1. Asian Institute of Technology
Food Engineering and Bioprocess Technology
DESIGN AND DEVELOPMENT OF AN EVAPORATIVE COOLING SYSTEM
FOR TROPICAL FRUITS AND VEGETABLES ON TRANSPORT VEHICLES
Prof. Athapol Noomhorm (Chairperson)
Present by
Nattriya Supmoon

2. Presentation Outlines
Rationale
Material and Methods
Results and Discussions
Conclusion
Recommendations

3. 1. Rationale

4. General background COLD CHAIN fruits and vegetables perishable
risk of post-harvest losses
COLD CHAIN
physiological
biochemical
microbiological activities
low temperature
high relative humidity
decreased
increases the vapor pressure of the air
decreases physiological weight loss
higher relative humidity

5. Statement of Problems more stress and hastens the decay
tropical country
hot and humid
tropical produce
high water content and respiration rate
transport
without regard for heat
more stress and hastens the decay
Postharvest loss
(Truck from Chiang Mai)
60% for cabbage and tomato
50% for head lettuce
30% for bell pepper
17% for Chinese cabbage
highly weight loss
15-20% fruits
20-25 % vegetables

6. Statement of Problems TEMPERATURE MANAGEMENT
Refrigeration and other commercial cold storage systems
heavy initial cost and demand high input of energy
low investment and less energy input
Evaporative cooling

7. Motivation of this thesis
Direct evaporative cooling system
have also been interesting for storage fruits and vegetables
but there is still no system yet on transport system

8. Statement of Problems 1 2 Cooling efficiency (η)
Thailand HOT AND HUMID
Sensible heat in the air is used to evaporate water
(transferred to latent heat in the moist air)
Direct evaporative cooler
limitation in dry bulb temperature drop
(Jain, 2008)
How to maximize temperature drop
lower than the T_wb of the ambient air
(Dessouky, 2004)

9. Factors effect on cooling efficiency
Statement of Problems
Factors effect on cooling efficiency
CAR SPEED VARIATION
TRAFFIC CONDITION

10. 2. Material and Methods Objective Objective 1 Objective 2
Design and construct a lab-scale evaporative cooler
Evaluate the effect of operating condition on cooling efficiency
Objective 1
Develop mathematical model of cooling efficiency
based on the steady state heat and mass transfer balance
Design and construct a modified evaporative cooling unit
used for storage tropical fruits and vegetables on transport vehicle
Objective 2
Experimental study and data collection to investigate
system performance of modified evaporative cooling unit

11. 2. Material and Methods Procedure steps Design and construct
Objective1: To determine the effect of operating conditions on the cooling efficiency
Procedure steps
Dry bulb temperature:
21.6, 23.7, 24.6, 25.7, 26.7 C
Wet bulb temperature:
18.5, 19.6, 21, 21.3, 21.5 C
Thickness of cooling media:
5, 10, 15, 20, 25 cm. (5 levels)
Inlet air velocity:
5 levels depend on capability of fan
Design and construct
a lab-scale evaporative cooling system
Experimental Test
Vary operating condition
Data collection
Parameter
T_db and T_wb
Cooling efficiency
Air velocity
Experimental results

12. 2. Material and Methods
Objective1: To determine the effect of operating conditions on the cooling efficiency
Construction of a lab-scale evaporative cooler unit

13. 2. Material and Methods
Objective1: To determine the effect of operating conditions on the cooling efficiency
Construction and instrumentation of a lab-scale evaporative cooler unit
Dry-bulb temperature (2-5)
using K-type thermocouple
Wet-bulb temperature (1)
kept moist by a wick dipped in a glass of water
Air velocity (6)
using vane anemometer
Water flow rate
using volumetric method
reading the time and a volume of water
corresponding to valve adjustment
Cool & moist air
Hot & dry air
Water stream
Air stream

14. 2. Material and Methods Cooling media RIGID MEDIA (CelDek 7090)
Objective1: To determine the effect of operating conditions on the cooling efficiency
Cooling media
Distribution pad
Cooling pad
RIGID MEDIA (CelDek 7090)

15. 3. Results and Discussions
Objective1: To determine the effect of operating conditions on the cooling efficiency
Effect of temperature of entering air
Thickness of cooling media =20cm
Inlet air velocity =1.2m/s
Relative humidity =57%
Thickness of cooling media =20cm
Inlet air velocity =1.2m/s
T_db =26C
No effect on cooling efficiency

16. 3. Results and Discussions
Objective1: To determine the effect of operating conditions on the cooling efficiency
Effect of the inlet air velocity
Effect of thickness of cooling media
Thickness of cooling media =5cm
Inlet air velocity =1.86±0.018 m/s
cooling efficiency
Thickness of cooling media
Inlet air velocity
Cooling efficiency Temperature drop
Increased contact time and surface area
Heat and mass transfer

17. 3. Results and Discussions
Mathematical models as applied to evaporative cooling system
Wu, et al. (2008) Heat and mass balance of direct evaporative cooler
sensible heat removed from air = latent heat gain by air through water

18. 3. Results and Discussions
Objective1: To determine the effect of operating conditions on the cooling efficiency
Mathematical model of cooling efficiency

19. 2. Material and Methods Procedure steps Design and construct
Objective2: To design and develop an evaporative cooler used for transport tropical fruits and vegetables on moving vehicles
Procedure steps
Evap configurations
-Single-stage EC
-Two-stage EC
Car velocity
40, 50, 60, 70, 80 km/hr
Design and construct
a modified evaporative cooling system
Experimental Test
Vary Evap configuration & Car velocity
Data collection
Parameter
T_db and T_wb
Cooling efficiency
Relative inlet air velocity
Experimental results

20. 3. Results and Discussions
Objective2: To design and develop an evaporative cooler used for transport tropical fruits and vegetables on moving vehicles
Selection of the operating condition
thickness of cooling media
25 cm
The more thickness of cooling media, the higher cooling efficiency
As low as possible
air velocity
The lesser inlet air velocity, the more cooling efficiency

21. 2. Material and Methods
Objective2: To design and develop an evaporative cooler used for transport tropical fruits and vegetables on moving vehicles
Construction of a modified evaporative cooler unit

22. 2. Material and Methods
Objective2: To design and develop an evaporative cooler used for transport tropical fruits and vegetables on moving vehicles
Construction of a modified evaporative cooler unit
Single-stage EC
Two-stage EC

23. 2. Material and Methods
Objective2: To design and develop an evaporative cooler used for transport tropical fruits and vegetables on moving vehicles
Construction of a modified evaporative cooler unit

24. 2. Material and Methods
Objective2: To design and develop an evaporative cooler used for transport tropical fruits and vegetables on moving vehicles
Construction of a modified evaporative cooler unit

25. 3. Results and Discussions
Objective2: To design and develop an evaporative cooler used for transport tropical fruits and vegetables on moving vehicles
Cooling efficiency

26. 3. Results and Discussions
Objective2: To design and develop an evaporative cooler used for transport tropical fruits and vegetables on moving vehicles
Temperature drop
One-stage EC
Temperature drop about 7C
Two-stage EC
Temperature drop about 10C

27. 3. Results and Discussions
Objective2: To design and develop an evaporative cooler used for transport tropical fruits and vegetables on moving vehicles
Adjustment the area of inlet air to control the air velocity

28. 4. Conclusions Objective 1
The predicted cooling efficiency model
for a direct evaporative cooler with rigid media as a cooling pad
based on heat and mass balance analysis of air and moisture.
This equation may be taken as a constant
when the variation range of air condition is small and the cooling media is given.
For the different material and configuration of cooling media, the number will take a different value.
main effects Thickness of cooling media () & inlet air velocity (V)

29. 4. Conclusions Objective 2 Single-stage evaporative cooling system
temperature drop by 7C
cooling efficiency ranged from 84% to 96%.
Two-stage evaporative cooling system
temperature drop by 10C
cooling efficiency ranged from 104% to 107%
Effect of car velocity on the relative inlet air velocity
Two-stage EC is less than Single-stage EC
results in less variation in temperature gradients

30. 5. Recommendations
Some fruit and vegetable located in the north or northeastern part of Thailand should be considered to be the testing for the evaporative cooling system on moving vehicle.
The cost analysis of the evaporative cooling system
on moving vehicle should be done
to check the energy costs and efficiency of the system.

31. 5. Recommendations Actual size
Factor to be considered is relative inlet air velocity
Desiccant Dehumidification
Reduce moisture of ambient air before passing through direct evaporative cooling system

32. Thank you