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Design and development of solar air dryer for medicinal and aromatic plants

Senior Design Project Report and Presentation

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Design and development of solar air dryer for medicinal and aromatic plants

  1. 1. DESIGN AND DEVELOPMENT OF SOLAR AIR DRYER FOR MEDICINAL AND AROMATIC PLANTS Group Members: NS Abdullah Bin Masood PC Mubashar Sharif NS Haider Iqbal Project DS: Asst. Prof. Ahmed Sohail
  2. 2. Introduction  There are several MAPs that naturally grow in northern areas of Pakistan.  These are in wet conditions when they are harvested.  These are conventionally being dried in open.  Our purpose is to dry these MAPs utilizing the solar energy, in a controlled environment.
  3. 3. Key Objectives  Literature Review  Quality assessment of MAPs  Analysis of Metrological data  Design Phase  Fabrication  Results  Future works
  4. 4. Literature Review
  5. 5. Quality assessment of MAPs
  6. 6. Selection of Ambient Temperature for Solar Dryer: No Botanical name Local name Part Harvesting months Drying Temperature (0C)/ Drying condition 1 Biostorta amplexicaulis Anjabar Roots/Rhizomes April to august 45-50/ Sunlight 2 Valariana jatamansi Mushk bala Roots/Rhizomes July to September 45-50/ Shade 3 Viola Spp (flowers) Banafsha Flowers March - April 45-50/ Shade 4 Paeonea emodi Mamekh Roots July to September 50-55/ Sunlight 6 Berberis lycium Kwaray Root Bark October to December 45-50/ Sunlight 6 Matricharia chamomilla Babona Flowers March to April 45-50/ Shade 7 Morchella spp Gochai Plant (stalk+pilus) March to April 40-45/ Diffused Sunlight 8 Trillium govanianum Matar jari Roots May to June 45-50/Sunlight
  7. 7. Dryer Load No Botanical name Local name Part Average Produce in Kg/Cluster 1 Biostorta amplexicaulis Anjabar Roots/Rhizomes 300 2 Valariana jatamansi Mushk bala Roots/Rhizomes 200 3 Viola Spp (flowers) Banafsha Flowers 5 4 Paeonea emodi Mamekh Roots 100 6 Berberis lycium Kwaray Root Bark 30 6 Matricharia chamomilla Babona Flowers 1 7 Morchella spp Gochai Plant (stalk+pilus) 5 8 Trillium govanianum Matar jari Roots 15
  8. 8. Final Moisture Content of the Product: No Botanical name Local name Part Recommended Moisture contents after drying 1 Biostorta amplexicaulis Anjabar Roots/Rhizomes Less than 15% 2 Valariana jatamansi Mushk bala Roots/Rhizomes do 3 Viola Spp (flowers) Banafsha Flowers Less than 10% 4 Paeonea emodi Mamekh Roots Less than 15% 6 Berberis lycium Kwaray Root Bark do 6 Matricharia chamomilla Babona Flowers Less than 10% 7 Morchella spp Gochai Plant (stalk+pilus) do 8 Trillium govanianum Matar jari Roots Less than 15%
  9. 9. Design Parameters for Solar Dryer  Drying Temperature: variable can be changed as desired However, drying air temperature between 50 and 60°C is feasible for drying a large variety of medicinal plants.  Dryer Load: Lab scale model, drying 6 Kg of MAPs  Moisture Content: from 70% to 10%
  10. 10. Design Phase
  11. 11. Meteorological Data
  12. 12.  Meteorological data obtained from PMD and METEONORM Satellite based data shows that annual average PSH (peak sun hours) available are sufficient to be utilized for solar drying operation.  Average clear sunny days: 270-300.  Average solar intensity: 4.5 kWh/m2-day.
  13. 13. Calculation of Average Irradiation  Ф= 33.67ᴼ  Slope of collector= β=30ᴼ  Collector is faced towards south For winter (from Duffie and Beckman)  β=30-15= 15ᴼ for summer  β=30+15= 45ᴼ  Average β=30ᴼ
  14. 14. Average Monthly Total Irradiation, HT
  15. 15. Solar Absorbed Irradiations, S
  16. 16. Proposed Design of Solar Dryer
  17. 17. Design specifications of Solar Dryer  Load capacity: 500 kg  Solar collectors: 30m2 (15x 2m2 collectors)  32 different MAPs can be dried simultaneously  Capable of drying volatile MAPs  No interference of moisture in atmosphere  Negligible energy losses due to walls insulation
  18. 18. Lab Scale/Scaled Down Model
  19. 19. Design specifications of Lab Scale Model  Load Capacity: 6 kg  Solar collector: 1m2  2 different MAPs can be dried simultaneously  Capable of drying volatile MAPs  Well insulated
  20. 20. Working Principle  Fresh air is heated in Solar Collector  Then transferred to chamber via Pipes  This heated air is passed over the MAPs in chamber  Thus hot air takes away their moisture contents
  21. 21. Solar Collector  Thermocol insulation at the bottom  Metal sheet with inclined ribs over thermocol sheet  a low iron content glass
  22. 22. Artificial Roughness and corrugation
  23. 23. Size of Solar Collector  Total load=M= 6kg  Initial moisture content= mi= 70%  Final moisture content= mf= 10%  Water to be removed=  Now since,  we get approx. 10-12 MJ/m2/day for the solar energy, with an efficiency of 50% of solar collector.
  24. 24. Collector Specfication  Plate to cover spacing=25mm  Plate emittance=0.98  Ta= 30ᴼC = 303K  Wind heat transfer coefficient= 10 W/m2 ᴼC  mass flow rate = 0.04 kg/sec  volume flow rate  Velocity=
  25. 25. Calculations of Losses in Solar Collector Thermal losses Back losses Edge losses
  26. 26. Edge and Back Losses  Ut  Ub  Ue  Now Total Losses in our collector are accumulated to be: UL
  27. 27. Outlet Temperature and efficiency of Solar Collector
  28. 28. Pipes  Length of pipe= 1.2 m  Pipe inlet temperature= 55 ᴼC = 328 K  Pipe outer Dia= 3 in = 0.076m  Thickness of pipe= 0.5 cm= 0.005m  Pipe inner Dia= 0.066m  Ambient temperature=30 ᴼC = 303 k  Heat transfer co-efficient outside the pipe= 18.9 W/m2 ᴼC  Velocity of air in the pipe= 2.46 m/sec  Heat transfer co-efficient inside the pipe= 31.12 W/m2 ᴼC
  29. 29. Pipe insulation Ri=1/h1A1 R1= [ln(r2/r1)]/[2 (3.14)K1 L] R2= [ln(r3/r2)]/[2 (3.14)K2 L] R3=1/h2A2 Rtotal = Ri + R1 + R2 + R0 Thickness of insulation is 0.0095 m = 0.950 cm Heat loss without insulation= 46 W/m Heat loss with insulation= 15 W/m
  30. 30. Mixing valves
  31. 31. Drying Chamber
  32. 32. Drying Chamber Initial moisture = 70% Final moisture = 10 % Total drying load=6 kg Moisture to be removed=4 kg Total energy required=9 MJ
  33. 33. Psychometric Analysis  Inlet air temperature =50ᴼC  Wet bulb temp of inlet air= 38ᴼC  Relative humidity of inlet air= 46%  Dew point temperature= 35.73 ᴼC  Enthalpy= 149.3 kJ/kg  Density= 1.07 kg/m3  Specific volume= 0.972 m3/kg
  34. 34. Required mass flow rate in chamber  Quantity of air required for drying can be calculated from energy balance equation as:  maCp (Tb-Tc)= mwL or,  Ma= mass of air  ΔWcb= change in humidity ratio  Mw= mass of water to be removed= 4kg  n= pickup factor= 0.25  Q= ma x Vs = 0.09 m3/s Here, Q is the volume flow rate, Vs is the specific volume of drying air.
  35. 35. Drying air conditions  Rate of evaporation= Kg x A x (Ys – Ya)= 1.98 x 10-4 kg/s  hc= 13.6 J/m2s ᴼC where, hc is the heat transfer co-efficient from air to water  Outlet temperature of air from drying chamber= 34ᴼC  Relative humidity of outlet air from drying chamber=
  36. 36. Drying time t = w (Xo- Xc) / (dw /dt)const. where (dw /dt )const. = k'gA(Ys -Ya)  the constant drying time comes out to be approx. 4 hours. t = w (Xo- Xc) / f (dw /dt)const.  Falling rate period comes out to be 3.1 hours.  So, our total drying time is 7.1 hours.
  37. 37. Responsibility Assignment Matrix
  38. 38. Gantt Chart
  39. 39. Results  After completing the fabrication of our lab scale model, experimental results validated our theoretical deductions and calculations upto an acceptable extent. Collector should increase the temperature by 23 ᴼC theoretically whereas we are getting an increase of 21 ᴼC experimentally.  Furthermore, the drying time that we had calculated theoretically was about 7.1 hours and experimentally we had dried the same load of MAPs reducing moisture contents from 70% to 10%; in approximately 7.5 hours.  The small difference between theoretical and experimental values is because we had not taken certain smaller or lesser affective factors into account theoretically to avoid complexity in our calculations.
  40. 40. Future Works  A biomass air heater along with a heat exchanger can be used in order to keep the plant running even if there is no Solar irradiation.  Also the working operation of this solar dryer can be fully automated; eliminating the need of continuous supervision of an operator, that if the MAPs placed in drying chamber have been dried to desired level or not. This can be done by installing a humidity sensor with an alarm and/or an actuator. The humidity sensor will continuously be checking the humidity of air exiting the drying chamber and when the MAPs have been dried up to a desired limit, the humidity of air exiting the chamber would also have fallen to that particular value. Now when the humidity of air falls to a required value, the alarm should start ringing so that operator comes and takes out the MAPs placed inside drying chamber; whereas the actuator will cut the supply of air to drying chamber by closing a valve on the main supply duct/pipe line.  Furthermore, another automatic system can be added which should load/unload the MAPs as and when required without any human effort.

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