PERFORMANCE EVALUATION OF TWO STAGE AIR COOLER IN DIFFERENT SPEED

http://www.iaeme.com/IJMET/index.asp 329 editor@iaeme.com
International Journal of Mechanical Engineering and Technology (IJMET)
Volume 7, Issue 3, May–June 2016, pp.329–341, Article ID: IJMET_07_03_030
Available online at
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=7&IType=3
Journal Impact Factor (2016): 9.2286 (Calculated by GISI) www.jifactor.com
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
PERFORMANCE EVALUATION OF TWO
STAGE AIR COOLER IN DIFFERENT
SPEED
MOHAMMAD UL HASSAN
Department of Mechanical Engineering,
NIT Patna, India
ABSTRACT
During summer use of khush curtains and water spraid over the khash
(fibre) curtain for air cooling is done. But the determination of the extent of
cooling is limited up to the wet bulb temperature in Conventional Cooler air is
passes at uniform rate through wetted pad. In this process humidity increases
sometimes which is not desirable. In Two Stage Air Cooler the primary air is
cooled by a contact surface which is maintained at lower temperature air and
water on the other side of the contact surface
After analysis it is found that in Two Stage Air Cooler Effective
temperature decreases COP increases up to 13 which are significantly higher
than normal cooler and conventional air conditioner. Refrigeration effect
increases. Makeup water recharges time increases for the same configuration
has been obtained for it is 24 hours 54 minutes and for conventional cooler it
is 15 hours 2 minutes. In two stage air cooler with cover noise has been
drastically reduce by the increase damping effect of covers Specific humidity
increase is significantly lower than that of in case of Conventional Cooler.
On the basis analysis it is recommended that two stage indirect air cooler
is energy effective, eco friendly, cost effective cooling system and with some
further modification it may be hope as replacement of air conditioner. In
direct cooler expected limit lower temperature was 22.6 where as
experimentally the temperature attains are 24. In indirect cooler system the
expected temp was 20.5 where as the actual temperature attain is 21.9 less
than the wet bulb temperature with lesser relative humidity than 100%)
Key words: Conventional Air Cooler, DBT, Heat Exchanger, Primary Pump,
Two Stage Air Cooler WBT
Cite this Article: Mohammad Ul Hassan, Performance Evaluation of Two
Stage Air Cooler In Different Speed. International Journal of Mechanical
Engineering and Technology, 7(3), 2016, pp. 329–341.
http://www.iaeme.com/currentissue.asp?JType=IJMET&VType=7&IType=3

Mohammad Ul Hassan
INTRODUCTION
Principle of evaporative cooling has been used since long back, during summer use of
khush (fibre) curtains and water sprayed over it for air cooling. Other example of
evaporative cooling are use of shurahi pot for water cooling, cooling tower, spray
ponds etc. But the determination of the extent of cooling is limited up to the wet bulb
temperature. In Conventional Cooler air is passes at uniform rate through wetted pad.
In this process humidity increases sometimes which is not desirable. In Two Stage Air
Cooler the primary air is cooled by a contact surface which is maintained at lower
than temperature of incoming atmospheric air. In both the process minimum
temperature can be achieved theoretically is wet bulb temperature (WBT) of the
incoming air.
PROPOSED MODIFICATION
The temperature of air decreases from ‘i’ to ‘o’ in Conventional Cooler. in indirect
evaporative cooler the temperature of ‘ i1’ is lower than temperature at‘ i’ and if
proceeding is done on the constant WBT Line then it goes up to‘O1’ which is lower
than the previous ‘O’. This indicates that if temperature of air at ‘ i ’is cooled to ‘
i1’prior to entry to main cooler by any means lower temperature can be achieved. This
suggests need of cooling of air prior or in other words two stages cooling. The
equipment based on this principle is designated as Two Stage Air Cooler and
theoretically one may reach up to the dew point temperature.
EXPERIMENTAL SETUP
The heat exchanger is fitted on the back panel of the cooler, the inlet is connected
with the secondary pump situated inside the cooler tank so that water supply from for
the exchanger is from the tank and outlet is connected with a pipe to discharge the
water in the same tank connected

Performance Evaluation of Two Stage Air Cooler In Different Speed
For measurement of temperature of cold water entering the heat exchanger a
thermometer probe is inserted in the inlet pipe and for measurement of hot water
temperature coming out of the heat exchanger a thermometer probe is inserted in the
outlet pipe. For measurement of air temperature at the inlet of heat exchange, outlet of
heat exchanger, outlet of cooler and ambient temperature four thermometers installed
at respective position. Also for the measurement of energy consumption at different
arrangement that is combined direct and indirect and direct only at various
speed/velocity energy meter was installed to get energy consumption in kwh.
Nomenclature
DBT = Dry bulb temperature
WBT = Wet bulb temperature
A1 = area of inlet of cooler
A3 = area of outlet of cooler
T1 dbt = dry bulb temperature of air inlet to heat exchanger
T2 dbt = dry bulb temperature of air after passing through heat exchanger

Mohammad Ul Hassan
T3 dbt = dry bulb temperature at outlet of cooler
T1wbt = wet bulb temperature at inlet of heat exchanger
T3wbt = wet bulb temperature at outlet of cooler
RH1 = Relative humidity at inlet to heat exchanger
RH3 = Relative humidity at outlet of cooler
W1 = specific humidity at inlet of heat exchanger
W3 = specific humidity at outlet of cooler
h1 = specific enthalpy at inlet to heat exchanger
h3 = specific enthalpy at outlet
Tw1 = Inlet temperature of water
Tw2= Outlet temperature of wate
Sw= specific heat of water
Sa = specific heat of air
DATA COLLECTION AND CALCULATION
Data was collected on various days on different time. All the parameter required for
calculation and performance evaluation of two stage air cooler needed has been
arranged in tabular form for convenience in visualisation and graph plotting.
Calculation of Velocity
Velocity was calculated at five different points then average of them is taken for both
inlet and outlet for high speed, medium speed and low speed respectively. The
velocity of air may vary for different atmospheric conditions
Table 1 Velocity at inlet of cooler at different points in different speed
Side Inlet Outlet
Points
High speed
(m/s)
Medium
speed
(m/s)
Low speed
(m/s)
High speed
(m/s)
Medium
speed
(m/s)
Low speed
(m/s)
1 3.70 3.10 2.80 4.20 3.45 3.15
2 3.10 2.80 2.50 3.30 3.10 2.70
3 2.75 2.40 2.10 1.10 0.90 0.80
4 3.20 2.90 2.50 1.20 1.10 1.00
5 3.00 2.80 2.60 1.20 1.20 1.10
Average 3.15 2.80 2.50 2.20 1.95 1.75
For performance evaluation and analysis experiment is performed in for different
cases as following
Case A. Two stage air Cooler
In this process both cooler pump and auxiliary pump was switched on air is first
cooled sensibly then evaporative cooling is done, side panel of cooler is covered with
insulating medium so that there is no mixing of hot air from side panel.

Table 2 DBT and WBT at different points at different velocity for two stage air Cooler
Speed Average Velocity DBT WBT
1 3 1 2 3 1 3
High 3.15 2.20 31.5 27.5 21.9 22.6 20.50
Medium 2.80 1.95 31.5 27.4 22.2 22.9 20.7
Low 2.50 1.75 31.5 27.4 23.2 23.2 21.0
Case B. Conventional Cooler
In this process auxiliary pump is switched off so only evaporative cooling of air is
done. Side panel of cooler is covered with insulating medium so that there is no
mixing of hot air from side panel.
Table 3 DBT and WBT at different points at different velocity for Conventional Cooler
Speed Average Velocity DBT WBT
1 3 1 3 1 3
High 3.15 2.20 31.5 24.0 22.5 21.4
Medium 2.80 2.00 31.5 24.3 22.8 21.7
Low 2.50 1.80 31.5 24.5 23.1 21.9
Table 4 Calculation of various parameters for Two stage Air Cooler
Speed Velocity
(m/sec)
Dry bulb
temperature ( )
Wet bulb
temperature ( )
Relative
humidity (%)
1 3 1 2 3 1 3 1 3
High 3.15 2.2 31.5 27.5 21.9 22.6 20.5 46.40 87.37
Medium 2.8 1.95 31.5 27.4 22.2 22.9 20.7 47.92 87.46
Low 2.5 1.75 31.5 27.4 22.5 23.2 21.0 49.46 87.55
Speed Dew point
temperature
Specific humidity
(kg/kg )
Mass flow rate of
air (kg/sec)
Specific volume
(m3
/Kg)
1 3 1 3 1 3 1 3
High 18.62 19.70 0.01346 0.01443 0.3540 0.3563 0.8809 0.8844
Medium 19.13 20.20 0.01392 0.01472 0.3114 0.3154 0.8815 0.8556
Low 20.33 20.22 0.01437 0.01501 0.2805 0.2830 0.8821 0.8569
Speed Specific enthalpy
(KJ/Kg)
∆H
(kJ/kg
)
∆w
(kg/kg )
Make
up
water
(kg/hr)
Area
(m2
)
1 3 (1-3) (3-1) 1 3
High 66.10 58.67 7.43 9.67*10-4 1.2441 0.099 0.1384
Medium 67.26 59.71 7.55 8.00*10-4 0.9083 0.099 0.1384
Low 68.43 60.43 7.67 6.40*10-4 0.6462 0.099 0.1384

Mohammad Ul Hassan
Speed Energy
consumption
Kwh
Time to refill
water tank
(hr)
Carnot COP COP
High 0.201 24:54 30.71 13.20
Medium 0.196 34:07 31.72 12.00
Low 0.191 47:54 32.46 11.36
Table 5: Calculation of various parameters for Conventional Cooler
Speed Velocity
(m/sec)
Dry bulb temperature Wet bulb
temperature
Relative
humidity (%)
1 3 1 2 3 1 3 1 3
High 3.15 2.2 31.5 31 24.0 22.5 21.4 45.89 79.56
Medium 2.8 2.0 31.5 31 24.3 22.8 21.7 47.41 79.70
Low 2.5 1.8 31.5 31 24.5 23.1 21.9 48.95 80.53
Speed Dew point
temperature
Specific humidity
(kg/kg )
Mass flow rate of
air (kg/s)
Specific volume
(m3
/kg)
1 3 1 3 1 3 1 3
High 18.44 20.25 0.01331 0.01493 0.3527 0.3535 0.8841 0.8612
Medium 18.96 20.57 0.01376 0.01524 0.3145 0.3193 0.8813 0.8624
Low 19.47 20.93 0.01422 0.01559 0.2806 0.2885 0.8819 0.8635
Speed
Specific enthalpy
(kJ/kg )
∆H
(kJ/kg )
∆w
(kg/kg )
Make up
water
(kg/hr)
Area
(m2
)
1 3 (1-3) (3-1) 1 3
High 65.72 62.12 3.60 1.62*10-3
2.0616 0.099 0.1384
Medium 66.87 63.20 3.67 1.48*10-3
1.7012 0.099 0.1384
Low 68.04 64.30 3.74 1.37*10-3
1.42282 0.099 0.1384
Speed
Energy
consumption
Kwh
Time to refill
water tank
(hr)
Carnot COP COP
High 0.183 15:02 39.6 6.9540
Medium 0.178 18:13 41.29 6.5833
Low 0.173 21:47 42.5 6.2369
RESULT AND DISCUSSION
Variation of Temperature at Outlet of Cooler with Fan speed
For data ref table no 4 and 5

Effects
 Temperature attained in Two Stage Air Cooler is lower than Conventional Cooler.
 As velocity/speed increases degree of cooling is increase
Reason
 In Two Stage Air Cooler the air is pre-cooled sensibly in the heat exchanger so the
better cooling is performed this departure of temperature may be better explain by
psychometric chart.
 Increased velocity provides increase of Reynolds no thence increase heat transfer
coefficient and better cooling.
 In high velocity/speed some water droplets may not find sufficient time for
evaporation and at the exit air is sensibly cooled
This departure may be considered due to water spray at wet bulb temperature
provides sensible cooling of air which has already humidified adiabatically.
Mass Flow Rate at Different Speed
Data ref table no 4 and 5
21.9
22.2
22.5
24
24.3 24.5
20
21
22
23
24
25
High Medium Low
Minimumtemperatureattain
Speed
Minimum temperature attain v/s speed

Mohammad Ul Hassan
Effect
As the velocity decreases mass flow rate also decreases
Reason:
Mass flow rate decreases with decreased velocity because area of inlet and outlet is
constant so mass flow rate varies according to velocity.
Variation in change in enthalpy
Data ref table no 4 and 5
Effect
 Change in enthalpy for incoming and outgoing air in combined arrangement is more
than direct cooling arrangement.
 Change in enthalpy increases with decrease in speed for the same setup.
 The change in enthalpy for Conventional Cooler should be zero because it is an
adiabatic cooling process.
Reason
The incoming air condition is same for both the arrangement but the outgoing air in
former case is much lower than Conventional Cooler so in case of Two Stage Air
Cooler arrangement change in enthalpy is more.
Refrigeration Effect
Data ref Table no 4 and 5
0
0.1
0.2
0.3
0.4
High Medium Low
0.3563
0.3154
0.2831
0.3535
0.3193
0.2885
MassflowrateKg/sec
Speed m/sec
Mass flow rate at different spped
Two stage air
cooler
Conventional
cooler
7.43 7.55 7.67
3.6 3.67 3.74
0
5
10
High Medium Low
Changeinenthalpy
Speed
Change in enthalpy v/s speed
Two stage air
cooler
Conventional
cooler

Effect
 Refrigeration effect for Two Stage Air Cooler is more than Conventional Cooler.
 Refrigeration effect decreases with decreased speed.
Reason
 Since the change in enthalpy in case of Two Stage Air Cooler is more than
Conventional Cooler only. So refrigeration effect in combined process is also more.
 As mass flow rate decreases with decrease in speed so the refrigeration effect also
decreases with decrease in speed
Energy Consumption
Effect
 Energy consumption for Two Stage Air Cooler is more than Conventional Cooler
only.
 The energy consumption is decreases with decrease in velocity.
Reason
 Energy consumption for Two Stage Air Cooler is higher than direct cooling only
because in former case along with fan and primary pump secondary pump is also
running but in direct cooling secondary pump is not running so energy consumption
is less.
2.6473
2.38127 2.27
1.2726 1.17183 1.07899
0
1
2
3
High Medium Low
Refrigerationeffect
Speed
Refigeration effect v/s Speed
Two stage air
cooler
Conventional
cooler
0.15
0.16
0.17
0.18
0.19
0.2
0.21
0.201
0.196
0.191
0.183
0.178
0.173
EnergyconsumptioninKwh
Speed m/s
Energy consumption v/s speed
Two stage
air cooler
Convention
al cooler

Mohammad Ul Hassan
 Energy consumption by the cooler fan is less for lower speed so it decreases with
decreasing speed.
Variation of COP with Speed
Effects
1. The COP for Two Stage Air Cooler is more than the Conventional Cooler only.
2. The COP for the same set up decreases with the decrease in speed.
Reason
 Instead of energy consumption is more in case of Two Stage Air Cooler the COP is
more because as compare to energy consumption the cooling is more in this case so
the refrigeration effect is also more hence COP is more in case of Two Stage Air
Cooler.
 COP decrease with the decrease in speed in both the cases because effect of the
decrease in energy consumption with decrease in speed is less as compared to the
effect of decrease of refrigeration effect
Make up Water Requirement
As in cooler the cooling of air is by the process of evaporative cooling so the water
evaporated continuously so make up water is need after particular interval of time
according to arrangement and use of cooler.
13.206
11.995 11.3644
6.954 6.583 6.237
0
5
10
15
High Medium Low
COP
Speed (m/s)
COP v/s Speed
Two stage Air
Cooler
Conventional
Cooler
0
0.5
1
1.5
2
2.5
High Medium Low
1.2441
0.9083
0.5502
2.0616
1.7012
1.42282
Makeupwaterrequiredper
hour
Speed
Make water requirement v/s Speed
Two stage Air
Cooler
Conventional
Cooler

Effect
 Make up water requirement is more for Conventional Cooler than Two Stage Air
Cooler.
 The makeup water requirement for the same set up decreases with the decrease in
speed for both the process.
Reason
 Difference in specific enthalpy at inlet and outlet of cooler is more in case of
Conventional Cooler only because at outlet specific enthalpy is more in case of
Conventional Cooler.
 For the same setup as the speed decreases the difference in specific enthalpy
decreases along with this the mass flow rate of air also decreases so the makeup water
require is also less.
Makeup Water Recharge Time
(May vary according to prevailing ambient condition)
As the makeup water needed so the tank has to be refill after particular interval of
time depending on the capacity of tank and use of cooler.
In this cooler the tank capacity is 31 litres so time to refill the tank for different
arrangement and different speed has been given below in tabular form.
Comparison of COP of Simple Air Cooler v/s Two Stage Air Cooler v/s
Conventional Window Air Conditioner
0:00:00 24:00:00 48:00:00
High
Medium
Low
24:54:00
34:07:00
47:54:00
15:02
18:13
21:47
Time after which refilling require
Speed
tme for reffiling of tank require v/s Speed
Conventinal
Cooler
APPLIANCES COP
Two Stage Air cooler 13.206
Simple Air Cooler 6.954
Window AC 2.846

Mohammad Ul Hassan
CONCLUSION
Following are the fruitful result outcome of indirect two stage air cooler their details
have been provided in result and discussion.
 Effective temperature decreases
 COP increases up to 13 which are significantly higher than normal cooler and
conventional air conditioner.
 Refrigeration effect increases.
 Makeup water recharges time increases for the same configuration has been obtained.
 In two stage air cooler with cover noise has been drastically reduce by the increase
damping effect of covers
 Specific humidity increase is significantly lower than that of in case of Conventional
Cooler.
RECOMMENDATIONS
 Two stage indirect air cooler is energy effective, eco friendly, cost effective cooling
system and with some further modification it may be hope as replacement of air
conditioner.
 In direct cooler expected limit lower temperature was 22.6 where as experimentally
the temperature attains is 24. In indirect cooler system the expected temp was 20.5
where as the actual temperature attain is 21.9 less than the wet bulb temperature with
lesser relative humidity than 100%.
REFERENCES
[1] Dowdy j. A. and Karbash N. S. (1987). Experimental determination of heat and
mass transfer coefficients in rigid imperegnated cellulose evaporative media,
ASHRAE Transactions, 93, Part 2, pp 382–395.
[2] Chen P. L., Qin H. M., Huang Y. J., Wu H. F. (1991). Ä heat and mass transfer
model for thermal and hydraulic calculations of indirect evaporative cooler
performance, ASHRATE Transactions, 97, Part 2, pp 852–865.
[3] Peterson J. L. (1993), An effectiveness model for indirect evaporative coolers,
ASHRAE Transactions, 99, Part 1, pp 392–399.
[4] El-Dessouky H. T. A., Al-Haddad A., Juwayhel F.I.(1996). Thermal and
hydraulic performance of a modified two-stage evaporative cooler, Renewable
Energy, 7(2), pp 165–176.
[5] Maheshwari G. P., Al-Ragom F., Suri R. K. (2001), Energy saving potential of an
indirect evaporative cooler, Applied Energy, 69(1), pp 69–76.
0
5
10
15
Two StageAir
cooler
Conventional
Air Cooler
Window AC
13.206
6.954
2.846
COP Appliances
COP for different appliances

[6] El- Dessouky H., Al—Zeefari A. (2004), Performance analysis of two stage
evaporative coolers, Chemical Engineering Journal 102(3), pp 255–266.
[7] Camrago J. R., Ebinuma C. D., Silveria J. L. (2005), Experimental performance
of a direct evaporative cooler operating during summer in Barzilian City,
International Journal of Refrigeration, 28 (7), pp 1124–1131.
[8] Jain D., (2007), Development and testing of two stage evaporative cooler,
Building and Environment, 42(7), pp 25–54.
[9] Heidarinejad G., Bozorgmehr M., Delfani S., Esmaeelian J. (2009). Experimental
investigation of two stage indirect/ Convetional Cooler system in various climatic
conditions. Building and Environment, 44(10), pp 2073–2079.
[10] Principle of Evaporative Cooling System, 2012,PDH online Course M231 (4
PDH)
[11] Mohd. Rehan Khan and Dr. Ajeet Kumar Rai, An Experimental Study of Exergy
In A Corrugated Plate Heat Exchanger. International Journal of Mechanical
Engineering and Technology, 6(11), 2015, pp. 16–22.
[12] Akshay Khot, Analysis of Various Designing Parameters for Earth Air Tunnel
Heat Exchanger System. International Journal of Mechanical Engineering and
Technology, 5(12), 2014, pp. 118–125.
[13] ASHRAE Handbook, 1995, chapter47, Evaporating Air–Cooling notes.

PERFORMANCE EVALUATION OF TWO STAGE AIR COOLER IN DIFFERENT SPEED

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to PERFORMANCE EVALUATION OF TWO STAGE AIR COOLER IN DIFFERENT SPEED

Similar to PERFORMANCE EVALUATION OF TWO STAGE AIR COOLER IN DIFFERENT SPEED (20)

More from IAEME Publication

More from IAEME Publication (20)

Recently uploaded

Recently uploaded (20)

PERFORMANCE EVALUATION OF TWO STAGE AIR COOLER IN DIFFERENT SPEED