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© 2019 by the authors; licensee Asian Online Journal Publishing Group 
 

Agriculture and Food Sciences Research 
Vol. 6, No. 1, 98-108, 2019 

ISSN(E) 2411-6653/ ISSN(P) 2518-0193 
DOI: 10.20448/journal.512.2019.61.98.108 

© 2019 by the authors; licensee Asian Online Journal Publishing Group 

    
 

 
 
 
Simulation of Grain Quantity, Fan and Solar Collector Sizes for an Experimental 
Forced Convection Grain Dryer 

 
Booker Osodo1 
Daudi Nyaanga2 
Jeremiah Kiplagat3 

 

 
( Corresponding Author) 

 
1Lecturer, Department of Industrial and Energy Engineering, Egerton University, Kenya,  

 
2Associate Professor, Department of Agricultural Engineering, Egerton University, Kenya. 

 
3Director, Institute of Energy Research, Kenya Power, Nairobi, Kenya.  

 

 
Abstract 

Forced convection grain dryers are more efficient and achieve greater drying rates than natural 
convection dryers. However, it is necessary to dry an appropriate grain layer thickness in such a 
dryer for the drying process to occur efficiently and at an appropriate rate. A well sized fan is also 
essential if the drying process is to proceed effectively. An oversize fan will be unnecessarily 
expensive to buy and operate due to high fan power, while an undersized one will not be able to 
supply adequate air flow. The solar collector must be properly sized if it is to heat the air to the 
required temperature. All these factors need to be addressed during the design of a grain dryer. 
Lengthy and expensive trial and error processes can be avoided by applying simulation in the 
design process. This study developed an experimental grain dryer, addressing the above 
mentioned issues in the process. Simulation of air flow within an initial model of the dryer was 
done and the results used to size the fan and drying cabinet. The solar collector was also sized. 
The experimental grain dryer developed consisted of a drying cabinet of dimensions 0.5 m x 0.5 m 
x 1.0 m and was equipped with a 0.039 kW centrifugal fan. The solar collector area was of 
dimensions 1.2 m x 1.8 m. 

 
Keywords: Simulation, Forced convection dryer, Dryer sizing, Fan, Drying cabinet, Solar collector. 

 
Citation | Booker Osodo; Daudi Nyaanga; Jeremiah Kiplagat 
(2019). Simulation of Grain Quantity, Fan and Solar Collector Sizes 
for an Experimental Forced Convection Grain Dryer. Agriculture 
and Food Sciences Research, 6(1): 98-108. 
History:  
Received: 28 February 2019 
Revised: 27 March 2019 
Accepted: 1 May 2019 
Published: 4 July 2019 
Licensed: This work is licensed under a Creative Commons 

Attribution 3.0 License  
Publisher:  Asian Online Journal Publishing Group 
 

Contribution/Acknowledgement: All authors contributed to the conception 
and design of the study. 
Funding: This study received no specific financial support. 
Competing Interests: The authors declare that they have no conflict of 
interests. 
Transparency: The authors confirm that the manuscript is an honest, 
accurate, and transparent account of the study was reported; that no vital 
features of the study have been omitted; and that any discrepancies from the 
study as planned have been explained. 
Ethical: This study follows all ethical practices during writing.   

 

 

Contents 
1. Introduction ...................................................................................................................................................................................... 99 
2. Materials and Methods ................................................................................................................................................................. 100 
3. Results and Discussion ................................................................................................................................................................. 103 
4. Conclusions ..................................................................................................................................................................................... 107 
References ............................................................................................................................................................................................ 107 
 

 

 

 

 

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Contribution of this paper to the literature 
This article demonstrates that it is possible to use simulation in sizing the various components of a solar 
dryer. This will result in savings in time and resources which usually results from the normal design 
process which involves design, fabrication and testing before a prototype is eventually made.   

 
1. Introduction 

A large proportion of food product is often lost between harvesting and consumption. Adebayo, et al. [1] 
stated that loss of crop occurs in the field (15%), during harvesting (13-20%), as well as during processing and 
storage (15-25%). Post-harvest loss of crop may be attributed to different causes. Pests, such as large grain borer 
account for 10-20% loss, while 5-10% of the losses may be attributed to poor storage facilities. Diseases, on the 
other hand, contribute to 5% of post-harvest crop loss [2]. The problem of post-harvest food loss is particularly 
significant in developing countries, where food losses are estimated to be of the order of 40%, though this can rise 
to be as high as 80% under very adverse conditions [3]. For example, incidences of post-harvest product loss in 
Kenya have been estimated at 30%, and can rise to be as high as 100% with the advent of afflotoxin [4]. Post-
harvest loss of maize in Kenya in 2007 was 21.1% [5].  One reason for loss of grain after harvesting is spoilage 
resulting from high moisture content. Moist and partly moist crop is prone to fungus infection, which renders it 
unusable. High moisture content also encourages loss due to attacks by insects, pests and increased respiration. 
Drying of grain is therefore necessary to avoid loss between harvesting and consumption Tiwari [6];Twidell and 
Weir [7]. Barawal and Tiwari [8] reported that drying of crop helps to achieve better product quality, longer safe 
storage and reduction of post-harvest loss hence ensuring more food is available for the growing world population. 

Grain drying may be carried out using different sources of energy. However, solar energy is preferred to other 
alternative sources of energy such as wind and shale since it is abundant, inexhaustible and non-polluting [9]. In 
Forced Convection solar drying, a fan is used to force the air through the grain in order to enhance the circulation 
of the heated air. Such dryers produce greater drying rates and make it easier to control the drying process [10, 
11]. The performance of a dryer may also be evaluated based on other criteria such as drying and dryer efficiency, 
uniformity of drying and quality of final product (extent of cracking and discoloration of grain) as well as total 
drying time [12, 13].  Determination of an optimum design that will ensure best ventilation for any particular 
application is essential to ensure best performance [14]. 

Although forced convection solar dryers achieve greater drying rates than natural convection dryers, their 
performance is often not optimal. One reason for this is inadequate distribution of air flow, resulting in inadequate 
drying air in some sections of the dryer and hence uneven drying of the grain. According to Misha, et al. [15] 
uneven drying is the consequence of poor air flow distribution in the drying chamber. Product closer to the air inlet 
is better dried than that further, due to reduced temperature and air velocity. Sometimes, the fan is undersized, 
leading to insufficient air flow (and velocity), or oversized, leading to excessive energy consumption and in extreme 
cases grain being blown upward. Also use of inappropriate grain layer thickness leads poor performance. If the 
grain layer is too thick, some sections do not dry well as they receive air which is saturated with moisture. If too 
thin, air exits while still having capacity to remove moisture, leading to low thermal efficiency. Design of dryers 
that meet these criteria, without use of simulation, would require troublesome development stages, involving trial 
and error, continued testing and use of prototypes, a process which would be expensive and time consuming. 
Simulation, which is the imitation or reproduction of the behavior of a system or process [16] is useful in the 
design process, as it saves on the time and resources that would otherwise be required to obtain optimal 
performance. In this study, the process of simulation was used to improve on the dryer design and performance. 
The objective of the study was to simulate the grain quantity, fan and solar collector sizes for an experimental 
forced convection grain dryer. 
 

1.1. Solar Thermal Collectors 
A Solar thermal collector serves the purpose of trapping solar radiation which is then used for heating the 

working fluid. It usually consists of a black surface, the absorber, and a transparent cover. The absorber does not 
trap all the incident energy from the sun. It incurs losses due to reflection by the encapsulation (cover) or the 
absorber itself, convection as a result of exchange with the surrounding air, as well as radiation from the hot 
absorber surface. The efficiency of the collector depends on two factors: the extent to which solar radiation is 
converted to heat, and the extent of heat losses to the surroundings [17]. 
For a flat plate collector, solar collector area Ac may be determined from Equation 1 used by Dabra, et al. [18] and 
Aduewa, et al. [19]. 

𝐴𝑐 =
�̇�𝑎𝑐𝑝𝑎(𝑇𝑜−𝑇𝑎)

𝐼𝑐𝜂
                       (1) 

In the equation, �̇�𝑎 and cpa represented air mass flow rate and specific heat capacity respectively, while 𝐼𝑐 and 𝜂 
stood for maximum insolation on collector surface and solar collector efficiency, also respectively. To and Ta were 
used to represent optimum dryer temperature and inlet temperature at ambient. 
 

1.2. Pressure Drop 
Jia, et al. [20] explain that air flow through packed material may be described using the Ergun Equation 2. 

According to this equation, pressure drop , for fluid velocity  depends on particle diameter ( , length 

of bed , fluid viscosity ( void space ( and fluid density (  The effect of cross sectional area (due to 

container diameter) is ignored in this equation. 

        (2) 

Although there are many channels through packed material, fluid will normally only flow through a few of 
them, a phenomenon called channeling. This leads to lack of distribution of fluid flow. Another limitation is that of 
formation of hot spots, which leads to damage to the bed and packing materials [21]. The pressure drop in the 



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drying chamber limits the number of trays that may be used. Due to high resistance to air flow through drying 
product, only a few drying shelves can be used without significantly affecting air movement [22]. 
 

1.3. Fan Sizing 
According to Wilcke and Morey [23] different crops have different airflow requirements for drying, 

necessitating selection of a fan that will deliver airflows within the recommended range. Greater airflows will 
require larger fans, leading to increased costs, while smaller ones may result in unacceptable crop quality. Also, the 
fan must develop sufficient pressure to overcome resistance to airflow. Typical air flow rates range from 0.25-0.51 
m3/s.m2 of perforated screen area, these flow rates creating relatively low static pressures of 0.249-1.25 kPa in 
cross flow and mixed-flow dryers. The fan to be used for such a dryer must be of sufficient capacity to overcome 
this static pressure, being the resistive force the fan works against while trying to push the air through the grain 
column [24]. 

Fan power ( may be obtained either from manufacturers’ charts or from Equation 3 and 4 as suggested by 

Wilcke and Morey [23] as well as Maier and Bakker-Arkema [24]. 

           (3) 

           (4) 

(V̇ is air volume flow rate while Ps  represents static pressure) 
The equations are similar, although for Equation 4 an impeller efficiency of 60% has been assumed and 

incorporated. Weiss and Buchinger [25] stated that fan efficiency ranges between 30 % and 70 %, hence the 
assumption is reasonable to cater for most fans if cost of fan and that of power is the major consideration. In the 
current study, Equation 4 was adopted to cater for a general situation where efficiency of fan does not have to be 
used every time. 
 

2. Materials and Methods 
2.1. Research Site 

The study was carried out in Njoro, Nakuru County, Kenya. Njoro is located 18 km South West of Nakuru 
town. It lies at an altitude of 1800 m above sea level, and experiences temperature ranges between 17-22 ºC. 
Nakuru County is a moderate to high solar energy potential area. The amount of available solar energy is season 
dependent, with the December-February season receiving the highest amount of insolation of 678 kWh/m2. The 
September-November season receives the least insolation of 602.6 kWh/m2. Harvesting is normally carried out 
between August and December, depending on the type of grain [26-28]. 
 

2.2. Simulation to Estimate Grain Layer Thickness and Number of Trays 
Simulation was carried out in order to determine the greatest grain layer thickness that would be penetrated by 

the drying air. This was determined by observing the velocity profile for simulated air flow up different layer 
thicknesses, with the expectation that air velocity would gradually increase up the layer. According to Ergun’s 
Equation 2 the governing equation in the simulation process, fluid velocity increases as pressure drop increases. 
The latter increases as fluid moves up the grain layer, hence fluid velocity is expected to vary in a similar manner. 
Simulation was first carried out of hot air flowing through a single grain layer of 0.1 m thickness, at an air velocity 
of 1 m/s. A parametric sweep was then carried out in order to simulate air flow through various grain layer 
thicknesses ranging between 0.1 m – 0.3 m for air velocities ranging between 1 m/s - 5 m/s. A parametric sweep 
enables simulation within the specified range of parameter values in one simulation process, without having to do it 
for discrete values. The purpose of the parametric sweep was to determine the maximum grain layer thickness that 
would allow the fan to overcome static resistance to airflow.  

Once the maximum allowable layer thickness was determined, simulation of air flow up increasing number of 
grain layers was carried out in order to determine the number of layers the air was able to penetrate. In this case, 
variation of pressure up the drying cabinet with different grain layer numbers was observed. It was expected that 
pressure would decrease gradually up the drying cabinet. Any behavior to the contrary would suggest air was not 
able to penetrate.  

The simulation process was carried out in two major stages: creation of the model and simulation of the model. 
Before simulating air flow up the drying cabinet, a 2-D model of it had to be developed using the software 
SolidWorks. Once created, the model was imported into the COMSOL MULTI-PHYSICS simulation software and 
the process of simulation carried out. The simulation process was also in two major stages: pre-processing and 
post-processing.  Figure 1 summarises the model creation process while Figure 2 summarises the preprocessing 
stage of simulation. 
 



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Figure-1. Model Creation. 

                        Source: Osodo [29]. 
 

 
Figure-2. Flow Chart of Preprocessing Stage of Simulation. 

                         Source: Osodo [29]. 
 

Once simulation was complete, post-processing, summarized in Figure 3, was carried out to extract the results 
in various forms as required. 
 

 
Figure-3. Post-processing Stage of Simulation.  

                            Source: Osodo [29]. 
 

2.3. Sizing of Solar Dryer 
2.3.1. Fan Power Determination 

Having found the grain layer thickness that would allow penetration by the air, the simulated pressure drop for 
this layer thickness was taken as being equivalent to the static pressure to be overcome by the suction fan. This 

static pressure (𝑃𝑆) as well as the corresponding air flow rate (�̇�) was applied in Equation 4 to determine the power 
of the appropriate fan.  
 

2.3.2. Drying Cabinet and Solar Collector 
i. Drying Cabinet 

To determine the cross sectional area of the drying cabinet, a capacity of 18 kg per tray (a mass that an average 
family would dry for milling, and also that can be carried comfortably when loading) was assumed. The volume 
(Vgr), of grain per tray was determined using Equation 5 the grain density for maize being 0.76 g/cc. The cross 



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sectional area of the drying cabinet Acb was then determined from Equation 6 the value of 𝑡𝑔𝑟 (maximum grain 

layer thickness) having been determined as 0.1 m.  

𝑉𝑔𝑟 =
𝑚𝑔𝑟

𝜌𝑔𝑟
             (5) 

𝐴𝑐𝑏 =  
𝑉𝑔𝑟

𝑡𝑔𝑟
            (6) 

(mgr and 𝜌𝑔𝑟 represent mass and density grain respectively) 

The height of the drying cabinet was sized to carry two trays, each holding a grain layer thickness equal to 𝑡𝑔𝑟. 

The void space between the trays, having a height equal to that of the grain layer, and a plenum chamber, as well 
as space above the second tray to accommodate the suction fan were also catered for.  
 
ii. Solar Collector 

The solar collector area (Ac) was determined using Equation 1. To find the air mass flow rate (�̇�𝑎) Equation 7 
and 8 were used. Air velocity was measured at dryer exit, which had a diameter of 0.1 m, using a thermo-
anemometer, cabinet cross sectional area having been found as shown above. 

𝑄 = 𝐴𝑣      (7) 

�̇� = 𝑄𝜌𝑎             (8) 

(Q = flow rate in m3/s, A= cross sectional area in m2, v = air velocity in m/s,  �̇� = mass flow rate in kg/s and 𝜌𝑎= 
density of air in kg/m3)  

Ti was taken to be 23°C (the ambient temperature measured in research area during drying period) and To as 
58°C (the maximum temperature to maintain grain quality). A value of 1200 W/m2 was used as Insolation Ic 

(estimated from measurements in the research area), while a solar collector efficiency (η) value of 83.28 % was used. 
This solar collector efficiency was similar to that reported by Aduewa, et al. [19] at insolation of 1199.46 W/m2. 
 

Plate-1. Side View of Experimental Solar Grain Dryer. 
Source: Osodo [29]. 
 

 
Plate-2. Rear View of Experimental Solar Grain Dryer. 

                      Source: Osodo [29]. 



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3. Results and Discussion 
3.1. Grain Layer Thickness  

In order to select the appropriate grain layer thickness, air flow up different layer thicknesses was simulated. 
The expectation was that air velocity would increase gradually up the grain layer. Any variation from this 
expectation would imply an inappropriate layer thickness. Figures 4 – 7 show velocity profiles for different layer 
thicknesses. 
 

 
Figure-4. Air Velocity up Single Grain Layer of Height 0.1 m & inlet Velocity 1 m/s. 

                       Source: Osodo [29]. 
 

 
Figure-5. Air Velocity up Single Grain Layer of Height 0.2 m & inlet Velocity 1 m/s. 

                            Source: Osodo [29]. 
 

 
Figure-6. Air Velocity up Single Grain Layer of Height 0.25 m & inlet Velocity 1 m/s. 

                            Source: Osodo [29]. 
 



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Figure-7. Air Velocity up Single Grain Layer of Height  0.3 m & inlet Velocity 1 m/s. 

                Source: Osodo [29]. 
 
It is evident that for grain layer thickness of 0.1 m, air velocity increased gradually up the entire grain layer, 

leveling off at the top. This was according to expectations. This implied that 0.1 m would be an appropriate grain 
layer thickness for this dryer, and that the suction fan would be able to overcome the static pressure i.e. resistance 
to air flow, in this case. For other layer thicknesses, this was not the case. For example for grain layer thickness of 
0.2 m at inlet velocities 1 m/s, velocity increased gradually up to a grain layer height of 0.04 m, before falling 
sharply. Air velocity was again showed to be increasing sharply at the upper sections of the grain layer. The trend 
at the section at a height between 0.07 m- 0.18 m did not show, making it difficult to explain what happened. 
However, because the expectation was for the air velocity to rise steadily up the grain layer, it was concluded that 
this was not an appropriate grain layer thickness to use. 

For the velocity profile up 0.25 m grain layer thickness at 1 m/s, air velocity increased up the grain layer, but 
only up to a height of 0.03 m before decreasing, showing again that this was not an appropriate grain layer 
thickness to use. In the case of a 0.3 m grain layer thickness, once again air velocity increased up the grain layer, 
but the increase was not sustained. The velocity dropped way before the top of the grain layer, at a height of about 
0.2 m. This showed that this was not an appropriate grain layer thickness to use. Thus it was concluded that the 
maximum grain layer thickness should be 0.1 m. 
 

3.2. Number of Layers and Trays 
Pressure profiles for simulated air flow up a drying cabinet with different numbers of grain layers are shown in 

Figures 8- 12.  
 

 
Figure-8. Variation of Pressure for Four (4) 0.1 m Thickness Grain Layers. 

                     Source: Osodo [29]. 
 



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Figure-9. Variation of Pressure for Five (5) 0.1 m Thickness Grain Layers. 

                       Source: Osodo [29]. 
 

 
Figure-10. Variation of Pressure for Eight (8) 0.1 m Thickness Grain Layers. 

                             Source: Osodo [29]. 
 

 
Figure-11. Variation of Pressure for Eleven (11) 0.1 m Thickness Grain Layers. 

                        Source: Osodo [29]. 
 



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Figure-12. Variation of Pressure for Sixteen (16) 0.1 m Thickness Grain Layers. 

                  Source: Osodo [29]. 

 
It was found that beyond four (4) grain layers, the linear trend in pressure drop ceased. From five (5) grain 

layers and above, there were sections where there was little or no change in pressure, suggesting that there was 
little or no air flow. Sections where the curve remained horizontal indicated no pressure drop. This trend 
intensified as number of grain layers increased, with the horizontal sections of the curve becoming longer, 
indicating no pressure drop for greater distances up the grain layers. This continued to the extent that for sixteen 
(16) grain layers and beyond, the graph was a horizontal line, showing that there was no pressure drop at all, hence 
suggesting that no air flow through the grain layers occurred. It was therefore concluded that the grain dryer 
should be loaded with at most four (4) trays, each with a maximum grain layer thickness of 0.1 m. 
 

3.3. Sizing of Drying Cabinet and Solar Collector 
Figure13 shows variation of pressure for simulated air flow up a single 0.1 m grain layer. It indicates that there 

was a linear drop in pressure from the lower section of a grain layer upwards.  
 

 
Figure-13. Variation of Pressure for a Single Layer of Thickness 0.1 m. 

                                Source: Osodo [29]. 
 

As shown in Figure 13 the total pressure drop for a single 0.1 m thick layer was 1.28 x 104 Pa, this being the 
difference between the highest (6.9533 MPa) and the lowest pressure (6.9405 MPa). For two layers or trays, the 
total pressure drop would therefore be equal to twice this value. This was due to the assumption that pressure drop 
would be the same for each layer, since they were of equal thickness. Equation 2 indicates that pressure drop 
depends on length of bed and void space which were constant. The other variables, namely particle size, fluid 
viscosity and density were also assumed to be constant. This yielded a total pressure drop of 2.56 x 104 Pa for two 

(2) grain layers, which was found to be equivalent to a static pressure 𝑃𝑠  of 102.8 inches of water. Using Equation 

5 – 8 the air volume flow rate 𝑉𝑠  was determined to be 1.984 cfm. By applying Equation 4 the fan power 𝑃𝑓  was 

found to be 0.053 Hp (0.039 kW).  
 
 

 



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3.3.1. Drying Cabinet Sizing 
Although it was found that maximum number of trays should be four, the experimental dryer was designed to 

carry two trays. Each drying tray with a capacity of 18 kg was sized to be of square cross section 0.5 m x 0.5 m. 
using Equation 5 and 6. The lowest tray was to be placed 0.3 m from the bottom to allow for the plenum chamber, 
and the second one 0.2 m above (0.1 m each for grain layer and void space). Leaving 0.3 m above the upper tray for 
fitting the fan, this resulted in a total drying cabinet height of 1 m.  
 

3.3.2. Solar Collector Sizing 
Using an air velocity, v of 0.3 m/s (the lowest recommended for drying of grains) and drying cabinet cross 

section 0.25 m2, the volume flow rate Q, through the collector was determined to be 0.075 𝑚3/s (mass flow rate �̇� 
= 0.092 kg/s), using Equation 7 and 8. Assuming a maximum temperature To of 58°C (to maintain grain quality), 
and an ambient temperature Ti of 23°C (measured in research area during drying period) as well as an insolation Ic 

of 1200 W/m2, the required solar collector area was determined to be 3.25 m2 after applying Equation 1. A solar 

collector efficiency η of 83.28 %, as achieved by Aduewa, et al. [19] at an insolation of 1199.46 W/m2 was used in 
the determination. 
 

4. Conclusions  
As a result of this study, an experimental grain dryer shown in Figures 4-6 and Plates 1 and 2 was sized and 

fabricated. Simulation led to the conclusion that the grain dryer should be loaded with at most four (4) trays, each 
with a maximum grain layer thickness of 0.1. Having decided to design a dryer with two drying trays, a drying 
cabinet of dimensions 0.5 m x 0.5 m x 1.0 m was adopted. It was designed to be equipped with a 0.039 kW 
centrifugal fan. The solar air heater was designed to have a collector area of 3.25 m2.  
 

References 
[1] A. B. Adebayo, G. Ndunguru, P. Mamiro, B. Alenkhe, N. Mlingi, and M. Bekunda, "Post-harvest food losses in a 

maize-based farming system of semi-arid savannah area of Tanzania," Journal of Stored Products Research, vol. 57, pp. 
49-57, 2014. Available at: https://doi.org/10.1016/j.jspr.2013.12.004. 

[2] C. Bett and R. Nguyo, "Post-harvest storage practices and techniques used by farmers in semi-arid Eastern and 
Central Kenya," in African Crop Science Conference Proceedings, 2007, pp. 1023-1222. 

[3] B. O. Bolaji and A. P. Olalusi, "Performance evaluation of a mixed mode solar dryer," AU Journal of Technology, vol. 
11, pp. 225-231, 2008. 

[4] J. Irungu, "Post harvest challenges to food security in Kenya," presented at the A paper presented at KCB Leadership 
Center, Karen, Nairobi, 2010. 

[5] R. Hodges, Supplying cereal grain postharvest losses information: The examples of ALPHIS (African postharvest Loss 
information system). UK: Natural Resources Institute, 2009. 

[6] G. N. Tiwari, Solar energy: Fundamentals, design, modeling and applications. Parybourne: Alpha Science International 
Limited, 2002. 

[7] J. W. Twidell and A. D. Weir, Renewable energy resources. London: English Language Book Society, 2006. 
[8] P. Barawal and G. N. Tiwari, "Grape drying by using photovoltaic thermal (PV/T) green house dryer: An 

experimental study of solar energy," Solar Energy, vol. 62, pp. 1131-1144, 2008. 
[9] O. A. Akinona, A. A. Akinyemi, and B. O. Bolaji, "Evaluation of traditional and solar fish drying systems towards 

enhancing fish storage and preservation in Nigeria," Fish International: Pakistan, vol. 1, pp. 44-49, 2006. 
[10] D. G. Mercer, "A comparison of the kinetics of Mango drying in open-air, solar and forced air dryers," African Journal 

of Food, Agriculture, Nutrition and Development, vol. 12, pp. 6835- 6852, 2012. 
[11] Y. I. Sallam, M. H. Aly, A. F. Nassar, and E. A. Mohamed, "Solar drying of whole mint plant under natural and forced 

convection," Journal of Advanced Research, vol. 6, pp. 171-178, 2013. Available at: 
https://doi.org/10.1016/j.jare.2013.12.001. 

[12] M. Mohanraj and P. Chandrasekar, "Performance of a forced convection solar drier integrated with gravel as heat 
storage material for chili drying," Journal of Engineering Science and Technology, vol. 4, pp. 305-314, 2009. 

[13] A. Kassem, M. A. Al-Sulaiman, A. Aboukarima, and S. Kassem, "Predicting drying efficiency during solar drying 
process of grapes clusters in a box dryer using artificial neural network," Australian Journal of Basic and Applied 
Sciences, vol. 5, pp. 230-241, 2011. 

[14] J. K. Afriyie, H. Rajakaruna, M. A. Nazha, and F. Forson, "Simulation and optimisation of the ventilation in a 
chimney-dependent solar crop dryer," Solar Energy, vol. 85, pp. 1560-1573, 2011. Available at: 
https://doi.org/10.1016/j.solener.2011.04.019. 

[15] S. Misha, S. Mat, M. A. M. Rosli, M. H. Ruslan, K. Sopian, and E. Salleh, "Simulation of air flow in a tray dryer by 
CFD," Recent Advances in Renewable Energy Sources, vol. 1, pp. 29-34, 2013. 

[16] C. A. Frangopoulos, M. R. Von Spakovsky, and E. Sciubba, "A brief review of methods for the design and synthesis 
optimization of energy systems," International Journal of Applied Thermodynamics, vol. 5, pp. 151-160, 2002. 

[17] J. Klaus, I. Olindo, H. M. S. Amo, A. C. Rene, and Z. Miro, "Solar energy: Fundamentals, technology and Systems," 
Delft University of Technology, 2014. 

[18] V. Dabra, L. Yadav, and A. Yadav, "The effect of tilt angle on the performance of evacuated tube solar air collector: 
experimental analysis," International Journal of Engineering, Science and Technology, vol. 5, pp. 100-110, 2013. Available 
at: https://doi.org/10.4314/ijest.v5i4.9. 

[19] T. O. Aduewa, A. S. Ogunlowo, and S. T. Ojo, "Development of hot air supplemented solar dryer for white yam 
(Dioscorea Rutundata) slices," IOSR Journal Of Agricultural And Veterinary Services, vol. 7, pp. 114-123, 2014. Available 
at: https://doi.org/10.9790/2380-07122114123. 

[20] Y. Jia, Y. Li, and D. Hlavka, "Flow through packed beds." Available: http:/ 
www.me.rochester.edu/courses/ME241/11-sand.pdf. [Accessed 14th September 2014], 2009. 

[21] S. Sachdeva, S. Pareek, B. Mahadevan, and A. Deshapande, "Modeling and simulation of single phase fluid flow and 
heat transfer in packed bed," in Proceedings of 2012 COMSOL Conference, Bangalore, 2012. 

[22] W. Aissa, M. El-Sallak, and A. Elhakem, "Performance of solar dryer chamber used for convective drying of sponge-
cotton," Thermal Science, vol. 18, pp. 451-462, 2014. Available at: https://doi.org/10.2298/tsci110710084a. 

[23] W. F. Wilcke and R. V. Morey, "Selecting fans and determining airflow for crop drying, cooling and storage. 
Available: http://www.extension.umn.edu/agriculture/crops. [Accessed 15th September 2015], 2015. 

http://www.me.rochester.edu/courses/ME241/11-sand.pdf
http://www.extension.umn.edu/agriculture/crops


Agriculture and Food Sciences Research, 2019, 6(1): 98-108 

108 
© 2019 by the authors; licensee Asian Online Journal Publishing Group 

 

 

[24] D. E. Maier and F. W. Bakker-Arkema, "Grain drying systems," in Paper Presented at Facility Design Conference of 
Grain Elevator and Processing Society held on July 28-31 in St Charles, Illinois, USA, 2002. 

[25] W. Weiss and J. Buchinger, Solar drying. Training course within the scope of the project establishment of a production, sales 
and consulting infrastructure for solar thermal plants in Zimbabwe. Australia: Australian Development Cooperation, 
Institute of Sustainable Technologies, 2012. 

[26] L. M. Omwando, "Assessment of solar energy potential for Nakuru, Kenya," Unpublished Masters Thesis, Jomo 
Kenyatta University of Agriculture & Technology, Kenya, 2012. 

[27] D. Walubengo, "Community-led actions in building resilience to climate change: A Kenya case study. Retrieved from 
pubs.iied.org/pdfs/go2310pdf . [Accessed 30th November 2015]," 2007. 

[28] H. Maloba, W. Shivonga, M. Muchiri, and S. N. Miller, "Use of benthic macro-invertebrates as indicators of water 
quality in Njoro River, Kenya," in Proceedings of TAAL 2007: the 12th World Lake Conference, 2008, pp. 2161-2168. 

[29] B. O. Osodo, "Simulation and optimisation of a drying model for a forced convection grain dryer." Unpublished PhD 
Thesis, Kenyatta University, Kenya, 2018. 

 

 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

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