M & I Air - Air Mixer

In HVAC systems especially in Air Handling units air stratification results from non-mixing of two types of air at different temperatures being brought to the plenum. Stratification causes serious problems resulting in freeze-stat trips and frozen coils inside the system. In many cases it has been seen that AHU’s had to be shut down during such problems causing unhealthy ambient conditions inside the building. Stratification problem can be both in winter as well as in summer when due to improper mixing of warm and cold air excessive energy is consumed.

In recent times, a lot of concern is placed on the working conditions inside buildings. As found out, an average individual spends more time indoors than outdoors either as a result of working in offices/ commercial complexes or simply staying at home. The concern was addressed by maintaining a healthy living condition inside by proper treatment of the fresh and return air. IAQ increased the stringency on air quality by mandating buildings to balance proportionate fresh to return air intake.

Various solutions have been proposed in the past to prevent air stratification and its negative effect on the air handling systems. Firstly, Glycol additives were used inside the coils preventing them from freeze ups during winter months. Glycol additive eases the problem to some extent, but reduces the overall cooling capacity of the system thereby entailing in higher BHP consumption. Secondly, dampers and high velocity jets were used but met with limited successes since system pressure drop was found to be enormous. In the past some static air mixers were also introduced but suffered some inherent defects in making air pass through narrow cross-section. These mixers fixed in position, generally consisting of baffles and blades arranged to induce mixing to a flow of air, required both upstream and downstream space for efficient mixing thereby increasing the footprint of the unit and more pressure drop due to non-uniform velocity profile.

M&I’s Air Mixer provides a complete solution for preventing air stratification in the plenum. It was created by integrating several new methods and optimized design using CFX-TASCflow software. The outstanding performance of M&I Air Mixer is achieved by three aspects of its design: layer by layer uniform distribution of two air streams across the whole space of plenum; effective mixing mechanisms and optimization of flowfield.

M&I revolutionized the traditional design of mixers where two air streams were passed through a narrow cross-section. M&I created a new technique to distribute the air from side entrance of plenum uniformly along the entire span. Such a technique makes it possible to mix multiple layers of warm and cold air effectively inside the whole cross section of the mixer, establishing the foundation of complete air stream mixing.

M&I Air Mixer takes advantage of heat exchange through thin sheet metal separating air streams interaction and generated aerodynamic stirring bars to accelerate mixing within short distance. There is extremely low-pressure drop in the system as no extra pressure losses are encountered at the coil or filter level since the air maintains a uniform downstream velocity profile. These unique qualities make M&I Air Mixer an important component of the air handling systems.

Features and benefits of M&I Mixer

Very economical.
Less space requirement. Can be either retrofitted or installed in new units with minimum space
No freezestat trips and coil freezeups.
More accurate control by delivering more homogeneous temperatures at sensing points.
Uniform velocity profile across coils, filters leading to optimum performance of coils and filters.
Wide effective working range allowing even mixing of outside with return air at any given ambient condition, fulfilling the IAQ requirement.
Low energy consumption leading to faster payback from the investment.
No upstream mixing required.
No servicing required.

Fig. 5 Temperature profile of M&I Mixer Type I
on cross-section perpendicular to the side air
flow direction (TRA-TOA=27°C, ROA=20%)
(Click for larger image)
Fig. 6 Temperature profile of M&I Mixer Type I
on cross-section parallel to both side and main
air flow directions (TRA-TOA=27°C, ROA=20%)
(Click for larger image)

Fig. 5 Temperature profile of M&I Mixer Type I
on cross-section perpendicular to main air
flow direction (TRA-TOA=27°C, ROA=20%)
(Click for larger image)

M&I PRODUCTS