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European Journal of Applied Sciences – Vol. 12, No. 3
Publication Date: June 25, 2024
DOI:10.14738/aivp.123.16907.
Mackpayen, A. O., Ekoe, A. A., & Pakouzou, M. (2024). Mathematical Modelling and Numerical Simulation of The Behaviour of
the Modified Icaro Dryer Sensor. European Journal of Applied Sciences, Vol - 12(3). 543-562.
Services for Science and Education – United Kingdom
Mathematical Modelling and Numerical Simulation of The
Behaviour of the Modified Icaro Dryer Sensor
Auguste Oscar Mackpayen
Laboratoire d’Energétique Carnot (L.E.C) / Université de Bangui,
B.P: 908 Bangui (RCA) and Laboratoire sur l’Energie Solaire (L.E.S)
/Université de Lomé, B.P: 1515 Lomé-(TOGO)
Aloys Martial Ekoe A Akata
Renewable Energy Systems Technologies Laboratory (RESTL),
University of Douala, P.O. Box 24157 Douala, Cameroon
Magloire Pakouzou
Laboratoire d’Energétique Carnot (L.E.C) /
Université de Bangui, B.P: 908 Bangui (RCA)
ABSTRACT
It has often been observed that traditionally dried coffee has a tainted taste, due to
the use of fortune devices. This study was undertaken to provide an approach to
solutions. The aim here is to model the modified Icaro solar dryer. This work
involves the study of a single-pass solar air collector for drying coffee. The
mathematical modelling of the collector is based on the nodal method applied to
the electrical analogy to study the thermal exchanges. The results of the
temperature profile are obtained for a velocity of 1.5 m.s-1 , an air flow rate of 0.16
kg.m-3 and an absorber surface area of 5.4 m2 . In addition, for surfaces and flow
rates varying respectively from 5 m2 to 7 m2 and 0.08 kg.h-1 and 0.35 kg.h-1, we
obtained peak temperatures of 72.37 °C and 80 °C respectively. This enabled us to
follow the behaviour of these temperatures from top to bottom and along the
length of the sensor.
Keywords: dryer, sensor, drying, coffee, modelling
INTRODUCTION
The use of flat-plate air collectors to supply hot air to dryers for agricultural products has
become a common technique in recent years, due to the quantities of energy required for a
drying operation and the increase in their cost. The implementation of drying processes
requires enough energy and the royal road for countries with a lot of sunshine, including
Central African Republic should be solar energy. The Central African Republic had a
population of 5.8 million (O’Toole et al., 2024) with relatively low energy production: 1) it is
estimated that 50% of the country is forested, and that 10% of this biomass is currently used
to meet energy needs (Zhao et al., 2024); 2) the hydroelectric power is estimated at 2,000 MW
(Hannah et al., 2020); 3) the country does not currently produce either petroleum or natural
gas. Energy selfsufficiency for the country stood at approximately 91 per cent; 4) Wind speeds
above 5 m/s exist implying the potential for wind energy. But so far, wind power use is still
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European Journal of Applied Sciences (EJAS) Vol. 12, Issue 3, June-2024
largely uncharted; 5) The average horizontal irradiation, which reaches 6.0 kWh/m2/day in
some areas, makes solar power a viable option. The Central African Republic (CAR) is a
country with a large solar resource averaging 5.4 kWh/m2/day, almost all year round (Chara- Dackou et al., 2022). Chara-Dackou developed three numerical models to estimate the solar
radiation in Birao, Central African Republic and evaluated the feasibility of a concentrating
solar power (CSP) plant. A techno-economic analysis presented in their study indicates that
the solar resource in CAR can support any system using solar technology (Chara-Dackou et al.,
2023).
The flat plate solar collector is a device designed to collect the energy transported by solar
radiation and convert it into thermal energy transmitted to a heat transfer fluid (gas or liquid)
by convection across the heat exchange surface. There are two types of collector: flat-plate
water collectors and flat-plate air collectors (Ahmed et al., 2007). Flat-plate collectors can
handle temperatures ranging from 30°C to 150°C and do not require the radiation to be
concentrated. Shemelin presented a theoretical analysis of flat plate solar collectors with a
vacuum glazing with different configurations based on a combined external and internal
energy balance. The results of the study show that, it is possible to achieve efficiency better
than vacuum tube collectors (Shemelin and Matuska, 2017). Flat plate solar collector can be
constructed with and without reflectors. The integration of reflectors increases the thermal
performance of the collector. The thermal efficiency obtained for the flat plate solar collector
with reflectors integrated is 51.8% whereas that of the collector without reflectors integrated
is 46.2% (Tigabe et al., 2022). The heat transfer of flat plate collector can be improved by
modifying the geometry of the collector. Many studies have been carried out to improve the
heat transfer rate of flat plate solar water collector by adding fins with helical, rectangular,
circular, trapezoidal and twisted cross-sections (Badgujar et al., 2017).
In the agricultural sector, notably solar food drying, the fluid used in collectors is air. The
flatplate air collector is a device consisting of one or more transparent glass covers over an
absorber plate, so that air (the fluid) can circulate above or below the absorber plates.
Sakouvogui conducted a study from March to April 2022 on a solar potato dryer built from
local materials in Guinea. The study focused on the main geometric parameters such as the
height, length and width of the drying chamber, the surface area of the drying grids and the
surface area of the heat accumulator they obtained an average drying rate of 0.074 kg/h
(Sakouvogui et al., 2023). Abou analyzed the effect of drying air velocity on tomato drying
kinetics in a forced convection solar drying tunnel in Niamey on the 1st and 5th of January
2019. Their study showed that drying air velocity has a significant impact on drying kinetics.
Higher drying air velocity leads to an earlier critical point and shorter drying time during the
drying process. (Abou et al., 2019). A comparative study of the technologies and operating
principles of direct, indirect, mixed and hybrid solar dryers has been presented by Kong and
Khalil. In particular, hybrid solar dryers integrated with electric heating, biomass energy,
thermal energy storage and wind power, to highlight their advantages and disadvantages.
They concluded that hybrid solar dryers can provide stable, continuous drying, effectively
improving dryer performance and product quality. They also highlighted the limitations of
using traditional solar dryers: longer drying times, low drying efficiency, difficulty in
controlling drying air temperature, impossibility of continuous drying during the day, and
lack of electricity in some remote areas to run the fan in forced convection mode. (Agarwal et
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Mackpayen, A. O., Ekoe, A. A., & Pakouzou, M. (2024). Mathematical Modelling and Numerical Simulation of The Behaviour of the Modified Icaro
Dryer Sensor. European Journal of Applied Sciences, Vol - 12(3). 543-562.
URL: http://dx.doi.org/10.14738/aivp.123.16907
al., 2021; Khalil et al., 2023; Kong et al., 2024). Numerous studies have also been carried out
to improve the performance of solar dryers. Vijay recommended that a solar dryer be fitted
with an inverted absorber and reflector to collect as much solar radiation as possible, in order
to optimize its performance. His study showed that parameters such as average collector
efficiency, drying efficiency and the dryer fitted with an inverted absorber and a reflector
were significantly higher than dryers without a reflector and without an absorber,
respectively (Khawale et al., 2023). According to the studies carried out by Sheelam and
Mosuru, dryers with a rough absorption surface improve convective heat transfer
characteristics compared to a flat surface (Mosuru and Chandramohan, 2024; Sheelam and
Velayudhan Parvathy, 2024).
The drying of agricultural products, such as coffee, cocoa and cassava produced in hot and
humid equatorial zones, is often difficult and imperfect. To overcome this, coffee must be
subjected to treatments. During these treatments, the nutritional and sensory quality of the
coffee can deteriorate, mainly due to the drying method used. The product has an altered
taste, due to the smell of the soil, the drying method used and above all, the makeshift devices
(Mackpayen et al., 2015). To ensure the success of such an operation, it is essential to combine
the drying enclosure with an appropriate collector, whose operating temperatures make it
possible to obtain a reduced drying time and a good quality dry product within an interesting
range of their efficiency.
This work deals with the experimental study using the modified Icaro solar dryer
implemented for coffee drying. The design and realization of this dryer were possible based
on the authors previous work (Bechis and Barigazzi, 2013; Pakouzou et al., 2022b). The
choice and modification of the old Icaro dryer must meet the requirements of the target
product, the availability of technology, manufacturing materials and climatic conditions. A
novel approach to mathematical modeling and numerical simulation of the modified Icaro
dryer, utilizing the nodal method applied to the electrical analogy for thermal exchanges is
under consideration to find the thermal behaviour of a single-pass solar air collector. The aim
is to arrive at a set of mathematical equations that will be solved by a numerical method.
MATERIALS AND METHOD
Description of the Air Collector
The air collector consists mainly of the glass pane, the absorber and the insulation. The air
entering the collector at ambient temperature is heated by solar radiation transmitted
through the glass. Once the air has entered the space between the collector and the drying
booth, it changes direction and is heated further by licking the back of the absorber as it
enters the drying booth at a temperature sufficient to heat the product in the booth. It collects
the energy given off by the absorber, has thermal insulation and a casing. Figure 1 shows the
various heat exchanges in the collector. There oT are temperatures of the sky, the glass
(external and internal), the insulation (external and internal), the ambient and the vacuum
absorber.