Science of Fluid Bed Heat Transfer
What’s the difference if drying or cooling air moves vertically through the fluid bed or at an angle? Angled air that flows at even slightly more or less than 90 degrees creates dead spaces in the fluid bed where drying is weak and hot spots where drying is too strong. The results are often:
- Uneven product flow
- Product charring
- Clogging
- Product layering
- Frequent stoppages for cleaning
- High reject rates
But in a Witte drying or cooling system, air flows vertically, perpendicular to the fluid bed deck, and at a constant velocity. This ensures uniform heat history throughout the entire length of the system. The result is a thin layer of product in intimate contact with the air flowing delicately and evenly from feed to discharge, with the first product in as the first product out – every time. This is the hallmark of the Witte Company and the foundation of Witte’s signature vertical air flow engineering.
Witte engineers have developed a series of advances that make consistent vertical air flow possible. When combined in a Witte system, these advances make drying and cooling virtually anything not only possible but also practical and cost-efficient.
Learn more about vertical air flow from your Witte engineer. Call 908.689.6500.
Witte engineers have developed a series of advances…
Air Distribution System:
Dual precision, CNC-machined air cages placed both above and below the fluid bed dryer deck generate a consistent, vertical air flow at constant velocity throughout the entire length of the fluid bed without requiring a reduction in pressure.
Wedge Wire Deck:
Witte’s deck features a triangular profile with a thin, shallow, tapered slot.
This design provides more open area for drying than an ordinary deck with drilled holes and operates at such shallow bed depth that material buildup is virtually impossible. It cleans easily, whereas an outdated drilled deck demands each hole be cleaned individually.
Autoweirs:
Witte’s air operated gates rotate 90 degrees above the deck on a cycle timer, allowing a pre-determined amount of product to advance. This provides the operator with unprecedented flexibility and real-time control over the flow, the bed depth and the retention time. Plus, by promoting product flow rather than the product blockage caused by fixed weirs, the autoweirs eliminate the potential for product degradation.
