ABSTRACT DETAILS COOLING TOWER Made by : Dev Mehta FTE MSU.
Cooling tower Basic definition:Cooling towers are heat removal devices usedto transfer process waste heat tothe atmosphere. Cooling towers may eitheruse the evaporation of water to removeprocess heat and cool the working fluid to nearthe wet-bulb air temperature
Uses Of Cooling Tower in industry Industrial cooling towers can be used to remove heatfrom various sources such as machinery or heated processmaterial. The primary use of large, industrial coolingtowers is to remove the heat absorbed in the circulatingcooling water systems used in power plants, petroleumrefineries, petrochemical plants, natural gas processingplants, food processing plants, semi-conductor plants, andfor other industrial facilities such as in condensers ofdistillation columns, for cooling liquid in crystallization, etc
Wet bulb temperature: Wet bulb temperature is the lowesttemperature that can be reached by theevaporation of water only. It is thetemperature you feel when your skin is wetand is exposed to moving air. Unlike dry bulbtemperature, wet bulb temperature is anindication of the amount of moisture in theair.
Heat Transfer Method:There are different mechanisms for differentcooling towers the method employed in thisparticular cooling tower design is on theprincipal of evaporation as the cooling towerdesigned is wet type.
Wet Type Cooling Tower:In a wet cooling tower, the warm water can be cooledto a temperature lower than the ambient air dry-bulbtemperature, if the air is relatively dry. As ambient airis drawn past a flow of water, an small portion of thewater evaporates, the energy required by that portionof the water to evaporate is taken from the remainingmass of water reducing its temperature. Evaporationresults in saturated air conditions, lowering thetemperature of the water process by the tower to avalue close to wet bulb air temperature, which is lowerthan the ambient dry bulb air temperature, thedifference determined by the humidity of the ambientair.
Air Flow Generation method employed:Mechanical draft, which uses power driven fan motors toforce or draw air through the tower. Induced draft: Mechanical draft tower with a fan at thedischarge which pulls air through tower. The fan induces hotmoist air out the discharge. This produces low entering andhigh exiting air velocities, reducing the possibilityof recirculation in which discharged air flows back into the airintake. The main advantage over natural draft is that naturaldraft is a comparatively slower process and also it demandslarge height of the tower. Advantage over forced draftmethod is it has low discharge velocities so air may enter alsoit requires a motor with greater horsepower as compared tothe induced draft .
Cooling Tower fills :To achieve better performance (more cooling), amedium called fill is used to increase the surface areaand the time of contact between the air and waterflows. Splash fill consists of material placed tointerrupt the water flow causing splashing. Film fill iscomposed of thin sheets of material upon which thewater flows. Both methods create increased surfacearea and time of contact between the fluid (water)and the gas (air). In this particular design both thetypes of fills are used
The large arrows show thePath of water first through the The small arrows show thesprinkler. Then on the metal direction of air. Atmospheric airplate which acts as a splash fill enters through various holeswhere tiny droplets are formed along all four sides of the plates,then the water passes through the small holes which arethe Perforated mesh which provided on all four sides at theremoves impurities from the shower and straw pad levelswater and then the water travels and enters the system wherethrough The straw pads which maximum dissipation of heatfurther act as a packing material takes place, then the air alongfor increased contact time with water vapor exits to theThen the water travels through atmosphere from the fan.the perforated plate having Slits at the bottom of the towerlarger diameters and again also suck in air and dischargethrough the Straw pads . The the air from the top of thewater then travels through the tower through the fan.inclined plates which act as film The positions of the holes arefill and increase the contact time such that leakage is preventedAnd finally the water is collectedin the hopper and then removedfrom the system. So the air moving upward will get humidified and the water looses its heat as some of it is
Closer view of theSprinkler and the perforatedplates
Material Used:The material used for the fabrication of this particular coolingtower is Mild Steel(M.S)The main advantages of mild steel are :1. The structure has high strength and hardness .2. Can withstand high pressures.3. Has high salvage/scrap value.4. Can be easily be cleaned and inspected .The disadvantages of mild steel are :1. Corrosion- this has been dealt with applying a zinc primer along with paint.2. Weight of the structure – cooling tower is not a mobile structure and so weight doesn’t play a major role
Cost Estimate:1 . Scrap M.S angle/scrap MS plate 50kgs*19 /- per kg =9502.Old fan =2003.Over head shower =1004.Piping/straw pad =1005.S.S grill and wire mesh =2006.Colour =1507.Labour charges for fabrication 50*8 =400Grand Total =2100 rs.