Presentation on Humidification and Cooling Towers

1. Humidification
and
Cooling Tower PRESENTED BY,
SHARIFUL ISLAM
(19ACE021)
DEPARTMENT OF APPLIED
CHEMISTRY AND CHEMICAL
ENGINEERING
BSMRSTU

2. Concept of Humidification
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What is Humidity?
Humidity is the quantity of the moister or water vapor in air or gas.
The mass of vapor carried out by a unit of dry air the ratio is called humidity.
What is Humidification?
Humidification is the process of constituting the water vapor content In a gas.
The process of increasing the water vapor content (humidity) of a gas is known as
humidification. while its reverse operation is known as dehumidification.

3. Definition of some term related with Humidification
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1. Dry-bulb temperature: It is temperature of air measured by a thermometer whose bulb
is dry. Also known as true temperature or ambient temperature.
2. Wet-bulb temperature: Air temperature measured by thermometer which bulb is
covered with moist wick.
3. Humid heat: The humid heat, cH, is the heat energy required to raise the temperature of
unit mass of dry air with the accompanying water vapor by one degree.
4. Dew point: If a vapor-gas mixture is gradually cooled at a constant pressure, the
temperature at which it just becomes saturated is also called its dew point.

4. Definition of some term related with Humidification
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5. Relative Humidity: Relative humidity is the ratio between the partial pressure of water
vapor and the vapor pressure of water at same temperature. Its measurement express
as percentage
6. Absolute Humidity: Absolute humidity is the amount of vapor in a given volume of gas.
Its measurement expressed by mg/L.
7. Humid Volume: It defined as the volume of unit mass of dry air with accompanying
water vapor at given temperature and pressure.
8. Enthalpy: The enthalpy is the measure of heat energy. The enthalpy of a vapor-gas
mixture is the sum of the relative enthalpies of gas and vapor content.

5. Psychrometric Chart
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Psychrometric charts are graphical representations of the psychrometric properties
of air. From this chart the following quantities can be estimated:
1. Humidity (absolute and relative H).
2. Specific volume of dry gas.
3. Enthalpy
4. Humid heat.
5. Dry and wet bulb temperature.
6. Dew and saturation temperature

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Psychrometric Chart
Dew point= 10

7. Cooling Tower
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The cooling tower is one of the most important Device in
chemical Industries. For example When the hot water.
Comes from industry We use Cooling tower to cool it.
Cooling tower is one of the heat exchanger that allows
water and air to come contact with each other the
prepose is to cool down water that get heated in industrial
process.
The purpose of cooling water is to cool relatively warm
water. By contracting with Unsaturated air. The
evaporation of water mainly provides cooling.

8. Working principle of Cooling Tower
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There are many different types of cooling tower, but the cooling tower working principle stay
pretty much the same. Most cooling tower works based on the principle of evaporative cooling.
The water to be cooled is put in contact with the air. Unsaturated air in contact with water tends
to increase its humidity; water evaporates and takes the latent heat of vaporization from itself
and therefore cools down.
A cooling tower is an evaporative type heat exchanger.
Water enters through the top of the tower. Inside there is a filling that improves contact and
promotes the exchange of mass and heat

9. Type of Cooling Tower
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Cooling towers are classified in 3 types based on air draft:
1. Atmospheric cooling tower
2. Natural draft cooling tower
3. Mechanical draft cooling tower
Mechanical draft Cooling towers further more classified in 2 types:
1. Forced draft cooling tower
2. Induced draft cooling tower
Again cooling towers are classified in 2 types based on air flow pattern.
1. Crossflow
2. Counterflow
In this presentation we discus about natural draft cooling tower and 2 types mechanical draft
cooling tower

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Natural Draft Cooling Tower
In this type of cooling tower, fan is not used
for circulating air.
The convection process helps circulate the air
within the tower. Because warm and moist air
naturally comes up and cold dry air goes
down, this creates a continuous cycle of air
without the need for electric consumption.
1. Hot air moves through tower
2. Fresh cool air is drawn into the tower
from bottom No fan required
3. Concrete tower <200 m

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Forced Draft Cooling Tower
In this system, a blower type fan at the intake
(fan located near the bottom and on the side).
An eliminator is used to prevent loss of water
droplets along with the forced air. The fan
forces air into the tower from bottom to top.
In this process the air is pushed by the fan and
so more air contact with water occurs.

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Induced Draft Cooling Tower
this type of cooling tower uses a
mechanical fan. With the use of the fan, the
air is actively blown within the tower. In this
way, the cooling process starts. This is
more effective than the natural draft, but it
is definitely much more expensive.
induced draught cooling tower contains
vertical shaft fan and it is placed at top of the
cooling tower.

13. Thank You
That’s All for today