percentage of moisture.