A NATURAL DRAFT Cooling Tower is so referred to as as a result of it don’t use followers for drawing air into the tower, as a substitute it makes use of the pure air which is drawn into the tower naturally by the means of Pure Convection for cooling the hot water. It may be Cylindrical or Hyperbolic in form. Hyperbolic form gives superior structural power and resistence to ambient wind loadings. Resulting from the large measurement of these towers, they’re usually used for water circulation rates above 45,000 m3/hr.Some of these towers are used mainly by Utility Power Stations.
A Natural DRAFTCOOLING TOWER consists of following important elements :
Scorching WATER INLET
The new water inlet is usually provided at the highest of the tower, below the Drift Eliminators and above the fill. It is connected to a collection of nozzles that sprays the water downwards on the fills current.
Nozzles are linked to Scorching Water Inlet and are present above the fill. Uniform water distribution at the highest of the fill could be very a lot essential to attain correct wetting of all the fill surface. Nozzles sprays water from the highest of the fill to uniformly wet all the fill.
Chilly AIR INLET
The cold air inlet is generally provided at the bottom of the tower, above the cold basin and beneath the fill. The cold air enters into the towers via this.
The Louvers are present on the Chilly Air Inlet. The aim of louvers is to equalise the air circulation into the fill. Also they assist in retaining the water inside the Coling Towers. They’re primarily used when the circulation of water and air is crossflow. Many counter circulation towers do not require Louvers.
Fills are current contained in the tower beneath the nozzles to offer a big floor space and time for air and water contact . Most towers have fills fabricated from plastic or wood because it facilitate good heat switch by maximising water and air contact.
Fill can either be splash or filmtype. In splash fill, water falls in successive layers and is repeatedly damaged it into smaller droplets, thereby wetting the complete fill surface.
Plastic splash fill provides higher heat transfer than the wood splash fill.
Film fill consists of skinny, intently spaced plastic surfaces(PVC) over which the water spreads uniformly forming a skinny film which is involved with the air. These surfaces may be flat, corrugated, honeycombed, or different patterns. The movie type of fill is more environment friendly than the splash fill and supplies similar heat switch in a smaller volume.
Typically it happens that the droplets of water are carried out of the cooling tower together with the recent exhaust air. The focus of impurities in these droplets is similar as that in the water coming into the tower. These might lead to environmental pollution. To cut back this baffle-like units, called as Drift Eliminators are installed above the nozzles. Drift Eliminators permit solely the air to go by way of it thereby removing water droplets from the air.
Cold WATER BASIN
The cold water basin, is situated at the underside of the tower. The cooled water that flows down via the tower and fill is collected by the Chilly Water Basin. These collected chilly water is then discharged and used for cooling other sizzling process fluids .
The recent water that is too be cooled in the cooling tower is pumped to the top of the tower at the new water inlet. The recent water inlet is related to a series of nozzles which sprays this water over the fills. Simultaneously air is launched from the underside of the tower which flows in upward route.The air is circulated inside the cooling tower by Natural Convection.The fills present a big floor space and time for air and water contact . The water then flows down via plastic or wooden fills. This causes drop formation. Whereas flowing down, the water emits heat which mixes with the air flowing upward, inflicting it to cool down. A part of the water evaporates, causing it to emit extra heat. Water vapor can sometimes be noticed over the cooling tower. The cooled water falls down into the chilly water basin which is discharged and will be then used for cooling numerous hot process fluids.
FAN Is not Put in AS NDCT’S Rely on Pure AIR
Straightforward To scrub
NO MECHANICAL NOISE
NO CORROSION Problems
MAINTAINANCE IS LOW
NO Restore Problems
NO RECIRCULATION OF AIR OCCURSAS THE PLUME IS REJECTED AT Excessive Degree
A really Lengthy Construction TIME Is required TO Assemble NDCT.
Huge WATER Move REQUIRED
NOT FOR ALL CLIMATIC Circumstances
Efficiency Relies on PREVAILING WIND VELOCITY AND Route.
AIR Motion Rely on INDUCTION FORCES
UNOBSTRUCTED LOCATION Crucial.
Natural DRAFT COOLING TOWERS REQUIRES VERY Giant Space.
The Natural DRAFT COOLING TOWERS are of two types :
- 1. SPRAY Type NDCT’S
- 2. SPLASH DECK Sort NDCT’S.