GATE

Vijay Ratna

Viscosity is an expression of the resistance to flow of a system under an applied
stress. The more viscous a system, the greater the applied force required to
make it flow at a particular rate.

The unit of viscosity is the poise, defined as the shearing force required to
produce a velocity of one centimeter per sec. between two parallel planes of
liquid each 1 centimeter square in area and separated by a distance of one
centimeter. The Cgs units for the poise are dyne sec cm^-2. The centipoises
are a more convenient unit of viscosity.

Viscosity is a property which characterizes the flow nature of a liquid. Study of
viscosity helps us in a number of situations and helps us in taking decisions.

Vijay Ratna

Compartment Tray Dryer :

1. Rectangular Chamber, whose walls contain a suitable
   heat insulating material.
2. Material kept on Trays.
3. Dryer is loaded, doors are closed and hot air is
   circulated over trays
4. Direction vanes for uniform velocity distribution of
   air on all the trays.
5. Air is recirculated for economic reasons.
6. Dampers, with the help of automatic instruments,
   control the percentage of fresh air introduced and the moist air
   discharged.
7. Wet scrubbers used for recovery of valuable solvents.
8. If different products are to be dried, thorough
   cleaning is necessary.

Problems:

1. Non-Uniform air flow