CURRENT TRENDS AND R&D NEEDS IN DRYING
Arun S. Mujumdar and Siau Kiang Chou
Department of Mechanical Engineering
National university of Singapore
Singapore
e-mail: mpeasm@nus.edu.sg
Abstract
Research and development activity in the inter- and cross-disciplinary
area of thermal drying has been escalating rapidly over the past two decades.
It is clearly motivated by economic incentive to improve the operation to
produce a better quality product at a lower cost in terms of resources,
energy consumption as well as environmental impact.
The focus to date has been on improving the engineering aspects of design
and operation to produce "engineered" products of desired characteristics.
Much remains to be achieved in the area of the material science aspects of
drying e.g. the prediction of quality parameters, which are product-
dependent. What is needed is a generalised drying theory that incorporates
the transient transport phenomena involved in drying along with appropriate
models to account for the morphological changes as well as chemical
processes that may occur during drying.
This presentation will focus on the current developments in drying as well
as recent trends. Some areas where more R&D is needed, which provide
opportunities to make definitive contribution will be identified. For
example, sophisticated analytical measurements at the micro-scale are
needed to examine the movement of moisture during drying and also any
changes in the physical structure as well as solute transport that can
occur in drying of foodstuffs or solids containing a dissolved solid in the
liquid phase. Even today, there is need to devise more efficient and
compact dryers.
Whether we will ever need "micro-scale" dryers is a speculative question
but certainly there will be the need to design dryers with high
"volumetric" efficiency unlike most dryers built today. Further, we
envisage development of "smart" dryers that will adjust local drying
conditions to optimise the quality and/or energy constraints using
artificial intelligence or model-based control. Finally, there will be
further developments and extended applications for superheated steam
dryers, heat pump-assisted hybrid dryers and multi-stage dryers using
different dryer types in each stage. Mathematical models for drying as well
as dryers will continue to be in demand to allow reliable design and scale
up as well as control of industrial dryers.
Keynote lecture by Dr Arun S. Mujumdar at NDC'01, Trondheim, Norway,
June 27-29, 2001
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