Numerical Investigation of Air Mixer Performance for HVAC Testing Applications

Abstract

The ever-increasing energy demand is one of the biggest challenges of the design processes in heating, ventilation, and air-conditioning (HVAC) systems. Accurate performance measurements of equipment in the laboratory requires air mixing to reduce measurement error. The National Bureau of Standards conducted in depth experimental research on the required air mixing devices in the late 1960s. At this point, very limited guidelines are available for air-mixers, with ASHRAE RP-1733 addressing this gap.

In this thesis, CFD analyses have been conducted to predict the mixing effectiveness and pressure losses of candidate air-mixers of RP-1733. Both existing and new air-mixer models have been investigated for their mixing effectiveness and pressure drop characteristics. It was found that the proposed static air mixing models, consisting of louvers-baffles, louvers, and orifice-target parts, add turbulence to the airstream to enhance the mixing process. I have also investigated the pressure drop characteristics with respect to the flowrate. I found that the louver-baffle mixer has significantly more pressure drop as compared to the louver mixer with a negligible small increase in mixing efficiency. Therefore, I conclude that the louver mixer (without baffle) is a better option when we consider the trade-off between mixing efficiency and pressure drop characteristics, which might provide further insights to our co-designed experimental studies.