Cooling Tower Dt.17.01.2015

DELHI METRO RAIL CORPORATION

COOLING TOWER

3/13/20151

Contents of PRESENTaTION3/13/2015 Cooling Tower Basics.

Types and components

DMRC Specification of cooling tower

Selection of Cooling Tower

Codes & Testing for Cooling Tower

2

What is a cooling Tower ?Cooling tower is the heat rejection device, which extracts heat to atmosphere through the cooling of water stream to a lower temperature.

3/13/2015

33/13/2015

Cross flow natural draft cooling tower.Natural draft cooling towerMechanical draft cooling towerForced draft cooling tower

3/13/20154 TYPES OF COOLING TOWERS

Counter flow natural draft cooling tower.

Induced draft cooling tower

Induced draft counter flow cooling tower

Induced draft cross flow tower

3/13/201521-Mar-14Natural draft cooling towerThe natural draft cooling tower is the tower which does not contains any induced or forced draft type fan.Generally this type of towers are used in thermal power plant having a large concrete structure5

3/13/201521-Mar-14Mechanical Draft Cooling Towers:-Forced draft type

Air blown through tower by centrifugal fan at air inlet6

3/13/2015Induced Draft Counter Flow CT:-Hot water enters at the topB. Air enters at bottom and exits at topC. Uses induced draft fans as shown.7

3/13/2015Induced Draft Cross Flow CT:-Water enters top and passes over fillB. Air enters on one side or opposite sidesC. Induced draft fan draws air across fill8

3/13/20159Sr. No. Counter Flow Cooling Tower Cross Flow Cooling Tower

1More complicated maintenance of the water distribution system.Easy maintenance access to vital parts.2Drift loss due to droplet distribution system.Reduced drift (water) loss due to the absence of water droplets.3operational cost of cooling tower is lower as compared to cross flow tower.Operational cost of cooling tower is higher .4Less place required for installation.More place required for installation.

Components3/13/201510

Frame and casing :-Most towers have structural frames of hot dipped galvanized frame designed to support the exterior enclosures (casings), motors, fans, and other components.

The casing is made of FRP(Fibre Reinforced Plastic)

3/13/201511

3/13/201512 Fill :-Most towers employ fills (made of plastic or wood) to facilitate heat transfer by maximizing water and air contact.

Basically fill is the primary heat transfer media.

Water falls over successive layers of horizontal splash bars, continuously breaking into smaller droplets, while also wetting the fill surface.

3/13/201513

COLD-WATER BASIN:-The cold-water basin is located at or near the lower part of the tower, and it receives the cooled water that flows down through the tower and fill.

The water basin shall be constructed of minimum 4 mm thick fibre glass reinforced plastic as per contract.

3/13/2015

14

3/13/201515Drift eliminators:-These capture water droplets entrapped in the air stream that otherwise would be lost to the atmosphere.

Drift eliminators is made PVC material.

Air inlet:-1) This is the point of entry for the air entering a tower.2)The inlet may take up an entire side of a tower (cross-flow design) or be located lower portion or the bottom of the tower (counter-flow design).

3/13/2015

Cross flow tower having Air Inlet Entire side of a tower 16

3/13/2015Louvers:-Both cross-flow & counter flow towers have inlet louvers. The purpose of louvers is to equalize air flow into the fill

Counter flow tower having air inlet lower portion of tower17

Cross flow tower having inlet louver

Nozzles:These are used to spray water to wet the fill.

The nozzle is made of Poly propylene material.

Uniform water distribution at the top of the fill is essential to achieve proper wetting of the entire fill surface which can achieved through it.

3/13/2015

18

3/13/201519Fans:-Generally, propeller fans are used in induced draft towers.

Fan hub is made of Cast iron.

The fan outlet velocity not exceeds than 10 m/s as per our contract requirement.

Fan Motor:-Three Phase,415V,50 Hz ,TEFC-Induction motor(IP-55),EFF-1, weather proof motor is required for cooling tower

Cooling tower motor either horizontally & Vertically mounted.3/13/201520

3/13/201521DMRC Specification of cooling towerS noParameterDetailed Description1Cooling Tower TypeInduced Draft(Counter/Cross Flow)2Construction MaterialFiber Reinforced Plastic, With a hot Dipped galvanized frame.3Water Basin-MaterialFiber reinforced Plastic4Total Water Loss1%(Combined of both drift & Evaporative loss)5Drain & Over FlowWith a valve arrangement in drain6FanMinimum Two numbers

3/13/201522DMRC Specification of cooling towerS noParameterDetailed Description7Fan Outlet VelocityShall not exceed 10m/s8BladeCast aluminum Alloy9HubCast Iron10Motor TypeTEFC Induction motor(IP-55), with weather protection, EFF-1 class11Number of CellsTwo12RPM of motor1400(Max)13Base frame & ladderMS hot dipped Galvanized

3/13/201523DMRC Specification of cooling towerS noParameterDetailed Description14Water Distribution systemPVC Sprinkler pipes15Drive ArrangementSpeed reduction gears/ V belt type arrangement.16AccessoriesLadders with hand rails minimum 300 mm wide17LadderMS hot dipped galvanized18Noise criteria85 dB at 1m distance.19Fill & drift eliminatorsPVC

3/13/201524Selection of Cooling Tower Model & Fan MotorVarious parameter of cooling tower:-

Wet bulb temperature of air(Moisture Content) Dry bulb temperature of air (Ambient air temp.) Cooling tower inlet water temperature Cooling tower outlet water temperature Exhaust air temperature Fan motors (KW) Water flow rate Air flow rate

253/13/2015

3/13/201526Approach :-CT Approach (C) = [CW outlet temp (C) Wet bulb temp (C)] Range :-A high CT Range means that the cooling tower has been able to reduce the water temperature effectively, and is thus performing well.

The formula is: CT Range (C) = [CW inlet temp (C) CW outlet temp (C)]

3/13/201527StationVVMK/RK/IIT/HZ/PP/GK/NPChirag DelhiKalkajiCooling tower model2-3156SD/12.5hp2-3155SD/12.5hp2-3155SD/12.5hp2- 3156SD/15hpNo of cells2(Two)2(Two)2(Two)2(Two)Required Capacity(KW)1528144513631652Proposed capacity(KW)1528144513631652Motor makeABB/Crompton/MarathonABB/Crompton/MarathonABB/Crompton/MarathonABB/Crompton/MarathonNumber of axial flow fans2222

CE-10 & 11 Lot-2 Cooling Tower Details

3/13/201528Detail Design of a single model(1652 KW)BOQ data:-

Capacity in KW - 1652 KWWater flow rate in LPS - 98.33 LPSHWT Deg C/ Deg F - 36.4/97.5CWT Deg C / Deg F - 32.2/90WBT Deg C /Deg F - 29/84.2Various Steps To find Tower Unit.Find Range & ApproachConvert LPS to USGPMCalculate WBCF & RF from wet bulb correction factor table & Rating factor table respectively

3/13/2015294. Find require tower unit & Available tower unit.5. Calculate motor HP 1. Range & Approach = HWT(Deg F)- CWT(Deg F)

=97.5-90

=7.5F

3/13/201530Approach=CWT(Deg F)- WBT(Deg F)=90-84.2=5.8 F2.Convert WFR in LPS to USGPM= 1 Lps is 15.88 USGPM= 98.33 Lps is 1558.56 USGPMWBCF from wet bulb correction factor table for 29 deg C(84.2 deg F)From WBCF table it is clear that at85 deg F WBCF is 0.848& at 84 deg F is 0.8693.Wet-bulb Correction factor & Rating Factor

3/13/201531WBCF at 84.2 deg F is 0.8648Similarly Rating Factor(RF) from RF table for range 7.5 & approach of 5.8 is 0.32054.Required Tower Unit=Flow rate in USGPM x RF x WBCF1558x 0.3205x 0.8648=431.82( For Two cell)For 1 cell tower unit is 431.82/2 i .e. 216

Available size is 227(for 1 cell)So that model is 2.3156s/15 HPRated tower unit for two cell is 227x2=454

3/13/201532As there is three air inlet available, TCCF from tower capacity correction factor table is 0.97.So rated tower unit will be=454x 0.97=440.38 The available tower unit is more than the required tower unit that is 440.38, which is greater than 432(Our requirement) 5.Selection of motor The required tower units for duty condition are 432 & available tower unit for model 2-3156SD/15 HP is 440.38.

3/13/201533In this regard refer note no 5 in thermal performance rating chart, on considering multiplication of cube root of designed tower unit/ Available tower unit & motor HP(15).

Motor HP= (432/440.38)x15

=14.15 HP(Available HP is 15)Similarly tower unit & motor details for other model can be calculated.

3/13/201534Test Specified in SpecificationAs Per Data SheetAs Per SpecificationTesting for Thermal PerformanceThe acceptance testing shall be conducted in accordance with the procedure specified in the CTI publication ATC 105CertificationCTI-STD 201-1991Cooling tower should be CTI certified, As per latest standard for cooling tower .Testing for noise levelThe noise level testing for the cooling tower conducted in accordance with the procedure specified in CTI publication ATC 128

3/13/201535Cooling Technology Institute(USA)The main objective of Cooling technology institute is to Certify the published rating of manufacturer.

To develop customer confidence

Establishing testing standard & performance analysis systems & Procedures.

Paharpur Make cooling tower is CTI certified by Certification validation number C51A-13R1 Dt. 19.05.2014 & valid through 2015.

3/13/201536CTI STD-201CTI STD-201: Standard for thermal performance certification of evaporative heat rejection equipments.

Purpose: Evaporative Heat Rejection equipment offered for sale by a specific Manufacturer, will perform thermally in accordance with the Manufacturer's published ratings.

Testing Procedure: Will be performed by Multi Agency testing as per provisions of the latest version of the CTI Test Code ATC-105 for cooling tower.

3/13/201537Certification Programme

3/13/201538Complaint Procedure

3/13/201539

3/13/201540Test to be conducted in factory.Visual & Dimension check of various cooling tower components as per Drawing.

Checking & verifying of mechanical equipment as per drawing & data sheet.

Review of internal inspection report.

3/13/201541For testing the following parameters to be measured

Water flow rate

Air Density

Fan HP

CWT(Cold water temperature)

HWT(Hot water temperature)

WBT(Wet bulb temperature)

3/13/201542Performance Test:-Performance test is done at site as per CTI ATC 105.

CTI 105 requires the manufacturer to submit the performance curves as mentioned below.

Three sets of graphs with three curves, each set corresponding to 110%, 100% & 90% of flow rate in which curves are plotted b/w wet bulb temperature and cold water temperature.

In each set three curves are drawn corresponding to 80%, 100% and 120% of design range.

3/13/201543

Based on the performance curves submitted by the manufacturer, a cross plot of the curves at test wet-bulb temperature is plotted.3/13/201544

Based on the derived performance curve as explained earlier, another cross plot is drawn at the test range.3/13/201545

From the above performance curve, the flow rate corresponding to actual test cold water temperature is the test flow rate.

From the test flow rate, adjusted test flow rate is derived from the formula:

Finally capability of cooling tower is defined as 3/13/201546Adjusted Test GPM= Test GPM x

Tower capability =

Acceptance CriteriaWet-bulb temperature- 15%Dry-bulb temperature- 25%Range- 20%Circulating water flow- 10%3/13/201547

3/13/2015Thank you 48