PULSE DRYING EXPERIMENT AND BURNER CONSTRUCTION Page: 2 of 64
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Paper drying consumes .6% of America's entire energy budget, but drying hood and
steam cylinder technologies are only 25% to 50% efficient. This grant investigated
pulsed impingement drying which may improve efficiencies by 100% to 300%.
This grant is the first time an apparatus has been built specifically to measure pulsed
impingement over a broad range of flow conditions. The most significant scientific
discoveries made during this project were:
1) A new resonance phenomena that enhances, and sometimes lowers, heat
transfer rate was discovered.
2) A new parameter, the Wave Number (Wn), was invented, and it accurately
characterizes sinusoidal pulsed flow.
3) The standard model for scaling steady flow is inaccurate in the pulsed regime,
showing the need for an improved theory.
4) Pulsed flows investigated here offer a practical way to dramatically improve
drying efficiency in the paper industry.
Past experimenters have reported drying efficiency improvements at extreme levels of
pulse intensity , but these are impractical for industrial use. The current grant has
detected these improvements at low pulse intensities, making them practical. For paper
drying, a retrofit of existing equipment improves efficiency 23%, pays back in 5 months,
and eventually saves the industry 48 Trillion BTU/Yr. Annual carbon dioxide emissions
would be reduced by 4.4 million tons, as well as reductions of .9 million pounds of
volatile organic compounds, and 48 million pounds of particulates.
Drying equipment optimized for pulse impingement could improve energy efficiency by
over 100%, saving the industry 234 Trillion BTU/Yr, or .2% of the total US energy
budget. This translates into an annual CO2 reduction of 21.5 millions tons, as well as
reductions of 5.8 million pounds of volatile organic compounds, and 234 million pounds
of particulates. Though attractive, these energy savings do not pay for the capital
expense of replacing existing paper dryers.
The resonance phenomena discovered in this grant helps explain failure of the pulse
drying tests performed by Proctor and Gamble, in collaboration with the Institute of
Paper Science and Technology. This high profile test detected no drying efficiency
improvements in the pulse domain, but the resonances found in the current study were
unknown to that research team. They may have accidentally fallen into a resonance
trough without knowing it.
Two basic hurtles now prevent commercialization of pulse drying in the paper industry.
First, the pulse evaporation process must be measured in greater detail and
characterized mathematically. Secondly, the pulse burner now used in the powder
industry must be re-engineered for paper drying.
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States, Robert. PULSE DRYING EXPERIMENT AND BURNER CONSTRUCTION, report, July 15, 2006; United States. (digital.library.unt.edu/ark:/67531/metadc884206/m1/2/: accessed November 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.