Cooling Tower Educational Standcairouniversity

Faculty of Engineering

Cairo University

Mechanical Power Departement

Cooling Tower Educational Stand

B.Sc. Graduation Project

Cairo University

Faculty of Engineering

Mechanical power department

B.Sc. Graduation Project 2008

Cooling Tower Educational Stand

• Prof. Dr. Adel Khalil

Project Supervisors:

• Prof. Dr. Hany Khater

• Dr. Galal Mostafa

- Acknowledgement. - Project description. - Nomenclatures.

Page

Chapter One: Introduction. 1. Objective. 2. Classification. 3. Components. 4. Water Treatment. Chapter Two: Literature review

1. Gunt. 2. Armfield. 3. P. A. Hilton. 4. Edibon.

Chapter Three: Cooling Tower Design Calculation 1. Column.

2. Cooling tower performance 3. Tanks.

i. Water tank. ii. Air tank. iii. Make up tank. iv. Drain tank. 4. Piping System and pump. 5. Blower and Butterfly Valve. 6. Water Injection Nozzle. 7. Stand.

Chapter Four: Measuring devices and auxiliaries. 1. Temperature Measurements.

2. Humidity Measurements. 3. Flow Measurements. 4. Displays.

5. Data acquisition card. 6. Calibration.

Chapter Five: Bill of Material and Cost. Chapter Six: Fabrication Procedure.

1. Welding.

2. Stand fabrication. 3. Painting and coating.

4. Pipes components and fittings. 5. The column.

6. Stand preparation. 7. Control panel.

8. Electronic and Electric devices installation. 9. Electric Connections. 10. Component assembly. 1 1 2 6 7 8 8 10 12 14 16 20 21 21 23 23 24 25 29 30 31 32 32 34 34 37 38 46 48 51 51 55 56 57 59 61 62 62 63 64

1. Procedure 2. Results

3. Relations summery and conclusion -Appendices. -References 66 67 70 71 105 .

First, we would like to thank Allah the merciful and compassionate for making all this work possible and for granting us with the best professors, family, friends, and colleagues that many people would wish and dream of having.

We would like to thank our

supervisors

•

Prof. Dr. Adel Khalil

•

Prof. Dr. Hany Khater

•

Dr. Galal Mostafa.

We are greatly indebted to them for their valuable supervision, kind guidance, and great help and effort to make this project possible. Words cannot express our deep gratitude and sincere

appreciation to them.

Group Members

Eng. Basel Amr Gouda

:

Eng. Hebatallah Abdel Moniem Mohamed

Eng. Mohamed El Sayed Rizk.

Eng. Al Hussain Mohamed Kamel

Eng. Ismail Gamal El Din Ismail.

Eng. Ahmed Samir Abdallah.

.

Special Thanks to:

• Eng. Somya Mohamed Abdel Rehim

- For Supplying us with materials and support

• Colleague Ahmed waheed

The students affiliating with the present project will be required to study, design and fabricate a Water Cooling Tower Educational Stand.

The Water Cooling Tower educational stand will eventually form a part of the undergraduate students “Heat Transfer Laboratory”.

In this step, the following will be accomplished: Step 1 : Water cooling tower fabrication.

 Study the different heat and mass transfer mechanisms.  Cooling tower heat load estimation.

 Design calculations of the water cooling tower showing different geometrical parameters and dimensions.

 Material selection of the different components.

 Working drawing sheets for the different cooling tower components.  Fabricating the different components and assembling the cooling tower.

In this step, the following will be accomplished:

Step 2 : Water cooling tower educational stand erection

 Selecting and preparing the types of the measuring sensors, devices and data acquisition system.

 Assembling the cooling tower together with, the storage tank with heaters, the make-up tank, the air blower and air chamber, the water circulating pump, water injection nozzle, the column, valves and hoses, and the different measuring devices on the stand.

 Finalizing all mechanical, electrical and electronic works needed for the stand.

In this step, the following will be accomplished:

Step 3 : Performance test on the water cooling tower educational stand

 Assuring the validity of all stand measuring devices.

 Studying the effect of different parameters on the cooling tower performance.  Comparing the experimental results with those calculated.

Chapter One

Introduction

1. Objective

Cooling towers (Fig. 1) are heat removal devices used to transfer process waste heat to the atmosphere. They may either use the evaporation of water to remove process heat and cool the working fluid to near the wet-bulb air temperature or rely solely on air to cool the working fluid to near the dry-bulb air temperature.

The objective of cooling towers can be divided into two categories:

HVAC

An HVAC cooling tower is a subcategory rejecting heat from a chiller. Water-cooled chillers are normally more energy efficient than air-cooled chillers due to heat rejection to tower water at or near wet-bulb temperatures. Air-cooled chillers must reject heat at the dry-bulb temperature, and thus have a lower average reverse-Carnot cycle effectiveness. Large office buildings, hospitals, and schools typically use one or more cooling towers as part of their air conditioning systems. Generally, industrial cooling towers are much larger than HVAC towers.

Industrial

Industrial cooling towers can be used to remove heat from various sources such as machinery or heated process material. The primary use of large, industrial cooling towers is to remove the heat absorbed in the circulating cooling water systems used in power plants, petroleum refineries, petrochemical plants, natural gas processing plants, food processing plants, semi-conductor plants, and other industrial facilities. The circulation rate of cooling water in a typical 700 MW coal-fired power plant with a cooling tower amounts to about 71,600 cubic metres an hour (315,000 U.S. gallons per minute) and the circulating water requires a supply water make-up rate of perhaps 5 percent (i.e., 3,600 cubic metres an hour).

2. Classification

Cooling towers can be classified into different categories as follows: ™ Heat transfer mode

• Wet cooling towers or simply cooling towers operate on the principle of evaporation. • Dry coolers operate by heat transfer through a surface that separates the working fluid

from ambient air, such as in a heat exchanger, utilizing convective heat transfer.

• Fluid coolers are hybrids that pass the working fluid through a tube bundle, upon which clean water is sprayed and a fan-induced draft applied. The resulting heat transfer performance is much closer to that of a wet cooling tower, with the advantage provided by a dry cooler of protecting the working fluid from environmental exposure.

In a wet cooling tower, the warm water can be cooled to a temperature lower than the ambient air dry-bulb temperature, if the air is relatively dry. As ambient air is drawn past a flow of water, evaporation occurs. Evaporation results in saturated air conditions, lowering the temperature of the water to the wet bulb air temperature, which is lower than the ambient dry bulb air temperature, the difference determined by the humidity of the ambient air

Air flow generation

With respect to drawing air through the tower, there are three types of cooling towers:

• Natural draft, which utilizes buoyancy via a tall chimney. Warm, moist air naturally

rises due to the density differential to the dry, cooler outside air. Warm moist air is less dense than drier air at the same pressure. This moist air buoyancy produces a current of air through the tower (Fig. 2).

• Mechanical draft, which uses power driven fan to force or draw air through the tower.

− Induced draft: A mechanical draft tower with a fan at the discharge which pulls

air through tower (Fig. 3). 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/fill arrangement is also known as draw-through.

Fig. (1.3) Induced draft fan cooling tower

− Forced draft: A mechanical draft tower with a blower type fan at the intake (Fig.

4). 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. The forced draft benefit is its ability to work with high static pressure. They can be installed in more confined spaces and even in some indoor situations. This fan/fill geometry is also known as blow-through.

Fig. (1.4) Forced draft fan cooling tower ™ Air-to-Water Flow

-Cross flow: Is a design in which the air flow is directed perpendicular to the water flow (Fig 5). Air flow enters one or more vertical faces of the cooling tower to meet the fill material. Water flows (perpendicular to the air) through the fill by gravity. The air continues through the fill and thus past the water flow into an open plenum area. A distribution or hot water basin consisting of a deep pan with holes or nozzles in the bottom is utilized in a cross flow tower. Gravity distributes the water through the nozzles uniformly across the fill material.

-Counter Flow: The air flow is directly opposite of the water flow (Fig 6). Air flow first

enters an open area beneath the fill media and is then drawn up vertically. The water is sprayed through pressurized nozzles and flows downward through the fill, opposite to the air flow.

Common to both designs:

• The interaction of the air and water flow allow a partial equalization and evaporation of water.

• The air, now saturated with water vapour, is discharged from the cooling tower.

• A collection or cold water basin is used to contain the water after its interaction with the air flow.

Both cross flow and counter flow designs can be used in natural draft and mechanical draft cooling towers.

Fig. (1.5) Cross Flow cooling tower

3. Components:

Inlet water distributors:

There are several types of water distributors, among them:

1. Gravity distributors: applied mainly for cross flow cooling towers and consist of vertical water riser that feed water into an open concrete basin, from which the water flows by gravity through orifices to the fill.

2. Spray distributors: used mainly with counter flow cooling towers and have cross pipe net with spray downward nozzles.

3. Rotary distributors: applied for cross flow cooling towers and consists of two slotted arms rotate about a central hub containing water supply pipe. The slots in the tow arms are directed downward but make small angle with the vertical direction to one side. The slots form a curtain angle and due to reaction force the arms rotate at a rotational speed of 25-to-30 rev/min.

Drift eliminators:

An assembly constructed of wood, plastic, cement board, or other material that serves to remove entrained moisture from the discharged air.

Circulating Pump:

The circulating pump transports the cooling water between the cooling tower and the condenser. The water is pumped from the cooling tower basin through to the condenser, where it is used as cooling medium. The water returns back for evaporative cooling in the cooling tower.

Fan:

A device for moving air in a mechanical draft tower. The fan design may be either an axial flow propeller or centrifugal blower. Also may be applied as induced draft or forced draft. Noticing that the induced type requires less power for same result.

Fills:

Is the heart of the cooling tower. The fill must provide good water-air contact area, high rates of heat and mass transfer and low air flow resistance. The fill also must be strong and deterioration resistant. The fill has mainly two forms

− Splash fill: breaks falling water into small drops. This Type is made of bars stacked in desks and may be narrow-edged, square bars, rough bars and grids. Different materials are used, such as redwood, high-impact polystyrene or polyethylene,

− Film fill: is made of vertical sheets that have a rough adsorbent surface and good wetness of water that allows water to fall as a film over the vertical surface. Film fill has different forms and materials; redwood battens, cellulose corrugated sheets, asbestos cement and waveform plastic.

Water Basin:

Is situated beneath the tower, collects and strains the water before pumped back to the circulating system. Large utility tower basins are generally made of concrete. Water leaves the basin via sloped canal at the bottom and through screens that prevent dust and foreign materials from entering the pump.

4. Water Treatment

The large variety of alternative construction materials allows users to match unit construction to the water quality available for their systems, while helping to protect the tower from temporary upsets. Water treatment programs must be designed for three requirements:

1. Scale control;

2. Protection of system components against corrosion; and

3. Control of biological contaminants, such as Legionella pneumophilia, the bacterium that causes Legionnaires' disease.

The first two requirements help to ensure energy efficiency and longevity of the cooling system, while the third ensures safe operation.

Biological control is relatively easy to accomplish and is essential to the safe operation of the tower. Cooling towers can collect and concentrate airborne dirt and debris over time. To control this buildup, the cooling tower should be located so as to minimize contaminant induction and a proper blowdown rate should be maintained. Sidestream filters or separators have proven valuable in this regard by effectively removing dirt and debris from the tower water. These devices are coupled with a basin-sweeping nozzle package, which is available either as original equipment in the tower or as a field-installed aftermarket item. Cleaner tower water makes water treatment regimens more effective while keeping the cooling loop cleaner, saving energy, reducing maintenance, and improving reliability of the entire cooling system.

Literature review

In this chapter we will introduce the specifications of the cooling tower educational stand that manufactured by different companies like Gunt, Armfield, P.A. Hilton, Edibon.

1. Gunt

Fig. (2-1) Gunt cooling tower educational stand.

Column: Dimensions: 150x150x630 mm Pacing density: 110 m2/m3 Orifice diameter: 80 mm Approx. weight: 5 Kg Heaters:

3 stages 0.5-1-1.5 KW. Thermostat switches off at 50⁰c.

Fan:

Radial fan: - Power consumption 0.25 KW. -max. Differential pressure 430 pa. -max. Flow rate 13 m3/min.

-Power consumption: 0.7 KW. -max. Head: 34 m.

-max. Flow rate: 34 L/min.

Instrumentation:

-Temp. Sensors at air inlet &outlet. -Temp Sensors at water inlet& outlet. -Water flow rate sensor.

-Humidity sensors at air inlet& outlet.

Dimensions: Height: 1.228 m. Length: 1.11 m. Width: 0.46 m. Weight: approx. 90 Kg. Service required: Electrical: -230 v, 50/60 HZ, 1 phase. or -230 v, 60 HZ, 3 phases.

Computer& Data acquisition:

Fig. (2-2) Armfield cooling tower educational stand.

Column:

Dimensions:150x150x600 mm Pacing density:110 m2/m3 (10 plates)

Heaters:

Centrifugal fan: Maximum air flows: 0.06 Kg/s-1

Instrumentation:

-thermocouple with digital read out.

-Variable area flow meter with control valve.

-Inclined manometer for orifice differential pressure measurement.

Dimensions: Height: 1.2 m. Length: 0.95 m. Width: 0.6 m. Weight: approx. 130 Kg. Volume: 0.7 m3. Service required: Electrical: -220-240 v/1 ph/50 HZ. or -120 v/1 ph/60 HZ. Water: 2 L/hr distilled.

Fig. (2-3) P.A.Hilton cooling tower educational stand

Column:

Dimensions: 150x150x60 mm

Pacing density: 110 m2/m3 transparent P.V.C Orifice diameter: 80 mm

Heaters:

0.5 &1 KW

Instrumentation:

-digital temp indicator with channel selector switch for all wet bulb, dry bulb & water temp variable area water temp flow meter & manometer air flow.

Height: 1.12 m. Length: 0.82 m. Width: 0.73m.

Weight: approx. 56 Kg. Gross weight: app. 96 Kg. Volume: 0.76 m3.

Service required:

Electrical: -1.6 KW, 220-240 v, 1 ph, 50 HZ (with earth ground). or -1.6 KW, 110-220 v, 1 ph, 60 HZ (with earth ground). Water: demineralised or distilled approx 2 Kg/hr.

Computer& Data acquisition:

An optional Data Acquisition Upgrade HC892A comprising of an electronic data logger, menu driven software and all necessary transducers, allow all relevant parameters to be simultaneously displayed and recorded on a suitable PC.

Fig. (2-4) Edibon cooling tower educational stand.

Column:

Dimensions: Total surface: 1.915 m2, Height of packaging: 650 mm. Pacing density: 58 m2/m3 (10 plates).

Dimensions: Height: 1.4m. Length: 1 m. Width: 0.45 m. Weight: approx. 100 Kg. Service required:

PCI Data acquisition board (National Instruments) to be placed in a computer slot. Bus PCI. Analog input: Number of channels= 16 single-ended or 8 differential.

Resolution=16 bits, 1 in 65536.

Sampling rate up to: 250 KS/s (Kilo samples per second). Input range (V)= 10V.

Data transfers=DMA, interrupts, programmed I/0. Number of DMA channels=6. Analog output: Number of channels=2.

Resolution=16 bits, 1 in 65536.

Maximum output rate up to: 833 KS/s. Output range(V)= 10V.

Data transfers=DMA, interrupts, programmed I/0. Digital Input/Output:

Number of channels=24 inputs/outputs.

D0 or DI Sample Clock frequency: 0 to 1 MHz. Timing: Counter/timers=2.

Chapter Three

Cooling Tower Design Calculation

1. Column

The column is divided into two parts as follows:

-The column body

The column body Fig. (3.1) is an important component of the cooling tower at which the water and air interface where heat and mass exchange occur.

The column material was manufactured from transparent plastic to allow viewing of water through the system.

It is oppened from endes to allow the water and air movement inside it, also to insert and renise fill from it eassly.

Column dimension estimation:

The inlet air conditions: Tai=35⁰C=308 K. Pai=101.3 kPa. RHi=40%. Fig.(3.1) columnbody ρai =_{R × T}Pai ai Where:

ρai: Air inlet density,kg/m3.

Pai: Air inlet pressure,kPa.

Tai: Air inlet temperature,K.

R: universal constant, ρai =101.3 × 10 3 287 × 308 yields �⎯⎯� ρai = 1.15 kg/m3

Assume air flow rate to be→ V̇_blower = 13 m3/min ṁblower = V̇blower × ρai

ṁ blower = 13_{60 × 1.15} yields

�⎯⎯� ṁ blower = 0.24 kg/s

From psychrometric chart at 35⁰c dry bulb temperature and 40% relative humidity;the humidity ratio ψai=0.01414 kg/kgda and wet bulb temperature wbtai=23.9⁰C.

ṁda = ṁ_{1 + ψ}blower ai

ṁda = _{1 + 0.01414}0.24

mdȧ = 0.238 kg/s

Where: ṁ : Dray air mass flow rate, kg/s. _da

The cooling tower characteristics (KaV/L) specifies the size of the tower necessary to achevie the maximum possible effectiveness.

The cooling tower characteristics,as a whole, are function of cooling range, tower approach, ambient wet bulb temperature and fluid flow ratio.these cooling tower characteristics represents also at the same time the fill characteristics required for a spacified job.the fill characteristics should be equal to the fill performance, which is a function of fluid flow ratio for a given matrix. As the evaluation of the cooling tower characteristics is time consuming procudure, in practice this is avoided by using the charts available by the Cooling Tower institute in Houston. In these charts the tower characteristic are expressed in terms of the cooling range,tower approach, ambient wet bulb temperature and the flow ratio.

Design conditions: - Twi=50⁰C. - Two=45⁰C. - Wbtai=23.9⁰C. - Vw=2 l/min. - ρw=1000 kg/m3. ṁ = Vw ẇ × ρw =2 × 10 −3 60 × 1000 ṁ = 0.0333 kg/s w

Where: V̇_w : Water volumetric flow rate, m3/s. ρw : Water density, kg/m3.

∴ L=0.0333 kg/s. “total water mass flow rate” G=0.238 kg/s. “total air mass flow rate”

L G = L′ G′= 0.0333_{0.238 = 0.14} Where; L′ : Water loading, kg/m2 s. G′ : Air loading, kg/m2 s.

Note:

The cross section area at which the air pass equal to that thwe water pass in counter flow cooling tower so →L G = L′ G′ Approach= Two-Wbtai Approach=35-23.9 Approach=21.1⁰C=38.16 ⁰F. Cooloing Range (CR)=Twi-Two=50-45 CR=5 ⁰C=9 ⁰F.

From the characteristic curves Appendix (6) the required cooling range doesn’t exist, Hence, make interpolation. From Appendix (6) at L′ G′ = 0.14 , Approach=38.16 ⁰F and CR=18 ⁰F=10 ⁰C → KaV L = 0.24 From Appendix (6) at L′ G′ = 0.14, Approach=38.16 ⁰F and CR=22 ⁰F=12.2⁰C → KaV L = 0.27 From Appendix (6) at L′ G′=0.14, Approach=38.16 ⁰F and CR=26 ⁰F=14.4 ⁰C → KaV L = 0.36

By interpolation using Appendix (6) at CR=9 ⁰F=5 ⁰C.

KaV

L = 0.17 →(1)

By using table (3.1) and assuming Height (Y)=3 ft=0.9144m we get; Constants

C=0.5 m=0.09 n=0.91

Substituting in the following equation; K a = c (L)m (G)n K a =0.5 (0.0333)0.09 (0.238)0.91 K a =0.0997 →(2) By substituiting (2) in (1) we get; KaV L = 0.17 0.0997 × V 0.0333 = 0.17 yields �⎯⎯� V = 0.0568 m3 V = A × Y A =0.0568_{0.9144 = 0.062 m}2 A ≅ 0.25 × 0.25 m2

-The column cap

It’s the upper component of the column. The spray nozzle, drift eliminator and the humidity and exit air tempreature sensors are located in the cap.

Hence, the cap hieght mustn’t be long and it’s cross section equal to that of the column body.

The cap dimensions=250×250×200 mm3.

Fig. (3.2) column cap.

-The packing/fill and drift elimenator

The packing(Fig. 3.3) used to increase the area of content between the air and water. The packing surface is corecated of P.V.C material.

The fill spacing shown inFig. (3.4).

The drift elimenator Fig.(3.5) is placed in the air exit way to decrease the water droplets carried by air.

Fig. (3.4) Fill spacing

Fig. (3.3) Packing

Fig. (3.5) Drift eliminator

2. Cooling tower performance

Water: Twi=50⁰C Two=45⁰C ṁ = 0.0333 kg/s w Cpw=4.18 kJ/kg C

Air in: Tai=35⁰C RHai=40% ṁ_da = 0.238 kg/s

From psychrometric chart : Wbtai=23.9⁰C Ψai=0.01414 kg/kgda hai=71.49 kJ/kg Cooling range and approach obtained

CR=Twi-Two=50-45=5⁰C

Approach= Two-Wbtai=35-23.9=21.1⁰C

QCT = ṁ × Cw p,w× CR

Where:

QCT : Cooling tower load.

mẇ : Water flow rate.

Cpw : specific heat at constant pressure

QCT = 0.033 × 4.18 × 5

QCT = 0.7 kW

QCT = ṁda × (hao − hai)

0.7 = 0.238 × (hao − 71.49)

hao = 74.42 kJ/kgda

From psychrometric at h_ao = 74.42 kJ/kg_da and RHao=100%

Tao=23.9⁰C Ψao=0.01877 kg/kgda

ṁevap = ṁda(ψ_ao − ψ_ai)

ṁevap = 0.238(0.01877 − 0.01414)

ṁevap = 1.10194 × 10−3kg/s

ϵ = _{Twi − Wbtai}Twi − Two

ϵ =_{45 − 23.9 × 100}50 − 45 ϵ = 23.697%

3. Tanks

i. Water tank

In the educational stand cooling tower the water tank considered as the heat load component (condenser), water is heated by an immersion heaters fitted from the back of tank. The heaters are metal tubes containing an insulated electric resistance heater which provide heat load about 1.5 kilowatts.

The water return pipe contains twelve holes to provide good mixing of cold and hot water. The tank was attached with eye glass to determine the level of water in the tank.

There is a baffle inside the tank to make good mixing of the hot water and cold water coming from the column.

Tank capacity estimation

𝑄𝑄 = 𝑚𝑚̇ × 𝐶𝐶𝐶𝐶 × ∆𝑇𝑇 𝑚𝑚̇ = 𝜌𝜌 ×𝑉𝑉_𝑡𝑡

Where:

Q: Heaters power, kW 𝑚𝑚̇: Mass flow rate, kg/s

CP: water specific heat, kJ/kg K

ΔT: Temperature difference, ⁰C

ρ: Water density, kg/m3

V: Water volume, m3

t: time need to heat the water, sec.

Q=1.5 kW ∆𝑇𝑇 = 𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 𝑡𝑡𝑡𝑡𝑚𝑚𝐶𝐶𝑡𝑡𝑡𝑡𝑓𝑓𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 𝑡𝑡𝑡𝑡𝑟𝑟𝑡𝑡𝑓𝑓𝑡𝑡𝑡𝑡𝑟𝑟 − 𝑓𝑓𝑓𝑓𝑡𝑡𝑓𝑓𝑡𝑡𝑓𝑓𝑓𝑓𝑓𝑓 𝑡𝑡𝑡𝑡𝑚𝑚𝐶𝐶𝑡𝑡𝑡𝑡𝑓𝑓𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 ∆𝑇𝑇 = 50 − 25 = 25°𝐶𝐶 Cp=4.18 kJ/kg K t=25 min.

Q = 𝜌𝜌 ×𝑉𝑉_{𝑡𝑡 × 𝐶𝐶𝐶𝐶 × ∆𝑇𝑇}

1.5 = 1000 ×_{25 × 60 × 4.18 × 25}𝑉𝑉 𝑦𝑦𝑓𝑓𝑡𝑡𝑓𝑓𝑟𝑟𝑦𝑦�⎯⎯⎯� 𝑉𝑉 = 0.0215 𝑚𝑚3

V ≅ 0.25 × 0.25 × 0.35 m3

The tank dimension = 250 × 250 × 450 mm3

ii. Air Tank

Air tank is designed to deliver the air from the blower also to hold the column and allow air to be introduced into the column.

So its dimensions must be suitable for carrying the column and also not large to force air to accelerate in the column (i.e. velocity is inversely proportional with area).

Design requirements:-

• Air velocity inside the tank doesn’t exceed 4m/s to reduce the friction losses inside the tank.

• Take in consideration that the drain tank dimensions (25*25).

• Air flow upward around drain to the column and the area must be sufficient to the velocity not exceed 4 m/s.

• The air tank must be higher than the water tank to give the chance to support the drain inside to let the water flow the drain to the water tank.

• When the water tank have the water at level 40 cm from the ground and the drain must have at least 7 cm to let air flow from the air tank to the column.

• Hence the air tank will be 50 cm height and then the area around the drain as flow Q = Av

13

60 = A ∗ 4 A = .054167m2

Aaround drain + Adrai n = 0.341 ∗ 0.341

Let the air tank dimensions to be 0.4 ∗ 0.4 ∗ 0.5 m. And at this condition.

v =_0.4213_{− 0.35}�60 ₂ = 2.222 m s⁄ Acceptable velocity.

iii. Make up tank

Is used to supply the system by the water loosest due to evaporation, drift, and blow down. The makeup water is piped to the water tank and at the end of the pipe a float valve exists to keep water level in the water tank constant.

Assume that the makeup tank support the system with makeup water for 1.5 hour, so the tank capacity can be calculated as follows.

ṁevap =ρ × Vmakeup_t 1.1662 × 10−3 ₌1000 × Vmakeup 1.5 × 60 × 60 yields �⎯⎯� Vmakeup = 6.3 × 10−3m3 Vmakeup = 18.5 × 18.5 × 18.5 cm3

So let the makeup tank dimensions to be 20×20×20 cm3.

iv. Drain tank

A tank that located in the air chamber under the column to collect the cooled water from the column and return it back to the water tank.

The tank is designed to be with inclined base to accelerate the water over it to return quickly to the water tank to be heated and recirculated.

Assume that the recirculated water to be stored in the drain tank for 2.5 minute so the drain tank capacity can be calculated as follows.

ṁcirculated =ρ × V_tdrain

0.0322 =1000 × V_{2.5 × 60} drain yields�⎯⎯� Vdrain = 0.005 m3

The drain tank dimensions are shown in figure (3.2) the base inclination is to force the water to be discharged from the pipe.

4. Piping system and pump

-piping system

Piping system conveys water between tanks to complete circulation. Piping system includes:

• Pipe • Fittings

- Three elbows. - One nibble. - Two boshes.

- Two screwed union. - One T joint.

• Orifice plate with flanges. • Valves - Check valve. - Gate valve. - Float valve. Drain line :- Design requirements:-

• Water velocity doesn’t exceed 0.07 m/sec • Water flow rate 2lit/min

Hence when V=0.07m/sec & 𝑚𝑚_𝑤𝑤̇ =(1/30)Kg/sec A=𝑚𝑚𝑤𝑤̇

𝜌𝜌 𝑉𝑉= (1/30) 1000∗0.07

Where 𝑚𝑚_𝑤𝑤̇ is the water flow rate & A is the inner area of the pipe 𝐴𝐴 = 4.7619 ∗ 10−4 _𝑚𝑚2

𝐷𝐷 = �4.7619 ∗ 10−4_∗4

𝜋𝜋 = 0.0246 𝑚𝑚

The nearest standard diameter 𝐷𝐷 = 1 𝑓𝑓𝑓𝑓 = 0.0254𝑚𝑚

Losses W.R.T. the velocity :

ℎ𝑓𝑓 = ℎ𝑓𝑓𝑡𝑡𝑓𝑓𝑒𝑒𝑒𝑒𝑤𝑤 + ℎ𝑓𝑓𝐶𝐶𝑓𝑓𝐶𝐶𝑡𝑡 + ℎ𝑓𝑓𝑒𝑒𝑡𝑡𝑓𝑓𝑓𝑓𝑓𝑓𝑜𝑜𝑡𝑡

ℎ𝑓𝑓𝐶𝐶𝑓𝑓𝐶𝐶𝑡𝑡 =

𝐹𝐹 𝐿𝐿 𝑉𝑉2

2 𝑔𝑔 𝐷𝐷 Where L is the pipe length & 𝐹𝐹 = 1

�2 log37_𝑅𝑅�2 Also 𝑅𝑅 = 𝐾𝐾 𝐷𝐷= .1 .0254 F = 0.26405 𝑦𝑦𝑡𝑡𝑡𝑡𝑓𝑓𝑓𝑓𝑔𝑔ℎ𝑡𝑡 𝑓𝑓𝑓𝑓𝑓𝑓𝑡𝑡 𝑓𝑓𝑒𝑒𝑦𝑦𝑦𝑦𝑡𝑡𝑦𝑦 = 2.0634 ∗ 10−3

For the orifice with 𝑓𝑓 = 12 ℎ𝑒𝑒𝑓𝑓𝑡𝑡𝑦𝑦 Design requirements:-

Orifice total area > pipe area.

For holes exit velocity < in pipe velocity

Let (1.25) * pipe area = ∑ holes area 𝐴𝐴ℎ𝑒𝑒𝑓𝑓𝑡𝑡𝑦𝑦 = (1.25)𝜋𝜋_{4 0.0254}2

𝐴𝐴_ℎ𝑒𝑒𝑓𝑓𝑡𝑡𝑦𝑦 = 6.334810−4_𝑚𝑚2

𝑡𝑡ℎ𝑡𝑡 𝑟𝑟𝑓𝑓𝑓𝑓𝑚𝑚𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 𝑒𝑒𝑓𝑓 𝑡𝑡𝑓𝑓𝑜𝑜ℎ ℎ𝑒𝑒𝑓𝑓𝑡𝑡 = 8.2 ∗ 102_𝑚𝑚

Which gives a velocity 𝐴𝐴_{ℎ𝑒𝑒𝑓𝑓𝑡𝑡} ∗ 𝑣𝑣 = 𝑄𝑄_{ℎ𝑒𝑒𝑓𝑓𝑡𝑡} = 𝑟𝑟𝑡𝑡𝑒𝑒𝑡𝑡

𝑓𝑓

Check the velocity through each hole

𝑣𝑣 = 𝑄𝑄𝑡𝑡𝑒𝑒𝑡𝑡_�𝑓𝑓 𝐴𝐴ℎ𝑒𝑒𝑓𝑓𝑡𝑡 = 0.0525 < 𝑣𝑣𝐶𝐶𝑓𝑓𝐶𝐶𝑡𝑡 𝑚𝑚 𝑦𝑦⁄ ℎ𝑓𝑓 =𝑘𝑘𝑣𝑣 2 2𝑔𝑔 + 𝑓𝑓𝑓𝑓𝑣𝑣2 2𝑔𝑔𝐷𝐷 + 𝑓𝑓𝑘𝑘(𝑣𝑣 ℎ𝑒𝑒𝑓𝑓𝑡𝑡⁄ )2_{∗ 2} 2𝑔𝑔 0.29 ∗ (0.06968)2 2 ∗ 9.81 + 2.0634 ∗ 10−3+ 12 ∗ 1 ∗ (0.0525)2_{∗ 2} 2𝑔𝑔 ℎ𝑡𝑡𝑒𝑒𝑡𝑡 = 6.1717 ∗ 10−3 𝑚𝑚

Losses in make up tank:- 𝑚𝑚𝑡𝑡𝑣𝑣. = 𝑚𝑚𝑚𝑚𝑡𝑡𝐶𝐶. = 4.635 ∗ 10−4𝐾𝐾𝑔𝑔 𝑦𝑦⁄ 2 𝑓𝑓𝑒𝑒𝑡𝑡 1 2� "𝑣𝑣𝐶𝐶𝑓𝑓𝐶𝐶𝑡𝑡 𝑟𝑟𝑓𝑓𝑓𝑓𝑚𝑚𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 𝑣𝑣 = 4 ∗ 4.635 ∗ 10−4 1000 ∗ 𝜋𝜋4 �12 ∗ 0.0254� 2 𝑣𝑣 = 3.659 ∗ 10−3_{𝑚𝑚 𝑦𝑦⁄} 𝑓𝑓𝑒𝑒𝑡𝑡 𝑡𝑡ℎ𝑡𝑡 𝐶𝐶𝑓𝑓𝐶𝐶𝑡𝑡 𝑓𝑓𝑡𝑡𝑓𝑓𝑔𝑔𝑡𝑡ℎ = 0.5 𝑚𝑚 𝑅𝑅 =_{0.0254 = 7.864}0.1 ∗ 2 𝑓𝑓 = 1 �2 log 37_{𝑅𝑅 �}2 = 0.554 ℎ𝑓𝑓 =𝑓𝑓 ∗ 𝑓𝑓 ∗ 𝑣𝑣 2 2𝑔𝑔𝐷𝐷 = 0.554 ∗ 0.5 ∗ 3.6592_{∗ 10}−6 2 ∗ 9.81 ∗ 0.5 ∗ 0.0254 = 1.487 ∗ 10−5 𝑚𝑚 ℎ𝑣𝑣𝑓𝑓𝑓𝑓𝑓𝑓𝑣𝑣𝑡𝑡𝑦𝑦 = 0.12 ∗ (3.659 ∗ 10 −3₎2 2 ∗ 9.81 = 8.18855 ∗ 10−8 𝑚𝑚 ℎ_{𝑓𝑓𝑡𝑡𝑒𝑒𝑡𝑡} = ℎ𝑓𝑓𝐶𝐶 + ℎ𝑓𝑓𝑣𝑣 = 1.4952 ∗ 10−5 𝑚𝑚

Pump discharge pipe head loss

Total head losses

𝐻𝐻𝑓𝑓 = ℎ_{𝑓𝑓𝐶𝐶𝑓𝑓𝐶𝐶𝑡𝑡} + ℎ𝑓𝑓𝑜𝑜ℎ𝑡𝑡𝑜𝑜𝑘𝑘𝑣𝑣𝑓𝑓𝑓𝑓𝑣𝑣𝑡𝑡 + ℎ𝑓𝑓𝑔𝑔𝑡𝑡𝑡𝑡𝑣𝑣𝑓𝑓𝑓𝑓𝑣𝑣𝑡𝑡 + ℎ𝑓𝑓𝑒𝑒𝑡𝑡𝑓𝑓𝑓𝑓𝑓𝑓𝑜𝑜𝑡𝑡 + ℎ𝑓𝑓𝑇𝑇 + ℎ𝑓𝑓𝑡𝑡𝑡𝑡𝑒𝑒𝑒𝑒𝑡𝑡𝑡𝑡 ℎ𝑒𝑒𝑦𝑦𝑡𝑡 + ℎ𝑓𝑓𝑓𝑓𝑒𝑒𝑛𝑛𝑛𝑛𝑓𝑓𝑡𝑡 ℎ𝑓𝑓𝐶𝐶𝑓𝑓𝐶𝐶𝑡𝑡 = 𝑓𝑓𝑓𝑓𝑣𝑣2 2𝑔𝑔𝐷𝐷 𝑓𝑓 = 1 �2 log 37_{𝑅𝑅 �}2 = 0.26405 , 𝑤𝑤ℎ𝑡𝑡𝑡𝑡𝑡𝑡 𝑅𝑅 =_0.02540.1 ℎ𝑓𝑓𝐶𝐶𝑓𝑓𝐶𝐶𝑡𝑡 = 0.26405 ∗ 1.8 ∗ 0.06572 2 ∗ 9.81 ∗ 0.0254 = 4.1167 ∗ 10−3 𝑚𝑚

ℎ𝑓𝑓𝑜𝑜ℎ𝑡𝑡𝑜𝑜𝑘𝑘𝑣𝑣𝑓𝑓𝑓𝑓𝑣𝑣𝑡𝑡 = 𝑘𝑘 ∗ 𝑣𝑣2 2𝑔𝑔 = 2.5 ∗ 0.06572 2 ∗ 9.81 = 5.5 ∗ 10−4 𝑚𝑚 ℎ𝑓𝑓𝑔𝑔𝑡𝑡𝑡𝑡𝑣𝑣𝑓𝑓𝑓𝑓𝑣𝑣𝑡𝑡 = 𝑘𝑘𝑣𝑣2 2𝑔𝑔 , 𝑤𝑤ℎ𝑡𝑡𝑡𝑡𝑡𝑡 𝑘𝑘 𝑓𝑓𝑡𝑡 𝑒𝑒𝑓𝑓𝑡𝑡 𝑟𝑟𝑡𝑡𝑓𝑓𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡 𝑒𝑒𝐶𝐶𝑡𝑡𝑓𝑓𝑟𝑟 ℎ𝑓𝑓𝑔𝑔𝑡𝑡𝑡𝑡𝑣𝑣𝑓𝑓𝑓𝑓𝑣𝑣𝑡𝑡 = 24 ∗ 0.06572 2 ∗ 9.81 = 5.28 ∗ 10−3 𝑚𝑚 ℎ𝑓𝑓𝑒𝑒𝑡𝑡𝑓𝑓𝑓𝑓𝑓𝑓𝑜𝑜𝑡𝑡 = 8.2(0.0659)2 2 ∗ 9.81 = 1.8 ∗ 10−3 𝑚𝑚 ℎ𝑓𝑓𝑇𝑇 = 0.9(0.26287)2 2 ∗ 9.81 = 3.16975 ∗ 10−3

Head losses across the nozzle by using of hand pump and measuring the pressure in the nozzle line we find that ΔP=2 bar

Using B.E. 𝐶𝐶1 𝜌𝜌𝑔𝑔 + 𝑛𝑛1+ 𝑣𝑣12 2𝑔𝑔 = 𝐶𝐶2 𝜌𝜌𝑔𝑔 + 𝑛𝑛2+ 𝑣𝑣22 2𝑔𝑔 + ℎ𝑓𝑓 (𝐶𝐶1− 𝐶𝐶2) 𝜌𝜌𝑔𝑔 + (𝑛𝑛1− 𝑛𝑛2) + 𝑣𝑣12− 𝑣𝑣22 2𝑔𝑔 = 𝐻𝐻𝑓𝑓 𝑤𝑤ℎ𝑡𝑡𝑡𝑡𝑡𝑡 𝑣𝑣1 = .0657 𝑚𝑚 𝑦𝑦⁄ 𝑣𝑣2 = 18.83672 𝑚𝑚 𝑦𝑦⁄ 𝐷𝐷1 = 2.54 𝑜𝑜𝑚𝑚 𝐷𝐷2 = 0.15 𝑜𝑜𝑚𝑚 𝐻𝐻𝑓𝑓 = 1.763 𝑚𝑚 𝐻𝐻𝑓𝑓𝑡𝑡𝑒𝑒𝑡𝑡 = (4.1167 + 0.55 + 5.28 + 1.8 + 3.16975) ∗ 10−3 + 1.763 𝐻𝐻𝑓𝑓𝑡𝑡𝑒𝑒𝑡𝑡 = 1.77791645 𝑚𝑚

-pump

Used to circulate the water through the system and also to overcome the losses in the pipes and valves.

the suitable Pump specifications are: • Power 0.5 HP. • Max. Flow 2.16 m3/hr. • Min. Flow 0.6 m3

/hr. • Max. delivery head 32.5 m. • Min. delivery head 5 m. • Power supply 230v, 50Hz.

4. Blower and Butter fly valve

-

The Blower has to overcome the system resistance, which is defined as the pressure loss, to move the air. The Blower output or work done by the Blower is the product of air flow and the pressure loss.

Specifications: Power supplies 230 V-50 HZ. • Power 100 W. • Flow rate 740 m3

/hr. • Pressure 473 Pa.

Fig. (3.3) Blower main dimensions. Blower

dimensions:

Type of ventilator Size, mm Mass,

Kg Φ d DΦ C A B L E

-Butterfly valve

A butterfly valve figure (3.4) is from a family of valves called quarter-turn valves. The "butterfly" is a metal disc mounted on a rod. When the valve is closed, the disc is turned so that it

completely blocks off the passageway. When the valve is fully open, the disc is rotated a quarter turn so that it allows an almost unrestricted passage of the process fluid. The valve may also be opened incrementally to regulate flow.

The butter fly used was fabricated to suit the blower suction diameter.

Fig (3.4) butterfly valve

5. Water Injection Nozzles

Two spray nozzles attached to sprinkler pipe.

The nozzle atomizes water to increase the heat exchange and mass transfer between air and water; also the nozzle must provide good water distribution over the column fill.

Fig(3.5) spray nozzles

The nozzle spray shape is cone 30⁰ angles with vertical.

6. Stand

The table which will carry all cooling tower components.

Length(cm) Width(cm) Height(cm)

Air Tank 40 40 50 Water Tank 25 25 45 Fits and Tolerance 10 10 - Display and Screen 100 - - Column 25 25 150 Connection Pipe 10 - - Stand 200 50 182

∑Length= 175 Cm (Length of air tank) < Length of Stand Max Width = 40 Cm (width of air tank) < width of Stand Max Height = 150 Cm (height of column) < Height of Stand 𝑇𝑇𝑒𝑒𝑡𝑡𝑓𝑓𝑓𝑓 𝑊𝑊𝑡𝑡𝑓𝑓𝑔𝑔ℎ𝑡𝑡 = 𝑤𝑤𝑡𝑡𝑓𝑓𝑓𝑓𝑘𝑘𝑦𝑦 + 𝑤𝑤𝐶𝐶𝑡𝑡𝑚𝑚𝐶𝐶 + 𝑤𝑤𝐶𝐶𝑡𝑡𝑚𝑚𝐶𝐶 + 𝑤𝑤𝑟𝑟𝑓𝑓𝑦𝑦𝐶𝐶𝑓𝑓𝑓𝑓𝑦𝑦 + 𝑤𝑤𝑤𝑤𝑒𝑒𝑒𝑒𝑟𝑟 + 𝑤𝑤𝑦𝑦𝑡𝑡𝑓𝑓𝑓𝑓𝑟𝑟

𝑇𝑇𝑒𝑒𝑡𝑡𝑓𝑓𝑓𝑓 𝑊𝑊𝑡𝑡𝑓𝑓𝑔𝑔ℎ𝑡𝑡 = 5 + 7 + 33.5 + 5 + 30 + 40 = 120.5𝐾𝐾𝑔𝑔 Max Weight for wheel=200Kg

𝑇𝑇𝑒𝑒𝑡𝑡𝑓𝑓𝑓𝑓 𝑊𝑊𝑡𝑡𝑓𝑓𝑔𝑔ℎ𝑡𝑡 < Max Weight for wheel 𝑆𝑆𝑓𝑓𝑓𝑓𝑡𝑡 𝐷𝐷𝑡𝑡𝑦𝑦𝑓𝑓𝑔𝑔𝑓𝑓

Measurement devices and data acquisition system

1. Temperature measurements

Three basic types of temperature measuring sensors • Thermocouples – Self Generating

- Two metals joined together at a junction which generate a very small voltage (millivolts) which is a function of temperature. Voltage goes up as temperature goes up.

• Resistance Temperature Devices (RTDs) – Resistive

- Measuring the change of resistance in a piece of metal due to temperature. Resistance goes up as temperature goes up.

• Thermistors – Resistive

- Measuring the change in resistance in a semiconductor material due to temperature. Resistance goes down as temperature goes up.

• Other methods exist – such as infrared detection and bimetallic strips

Characteristic Thermocouple RTD Thermistor

Excitation Self-Generating External Required External Required

Output Signal millivolts Typically volts for

coarse measurements.. Can be millivolts for high accuracy

Typically Volts Can be millivolts for high accuracy.

Ground/Noise/Error Floating,

susceptibility to noise

Grounded, susceptible to lead wire resistance

Grounded,

susceptible to lead wire resistance

Signal Increase with

temperature Increases with temperature Decreases with temperature if NTC, Increases with PTC Range - 200 deg c to +1200 deg C depending on type -200 to +800 DegC for platinum -100 to + 200 DegC

Pro’s Inexpensive and

rugged

Stability and linearity High Sensitivity

Con’s Floating measurement

requires careful attention

Expense, Slow Response Time, Low Sensitivity, Self Heating Smaller Temperature Range, NonLinear, Self Heating

Resistance Temperature Detectors (RTDs) – a device used to relate change in resistance to change in temperature. Typically made from platinum, the controlling equation for an RTD is given by:

𝑅𝑅𝑇𝑇 = 𝑅𝑅𝑜𝑜[1 + 𝛼𝛼 (𝑇𝑇 − 𝑇𝑇𝑜𝑜)]

RT is the resistance of the RTD at temperature T (measured in °C)

R0 is the resistance of the RTD at the reference temperature T0 (usually 0°C)

𝛼𝛼 s the temperature coefficient of the RTD

Platinum wire-wound detectors comprise a pure platinum wire wound into a miniature spiral and located within axial holes in a high purity alumina rod. The freedom of movement of the platinum wire gives good long term stability.

Specifications: Ro 100 Ohms

Temperature range -200 to +800°C

PT100

Fig. (4.1) Resistance Temperature curve for PT 100.

Is composed of a resistance where its ohm varies with the humidity of air.

General Description

The EWHS 280 humidity sensor is a probe designed to be connected to a humidity measuring device. Output signal is a current signal (4...20 mA).

Specifications

Power input 9 – 28 Volt DC Measurement range 15 – 100 % Maximum Load 250 Ohm Accuracy +/- 5%

3. Flow Measurements

3.1 Pipe Flow rate Meters

Fig. (4.2) orifice plate

Three of the most common devices used to measure the instantaneous flow rate in pipes are

The orifice meter, the nozzle meter, and the Venturi meter. Each of these meters operates on the principle that a decrease in flow area in a pipe causes an increase in velocity that is accompanied by a decrease in pressure. Correlation of the pressure difference with the velocity provides a means of measuring the

flowrate. In the absence of viscous effects and under the assumption of a horizontal pipe, application of both the Continuity and Bernoulli equations between points (1) and (2) shown in the following figure gave

Q

= A

V

= A

�

A typical orifice meter is constructed by inserting between two flanges of a pipe a flat plate with a hole. The pressure at point (2) within the vena contracta is less than that at point (1). Nonideal effects occur for two reasons. First, the vena contracta area, (A2), is less than the area of the hole, (A0), by an unknown amount.

Thus, A2=KA0, where Cc is the contraction coefficient (Cc<1). Second, the swirling flow and turbulent

motion near the orifice plate introduce a head loss that cannot be calculated theoretically. Thus, an orifice discharge coefficient, K, is used to take these effects into account. That is

𝑄𝑄 = 𝐾𝐾𝑄𝑄𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖 = 𝐾𝐾𝐴𝐴0�2∆𝑃𝑃_𝜌𝜌

Where 𝐴𝐴₀ = 𝜋𝜋𝑖𝑖2/4 is the area of the hole in the orifice plate. The value of C0 is a function of 𝛽𝛽 = 𝑖𝑖/𝐷𝐷

and the Reynolds number = 𝜌𝜌𝜌𝜌𝐷𝐷/𝜇𝜇 , where 𝜌𝜌 = 𝑄𝑄/𝐴𝐴₁. Typical values of C0

Fig (4.4) Typical pipe flow meter geometry.

(i.e., the placement of the pressure taps, whether the orifice plate edge is square or beveled, etc.). Very precise conditions governing the construction of standard orifice meters have been established to provide the greatest accuracy possible.

Orifice Design

Operating flow rate 𝜌𝜌̇ = 2 𝑖𝑖/𝑚𝑚𝑖𝑖𝑚𝑚

= 3.333 ∗ 10−5 _𝑚𝑚3_{/𝑠𝑠𝑖𝑖𝑠𝑠}

𝐷𝐷 = 25.4 𝑚𝑚𝑚𝑚 𝛽𝛽 = 0.2 =_𝐷𝐷𝑖𝑖

We assumed β a small value in order to obtain a large pressure drop over the orifice giving a more clearer reading by the differential pressure transmitter.

𝐴𝐴𝑃𝑃𝑖𝑖𝑃𝑃𝑖𝑖 = 𝜋𝜋₄(𝐷𝐷)2 = 5.0671 ∗ 10−4 𝑚𝑚2

𝜌𝜌𝑃𝑃𝑖𝑖𝑃𝑃𝑖𝑖 = 𝜌𝜌·_{𝐴𝐴 = 0.06578 𝑚𝑚/𝑠𝑠𝑖𝑖𝑠𝑠}

𝐴𝐴𝑜𝑜𝑜𝑜𝑖𝑖𝑜𝑜𝑖𝑖𝑠𝑠𝑖𝑖 = 𝜋𝜋₄(𝑖𝑖)2 = 2.02683 ∗ 10−5 𝑚𝑚2

𝜌𝜌𝑜𝑜𝑜𝑜𝑖𝑖𝑜𝑜𝑖𝑖𝑠𝑠𝑖𝑖 = 1.645 𝑚𝑚/𝑠𝑠

𝑅𝑅𝑖𝑖0 = 𝜌𝜌𝜌𝜌𝑜𝑜𝑜𝑜𝑖𝑖𝑜𝑜𝑖𝑖𝑠𝑠𝑖𝑖_𝜇𝜇 𝑖𝑖= 988 ∗ 1.645 ∗ 0.00508_{5.47 ∗ 10−4} = 15090.04

From chart (according to ASME standard) 𝛽𝛽 = 0.2 𝑅𝑅𝑖𝑖 = 15090.04 Therefore 𝐾𝐾 = 0.605 𝑄𝑄 = 𝐾𝐾𝐴𝐴𝑜𝑜𝑜𝑜𝑖𝑖𝑜𝑜𝑖𝑖𝑠𝑠𝑖𝑖�2∆𝑃𝑃_𝜌𝜌 𝜌𝜌̇ = 0.605 ∗ 2.0268 ∗ 10−5_{∗ �}2∆𝑃𝑃 988

3.33 ∗ 10−5 _{= 5.5169979 ∗ 10}−7_{√∆𝑃𝑃}

∴ ∆𝑃𝑃 = 3643.2 𝑃𝑃𝑖𝑖 = 3.6432 𝐾𝐾𝑃𝑃𝑖𝑖 Theoretical reading = 0.53 psi

Error ± 2 %

Error = 5 * 0.02 = 0.1 Actual reading = 0.53 ± 0.1 = 0.63

= 0.43 (for 2 l/min water) Error analysis = 0.1

0.53 = 18.8%

4- Displays

Microprocessor based and fully programmable process controllers for single setpoint applications; the output provides ON-OFF and analog output 4-20 mA

Fig.(4.7) schematic diagram for DAQ card connection

It is a basic A/D converter that allows a personal computer to control its actions, also computer acquires the values of the Analog or digital signals being processed. A data acquisition card plugs directly into a PC bus, like PCI, or USB….etc.

Analog Signal – any value continuously

within the range, continuous over time

Digital Signal – Maps to one of eight discrete values at only has those values at discrete times that it was sampled and

converted

Elements of an End to End Data Acquisition System

• Transducer/Sensor

– May generate their own electrical signal (thermocouple or piezoelectric) or require external excitation (power)

– Converts one physical Quantity Under Measurement (QUM) into another – Typical output is in volts to microvolts

• Data Acquisition Unit (DAU) – Samples and holds – Digitizes

– Multiplexes (combines with other measurements) – Converts for transmission

– Transmits

– Typical output is in binary digits (bits) • Recording, Storage and Display

• Transducer/Sensor is Platinum Resistance Temperature Detector (RTD)

• Signal Conditioning is power supply for excitation (power) and resistor to complete the circuit • Data Acquisition fig. (4.9)Unit is the NI 6008

• It communicates over a Universal Serial Bus (USB) to the laptop computer • The laptop Computer is running a LabVIEW Virtual Instrument (VI) • Example is RTD Acq One Sample w loop and waveform chart.vi

Fig. (4.8) Example for temperature measurement

Unit installation

LabVIEW (Laboratory Virtual Instrument Engineering Workbench) is a graphical programming language that uses icons instead of lines of text to create applications. In contrast to text-based programming languages, where instructions determine the order of program execution, LabVIEW uses dataflow programming, where the flow of data through the nodes on the block diagram determines the execution order of the VIs and functions. VIs, or virtual instruments, are LabVIEW programs that imitate physical instruments.

In LabVIEW, you build a user interface by using a set of tools and objects. The user interface is known as the front panel. You then add code using graphical representations of functions to control the front panel objects. This graphical source code is also known as G code or block diagram code. The block diagram contains this code. In some ways, the block diagram resembles a flowchart

In figure (4.11), the sensor sends signals to the display unit, in turn the display transmits an analog output signal 4 ~ 20 mA, a resistance is needed since the DAQ only accepts Voltage analog signal of range -10 ~ 10 Volt .

Preferring a range from 1 ~ 5 Volt a resistance is required to be put in parallel. Returning to Ohm’s law

𝜌𝜌 = 𝐼𝐼 × 𝑅𝑅 Also assuming minimum values for both V and I

1 = 4 × 10−3 _{× 𝑅𝑅}

Therefore the required resistance will be

𝑅𝑅 = 250 Ω

Due to there is no standard resistance 250 Ω, we selected the nearest available resistance 270 Ω. By recalculating the voltage range, it varied to become 1.08 ~ 5.4 Volt.

We programmed the display unit to transmit a minimum signal of 4 mA corresponding to 10 °C, and a maximum signal of 20 mA corresponding to 70°C.

Fig(4.11) wiring diagram for temperature measurements

For the humidity sensor there was no display with analog output available in the market and the available sensor had one terminal wire, therefore we added a resistance in series with joining the resistance terminals with the sensor’s output wires and the display, creating a voltage variation across the resistance terminals transmitted to the DAQ. Figure (4.12 ) illustrates the previous operation.

Fig. (4.13) solving the analog output problem for the humidity sensors

1. For programming temperature values on LABVIEW, we programmed the DAQ card to translate the voltage signal to temperature values, having a linear relation between voltage and temperature

𝑇𝑇 = 𝑖𝑖𝜌𝜌 + 𝑏𝑏

a,bconstants Ttemperature (°C) Vvoltage

Initial conditions:

I. V=1.08 Volt at T=10°C II. V=5.4 Volt at T=70°C

10 = 1.08𝑖𝑖 + 𝑏𝑏 (1) 70 = 5.4𝑖𝑖 + 𝑏𝑏 (2) By solving equations (1) and (2)

a=13.8889 b= -5

Therefore the final equation is

𝑇𝑇 = 13.8889𝜌𝜌 − 5

Ω. In order to avoid producing high ampere causing damage to sensor. So the resistance added is 300Ω. Determining the maximum and minimum voltages, and returning to Ohm’s law

𝜌𝜌 = 𝐼𝐼 × 𝑅𝑅 𝜌𝜌𝑚𝑚𝑖𝑖𝑚𝑚 = 𝐼𝐼𝑚𝑚𝑖𝑖𝑚𝑚 × 𝑅𝑅 𝜌𝜌𝑚𝑚𝑖𝑖𝑚𝑚 = 3 × 10−3 × 300 𝜌𝜌𝑚𝑚𝑖𝑖𝑚𝑚 = 0.9 𝜌𝜌𝑜𝑜𝑖𝑖𝑉𝑉 𝜌𝜌𝑚𝑚𝑖𝑖𝑚𝑚 = 18 × 10−3× 300 𝜌𝜌𝑚𝑚𝑖𝑖𝑚𝑚 = 5.4 𝜌𝜌𝑜𝑜𝑖𝑖𝑉𝑉

Due to signal splitting there are some errors in the two signals, one for display and other for data acquisition card. So calibration must be done for both of them by an accurate device.

For programming humidity values on LABVIEW, we programmed the DAQ card to translate the voltage signal to temperature values, having a linear relation between voltage and temperature

𝑅𝑅𝑅𝑅% = 𝑖𝑖𝜌𝜌 + 𝑏𝑏

a,bconstants RHRelative humidity (%) Vvoltage

Initial conditions:

III. V=0.9 Volt at RH=15% IV. V=5.4 Volt at RH=90%

15 = 0.9𝑖𝑖 + 𝑏𝑏 (1) 90 = 5.4𝑖𝑖 + 𝑏𝑏 (2) By solving equations (1) and (2)

a=16.66667 b= 0

Therefore the final equation is

1. Humidity sensor 1.1. Inlet humidity sensor

Humidity sensor without analog output

Humidity sensor with analog output

DAQ reading Hygrometer

57 53 32.66 58.7 65 61 41.01 66.5 70 66 45.834 72 76 72 51.334 78.5 83 79 58.765 84.3 90 85 64.789 91.8 100 95 76.122 100

Fig.(4.17) inlet Humidity sensor calibration table

After updating the humidity sensor to give an output signal to the DAQ card there is a zero error = -4% so we calibrated the display to increase the displayed value about -4% to give the actual reading. Ex: Measured value = 50 % so the display will indicate 54%

In the DAQ reading there is a zero error = -25%, therefore calibrated to increase the indicated value a 25% to give actual reading.

1.2. Outlet humidity sensor

Humidity sensor without analog output

Humidity sensor with analog output

DAQ reading Hygrometer

57 52 29.3453 58.7 65 60 39.014 67.2 70 65 44.134 73.3 76 71 50.334 77.9 83 72 56.765 83.1 90 85 62.789 92.4 100 95 74.724 100

Fig.(4.18) outlet Humidity sensor calibration table

Thermocouple K-Type °C PT 100 class B sensor °C DAQ Reading °C 30 30.2 29.9 40 40.5 40.2 50 50.7 50.6 60 60.5 60.1 70 70.2 70.002 80 80.3 80.07 90 90.7 90.4 100 100 100.04

Fig.(4.19) PT 100 sensor calibration table

We see that the DAQ reading is less than the PT 100 sensor for about 0.3 °C and this is more accurate than the sensor display because Sensor display has a sampling rate for about 10 samples per sec but the DAQ card has sampling rate 1000 samples per sec.

Chapter Five

Bill of Materials and Cost

SERIAL NO. Item no Item name Quan tity Make or Buy Description & Specifications

Material price per each(LE)

total price (LE)

1 100 Stand 1 make steel 790.5 790.5

1.1 101 Frame ₁ make steel 54.55 54.55

1.2 103

wheels 4

buy 4 wheels carry up to 200 Kg

55 220 1.3 105 _{Bords 2} buy _{1.22x2.44 (m)} Formica 350 700

1.4 109 _{Al edges 1} buy Aluminum 30 30

1.5 _{Staneless steel 1} buy _{60x60 cm} st.st 158.4 158.4

1.6 Cutting cup set 1 buy 71.5 71.5

2 200 Tanks make steel 0

2.1 203 _{Metal sheets 1} make steel 186.5 186.5

2.2 _{Gaskets 1} buy 49.5 49.5 2.3 _{Teflon 4} buy 2 8 2.4 _{Silicon 2} buy 45 90 3 300 Heaters 3 buy 0.5 KW,length= ,flange diameter= 290.5 871.5 4 400 _Column 1 make P.V.C 720 720

4.1 401 Column body 1 make dimensions 25x25x113 cm P.V.C 0 0

5 406 cap 1 make dimensions 25x25x20 cm P.V.C 0 0

5.1 500 Metal

connections 6

buy 0

5.2 501 Butter fly valve 1 buy 3'' 60 60

5.3 502 Drain valve 1 buy 0

5.4

Gate valve 1

buy D=3/4'', Oriffice Dia.=20mm

5.5 _{Check valve 1} buy copper 26 26

5.6 _{Float valve 1} buy plastic 15 15

5.7 _{Gelb 3} buy 1.25" iron 26.125 78.375

5.8 _{Gelb 2} buy 1.5" iron 3.3 6.6

5.9 _{Gelb 1} buy 0.5" 20 20

5.11 _{screws+nuts 20} buy iron 4 80

5.11 _{screws+nuts 1} buy _{no. of units=52} st.st. 98.35 98.35

5.7 _{nozzles 2} make copper 60 120

5.8 _{Welding rods 2} buy 27 54

5.11 _{Sight glass 1} buy copper 122 122

5.12 _{Elbow 1} buy 1" , 90 deg. 4.4 4.4

5.13 _{Copper rod 1} buy 19mm Hexagonal copper 45 45

6 Copper rod 1 buy 3mm dia. copper 7 7

7

Blower 1

buy flow rate max.=740 (m^3/hr)

710.7 710.7

7.1 pumping system make 0

7.2 _{pump 1} buy _{P=0.5 hp, Hmax=35 m, Qmax=35 L/min} 230 230

7.3 _{pipes 1} buy _{1.5 m length} steel 35 35

7.4 Hose 1 buy 6 m length, 10 Bar PVC 56.35 56.35

8 Nozzle 1 make copper 120 120

8.1 Electronics buy 0

8.1-1 Displays 6 buy 0

8.1-2 Temp display for

air 2

buy 880 1760

8.1-3 Temp display for

water 2 buy 880 1760 8.2 Humidity display+Sensors 2 buy 2200 4400 8.2-2 sensors buy 0

8.2-4 Water temp

sensor 2

buy

PT 100

platinum 205.7 411.4

8.2-5 _{Orifice Meter 1} buy stainless 1100 1100

8.4 Tempreature Controller 3 buy PT 100 200.2 600.6 8.5 Circuit components 7 buy 0 8.5-1 Main C.B 1 buy 16 16 8.5-2 _{Blower C.B 1} buy 12 12 8.5-3 _{Pump C.B 1} buy 12 12 8.5-4 _{Heaters C.B 1} buy 12 12 8.5-4 _{Displays C.B 1} buy 12 12 Diff. pressure sensor C.B 1 buy 12 12 8.5-5 Contactor 1 buy 46.2 46.2

8.5-6 _{Bridge 1} buy 6 Amperes 5.5 5.5

8.5-7 Leds 13 buy 1.1 14.3 8.5-8 _{Resistors 50} 0.1 5 8.6 Switches 5 buy 11 55 8.7 Data acquisation card 2 buy 1540 3080 8.8 _Cables buy 0

8.8-1 _{Cables ducts 1} buy 15 15

8.8-2 Cable 6x0.22 1 buy 58.75 58.75

8.8-2 wiring 1 buy 6mm dia 45 45

9 Computer buy 0

9.1 LCD screen 1 buy 1155 1155

9.2 _{Desktop 1} buy 0

Project Total Cost 20871.375

Chapter Six

Fabrication procedure

1. Welding

Water tank:

Fig. (6.1) Pipe with twelve nozzles attached to elbow both of 1 inch diameters, welded to the left side of the water tank

Fig. (6.2) Section of water tank showing inner baffle attached by welding, with hole of 1 inch for pump suction pipe (left side in picture)

Fig. (6.3) Attaching the final side containing the positions through which the heaters will be inserted into tank.

Make up tank:

Fig. (6.5) the sides of the makeup tank being welded except the top cover for later internal painting.

Fig. (6.6) Make up tank after painting the internal with epoxy resin and completing welding, appearing in the figure an eye sight glass, four adjustable legs and a lid with air passage through its center.

Air tank and its attached components:

Fig. (6.7) Air tank after complete welding, appearing (on the right) the exit pipe of drain, and (on the left) the opening through which the blower is attached as shown.

Fig. (6.8) Water drain basin, receives the water falling from the column and delivers it to the water tank, the basin is placed inside the air tank.

Fig. (6.9) butterfly handmade with various degrees of opening attached to the blower suction side, all attached to the left side of air tank.

2. Stand fabrication

Fig. (6.10) The stands structure is constructed of bars welded together, with four wheels attached which is capable of carrying the stand holding components weight.

Fig. (6.11) wood boards after being cut to designed dimensions, and the exterior frames which will be attached to the edges to protect the wood.

3. Painting and coating

Fig. (6.13) tanks after painting the first layer (all tanks needed to be coated inside and outside with a primary layer of epoxy to protect it from corrosion).

4. Pipe components and fittings:

Referring to the designs of the pipe line, we cut the pipes with the required lengths (and screwing its ends), then connecting the elbows, screwed union, orifice meter, throttle and check valves.

Fig. (6.15) T joint, screwed union, elbow, nibbles. Fig.(6.16) swing check valve.

Fig. (6.17) Orifice plate, flanges and pipe.

Fig. (6.20) T joint (one branch is attached by the bush showing in the figure, the other branch by the pipe discharge line and the main branch by the Hose.

Fig. (6.21) pump after fixation on the stand and attaching the suction and delivery pipes with their fittings.

Fig. (6.22) The pump delivery line after attaching the fittings and valves.

5.

The Column

The column consists of two main parts; the lower part which holds the fills and the upper part (the cap) which holds the water distributers and drift eliminator.

The column body (lower part):

• The body material is transparent PVC to provide clear view of the actions occurring inside the tower for the students, there are small holders attached on the inner surface of the column to hang the fill on. Also the column bottom is bending with 45⁰ to affirm that all water falls into drain basin. The column appears in Figure (6.23).

• The fill (Fig 6.24) was cut to calculated size and required number of layers, and penetrated with two bars horizontally near the top and one at the bottom, to settle down on the holders inside the column.

Also to confirm uniform distribution of fill layers, stainless strips were added to constrain the fill. Figure (6.25) show the final shape of column body.

Fig. (6.22) column body. Fig. (6.24) The Fill.

The column Cap (upper part):

• The column cap Fig. (6.26) was fabricated similar to the column body, also with adding two opposite holders to carry the eliminator, with adding two opposite holes to install the water spray line.

• The drift eliminator was also fabricated from the same material of the fill, penetrated with three bars to confirm alignment of layers Fig. (6.27).

• The water spray nozzles were attached to a hexagonal pipe of copper vertically, with an external connection to hose supplying income water from main pipe line, and then installed in the cap Fig. (6.28).

Fig. (6.26) The Cap. Fig. (6.27) The drift eliminators attached to the cap.

6.

Stand preparation

Mark the areas required to be cut on the stand to be opened for the following requirements: 1. Pump Suction and delivery pipes holes and drain pipes holes Fig. (6.29).

2. Digital displays openings Fig. (6.30). 3. LCD screen opening Fig (6.31).

4. Control panel switches and indication light holes Fig. (6.32).

Fig. (6.29) pipes holes. Fig. (6.30) digital displays openings.

Fig. (6.32) Control panel holes. Fig. (6.31) LCD opening with circle holes

7. Control panel

Since the project is an educational cooling tower, it was preferred to show the switches on a schematic drawing of the cycle with apparent indication lights. A stainless steel sheet being drilled to pass the switches and indication lights Fig. (6.33), then the schematic drawing was attached to the stainless sheet, finally the switches and lights where installed, and fixed on the stand as shown in figure (6.34).

Fig. (6.33) preparing the stainless steel sheet. Fig. (6.34) control panel final shape.

8. Electronic and Electric devices installation

After preparing the stand install the electronic devices (digital displays, pressure deffrance transmitter, temperature controller), the electric devices (LCD screen, PC) and control panel fig. (6.35).

9. Electric connections

Before connecting any device to electricity, we classified them according to their operating voltage. All devices operate at 220 volt except for the differential pressure transmitter which works at 24 volt. Therefore we used one adapter to convert 220 volt to 24 volt.

We designed the circuit loop by adding a main circuit breaker of maximum load of 40 Ampere at the beginning of the line. Then we branched the main line into five lines, each passing through a suitable circuit breaker each device:-

• Pump, blower, displays and differential pressure transmitter required circuit breakers of 10 ampere.

• Heaters required a circuit breaker of 16 ampere.

Finally we added a switch and indication light in series on the five sub-lines, appearing on the control panel.

(a) (b)

(c)

(d)

10. Components assembly

After preparing all cooling tower educational stand components as shown in previous sections, assembly the components together figures (6.37), (6.38), (6.39) and (6.40).

Fig. (6.37) assemble the air tank with water tank by means of screwed union and pipes.

Fig. (6.39) assemble water tank with makeup tank and insert

the water tank sight glass. Fig. (6.38) assemble air tank with column.

Chapter seven

Tests and results

After installing the educational stand cooling tower take some readings .

Procedure:

1. Turn on the main switch then the main circuit breaker (orange key). 2. Turn the CPU and LCD on.

3. Turn the heaters and displays switches on and wait until reaching the required heating temperature; i.e. when the heaters disconnected by the temperature controller.

4. Turn the blower, differential pressure and pump switches on. 5. Adjust the pump (water) flow rate and blower (air) flow rate. 6. Wait until steady state the take the readings.

7. Repeat the procedure by changing water and air flow rates. 8. Turn off the CPU and all switches.

9. Tabulate the results and calculate the cooling tower performance parameters.

Results:

1- Fix the air flow rate and change water flow rate.

θ ∆P (psi) Two Twi Tai Tao RHo% RHi%

0 0.4 28.1 41.3 28.1 28.8 88 57

0 0.12 27.1 41.4 28.5 28.4 79 57

0 0.03 27.1 41.6 28.6 28.1 78 57

2-Fix the water flow rate and changes the air flow rate.

θ ∆P (psi) Two Twi Tai Tao RHo% RHi%

0 0.22 26.8 42.9 29.6 28.3 79 57

30 0.22 27.5 43.8 29 28.9 79 57