3.DESCRIPTI0N
3.1.
PRINCIPLE AND AIRFLOW
The well insulated cabinet interior is divided into working and treatment chambers, as
shown in the diagram (fig.
1).
Air is circulated by a fan from the treatment (conditioning)
chamber into the working chamber through the right hand wall plenum in which the wet
and dry bulb sensing elements are situated in the optimum position for rapid response.
The conditioned air passes through the working chamber in a turbulent manner, ensuring
minimum temperature gradients, before returning to the treatment chamber through the
left hand wall plenum.
All performance tolerances are to within 50mm of the walls of the working chamber.
This is the working envelope in which the test load is not affected by heat sources such
as fans, heaters or cooling coils.
The temperature and relative humidity of the air are maintained at the conditions set by
the operator via the control system. A sloping false roof is fitted to the working chamber
to prevent condensation dripping onto the test load. The base of the working chamber
is double skinned to prevent hot and cold "spots" forming due to radiated heat/cold from
the treatment chamber. If required, the base of the working chamber may be used as
another
shelf.
direct
cooling^
coil
working chamber
heaters
111
temperature
sensors
vapour phase
generator
refrigeration unit
drain
Figure 1
