346 research outputs found
Thermal drying technologies : new developments and future R&D potential
Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.Thermal dehydration processes are highly energy-intensive
and are found in almost all industrial sectors, accounting for 10
to 20 percent on national industrial energy consumption in
developed countries. With escalating energy costs and need to
mitigate environmental pollution due to emissions from
combustion of fossil fuels, it is increasingly important to
develop innovative drying technologies. Furthermore, drying
also affects quality of the dried product due to physical and/or
chemical transformations that may occur during the heat and
mass transfer operation. With tens of thousands of products that
are dried in hundreds of dryer types, it is a formidable task
indeed to develop design and scale-up procedures of wide
applicability. Attempts have been made over the past three
decades to make fundamental and applied contributions to
transport phenomena and material science aspects in drying of
various forms of wet solids, pastes and liquids. This
presentation will attempt to summarize the state-of-the-art as
far as theoretical understanding of drying processes and provide
examples of some new technologies being developed.
Opportunities for challenging fundamental and modeling
studies to enhance drying technologies will be identified.
Illustrative results will be presented to show how mathematical
modeling of spray, spouted bed and heat pump dryers can be
utilized to develop new conceptual designs and to optimize
operating conditions as a cost-effective route to intensify
innovation in thermal dryer design.cs201
Influence of Temperature, Air Velocity, and Ultrasound Application on Drying Kinetics of Grape Seeds
The objective of this work was to determine the influence of
temperature, air velocity, and ultrasound application on the drying
kinetics of grape seeds. The drying kinetics were determined at
1.0, 1.5, 2.0, and 3.0 m/s and at 40, 50, 60, and 70 C. At 1.0
and 1.5 m/s, the experiments were carried out with and without
ultrasound application. To establish the influence of the variables
on the drying kinetics, the results were modeled by means of both
the Peleg and a diffusion model. The activation energy was determined
(Arrhenius equation). For an air velocity of over 1.5 m/s,
it was determined that the external resistance to mass transfer
was negligible. No influence of ultrasound application was observed,
probably due to the fact that grape seeds are very hard and have
a low level of porosity.The authors of this article acknowledge financial support from the Valencian Government ("Generalitat Valenciana,'' Valencia, Spain, PROMETEO/2010/062).Clemente Polo, G.; Sanjuán Pellicer, MN.; Cárcel Carrión, JA.; Mulet Pons, A. (2014). Influence of Temperature, Air Velocity, and Ultrasound Application on Drying Kinetics of Grape Seeds. Drying Technology. 32(1):68-76. https://doi.org/10.1080/07373937.2013.811592S687632
A numerical study and design of multiple jet impingement in a PEMFC
Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.Impinging jets are widely used in applications where high rates
of heat and mass transfer are required. Similarly, an efficient
operation of the Proton Exchange Membrane Fuel Cell
(PEMFC) relies on high heat and mass transfer rates to and
from the catalyst layers on the anode and cathode side, which
raises the question of whether jet impingement could be
employed for a PEMFC as well. To answer this question, a
laminar non-isothermal gas-phase model for a PEMFC
equipped with a porous flow field is solved numerically for five
different cases: (i) single jet (cathode); (ii) double jet (cathode);
(iii) triple jet (cathode); (iv) single jets (anode, cathode); (v)
ordinary flow without jets. It is found that the jets reduce the
size of the concentration boundary layers in the net at the flow
field/gas diffusion layer interface (GDL), but do not penetrate
significantly into the GDL for low permeabilies of around 10-12
m2. For macroporous layers with permeabilities of around 10-9
m2, the jets are able to penetrate deeply. For multiple jets, the
risk of entrainment with oxygen depletion between jets is
demonstrated, with a resulting loss in cell performance.
Overall, this initial study indicates that jets can enhance cell
performance, but care must be taken so as to avoid entrainment
effects when employing multiple jets in a PEMFC.vk201
A Study of Particle Histories during Spray Drying Using Computational Fluid Dynamic Simulations
Editorial: Role of R&D in Innovation
10.1080/07373937.2013.813217Drying Technology3211-DRTE
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