Experimental validation of the multiple-zone system ventilation efficiency equation of ANSI/ASHRAE Standard 62.1 (1276-RP)

This article describes an experiment that was carried out on an existing building to test the validity of the system ventilation efficiency equation for multiple-zone recirculating systems of ANSI/ASHRAE Standard 62.1. The system ventilation efficiency equation (SVEE) can be applied to buildings that use a recirculating air distribution system. It accounts for the fact that the return air carries some unused outdoor air, so that the amount of new outdoor air introduced at the air handler can be reduced. The SVEE is based on a mass balance, but infiltration and interzonal mixing are not included in the formulation. Since infiltration is unpredictable, it can't be relied upon to ventilate a space, so the validation focuses on interzonal mixing. The experiment uses tracer gas techniques to study the air distribution in an existing office building, with four zones being treated as nominal critical zones. The tests are conducted with constant flow rates under a range of conditions. The SVEE is found to be a very good predictor of ventilation distribution in the building.