Radiating technologies are particularly interesting in
a drying operation in that they allow immediate and
significant energy input to the product to be processed.
However, the high power density applied to the material
can significantly alter the usual drying kinetics and
bring about important constraints. When using infrared,
too high power density can cause caking phenomena.
Microwave can also cause high pressures within the
material, which increase mass transfers but also generate
significant mechanical stresses [1–4].
Traditional drying methods are well documented by
numerous experimental and theoretical studies, which is
not the case with so-called mixed processes (convection
and radiation) [4–13]. The purpose of the current research
in our laboratory is to optimise the combined use
of microwaves and infrared in a drying operation. Also,
we have developed a pilot and a numerical model
allowing assessing the evolution of temperature, moisture
content and pressure during the drying of a porous
material placed in the test kiln.
This paper essentially deals with the validation of the
simulations. First comes a presentation of the physical
model designed to describe mass and heat transfer
within the porous material. We then introduce the energy
inputs generated by both types of electromagnetic
radiation. The second part describes the drying pilot.
This is followed by a presentation of numerical simulation
results, which will be compared to combined drying
tests conducted on cellular concrete
by the Lambert–Beer law. Comparison of experimental and simulated results on cellular concrete shows the relevance
of this model for studies on combined drying.