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C-T Principles

Preface Introduction Definition Principle of operation
Terminology Better Air Flow Pumping Head Life Factor
Smaller Fan Motors Casing Classification Thermal Design
Sump Suction tank/auxiliary tank Tower Structures Fills
Sprinkler Fan/ Fan Blades Fan Drive Motor Grills
Drift Eliminators Installation Towers
Sprinkler Assembly
Normal Conditions Water quality Control Post Erection Checks Pre-commissioning checks
Maintenance Schedule

This manual is intended for use by erectors, operators and service maintenance staff to correct installation, proper operation and maintenance of the Cooling tower. This manual should be studied thoroughly and used as an aid to keep your Cooling Tower in good operating condition through timely and proper preventive maintenance practice. Users will also gain an understanding of cooling towers, principles of problems and methods for effectively dealing with them as and when they occur.

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A Cooling Tower is a direct contact heat exchanger, generally used to dissipate the heat in circulating water. The heat is dissipated to the ambient air via a process of heat and mass transfer from the circulating water. The water thus cooled is circulated again through the process, heat exchanger or condenser. The heat is transferred to the water either in a condenser like refrigeration or air-conditioning system or chemical processes or heat exchangers in cooling process, generating sets, engines, furnaces etc.
The cooling tower design has changed over the years to incorporate new materials, as and when available.
1. Perform to required specification.
2. More compact
3. Weigh less
4. Consume least power
5. More long lasting, withstand corrosion and have good finish looks.

With the introduction of Fiberglass Reinforced Plastics the above benefits are achieved in the Counterflow, Bottle shape FRP, induced Draft Cooling Towers.

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A wet cooling tower is an enclosed device used to dispose waste heat by evaporation from industrial processes and refrigeration or air conditioning system, where it is operated based on the direct contact of the earth's most common substances: Air and Water.

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Principle of Operation
The automatic rotating sprinkler system distributes the hot water evenly over the entire fill section. Dry air is simultaneously drafted upward causing evaporation. The cooled water falls into the basin and is pumped to the heat source for recirculation.

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It is necessary to define the most common terms in the cooling tower operation.
i. Range is the difference in temperature between the inlet hot water and the outlet cold water. For 40°C inlet and 35°C outlet, the range is 5°C.
ii. Approach is the difference in temperature between the outlet cold water and the wet bulb of the entering air. For 35°C water out let and 27°C wet bulb temperature, the approach is 8°C.
iii. Circulating water rate is the quantity of hot water entering the tower.
iv. Fills which are placed within the tower to effect heat and mass transfer between the circulating water and the air flowing through the tower.
v. Casing is a vertical enclosing sidewall which surrounds the fill and retains the water within the tower.
vi. Distribution system begins with the inlet connection for distribution of circulating hot water within the tower to the points, where it comes in contact with air.
vii. Eliminator is an assembly which serves to remove entrained moisture from the discharged air.

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Better Air Flow
The rotating water sprinkler head distributes the hot water within forming a fine spray, and hence does not need the conventional type of moisture eliminator. This is because the water header has large number of holes giving a 'steam' type flow directly into the infill. Towers with fixed nozzles cannot obtain the coverage, which is needed for optimum cooling. We should not overlook that in rectangular type towers, eliminators provide a pressure drop which evens out the flow particularity into the corner.
The 'Advance' tower being round, plus its conical fan inlet can better provide an even air flow through the infill, with a lower pressure drop, and without the additional pressure drop caused by the eliminator needed on other towers.
Fan KW depends on the mass of air delivered, the pressure generated and the blade efficiency. "Advance" air volumes are similar to competitor's sizes. The influencing factor for lower power is 'pressure' and 'efficiency'.
1. The "Advance" tower has large air inlet area, with low air velocity, low pressure drop.
2. The "Advance" tower is of the induced draft type.

The fan is in the ideal position, to discharge the air at a high velocity upward and allow natural convection to prevent recirculation, as can happen with the forced draft tower arrangement, where air leaves the eliminators at low velocity.

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Pumping Head
As seen already, the water distribution by a rotating header, is a significant part of the "Advance" tower design. The large diameter holes in the rotating header give a gentle stream of water at negligible pressure loss. Also, there is no risk of 'clogging', as can easily happen with spray nozzles in other types of towers.
It should be noted that pumping heads quoted for "Advance" towers include both of these as well as the piping inside the pressure loss of the sprays. To this must be added the static lift to the spray header from the basic water level, plus the external piping friction loss. In many cases the pumping head required for an "Advance" tower is about 50% less than for some other towers.

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Life Factor
Although we generally refer to the towers as being constructed of fiberglass, we should actually refer to them as being FRP (Fiberglass Reinforced Plastic)
FRP should not be confused with the translucent fiberglass roofing panels, and in particular with the cheaper grades which have given poor results even only in a few years. Without an adequate protective layer, the sun's ultra violet rays draw the fibers upward so that 'hairs' appear to be growing on the panels as with fiberglass hulls, the "Advance" tower casings have a protective Neopently Glycol gel coat, which apart from containing the pigment colour, entirely resists the sun's rays. As a result, "Advance" towers do not need painting. However, if a client wishes to have a colour scheme changed, painting is possible.
Compared with timber towers which will ultimately rot, or steel towers which will rust despite increased maintenance, the fiberglass tower has a tremendous financial advantage for the wise investor. Unfortunately, many buyers appear to be only concerned to maintenance, running costs or rate of deterioration.

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Smaller Fan Motors

DMD 1680 has an Installed Fan Motor of 10 HP, whereas other reputed manufacturers offer Cooling Towers with either 15 HP or 20 HP motor for the same capacity.

The lower HP rating of the motor used in "Advance" towers therefore leads to a substantial saving in annual energy cost as illustrated below:
HP Difference 5 HP 10 HP
K.W. 3.7KW 7.5KW
Assumed Unit Rate (Rs) RS 3.5 RS 3.5
No. of Working Hours (p.a.) 8640 8640
Energy Cost p.a.(RS) RS 1,11,888/- RS 2,26,800/-

Therefore in Case No. 1 you will spend an extra RS 1,11,88/- p.a. and Case No. 11 RS 2,26,800/- p.a. on Electricity Bills if you choose to buy a tower with a higher HP motor rating as compared with "Advance". "Advance" are the only High Performance FRP Cooling Towers designed for long life and low maintenance at a competitive price. The money you save on maintenance and electricity bills make "ADVANCE" your best Cooling Tower investment from installation and years thereafter.

When you invest in "ADVANCE" Cooling Towers, you are assured of the following:

1. Superior laminate strength, with Isopthalic Resin (ISO) reducing vibration and increasing tower life.
2. Neopently Glycol (NPG) gelcoat finish for UV protection and color retention with improved surface finish.
3. Auxiliary drain tank totally in corrosion resistant FRP.
Fans, hubs and sprinklers in gravity die cast aluminum allow LM-6 together with dynamically balanced fan assemblies ensuring smoother operation, longer bearing and motor life.
5. PVC fills made from vacuum formed virgin PVC sheets.
6. Power saving leads to lower annual electric bills due to our direct drive motors with IP-55 protection and 'F' class insulation.
7. Protection against malfunctioning parts including Motors through a 15 months warranty from date of your "ADVANCE" tower.

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