Cooling Tower
Content
INSTRUCTION MANUAL.
COOLING TOWER
SET UP
DESCRIPTION
SPECIFICATIONS
INSTALLATION REQUIREMENTS
INSTALLATION AND CONNECTIONS
PRECAUTIONS
TROUBLE SHOOTING
EXPREMENTATION
THEORY
OPERATING PROCEDURE’
SYSTEM CONSTANTS
OBSERVATION TABLE
CALCULATIONS
COOLING TOWER.
Aim:
To determine of performance of Cooling Tower.
INTRODUCTION:
The cooling tower is an enclosed device for the evaporative cooling of water
by contact with air.
DESCRIPTION:
1. Casing or shell: This is the structure which encloses the heat transfer
process and also acts as a support for other items.
2. Air inlet and outlet: the position at which air enters and leaves the
tower.
3. Fan: the fan is provided to move the required amount of air through the
water to be cooled.
4. Drift or mist eliminators: These are positioned at or near the air outlet
and present droplets of water from being carried through the tower by
the air stream.
5. Water inlet: This is the point at which water enters the tower.
6. Water distribution system: For maximum effect the water entering the
tower must spread evenly over the top of the packing. It is to achieve
this that the distribution system is used.
7. Packing: In order to provide a large surface area to assist heat transfer
a number of baffles form the packing. Pitch is so arranged that air and
water which is so arranged that air and water which must pass through
it come into direct contact in the process.
8. Tank or sump: This provided at the base of the tower and is often
integral with the casing. Its function is to collect the cooled water
before it is returned to the process which it is cooling.
ANALYSIS OF COOLING TOWER PERFORMANCE:
Meskel has analyzed cooling towers based on Enthalpy Potential difference as
the driving force.
Each particle of water is assumed to the surrounded by a film of air and the
enthalpy difference between the film and surrounding.
driving force for the cooling process.
Air provides the
In the integrated form, the Meskel
equation is:
∫
KaV =
dT
----------- (1)
L
H’ –H
Where K = mass transfer coefficient, Kg/hr m²
a = contact area, m²/m³ of Tower volume.
L = Water rate Kg/hr.
V= Active cooling volume M³/M² of pan over.
H’ = Enthalpy of saturated air at water temperature, K.cal/Kg.
H = Enthalpy of air stream, K.cal/Kg.
T1 and T2 entering and leaving water temperatures, °c.
The RHS of equation. (1) Is entirely in terms of air and water properties and is
independent of tower dimensions.
Cooling tower represents water and air relationships and the driving potential
which exist in a counter flow cooling tower, where air flows parallel but
opposite in direction to water flow.
An understanding of this diagram is
important in visualizing the cooling tower process.
The tower characteristics are determined from experimental data as follows:
Sr.
T⁰C.
H
no.
water
(Hw)
H air (Ha)
Hw-
1/H
Kcal/kg
Ha
.
Kcal/kg.
T2 = ⁰C.
H1 = -----
T2 + 0.1(T1-T2)
H1 + 0.1 L/G (T1-T2)
H1
T2 + 0.4(T1-T2)
H1 + 0.4L/G (T1-T2)
=
T1 – 0.4(T1-T2)
H2 – 0.4L/G (T1- T2)
H2
T1 – 0.1(T1-T2)
H2 – 0.1L/G (T1-T2)
=
T1 = ….⁰C.
H3
=
H4
=
CALCULATIONS:
NOW
T1
KaV
dt
=∫ '
L
T 2 H −H
[
KaV T 1−T 2
1
1
1
1
=
+
+
+
L
4
∆ H1 ∆ H2 ∆ H3 ∆ H 4
]
Hw = ENTHALPY of air water vapor mixture at bulk water temp. kcal/kg of dry
air.
Ha = ENTHALPY of air water vapor mixture at wet bulb temp. kcal/kg og dry
air.
H1 = VALUE OF (Hw – Ha) at T2 + 0.1(T1-T2)
H2 = VALUE OF (Hw – Ha) at T2 + 0.4(T1-T2)
H3 = VALUE OF (Hw – Ha) at T1 - 0.4(T1-T2)
H4 = VALUE OF (Hw – Ha) at T1 + 0.1(T1-T2)
Hw & Ha can be found from psychrometric chart.
L = water flow rate = kg/hr.
G = AIR mass flow rate kg/hr. (air flow rate X pipe dia. X density of air) kg/m 3.
J1 is found out from psychometric chart. Knowing wet bulb temperature of
entering air.
Then
h2 = h1 + L (T1 – T2)
---G
The tabulation of experimental data is done as follows:
RUN
WATE
AIR
Wate
WATE
AIR
AIR
DBT
WBT
DBT
WB
NO
R
FLO
r
R
INLE
OUTL
AIR
AIR
AIR
T
FLOW
W
INLE
OUTL
T
ET
INLE
OUTL
OUTL
AIR
T
ET
TEM
TEMP
T
ET
ET
OU
TEM
TEMP
P
P
⁰C
⁰C
⁰C
LPM
T
⁰C
⁰C
⁰C
⁰C
Experimental data in collected as follows:
1. Run no.
2. Water flow rate : L 1 lpm
3. Air flow orifice reading : h, mm H2O
4. Entering water temp. : T1, º C
5. Leaving water temp. T 2 º C
6. Air temp. At inlet.
Dry bulb t db1, º C
Wet bulb twb1 º C
7. Air temp. at exit
Dry bulb t db1, º C
Wet bulb twb1 º C
CALCULATIONS:
1. Water mass flow rate
L = Kg/hr
Where water density is to be evaluate at the temperature T1
⁰C
2. Air mass flow rate , G
G = Volumetric flow rate X = Kg/hr
Where Cd coefficient of discharge of orifice – 0.61
A = Orifice throat area
= Πd²/4
d= Orifice throat dia = 0.033 m
K= Orifice constant.
h = Pressure drop across orifice m H2O
a = density of air at orifice location kg /m³
3. From the above L/G ratio is determined.
4. The tower characteristics are then determined as below :
Σ
1 = 1
+
1 +
1 +
1
-------------------∆ h = ∆ h1
∆ h2
∆ h3
∆ h4
The enthalpy ha1 of the entering air is determined from psychometric chart
knowing its wet bulb temperature twb1. Then he enthalpy of leaving air:
Ha2 = ha1
+ L/G ( T1 - T2)
Values of ha1 and ha2 are inserted in Table –1
Experiments are repeated for different ratios L/G and (Kav/L) is found for each
case.
A plot of Kav/L & L/G is then made to determine the packing
characteristics of the tower.
COOLING TOWER
SET UP
DESCRIPTION
SPECIFICATIONS
INSTALLATION REQUIREMENTS
INSTALLATION AND CONNECTIONS
PRECAUTIONS
TROUBLE SHOOTING
EXPREMENTATION
THEORY
OPERATING PROCEDURE’
SYSTEM CONSTANTS
OBSERVATION TABLE
CALCULATIONS
COOLING TOWER.
Aim:
To determine of performance of Cooling Tower.
INTRODUCTION:
The cooling tower is an enclosed device for the evaporative cooling of water
by contact with air.
DESCRIPTION:
1. Casing or shell: This is the structure which encloses the heat transfer
process and also acts as a support for other items.
2. Air inlet and outlet: the position at which air enters and leaves the
tower.
3. Fan: the fan is provided to move the required amount of air through the
water to be cooled.
4. Drift or mist eliminators: These are positioned at or near the air outlet
and present droplets of water from being carried through the tower by
the air stream.
5. Water inlet: This is the point at which water enters the tower.
6. Water distribution system: For maximum effect the water entering the
tower must spread evenly over the top of the packing. It is to achieve
this that the distribution system is used.
7. Packing: In order to provide a large surface area to assist heat transfer
a number of baffles form the packing. Pitch is so arranged that air and
water which is so arranged that air and water which must pass through
it come into direct contact in the process.
8. Tank or sump: This provided at the base of the tower and is often
integral with the casing. Its function is to collect the cooled water
before it is returned to the process which it is cooling.
ANALYSIS OF COOLING TOWER PERFORMANCE:
Meskel has analyzed cooling towers based on Enthalpy Potential difference as
the driving force.
Each particle of water is assumed to the surrounded by a film of air and the
enthalpy difference between the film and surrounding.
driving force for the cooling process.
Air provides the
In the integrated form, the Meskel
equation is:
∫
KaV =
dT
----------- (1)
L
H’ –H
Where K = mass transfer coefficient, Kg/hr m²
a = contact area, m²/m³ of Tower volume.
L = Water rate Kg/hr.
V= Active cooling volume M³/M² of pan over.
H’ = Enthalpy of saturated air at water temperature, K.cal/Kg.
H = Enthalpy of air stream, K.cal/Kg.
T1 and T2 entering and leaving water temperatures, °c.
The RHS of equation. (1) Is entirely in terms of air and water properties and is
independent of tower dimensions.
Cooling tower represents water and air relationships and the driving potential
which exist in a counter flow cooling tower, where air flows parallel but
opposite in direction to water flow.
An understanding of this diagram is
important in visualizing the cooling tower process.
The tower characteristics are determined from experimental data as follows:
Sr.
T⁰C.
H
no.
water
(Hw)
H air (Ha)
Hw-
1/H
Kcal/kg
Ha
.
Kcal/kg.
T2 = ⁰C.
H1 = -----
T2 + 0.1(T1-T2)
H1 + 0.1 L/G (T1-T2)
H1
T2 + 0.4(T1-T2)
H1 + 0.4L/G (T1-T2)
=
T1 – 0.4(T1-T2)
H2 – 0.4L/G (T1- T2)
H2
T1 – 0.1(T1-T2)
H2 – 0.1L/G (T1-T2)
=
T1 = ….⁰C.
H3
=
H4
=
CALCULATIONS:
NOW
T1
KaV
dt
=∫ '
L
T 2 H −H
[
KaV T 1−T 2
1
1
1
1
=
+
+
+
L
4
∆ H1 ∆ H2 ∆ H3 ∆ H 4
]
Hw = ENTHALPY of air water vapor mixture at bulk water temp. kcal/kg of dry
air.
Ha = ENTHALPY of air water vapor mixture at wet bulb temp. kcal/kg og dry
air.
H1 = VALUE OF (Hw – Ha) at T2 + 0.1(T1-T2)
H2 = VALUE OF (Hw – Ha) at T2 + 0.4(T1-T2)
H3 = VALUE OF (Hw – Ha) at T1 - 0.4(T1-T2)
H4 = VALUE OF (Hw – Ha) at T1 + 0.1(T1-T2)
Hw & Ha can be found from psychrometric chart.
L = water flow rate = kg/hr.
G = AIR mass flow rate kg/hr. (air flow rate X pipe dia. X density of air) kg/m 3.
J1 is found out from psychometric chart. Knowing wet bulb temperature of
entering air.
Then
h2 = h1 + L (T1 – T2)
---G
The tabulation of experimental data is done as follows:
RUN
WATE
AIR
Wate
WATE
AIR
AIR
DBT
WBT
DBT
WB
NO
R
FLO
r
R
INLE
OUTL
AIR
AIR
AIR
T
FLOW
W
INLE
OUTL
T
ET
INLE
OUTL
OUTL
AIR
T
ET
TEM
TEMP
T
ET
ET
OU
TEM
TEMP
P
P
⁰C
⁰C
⁰C
LPM
T
⁰C
⁰C
⁰C
⁰C
Experimental data in collected as follows:
1. Run no.
2. Water flow rate : L 1 lpm
3. Air flow orifice reading : h, mm H2O
4. Entering water temp. : T1, º C
5. Leaving water temp. T 2 º C
6. Air temp. At inlet.
Dry bulb t db1, º C
Wet bulb twb1 º C
7. Air temp. at exit
Dry bulb t db1, º C
Wet bulb twb1 º C
CALCULATIONS:
1. Water mass flow rate
L = Kg/hr
Where water density is to be evaluate at the temperature T1
⁰C
2. Air mass flow rate , G
G = Volumetric flow rate X = Kg/hr
Where Cd coefficient of discharge of orifice – 0.61
A = Orifice throat area
= Πd²/4
d= Orifice throat dia = 0.033 m
K= Orifice constant.
h = Pressure drop across orifice m H2O
a = density of air at orifice location kg /m³
3. From the above L/G ratio is determined.
4. The tower characteristics are then determined as below :
Σ
1 = 1
+
1 +
1 +
1
-------------------∆ h = ∆ h1
∆ h2
∆ h3
∆ h4
The enthalpy ha1 of the entering air is determined from psychometric chart
knowing its wet bulb temperature twb1. Then he enthalpy of leaving air:
Ha2 = ha1
+ L/G ( T1 - T2)
Values of ha1 and ha2 are inserted in Table –1
Experiments are repeated for different ratios L/G and (Kav/L) is found for each
case.
A plot of Kav/L & L/G is then made to determine the packing
characteristics of the tower.
