Neelam Dubey1, Dr. Shilpa Tripathi2, Dr. Sharad Chaudhary3
1Assistant Professor, Mechanical Engineering Department, Medi-Caps University, Indore– MP, India
2Professor,MechanicalEngineering Department, Medi-Caps University, Indore– MP, India
3Professor,MechanicalEngineering Department, IET- DAVV, Indore– MP, India
Abstract - The performance analysis of different evaporative pad materials, such as charcoal, activated charcoal, sponge gourd sponge, brick bat sand a combination of charcoal and wood wool has been done in the evaporative cooling system (Cooler). The objective is to analyze the cooling effectiveness sand the cooling capacity at different air velocities. The studies have been done at Indore in M.P. state where the temperature ranges from 390C to 420Cin summer season with relative humidity of 22% to 29%.The cooling capacities have been observed as2.35kJ/s with cooling effectiveness 80.5 %for charcoal,1.45kJ/s with cooling effectiveness 73.8% for activated charcoal, 2.58kJ/s for sponge gourd sponge, for brickbats1.68kJ/s,2.38kJ/s for Khu sand for a combination of charcoal and wood wool 3.28 kJ/s, with cooling effectiveness 80.5% for charcoal, 73.8% for activated charcoal, 85.16% for sponge gourd sponge, 74.5% for brick bats and 97.3% for a combination of charcoal and wood wool have been obtained at 7 m/s air velocity. The cooling effectiveness of wood wool & charcoal has been found to be maximum among all six materials.
Keywords: Charcoal, Activated Charcoal, Brick Bats, Sponge (Sponge Gourd), Khus &
combination of wood wool and Charcoal.
1. INTRODUCTION
Evaporative cooling is a simple technology and proves to be economic a lin Indian climate conditions. Evaporative cooling technology is an ancient technology but we have tried to relook it from a new perspective. An energy efficient system based on evaporative cooling phenomenon has been made and tested to get sufficient cooling.
Evaporative cooling not only lowers the temperature but it also increases the moisture content of the air, this helps to prevent the food from getting dry and therefore extends its shelf life. We began this study with reasoning that a vegetarian food can be stored for a long time with temperature around 100 C to150C lower than the room temperature in summers. This can be achieved by means of evaporative cooling in dry and hot climate. High temperature sand unprotected storage areas greatly increase the post-harvest losses and reduce the profit margin of the farmers. The evaporative coolers are simple to make as they are neither material nor energy intensive and require very less energy for their operation.
Different researchers have made the efforts to clear the concept of evaporative cooling and to search an appropriate media, design and process to make the evaporation most effective. Mud,
Charcoal, Cellulose, aspen wood, corrugated paper, wood wool, high density polythene are some materials have been used as evaporative pad materials. The main aims behind their studies have been to find out the material which most suited to evaporative cooling and are able to provide maximum performance in respect of maximum cooling capacity and effectiveness. This project is an approach in same direction by using some materials which are locally available and can be obtained at low cost.
A theoretical performance analysis of cooling pads of different materials for evaporative cooler has been made by Mr.
Kulkarni R.K Rajput S.P.S. [4]Rectangular pads with rigid cellulose, corrugated paper, high density polythene and aspen fibre material are considered for cooling pad materials.
An evaporative cooler was developed with clay and other locally available materials by Mr. M. C. Ndukwu [6] for preservation of fruits and vegetables. The performance of cooler was evaluated in terms of temperature drop, evaporative effectiveness and cooling capacity.
In a technical paper on understanding evaporative cooling Mr.
Eric Rustin [3] has elaborated the basic principle of evaporation, various factors
2 affecting evaporation and different types of direct and indirect evaporative coolers.
The theoretical performance analysis of cooling pads of other materials such as rectangular pads with rigid cellulose, corrugated paper, high density polythene, as pen wood has been done by various researchers. The present study has been done on a special evaporative cooler maintaining cool interior temperature for food preservation purpose.
Objective of analysis is to initially prepare a proto type and testing it for different size sand type of materials like activated charcoal, charcoal, sponge gourd, combination of wood wool and charcoal, brick bats and Khus.
After determining the inside temperatures and humidity for different materials, cooling effectiveness and cooling capacity were also checked. In order to obtain effective results the testing has been carried out during summer days.
2. METHODOLOGY
Based on summer data of Indore region, most frequently occurring condition of average maximum DBT was 40.10C and average humidity was 22.14% .With present efficiency the temperature difference of out side and inside of cooler in hot and dry climate of Indore region is estimated to be 13C to15◦C. Experimental work has been carried out in summer days and the results were compared with various evaporative pad materials.
The study has been done in the month of November and December and March-April. The cooling effectiveness is 80.5% for Charcoal, 73.8% for Activated Charcoal, 85.16% for Sponge of Sponge Gourd, 74.48% for Brick bats, 84.12 % for Khus and 97.32% for combination of Wood Wool and Charcoal at air velocity 5 m/s.
The cooling capacity is 2.35 kJ/s for Charcoal, 1.45 kJ/s for Activated Charcoal, 2.58 kJ/s for Sponge of Sponge Gourd, 1.68kJ/s for Brickbats, 2.32kJ/s for Khus and 2.44kJ/s for combination of Wood Wool and Charcoal at air velocity7 m/s.
Step-1: A design with cooler height and fan power was finalized for 850 mm*
850mm*850 mm sides. A n exhaust fan air has been utilized for air circulation.
Step-2:After construction of the present unit, the walls of cooler were filled with various materials one after one which included Activated Charcoal, Charcoal, Sponge gourd sponge, Brick bats, Khus (Vetiver) and a combination of Wood wool and Charcoal, keeping them continuously moist by circulating the water with the help of as mall pump.
Step-4: This unit is used as an evaporative cooler. It has been tested for inside temperature and relative humidity and finally calculated cooling effectiveness and cooling capacity for the same. The exhaust air velocity was varied from 3 m/s to 7 m/s. The study has also been done without using the exhaust fan.
The experiments have been done by the method explained in the previous paragraph. The calculations have been done and the actual results are shown in the tables. Analysis can be seen in bar charts with respective tables.
Fig.1.Khus (Vetiver) filled walls
Fig.2. Charcoal filled walls
Fig.3.Brick bats and brick bat cooler
Fig.4. Spongegourd sponge(Closedand opened conditions)
Fig.5.Activated Charcoal
Fig.6. Instruments used for measurement (Anemometer, Psychro
meter)
3. OBSERVAIONS AND CALCULATIONS Cooling effectiveness has been determined by using following relation:
...Eq. (1) [ 4]
t1=Dry bulb temperature (outside air)C t2=Dry bulb temperature (inside air)C
tbt=Wet bulb temperature (outside air)C Cooling Capacity has been determined by using following relation:
…..Eq. (2) [2]
Here Cpu is specific heat of moist air ink J/kgK, can be calculated as:
…….Eq. (3) [2]
Cpa=specific heat of inlet air (kJ/ kgK) Cpv =specific heat of water vapor (kJ/kgK) ωa=specific humidity of inlet ambient air (kg/kg of inlet air)
Table 1:Performanceanalysis of KHUS (Vetiver)based evaporative cooler
Fig. 7 Performance analysis of KHUS (Vetiver) based evaporative cooler
Table 2: Performance analysis of ACTIVATED CHARCOAL based
evaporative cooler 1 Without
Fan 34.8 19.6 22.3 23.4 77.0 75.1 0.133
2 3 34.9 19.4 21.3 22 78.0 79.9 0.904
3 4 34.8 19.1 22.3 21.9 80.0 82.2 1.205
4 5 36.6 19.6 18.2 22.3 85.0 84.1 1.669
5 7 36.7 19.7 18.3 22.5 85.1 84.2 2.321
Cooling Effectiveness
(%) Cooling Capacity (kJ/s) Inside
Temperature (◦C)
Φ Inside (%) Sr.
No.
Air Velocity (m/s)
DBT (◦C)
WBT (◦C)
Φ Outside (%)
1 Without
Fan 26.1 16 33.4 20 58.4 60.4 0.0712
2 3 m/s 25.8 15.9 34.1 19.3 55.3 65.7 0.4552
3 4 m/s 26 16 33.8 19 69.3 70.0 0.6536
4 5 m/s 23.4 15.8 44.4 17.8 0.6 73.7 0.6546
5 7 m/s 25 15.9 35.0 18 67.0 76.9 1.1445
Sr.
No.
Air Velocity (m/s)
DBT (◦C)
WBT (◦C)
Φ Outside (%)
Inside Temperature
(◦C) Φ Inside
(%) Cooling Effectiveness
(%)
Cooling
Capacity
(kJ/s)
4 Fig. 8 Performance analysis of
ACTIVATED CHARCOAL based evaporative cooler
Table 3 :Performance analysis of BRICK BAT based evaporative cooler
Fig. 9 Performanceanalysis of BRICKBATbased evaporative cooler
Table 4: Performance analysis of Sponge Gourd sponge based evaporative cooler
Fig. 10 Performance analysis of Sponge Gourd sponge based evaporative cooler
Table 5: Performance analysis of CHARCOAL based evaporative cooler
1 Without
Fan 36 18.6 16.0 25.2 43.0 62.1 0.1258
2 3 m/s 36.2 18.7 16.0 24.5 46.4 66.9 0.8179
3 4 m/s 32.2 18.1 23.1 22 60.4 72.3 0.9525
4 5 m/s 37.2 19.2 15.6 22.7 66.8 80.6 1.6901
5 7 m/s 37 19.3 15.5 22.6 66.9 81.4 2.3509
Φ Inside (%)
Cooling Effectiveness
(%)
Cooling Capacity (kJ/s) Sr. No.
Air Velocity (m/s)
DBT (◦C)
WBT (◦C)
Φ Outside
(%)
Inside Temperature
(◦C)
Fig. 11 Performance analysis of CHARCOAL based evaporative cooler Table 6: Performance analysis of WOOD
WOOL AND CHARCOAL based evaporative cooler
Fig. 12 Performance analysis of WOOD WOOL AND CHARCOAL based
evaporative cooler
Table 7: Comparative Analysis of different evaporative pad materials
Fig. 13 Comparative Analysis of different evaporative pad materials Performance of evaporative cooler with charcoal, activated charcoal, sponge gourd sponge, brick bat sand a combination of charcoal and wood wool filled sides have been shown in table number 1 to 6 and their comparative analysis has been shown in table number 7.
At different fan speeds, exhaust air velocity was checked with the help of digital anemometer with this the ambient dry bulb and wet bulb temperature (checked by sling psychrometer) compared to inside temperature and inside relative humidity were checked to obtain cooling effectiveness and cooling capacities.
It has been observed that at lower air velocity the value of cooling effectiveness and cooling capacity were less. As the air velocity increases, cooling effectiveness and cooling capacity also
1 Without
Fan 34.8 20.3 25.0 22.5 60.8 84.7 0.144
2 3 m/s 35.2 20.2 23.5 26.7 42.0 90.3 0.597
3 4 m/s 35 20.1 23.7 21 70.0 94.7 1.31
4 5 m/s 34.6 19.7 23.2 20.1 73.4 97.3 1.696
5 7 m/s 34.7 19.7 23.0 19.8 73.5 97.3 2.439
Cooling Effectiveness
(%) Cooling Capacity (kJ/s) Sr. No.
Air Velocity (m/s)
DBT (◦C)
WBT (◦C)
Φ Outside (%)
Inside Temperature
(◦C) Φ Inside
(%)
1 Khus 84.1
2 Activated Charcoal 73.8
3 Brick bats 74.5
4 Sponge Gourd 85.2
5 Charcoal 80.5
6 Wood wool & Charcoal 97.3
Cooling effectiveness (%) ( at 7 m/s)
Evaporative pad materials Sr.
No.
6 increases. As air velocity changed from 3m/s to 7 m/s the value of cooling effectiveness changes appreciably.
Hence velocity of air is an important parameter which affects evaporative cooler’s performance. The same analysis can be visualized by the charts. Charts show the relationship between Air velocity (X- Axis) and Cooling Effectiveness (Y-Axis), along with the respective values of inside temperature and relative humidity.
CONCLUSION
Fabrication and material based performance analysis of Direct Evaporative Cooler has been done and results have been compared. The study has been done in November to December and April to June. The cooling effectiveness has been found to be varying from 74% to 98% for all the six materials that were kept under observation. The cooling effectiveness of wood wool &
charcoal was found to be highest among all six materials.
NOMENCLATURE
S.No. Nomenclature Description
1. Cpa Specific heat of inlet air(kJ/kg K)
2. Cpu Specific heat of moist air (kJ/kgK)
3. Cpv Specific heat of water vapor (kJ/kgK)
4. m Mass flow rate of air (kg/s) 5. Qc Cooling Capacity(kJ/s)
6. t1 Dry Bulb Temperature (◦C) Ambient
7. t2 Dry Bulb Temperature Inside Cooler(◦C)
8. tbt Wet Bulb Temperature(◦C) Ambient
9. ηc Cooling Effectiveness (%) 10. wi specific humidity of inlet air
(kg/kg of in let air)
11. wa Specific humidity of ambient air (kg/kg of inlet air)
12. Φ Relative Humidity(%) REFERENCES
1. Charcoal cooler prototype construction and
analysis details, 2011.
http://www.appropedia.org/Engineering_fo r_Sustainable_Development.
2. C.P. Arora, (1985).“Refrigeration and Air Conditioning”, Tata McGraw-Hill, Third Edition, pp. 452 – 459, 477 – 479, 651.
3. Eric Rustin, “Understanding Evaporative Cooling”, Volunteers in Technical Assistance, Technical paper no.3.
4. Kulkarni R.K., S.P.S.
Rajput,2011.“Comparative performance of evaporative cooling pads of alternative materials”, International Journal Of Advanced Engineering Sciences and Technologies, Volume –10, pp. 239– 244.
5. Indore weather data retrieved from www.tutiempo.net
6. Ndukwu. M.C., 2011.“Development of a Low Cost Mud Evaporative Cooler for Preservation of Fruits and Vegetables”, Agricultural Engineering International:
CIGR Journal, Volume – 13, pp. 1-8 7. Bhushan D. Chaudhari, Tushar R.
Sonawane, Shubham M. Patil, 2015 “ A review on evaporative cooling technology”
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“Design of new evaporative cooler and usage of different cooling pad materials for improved cooling efficiency.” International Research Journal of Engineering and Technology ( IRJET)Volume: 04 Issue: 09.
