Air Conditioning and Humidification

Air Conditioning and Humidification

INTRODUCTION

Air conditioning is a familiar phenomenon in households and public spaces around the world. Its application for comfort means the provision of warm (achieved by heating or cooling), filtered air. High moisture content or humidity is oppressive, but a low humidity may cause irritation by excessive loss of moisture from the skin. In some climates, steps may be taken to add or remove water vapor from the air. The air is cleaned, usually by passage through a fabric filter, which may be dry or moistened with a viscous liquid, and heated elec-trically or by banks of finned tubes supplied with steam or hot water over which the air is blown. Electrostatic precipitation provides an alternative method of air cleaning. The fine particles entrained in the air are charged by the absorption of electrons as they pass between two electrodes. The charged particle then migrates in the electrical field and is finally arrested on one electrode.

The same general principles apply to the supply of air in some pharma-ceutical processes. However, the control of its quality may be more stringent. In areas in which sterile materials are made and handled, for example, the air cleaning must remove bacteria. In other processes, it may be necessary to remove water vapor. The flow of powders is a sensitive function of moisture content. The equilibrium moisture content of a material is determined by the humidity. Some tabletting processes break down if the humidity is too high. In such processes, the scale of the air conditioning varies. It may be necessary to supply a whole room with air of a certain quality. Alternatively, conditioning may be restricted to a small area surrounding a particular piece of equipment.