Air curtain doors have found increasing acc,eptance in recent years as replacements for solid doors. An air curtain door is a stream or a combination of streams of air blowing across an opening at a specified velocity and angle such that it greatly reduces natural circulation of the air between the inside and the outside of the structure. A schematic diagram of a recirculated single jet plane air curtain is shown in Fig. 1. In addition to acting as a barrier for heat and moisture at a doorway, many air curtains are also designed so as to restrict the penetration of insects, dirt, and cross winds. The performance of an air curtain door is affected by many variables, including the number of jets, thickness of the air door, width of the doorway, heighth of the doorway, jet velocity, initial jet turbulence level, and the pressure and temperature difference across the jet. Energy conservation considerations require the minimization of air' flow between the controlled environment and the surroundings.

When compared to an open doorway, the air curtain door provides the necessary restriction to air flow while maintaining optimum traffic flow. However, optimum design values for the, air curtain variables must be found in order to assure the sealing power of the air curtain while minimizing the transfer of heat, moisture, and contaminants.