Senior Design Project Report and Presentation

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. 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. Key Objectives
 Literature Review
 Quality assessment of MAPs
 Analysis of Metrological data
 Design Phase
 Fabrication
 Results
 Future works

4. Literature Review

5. Quality assessment of
MAPs

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. 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. 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. 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. Design Phase

11. Meteorological Data

15.  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.

16. 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

17. Average Monthly Total Irradiation,
HT

18. Solar Absorbed Irradiations, S

19. Proposed Design of Solar Dryer

20. 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

21. Lab Scale/Scaled Down Model

22. 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

23. 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

24. Solar Collector
 Thermocol
insulation at the
bottom
 Metal sheet with
inclined ribs over
thermocol sheet
 a low iron content
glass

25. Artificial Roughness and
corrugation

26. 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.

27. 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=

28. Calculations of Losses in Solar
Collector
Thermal losses
Back losses
Edge losses

29. Edge and Back Losses
 Ut
 Ub
 Ue
 Now Total Losses in our collector are
accumulated to be:
UL

30. Outlet Temperature and efficiency
of Solar Collector

31. 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

32. 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

33. Mixing valves

34. Drying Chamber

35. Drying Chamber
Initial moisture = 70%
Final moisture = 10 %
Total drying load=6 kg
Moisture to be removed=4 kg
Total energy required=9 MJ

36. 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

37. 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.

38. 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=

39. 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.

40. Responsibility Assignment
Matrix

41. Gantt Chart

42. 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.

43. 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.