Dimensioning and economical optimisation of an air curtain device.

The usage of Air curtain units, installed on the large openings of industrial buildings is one of the most practical and effective preventive methods applied against the uncontrolled outdoor cold air flows through the open doorways. The prevailing outdoor conditions and sometimes the indoor mechanical ventilation conditions do vary during the opening periods of the doorways of an industrial building. Consequently, the calculation of the rate of the penetrating outdoor cold air flows and their temperature, as well as the value of the pressure difference across the opening is a laborious task and should be approximated by the use of a dynamic calculation model. Also the dimensioning of an air curtain device is a matter of technical optimization which involves many effecting factors in the process (1) In order to facilitate and simplify the above mentioned task in different industrial building sites, a calculation model (DIECO) has been developed. It is also possible to determine the economy of an air curtain and its pay-back time by using this model. This calculation model is composed of several independent parts and the following is a brief description of them. In this presentation of the method, the dimensioning of the air curtain is based on calculation of the pressure difference at floor level in order to achieve balance between the applying forces of the air jet. The leakage of the air curtain is estimated on the basis of the empirical results.