1. OPTIMAL DESIGN OF A HYPERBOLOIDAL COOLING TOWER
2. INTRODUCTION What is a (wet, atmospheric) cooling tower? A
cooling tower is a heat rejection device, which extracts waste heat
to the atmosphere though the cooling of a water stream to a lower
temperature. The type of heat rejection in a cooling tower is
termed "evaporative" in that it allows a small portion of the water
being cooled to evaporate into a moving air stream to provide
significant cooling to the rest of that water stream. The heat from
the water stream transferred to the air stream raises the air's
temperature and its relative humidity to 100%, and this air is
discharged to the atmosphere. Evaporative heat rejection devices
such as cooling towers are commonly used to provide significantly
lower water temperatures than achievable with "air cooled" or "dry"
heat rejection devices, like the radiator in a car, thereby
achieving more cost-effective and energy efficient operation of
systems in need of cooling. Think of the times you've seen
something hot be rapidly cooled by putting water on it, which
evaporates, cooling rapidly, such as an overheated car radiator.
The cooling potential of a wet surface is much better than a dry
one.
3. Broad classification:- With respect to drawing air through
the tower, there are three types of cooling towers: 1. Natural
draft Utilizes buoyancy via a tall chimney. Warm, moist air
naturally rises due to the density differential compared to the
dry, cooler outside air. Warm moist air is less dense than drier
air at the same pressure. This moist air buoyancy produces an
upwards current of air through the tower.
4. 2. Mechanical draft Uses power-driven fan motors to force or
draw air through the tower. (A) Induced draft A mechanical draft
tower with a fan at the discharge (at the top) which pulls air up
through the tower. The fan induces hot moist air out the discharge.
This produces low entering and high exiting air velocities,
reducing the possibility of recirculation in which discharged air
flows back into the air intake. This fan/fin arrangement is also
known as draw-through. (B) Forced draft A mechanical draft tower
with a blower type fan at the intake. The fan forces air into the
tower, creating high entering and low exiting air velocities. The
low exiting velocity is much more susceptible to recirculation.
With the fan on the air intake, the fan is more susceptible to
complications due to freezing conditions. Another disadvantage is
that a forced draft design typically requires more motor horsepower
than an equivalent induced draft design.
5. The basic components of a cooling tower are:- 1.Frame and
casing. 2.Fill. 3.Cold-water basin. The cold-water basin is located
at or near the bottom of the tower. 4.Drift eliminators. 5.Air
inlet. 6.Nozzles. 7.Fans.
8. Hyperboloid (sometimes incorrectly known as hyperbolic)
cooling towers have become the design standard for all
natural-draft cooling towers because of their structural strength
and minimum usage of material. The hyperboloid shape also aids in
accelerating the upward convective air flow, improving cooling
efficiency. These designs are popularly associated with nuclear
power plants. However, this association is misleading, as the same
kind of cooling towers are often used at large coal-fired power
plants as well. Conversely, not all nuclear power plants have
cooling towers, and some instead cool their heat exchangers with
lake, river or ocean water.
9. PROBLEM CAUSE EFFECT PROPOSED SOLUTION Scale deposits form
on the surface of the fill, chemical pipes, and nozzles.
Evaporation and water treatment problems Amount of heat transfer
from water to air reduced, operation efficiency reduced Measure the
water treatment chemicals in each cycle circulation. Spray nozzles
clogged Algae and sediment formation Improper cooling, reduced flow
Clean the strainer very regularly. Uneven water and air flow Spray
nozzles clogged Unexpected higher temperature Sediment suppression
Our idea is to use the soot blowers to remove the scale and sludge
formation that need not to sustain the shutdown thus increasing
running time and higher efficiency.
10. AS THE INDUSTRIES AT DIFFERENT LEVEL ARE MUSHROOMING EVERY
DAY, THEY INVOLVE DIRECT OR INDIRECT USE OF COOLING TOWERS AS HEAT
EXCHANGERS. THUS TO MEET DOMESTIC AND OTHER INDUSTRIAL NEEDS IN THE
MOST EFFICIENT AND ECONOMICAL MEANS,IT NEEDS TO KEEP ON UPGRADATION
OF COOLING TOWERS. A VARIETY OF FIRMS SUCH AS POWER SECTOR, STEEL
PLANTS, CEMENT INDUSTRIES, GALVANISING UNITS ETC EMPLOY COOLING
TOWERS. THUS IT HAS A VERY WIDE SCOPE OF IMPROVISATION AND
APPLICATION WHEREVER PHENOMENON OF EXCHANGE OF HEAT OR COOLING IS
SUPPOSED TO OCCUR.
11. We first aim to study thoroughly the hyperboloidal cooling
tower and study upon its following aspects:- Familiarization
History and development Uses of cooling tower , fields of
application Designing parameters Efficiency Water chemistry Scopes
of improvement Improvisation over present design
12. APPLICATION HEAT EXCHANGING THERMAL POEWR PLANTS MANY OTHER
INDUSTRIES STEEL AND ROLLING MILLS NUCLEAR POWER PLANTS
13. Field erection type cooling tower
14. Air suction channels of a cooling tower.
15. PREPARED BY:- GROUP NUMBER 7,MECHANICAL 7th (A) PROJECT
GUIDE:-Mr. NILMANI SAHU GROP MEMBERS:- 1. SUMIT KUMAR SAHU-45 2.
MINTU PRASAD-13 3. SOURAV LAHIRI-44 4. RAHUL KURMI-40