CASTING INNOVATIONS
Creating Positive Air Flow in a Large Roof-Vented Facility Operations such as steel/iron
works, glass/ceramic production and diecasting often experience issues with employee comfort and morale due to high temperatures. Redesign- ing building configurations can be cost-prohibitive, particularly if the issue is only present a few months out of the year. With this in mind, Trace Die
Cast Inc. (Bowling Green, Ken- tucky) sought help cooling its personnel working at aluminum diecasting stations by implementing a solution that would improve posi-
tive air flow toward the roof vent. Te facility has a natural airflow system with fan-driven vents, a pitched ceiling, and no HVAC. Te production rooms are four
separated, unconfined areas that share a central passage in two rows, leading to openings on either side of the facility. Te walls of the building have vents with slowly churning fans that draw air into the 350,000 ft3 (9910 m3
) space and a 150 ft2 (14 m2
pitched roof vent on the ceiling that exhausts the hot air. Typically, the temperature
)
outside is around 10F cooler than inside the facility. However, dur- ing the summer the ambient tem- perature at the workstations can be as high as 110F (43C), with an upper roof vent temperature of approximately 140F (60C). Ken- tucky summers also can include periods of low-wind speeds. Wind is one of the essential ele- ments of creating positive airflow in rooftop venting systems. Te action of horizontal wind pressure across a vent is expressed in Bernoulli’s principle of flow dynamics, which explains how air exhaust can induce the compression and expansion of air inside the facility. In this application, Bernoulli’s
Wind passing over a vertical shaft will pull lower pressure air up through the pitched roof vent.
principle describes how higher pres- sure horizontal air (wind) passing over a vertical shaft will pull lower pressure air within the facility up through the pitched roof vent. Te pressure difference results in a net force, which causes an acceleration of the internal air upward. In Trace Die Cast’s facility, the absence of consistent air flow across the vertical roof vent during the summer created a negative pres- sure situation. Heated air would build up at the ceiling, causing the pressure on the inside to exceed that of the outside and preventing it from being properly exhausted. Tis allowed stagnant air to get trapped in pockets, raising the ambient tem- perature throughout the facility. “A local colleague of mine had a similar issue in his smelting operation,” said Kent Guthrie, vice president of facilities. “I checked out his solution using fan-driven atom- ized mist cannons with the water function shut off, and it worked so well for him that we called Dust Control Technology and rented two KoolBoss units.” The machines are designed
The cannons were located at opposite ends of the facility, directing air flow down the central aisle. 78 | MODERN CASTING March 2017
to atomize a water supply into millions of tiny droplets, which are propelled by a powerful fan forcing air through a cone-shaped barrel. By turning off the water, a dry air stream is created, allowing
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