1. GREEN HOUSE DRYER
Presented by
Mr. DINESH
Roll no. 18AG63R17
Department of Agricultural and Food Engineering
IIT Kharagpur
2. Content
• Drying
• Introduction
• Working principle
• Classification of Green house dryer
• Advantages of Green house dryer
• Case study
• Graphical representation
• Results and discussion
• Conclusion
• References
3. Drying
• It is the removal of moisture from the food
product to safe level.
• It increase the shelf life of the product.
• It is the basic unit operation used in the food
processing.
4. Drying
• Drying rate depends on external parameters
• It also depends on internal parameter.
• It involves two phenomenon:
1. heat transfer
2. mass transfer
5. Introduction
• Sun drying is the most common method used to
preserve agricultural food products.
• Due to drying of products on open grounds or
mats, it is influenced by birds, rodents, rain and
microorganisms.
• So, the quality of the dried product is lowered.
• As a result, dried product could not get the better
price.
• To avoid this situation and post harvest losses, a
new concept of green house solar dryer arises.
6. Green house dryer
• Greenhouse structure used for drying is
called greenhouse dryer.
• Inside greenhouse dryer materials are dried using
the solar thermal energy.
• It works on the principle of Green House effect.
11. Classification of dryer
• On the basis of covering material
1. Polythene covered
2. Polycarbonate sheet covered
3. Glass covered
• On the basis of structure
1. Even span roof type
2. Parabolic shaped
• On the basis of floor
1. Concrete floor
2. PVC sheet floor
3. Rock bed or sand floor
13. Advantages
• The advantage of solar greenhouse is the use of
renewable energy sources, which reduces the cost
of drying .
• Greenhouse dryer have a better quality product
than open sun drying.
• Greenhouse drying reduces moisture content in a
very less time compare to open sun drying.
• It has also advantages that the material to be dried is
protected from dust and rain.
14. Case study
Description
• Parabolic roof structure
• Polycarbonate sheet cover (thick=6mm)
• Concrete floor
• length= 20m,width=7.5m,height=3.5m
• Capacity= 1000kg
Large greenhouse solar dryer
15. Case study
• Materials used:-
1. Chilli (300kg)
2. Pyranometer
3. Hygrometer
4. Anemometer
5. Thermocouple
16. Fig : The dimension and the positions of the thermocouples (T)
hygrometers (Rh) and product samples for weights (M)
22. • The moisture content of chilli in the green
house dryer was reduced from an initial value
of 75%(wb) to a final value of 15% (wb)
within 3 days.
• Whereas the moisture content of the natural
sun-dried samples was reduced to 42%(wb) in
the same period.
• Dried chilli colour in green house dryer was
better than open sun dried sample.
Result and Discussion
23. • Moisture removing rate is more in green house
dryer compare to natural sun drying.
• Max. temperature is obtained up to 57-59 °C.
• High quality of dried products.
• Drying is uniform.
• Large quantity of crops, grain, etc., can be dried in
less time.
• The greenhouse dryer under forced convection
mode is found to be best for high moisture
content crops.
Conclusion
24. References
• Hossain MA. Forced convection solar drying of chilli,
Ph.D. thesis. Bangladesh Agricultural University,
Bangladesh, Mymensingh; 2003.
• Janjai S, Keawprasert T. Design and performance
evaluation of a solar tunnel dryer with polycarbonate
cover. International Energy Journal 2006;7:187-194.
• Muhlbauer W. Present status of solar crop drying. Energy
in Agriculture 1986;5:121-137
• Sharma VK, Colangelo A, Spagna G. Experimental
investigation of different solar driers suitable for fruits and
vegetable drying. Renewable Energy 1995;6:413-424.
