2. • If water passes through a nozzle capable of
producing small droplets, a large surface becomes
available for air-water contact.
• Since the water-air interface is also the heat transfer
surface, the use of nozzle permits the attainment of
considerable performance per cubic foot of contact
apparatus.
• This is the principle of the spray pond and the spray
tower
3. • Liquid fed to it falls through by
gravity.
• A droplet of water will fall
through the height of the
tower in 1sec.
• If liquid is fed at the rate of one
droplet per second and there is
no obstruction, one droplet will
always be present in the tower
and one droplet may be
continuously removed from the
tower per second.
4. • By introducing some geometrical
forms on which a droplet may
impinge or be deflected it is
possible to make a droplet take 4
sec to fall through the height of
the tower.
• One droplet is fed per second at
the top and one droplet is
continuously removed at the
bottom but 4 droplets remain in
the tower.
• The effective surface in this
case is that of 4 droplets or 4
times the free fall surface.
5. • The function of fill :-
– is to increase the available surface in the tower
either by spreading the liquid over a greater
surface or by retarding the rate of fall of the
droplet surface through the apparatus.
• Because of the requirement of a large air volume and
small allowable pressure drop, spaced wooden slats
of triangular or rectangular cross section, leaving the
tower substantially unobstructed.
6.
7. • Some of the liquid striking the top of a slat splatters,
but a large part flows about it and breaks into
turbulent flow at the bottom so as to form new
droplets automatically and recreate new droplet
surface.
• The mechanism of producing droplets below each
horizontal row relies upon the draining liquid
breaking into turbulent flow.
• The method by which droplets are formed at the top
of the tower is of little consequence to the overall
formation of surface as long as there is a uniform
distribution of liquid over the entire cross section of
the tower.
