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Tissue Paper Making --- Yankee Dryer Hood Model

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UtilityLouie

Mechanical
May 3, 2001
102
I'm looking for suggestions on the best reference articles to build a spreadsheet to model Yankee hood performance on tissue machines. We have a number of machines. We also have multiple hood types (once through vs. recirc). So I may have to build two models to accurately evaluate certain situations.

I'd also like to hear suggestions for areas to place "adjustment" factors to have the model match existing conditions. I have access to a compiled Visual Basic program that doesn't work well (that I can't reverse engineer). You have to play with certain factors (sheet wetness or hood gap) to get the model to match up with the actual performance at one machine speed, but I'm not convinced the model created by making those assumptions can be applied to the same machine at higher speeds.

I'm just getting started on this and, of course, don't have enough time to work full time on this (per management). So, I'm going to have "be the tortoise", i.e.: slow and steady wins the race.

Any help would be much appreciated!
 
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Good luck with this. You are lucky to work for a company that will let you work on this project. Drying rate problems are difficult. Most manufacturers want to find a contractor that they can beat-up on instead of understanding and developing knowledge in-house.

I created some spreadsheets for drying rate on other materials and processes several years ago. I think that ASHRAE handbooks have some information, but the best information I found was from a textbook named "Mass Transfer Operations" by Robert Treybal. I checked the book out from a library a long time ago, so I can't say whether there would be any information useful to you.

I recommend you understand the physics of drying and incorporate those physics into your model, instead of applying a statistical approach. You will also need to be able to track the actual process. For a thin web it sounds difficult monitoring temperature and humidity. I would imagine that your process will be split into three distinct zones: warming liquid water and web up to dew point temperature; transforming liquid water to vapor at same dew point temperature; and driving off water vapor and elevating web temperature to final set temperature.

Not much specific help, but hang in there, you will find the right set of references and everything will come together.
 
UtilityLouie,
Did some similar work on IR dryer and hood for off m/c coater drying performance. That was many moons ago. The work was done preExcell! From memory I modeled the heat transfer and thermodynamics from first principals as dvd has suggested. In relation to the hood the aim was to optimise the humidity of recirculated air for optimum drying, It was an energy saving exercise that I was working on.
Things to consider;
All heat transfer is related to temperature diference.
Temperature rise is time related.
The web is moving!
You will be gaining heat from the dryer drum below the web. The yankey dryer hood combines the steam drum heating and extracting the humid air over the drum to enhance mass transfer from the web.
As the moisture content in the web changes so does the thermal properties.
Look at the "bulk" properties may be a method to "simplify" youor model.
Sounds like a very interesting project!

Mark Hutton


 
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