Scientia et Technica Año XXVIII, Vol. 28, No. 01, enero-marzo de 2023. Universidad Tecnológica de Pereira. ISSN 0122-1701 y ISSN: 2344-7214
15
Simulation of a flat solar collector with thermal
storage for drying food
Simulación de un colector solar plano con almacenamiento térmico para el secado
de alimentos
A D Rincón-Quintero ; L A del Portillo-Valdés ; C L Sandoval-Rodríguez ;
B E Tarazona-Romero ; W L Rondón-Romero
DOI: https://doi.org/10.22517/23447214.24835
Scientific and technological research paper
Abstract—This research addresses the numerical simulation of a
working fluid, using specialized SolidWorks Flow Simulation
Software, analyzing the behavior of a drying air in a flat solar
collector with thermal energy storage. In addition, one of the main
centers of computational study is the relationship between flow,
air temperature at the outlet of the collector and efficiency; This
study allows researchers a vision of the principles of the design of
these technologies, especially if it focuses on the drying of food.
Then, a proposal is made on the requirements to be taken into
account for the sizing of collectors based on the requirements of
the product to be dried. Among the results obtained, it is
established that a correctly designed collector and under a
variable air flow, based on the intensity of the irradiation in
specific coordinates and location, can reach efficiencies close to
30% with temperatures close to 60 ° C, being ideal for injecting
this fluid into a drying chamber, where the food to be dehydrated
is available. For the selection of the volume of the material for
energy storage, it is recommended to take the melting
temperatures as a base, with a constant flow of air, it is normal
that within the system, the temperature varies depending on the
position, therefore it is recommending the application of materials
with different melting temperatures, which are strategically
located within the storage tank.
Index Terms— drying; numerical fluid simulation; solar
collector; solar energy; thermal energy storage.
Resumen—Esta investigación aborda la simulación numérica de
un fluido de trabajo, utilizando el software especializado
SolidWorks Flow Simulation, analizando el comportamiento de un
aire de secado en un colector solar plano con almacenamiento de
energía térmica. Además, uno de los principales centros de estudio
computacional es la relación entre caudal, temperatura del aire a
la salida del colector y eficiencia; Este estudio permite a los
investigadores una visión de los principios del diseño de estas
tecnologías, especialmente si se enfoca en el secado de alimentos. A
continuación, se hace una propuesta sobre los requisitos a tener en
cuenta para el dimensionamiento de los colectores en función de
los requisitos del producto a secar. Entre los resultados obtenidos,
This manuscript was submitted on June 29, 2021 and accepted on March 09,
2023 and published on March 31, 2023.
Derived product of the research project “Simulation of a flat solar collector
with thermal storage for drying food”, presented by the research group in design
and materials DIMAT, Faculty of Natural Sciences and Engineering. Unidades
Tecnológicas de Santander.
A D Rincón-Quintero, Unidades Tecnológicas de Santander, Bucaramanga,
Colombia, Calle de los estudiantes, 680005 CO (arincon@correo.uts.edu.co).
se establece que un colector correctamente diseñado y bajo un
flujo de aire variable, en función de la intensidad de la irradiación
en coordenadas y ubicación específicas, puede alcanzar eficiencias
cercanas al 30% con temperaturas cercanas a los 60 ° C, siendo
ideal para inyectar este fluido en una cámara de secado, donde se
encuentra disponible el alimento a deshidratar. Para la selección
del volumen del material para almacenamiento de energía, se
recomienda tomar como base las temperaturas de fusión, con un
flujo de aire constante, es normal que, dentro del sistema, la
temperatura varíe dependiendo de la posición, por lo tanto,
recomienda la aplicación de materiales con diferentes
temperaturas de fusión, los cuales se encuentran estratégicamente
ubicados dentro del tanque de almacenamiento.
Palabras claves— almacenamiento de energía térmica; colector
solar; energía solar; secado; simulación numérica de fluidos.
I.
INTRODUCTION
RYING is an excellent agricultural activity to overcome
spoilage problems in foods such as fruits, vegetables, and
grains. Due to the high energy consumption, this process
represents an important cost in the industry, because it is
required for storage and transportation, it is estimated that this
represents between 10-15% of the total industrial energy
consumption [1]–[3].Additionally, the energy domain is
experiencing an accelerated effort to find solutions to the
current energy crisis, due to the excessive use of fossil fuels for
thermal processes [4].
Renewable energy sources and energy storage are addressed
as possible solutions. An example of this is the use of the sun in
rural areas for drying food, which is naturally used by different
farmers. Within a sustainable development for the efficient use
of renewable energies, different types of solar collectors have
been proposed to generate a drying control, reducing times and
guaranteeing the quality of the product in each of the harvests.
L A del Portillo-Valdés. Universidad del País Vasco UPV/EHU Bilbao,
España, Plaza Ingeniero Torres Quevedo.1 48013 (luis.delportillo@ehu.eus).
C L Sandoval-Rodríguez, Unidades Tecnológicas de Santander,
Bucaramanga, Colombia, Calle de los estudiantes, 680005 CO
(csandoval@correo.uts.edu.co).
B E Tarazona-Romero, Unidades Tecnológicas de Santander, Bucaramanga,
Colombia, Calle de los estudiantes, 680005 CO (btarazona@correo.uts.edu.co).
W L Rondón-Romero, Unidades Tecnológicas de Santander, Bucaramanga,
Colombia, Calle de los estudiantes, 680005 CO (wrondon@correo.uts.edu.co).
D
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Scientia et Technica Año XXVIII, Vol. 28, No. 01, enero-marzo de 2023. Universidad Tecnológica de Pereira
Leaving aside the dependence on atmospheric and
environmental conditions [5]–[7].
When it comes to the development of drying systems in
developing countries that take advantage of solar energy, the
flat collector and the storage of thermal energy become an
effective tool. Additionally, when an efficient use of solar
radiation is applied through an absorbent metal plate and
adequate insulation, improvements in drying times are reflected
in research [8].
In this research, numerical computational simulation is used
to address the analysis of the behavior of fluids, within a solar
collector with latent thermal energy storage, in order to seek the
highest efficiency, simulating a flow control and seeking to
maintain values of temperature that contributes to quality
drying [9].
II.
MATERIALS AND METHODS
The purpose of this research is focused on achieving a more
complete understanding of the behavior of air heating systems
using flat solar collectors, using thermal energy storage to
improve stability in a real environment. When we talk about
solar radiation, the condition of instability is present, due to the
different environmental variables that can affect the power of
the radiation that affects a certain point or place on earth.
Variables such as inclination, position, time of day, atmospheric
conditions, the ability of a material to absorb, reflect and
transfer this energy, are issues that must be considered when
designing a solar collector. Additionally, the application or
energy requirement of the collector is essential when making
decisions about its sizing [10]–[12].
To begin addressing the proposed research, a foray into
databases is made, reading different scientific articles and
books on food dryers. In this search, the classification of these
is identified, whose main distinguishing characteristic is
oriented to the form of use of solar energy. The systems that
allow direct radiation from the sun to the product are called
direct dryers; Those that use a solar collector to heat the air,
which is directed to a chamber containing the product, is called
indirect dryer and those that combine these two concepts are
called mixed dryers. Additionally, when another source of
energy is added to compensate for the instability of the sun, it
can be defined as a hybrid dryer [13], [14].
Solar collectors are mainly composed of a metal plate with a
special coating to improve the absorption capacity of solar
energy, additionally they have a transparent cover or layer,
which has the function of allowing the passage of solar rays so
that they can impact on the absorbent plate and fulfill the role
of thermally insulating the system so that heat is not transferred
to the environment in an accelerated way. Under the conditions
described above, a collector efficiently takes advantage of solar
radiation to heat fluids such as water and air [15].
In order to make a simulation as close to reality, it is
important to define characteristics, such as the collector
material that defines its thermal resistance, solar radiation
(power and direction or angle of incidence), air flow, among
other specifications necessary for a correct execution of the
Flow Simulation program. In order to identify the properties
that are used in a flat solar collector, databases are approached
in the search for scientific articles that present information on
computational numerical simulations.
A.
Characteristics of the simulation of the manifold for drying.
As previously stated, the project focuses on the design of a
collector for drying cocoa or other agricultural products such as
coffee. Based on the literature, these systems must reach
temperatures close to 60 ° C to generate quality drying without
damaging the organoleptic properties of the product.
For design purposes, four main components will be used, a
wooden box which has the function of containing and
structurally supporting the system. The wood with which the
box is built has the advantage of thermally isolating the air to
be heated to minimize heat losses and, due to its accessibility
and economy, it becomes a suitable material for agricultural
applications.
The second component is the absorbent metal plate which is
applied a special coating to improve its ability to capture solar
radiation and heat up over time, for the simulation it is defined
as copper because it has appropriate heat transfer characteristics
for the study. The third component is the transparent cover that
allows the passage of solar radiation and is defined as glass,
which is a material present in the program that facilitates the
simulation of collectors.
The final component is the thermal energy storage material,
the main subject of study for this project is the incorporation of
heat storage, with the purpose of stabilizing drying
temperatures taking into account the variability of solar
radiation and prolonging times. Based on the bibliography,
there are two types of materials for storing thermal energy:
latent heat and sensible heat. When talking about latent heat, the
phase change of the substance is explicit and for sensible heat
the phase change is not achieved.
Within the literature it is highlighted that phase change
materials have a greater capacity to store energy due to the fact
that they absorb heat in large quantities during the phase change
stage and release it efficiently when it returns to its original
state.
In the databases there are different types of materials used for
energy storage, but each of these must be used based on the
specific requirements of the application, such as operating
temperature, construction materials due to possible oxidations
or chemical reactions, toxicity, costs, among others. Under
these criteria different authors [16]–[18] point out the
advantage of paraffin for drying applications due to its low cost,
long useful life, its melting temperature below 60 °C and low
toxicity. Due to its properties, it can have thousands of energy
charge and discharge cycles without undergoing changes in its
composition.
For the reasons described above, paraffin is selected for the
investigation of the flat solar collector with thermal energy
storage. Therefore, it is necessary to define its thermal
properties to feed the simulation software database. A study that
stands out for analyzing in detail the behavior of different
paraffins is that carried out by [19], With his research he
manages to define the properties with which the program is fed
Scientia et Technica Año XXVIII, Vol. 28, No. 01, enero-marzo de 2023. Universidad Tecnológica de Pereira.
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for the simulation. These data are tabulated as shown below
(TABLE I).
For research terms, 60 ° C is defined as working temperature,
which means that in operation a control system must approach
this control point, for this reason a paraffin with a melting
temperature close to this value, hardly it may change state in its
entire volume, for this reason you should choose a paraffin
whose melting temperature is less than 60 or at least 10 degrees.
For the purposes of the development of the project, PW48 is
selected because it is commercially accessible and has the
necessary characteristics for the execution of the research.
TABLE I
SUMMARY OF THE THERMO-PHYSICAL PROPERTIES OF PW48 PARAFFIN
Thermo-physical
properties
Value
Density
780 (
𝑘𝑔
⁄
)
�
3
Dynamic viscosity
0.024
(
𝑃𝑎 ∗ 𝑠
)
Specific heat CP
2300
(
�
)
⁄
𝑘𝑔 ∗ 𝐾
292.15 K
Thermal conductivity
0.3
(
𝑊
⁄
𝑚 ∗ 𝐾
)
343.15 K
0.23
(
𝑊
⁄
𝑚 ∗ 𝐾
)
B.
Boundary Conditions.
By defining the different conditions through reading the
different scientific articles mentioned above, it is possible to
approach the SolidWorks CAD simulation software and its
Flow Simulation application. To carry out the test, a 1 m2
collector is modeled under the following boundary conditions.
o
Room temperature𝑇
𝑎𝑚𝑏
20.5 °C.
o
Initial temperature of the fluids (Air and paraffin) 20.5
°C.
o
Solar irradiation of 500 - 1000 W/m
2
the angle of
incidence (θ) at 0° to emphasize the thermal study of
the collector
o
Diameter of the collector air inlet 10 cm.
o
The properties of reflection, absorption and thermal
conductivity are applied under the predefined
parameters in the software for materials such as wood,
iron and glass.
The air velocity inside the collector is varied in m / s, in order
to analyze the behavior of the system.
C.
Circulation system proposals.
Correct air circulation is important for the design of a
collector, in order to efficiently absorb solar radiation and
transfer it to the fluid used in drying, with this premise in mind,
a model is developed for a 2 m
2
(1m x 2m) collector, as seen
below. Additionally, the absorption plate allows the transfer of
thermal energy to the paraffin, storing energy during its phase
change (see Fig. 1).
Fig. 1 Solar absorption plate with energy storage. The paraffin container tanks
generate a forced movement of the air circulating inside the collector.
This plate is modeled with the aim of containing 2 stores for the
paraffin, additionally two separate spaces are created with a
through hole, as seen in the figure to generate a directed
circulation within the collector. For the simulation, three air
flow velocities are applied, one at 2 m/s, another at 1 m/s and
the final one at 0.5 m/s. As can be seen in the following figure,
the increase in temperature inside the collector is affected by
the separation applied to the plate.
Bearing in mind the different aspects of radiation absorption
and the area of heat transfer, a proposal is made for a solar
collector for drying that allows the air to circulate efficiently
through it. Additionally, it must also allow the heat transfer air
to the paraffin to be comparable to that of the air, so that both
fluids have access to solar energy. The proposed recirculation
system with energy storage is shown in Fig. 2.
(a)
(b)
Fig. 2 Temperature of the fluids inside the collector, a) Top view, b) Side
view.
It is also possible to appreciate the behavior of the air inside
the collector, in which eddies are created, showing turbulence
due to the air inlet and its speed [20]. The temperatures
obtained are tabulated in TABLE II.
TABLE II
FLUID TEMPERATURE
Air inlet
velocity
(
𝒎
⁄
𝒔
)
Outlet air
temperature
(
°𝑪
)
Maximum
paraffin
temperature
(
°𝑪
)
2
38.48
44
1
42.17
49
0.5
48.31
51
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Scientia et Technica Año XXVIII, Vol. 28, No. 01, enero-marzo de 2023. Universidad Tecnológica de Pereira
Fig. 3 Recirculation and energy storage proposal.
As can be seen, the radiation receptor consists of a lower
chamber for storing the paraffin and dividing sheets are
implemented that generate a forced air circulation (see Fig. 3).
The pyramidal plates have the function of creating turbulence
within the collector in order to improve heat transfer, in
addition, by increasing the contact area between air and metal,
it also contributes in this aspect [21].
With the simulation of this model, an air velocity of 3 m/s is
applied in the first instance and the area of the circular inlet with
a diameter of 10 cm is kept constant, to carry out a detailed
analysis two additional velocities of 1 and 2 m/s. The irradiance
is kept constant at 600 W/m
2
, a value that serves as a
comparative to define the efficiency of the collectors applied in
the simulations.
TABLE III
BEHAVIOR OF FLUIDS
Air inlet
velocity
(
𝑚
⁄
𝑠
)
Outlet air
temperature
(
°𝐶
)
Maximum
paraffin
temperature
(
°𝐶
)
Efficiency
(%)
3
34.04
37
32.3
2
37.21
41
26.4
1
43.54
45
18
To obtain the efficiency of the collector , the equations found in
the article of [22], are used, the first is to find the power of
energy absorbed by the air by means (1):
𝑄 = 𝑚̇ ∗ 𝐶
𝑝
(
∆𝑇
)
(1)
Where 𝑄 is the heat generated or absorbed, 𝑚̇ is the mass
flow of the air that can be found by the air velocity and the inlet
area. 𝐶
𝑝
is the specific heat at constant pressure that is tabulated
in the literature according to temperature and ∆𝑇 is the
difference between the outlet and inlet temperatures, which, as
defined from the beginning, is 20 °C. For efficiency (2) is used
[23], [24].
� =
�
�
�
�
(2)
(a)
(b)
Fig. 4 Temperature of the fluids inside the collector a) Side view, b) Top
view.
In figs 3 and 4, it is possible to appreciate the heating of the
air as it advances through the solar collector, the dividing
plates that force the air to circulate along the path allow to
show the path that the fluid follows, until reaching a
temperature of 34 °C at the outlet. The paraffin for this case
reaches a maximum temperature of 39 ° C, which shows that
both fluids reach similar temperatures. Additionally, TABLE
III shows the tabulated results of the speed and temperature
of the working fluid (air), the maximum temperature reached
by the paraffin and the approximate efficiency of the
collector.
Where η is the efficiency, 𝑄
𝑎
is the heat absorbed by the air
and 𝑄
𝑇
is the heat of incidence on the collector obtained by
multiplying the total area by the irradiation, which for this
specific case would be 600 W/m
2
* 2 m
2
= 1200 W.
From the models discussed above (Figs 2 and 4) it is possible
to begin to highlight notable similarities and differences. The
first similarity is found in the temperatures and efficiencies
achieved, the two collector proposals achieve very close values
in the heat absorbed by the air as it passes through the system.
This is mainly due to the length traveled by the air inside it, both
collectors are divided into 4 sections, regardless of the shapes
or curvatures that are applied inside the collector, what prevails
is the length traveled by the air and the heat transfer area
between the metal plate and the air.
The most notable difference is the temperature reached by
the stored paraffin in the case of the model in fig 5, it reaches
temperatures between 40 and 50 °C and in the previous model
its temperature remains below 45 °C. It is important to be clear
about what a stable state refers to, it is the point at which the
system does not drastically vary the temperature of the fluid, for
this specific case, air is used as a reference point, which means
that when it reaches its stable state at the outlet of the collector,
the simulation is stopped, so it is not clear what is the time
required to reach the maximum temperatures of the paraffin and
if this is the limit that it can reach.
For the purposes of these simulations it is possible to identify
that the proposed models have an important difference and it is
the total volume of the paraffin, for Fig 5, the volume of the
paraffin is 0.078 m
3
and for fig 8 the volume is 0.26 m
3
. In
percentage relationships, the first model has 30% of the mass
that the second has, which represents a considerable difference
in thermal load. Due to the temperature relationships of the
fluids, it is possible to point out that the efficiency for heating
Scientia et Technica Año XXVIII, Vol. 28, No. 01, enero-marzo de 2023. Universidad Tecnológica de Pereira.
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the air is not affected by the amount of paraffin, because in both
cases the temperatures reached were very similar. The
hypothesis raised with this analysis is that the amount of PCM
(Phase Change Material) for energy storage affects only the
heating times of the same and this does not affect the
temperatures reached by the air, which do depend on the speed
(Volumetric or mass flow) and the length by which it circulates
inside the collector.
TABLE IV
SUMMARY OF DATA OBTAINED IN THE SIMULATIONS
III.
RESULTS
The proposed collector design is based on the storage of thermal
energy based on the reached temperature of the paraffin in each
one of the analyzed conditions. The paraffin content is 0.6 m
3
,
uniformly distributed throughout the collector, the total area is
8 m
2
and the applied materials continue under the same
boundary conditions that have been established in the previous
simulations. Shown below is the metal plate of the manifold.
Fig. 5 Receiver plate (8 m
2
).
The plate has 8 divisions or sections through which the air
passes while it is heated, the solar radiation applied in the
simulation is configured at 500 and 1000 W/m
2
, with the aim of
identifying the temperature under conditions of average or
average radiation and high for midday hours when intensity is
highest.
The results of the simulations for irradiation of 500 and 1000
W/m
2
are shown in TABLE IV, where the speed and
temperature of the air, the temperature reached by the paraffin
and the efficiency that the collector would reach are observed.
Fig. 6 Air temperature inside manifold 8 m
2
.
As can be seen in Figs 6 and 7, with these conditions it is
possible to exceed 60 °C and by applying correct air flow
control, by maintaining the levels required for quality drying
and energy efficiency. The different simulations carried out are
tabulated to be analyzed precisely as shown below.
It is necessary to have a context of the behavior of the air in the
hours of maximum irradiation, this allows dimensioning the air
flow requirements to keep the drying temperature below 60 °C.
As can be seen from the simulations, in this collector it is
possible to apply air flows between 1 m/s and 7 m/s and thus
guarantee efficiency and temperature depending on the
radiation present. But using temperature as a monitoring
variable does not guarantee full use of radiation, due to the low
efficiency when minimum fluxes are applied, as is the case of 1
m/s at 500 W/m
2
reaching the ideal temperature, but at a
minimum efficiency. Therefore, it should be a priority for the
research to use the solar radiation present in the area as a
reference to establish air flows, seeking to maintain optimal
efficiency ranges and adequate temperatures for drying.
Maintaining a constant flow of air with temperatures above 40
°C with a collector efficiency greater than 20%, favors drying
times, due to the ability to extract steam from the air.
An important factor that must be appreciated by different
researchers is the non-uniformity of the paraffin temperature,
which follows the same air pattern as observed below.
Fig. 7 Paraffin temperature
What the previous image shows is that the material for energy
storage does not reach the phase change in its entire volume, so
under the different working conditions there would always be a
part in solid state and another in liquid state, which implies that
it has the capacity to store even more energy. Under these
conditions it is possible to apply different types of phase change
materials or different types of paraffin, based on their melting
Air inlet
velocity
(
𝒎
⁄
𝒔
)
Outlet air
temperature
(
°𝑪
)
Maximum
paraffin
temperature
(
°𝑪
)
Efficiency
(%)
500 W/m
2
1
57
52
8.5
3
49
47
20
5
43
43
26.58
1000 W/m
2
3
72
71
17.95
5
64.6
66
25.66
7
59
62
31.41
20
Scientia et Technica Año XXVIII, Vol. 28, No. 01, enero-marzo de 2023. Universidad Tecnológica de Pereira
⁄
point, creating separate storage chambers. This in order to
improve the efficiency of energy absorption due to the fact that
paraffin has better heat transfer conditions as it is in a liquid
state.
IV.
DISCUSSION
As part of the initiative for this research, there is an interest in
knowing an adequate volume of material for energy storage
within the collector, this in order to allow future researchers to
decide on the incorporation of these materials within a system
of thermal energy, as is a collector. Consequently, this initiative
evaluates different points that must be taken into account when
defining a volume for energy storage.
o
The first and most important is the heat transfer area,
because in this case the metal plate, in charge of
absorbing solar radiation, transfers the energy both to
the air and the paraffin, this must be reasonably
distributed throughout the transfer area.
o
When applying low volumes of material, it is possible
to achieve uniformity in the overall fluid temperature.
In contrast, when considerable volumes are applied
inside the collector, it is normal to obtain differences in
the states, having a liquid and a solid percentage.
o
It is not possible to define a volume relation for the
solar collector, this because there are different
possibilities when it comes to solving problems such as
the melting temperature of the material.
It is identified with this behavior that, depending on the
specific needs of the drying system, such as an amortization of
sudden changes in temperature generated by the sun (changes
in irradiation over time), a small volume of paraffin can be used.
and of a single type. For those cases in which it is desired to
extend the drying times and a large volume of material is
required inside the collector, different types of paraffin must be
used based on its melting temperature, always looking for the
position in which it is located. within it, generate a change in its
state from solid to liquid [13], [17], [18].
The constant search to maintain efficiency levels should be a
priority when designing and sizing a solar collector. When the
investigation begins, it starts with the objective of reaching
temperatures close to 60 ° C, but this is not a factor that
indicates a correct operation in drying. The main priority is the
use of heat, since the increases in temperatures generated in the
air contribute to the improvement of its ability to extract the
steam inside the products. Therefore, when designing a control
system, the measurement of solar irradiation must be taken into
account, so that it contributes to the calculation of efficiency
[2], [3], [8], [24].
V.
CONCLUSIONS
With the research carried out, it was possible to have a better
understanding of the dimensions required in a flat solar
collector for food drying applications such as cocoa and coffee.
Due to the energy requirements, it is identified that energy
efficiency should be given priority over the temperature range.
In the different simulations it was possible to improve the
capacity of the air to absorb steam.
Paraffin selection is a critical part of energy storage
collector design due to its latent heat storage advantages. A
designer may require a different thermal storage material than
the one used in this study depending on the energy requirements
of the drying system, normal operating temperatures and the
storage capacity of the structure. The priority when selecting
this material is the melting temperature, because if this limit is
not exceeded, the material does not fulfill its function
efficiently.
Air flow control and monitoring of solar irradiation become
an essential part for the construction of a drying system with the
solar collector, due to the importance of making efficient use of
the heat generated.
It is recommended for future research work to carry out a
complete design, integrating both the collector and the drying
chamber, due to the required understanding of the air flow
within the dryer. It is important to take into account that there
are different drying stages and they depend to a great extent on
the type of the product, therefore it is recommended to analyze
in more detail the specific needs of the drying of cocoa or other
products, to define in which stages a accelerated flow to remove
moisture and in which an increase in temperature is required to
generate evaporation of the water contained in the center of the
product.
The development of an advanced control system, whose
monitoring variables are air flow, temperature, solar radiation,
among other factors that affect the efficiency of the collector. It
becomes a major challenge for the advancement of this type of
initiative, due to the complexity represented by the drying of
food (product quality) and the transfer of heat and mass. For
them, it is advisable to have an interdisciplinary team that
contributes to achieving the standards of efficiency and quality
of the process.
Regarding the improvement of heat transfer, the
incorporation of conductive metallic structures is openly
recommended, which improve thermal efficiency when storing
heat in the phase change material such as paraffin. There are
different studies that also propose the incorporation of metallic
nano-particles that mix with the fluid, to contribute to the
conductivity.
Nomenclature
C Specific heat (
𝐽
𝐾𝑔 ∗ 𝐾
)
Q Heat (W)
𝑚̇ mass flow (
𝐾𝑔
⁄
𝑠
)
T Temperature (°C)
Greek letters
η efficiency (%)
Scientia et Technica Año XXVIII, Vol. 28, No. 01, enero-marzo de 2023. Universidad Tecnológica de Pereira.
21
Subscripts
a absorbed
p constant pressure
T Total
VI.
ACKNOWLEDGMENT
We are grateful to the directors of the Unidades Tecnológicas
de Santander, especially the Research and Extension
Directorate
REFERENCES
[1] D. Kizildag, J. Castro, H. Kessentini, E. Schillaci, and J. Rigola,
“First test field performance of highly efficient flat plate solar
collectors with transparent insulation and low-cost overheating
protection,” Sol. Energy, vol. 236, no. February, pp. 239–248, 2022.
DOI: 10.1016/j.solener.2022.02.007.
[2] B. V. Balakin, M. Stava, and A. Kosinska, “Photothermal convection
of a magnetic nanofluid in a direct absorption solar collector,” Sol.
Energy, vol. 239, no. April, pp. 33–39, 2022. DOI:
10.1016/j.solener.2022.04.027.
[3] W. Ajbar, J. A. Hernández, A. Parrales, and L. Torres, “Thermal
efficiency improvement of parabolic trough solar collector using
different kinds of hybrid nanofluids,” Case Stud. Therm. Eng., vol.
42, no. November 2022, p. 102759, 2023. DOI:
10.1016/j.csite.2023.102759.
[4] D. García-Menéndez, J. C. Ríos-Fernández, A. M. Blanco-Marigorta,
and M. J. Suárez-López, “Dynamic simulation and exergetic analysis
of a solar thermal collector installation,” Alexandria Eng. J., vol. 61,
no. 2, pp. 1665–1677, 2022. DOI: 10.1016/j.aej.2021.06.075.
[5] A. A. Al-Tabbakh, “Numerical transient modeling of a flat plate solar
collector,” Results Eng., vol. 15, no. August, p. 100580, 2022, DOI:
10.1016/j.rineng.2022.100580.
[6] D. De Maio, C. D’Alessandro, A. Caldarelli, M. Musto, and R. Russo,
“Solar selective coatings for evacuated flat plate collectors:
Optimisation and efficiency robustness analysis,” Sol. Energy Mater.
Sol. Cells, vol. 242, no. February, p. 111749, 2022. DOI:
10.1016/j.solmat.2022.111749.
[7] A. Dhaundiyal and D. Atsu, “The effect of thermo-fluid properties of
air on the solar collector system,” Alexandria Eng. J., vol. 61, no. 4,
pp. 2825–2839, 2022. DOI: 10.1016/j.aej.2021.08.015.
[8] K. N. Yehualashet, O. Fatoba, and S. M. Asfaw, “Experimental study
and numerical analysis of thermal performance of corrugated plate
solar collector,” Mater. Today Proc., vol. 62, pp. 2849–2856. 2022,
DOI: 10.1016/j.matpr.2022.02.414.
[9] A. O. Al-Sulttani et al., “Thermal effectiveness of solar collector
using Graphene nanostructures suspended in ethylene glycol–water
mixtures,” Energy Reports, vol. 8, pp. 1867–1882, 2022. DOI:
10.1016/j.egyr.2022.01.007.
[10] A. M. Ajeena, P. Víg, and I. Farkas, “A comprehensive analysis of
nanofluids and their practical applications for flat plate solar
collectors: Fundamentals, thermophysical properties, stability, and
difficulties,” Energy Reports, vol. 8, pp. 4461–4490, 2022. DOI:
10.1016/j.egyr.2022.03.088.
[11] O. Panagopoulos, A. A. Argiriou, A. Dokouzis, S. O. Alexopoulos,
and J. Göttsche, “Optical and thermal performance simulation of a
micro-mirror solar collector,” Energy Reports, vol. 8, pp. 6624–6632,
2022. DOI: 10.1016/j.egyr.2022.05.007.
[12] L. Xu, A. Khalifeh, A. Khandakar, and B. Vaferi, “Numerical
investigating the effect of Al2O3-water nanofluids on the thermal
efficiency of flat plate solar collectors,” Energy Reports, vol. 8, pp.
6530–6542, 2022. DOI: 10.1016/j.egyr.2022.05.012.
[13] E. Gaudino, M. Musto, A. Caldarelli, D. De Luca, E. Di Gennaro, and
R. Russo, “Evaluation of the absorber temperature frequency function
valid for evacuated flat plate collectors,” Energy Reports, vol. 8, pp.
1071–1080, 2022. DOI: 10.1016/j.egyr.2022.05.275.
[14] Y. Wenceslas Koholé, F. Cyrille Vincelas Fohagui, and G. Tchuen,
“Flat-plate solar collector thermal performance assessment via
energy, exergy and irreversibility analysis,” Energy Convers. Manag.
X, vol. 15, no. June, 2022. DOI: 10.1016/j.ecmx.2022.100247.
[15] A. Al-Manea, R. Al-Rbaihat, H. T. Kadhim, A. Alahmer, T. Yusaf,
and K. Egab, “Experimental and numerical study to develop
TRANSYS model for an active flat plate solar collector with an
internally serpentine tube receiver,” Int. J. Thermofluids, vol. 15, no.
August, p. 100189, 2022. DOI: 10.1016/j.ijft.2022.100189.
[16] T. desisa Rago, “Experimental and Numerical Investigation of Heat
Transfer Characteristics in Solar Flat Plate Collector Using
Nanofluids,” SSRN Electron. J., vol. 18, no. March, p. 100325, 2022.
DOI: 10.2139/ssrn.4282071.
[17] P. Pourmoghadam, M. Farighi, F. Pourfayaz, and A. Kasaeian,
“Annual transient analysis of energetic, exergetic, and economic
performances of solar cascade organic Rankine cycles integrated with
PCM-based thermal energy storage systems,” Case Stud. Therm.
Eng., vol. 28, p. 101388, 2021. DOI: 10.1016/j.csite.2021.101388.
[18] K. Lentswe, A. Mawire, P. Owusu, and A. Shobo, “A review of
parabolic solar cookers with thermal energy storage,” Heliyon, vol. 7,
no. 10, p. e08226, 2021. DOI: 10.1016/j.heliyon.2021.e08226.
[19] G. Sadeghi, M. Najafzadeh, and H. Safarzadeh, “Utilizing Gene-
Expression Programming in Modelling the Thermal Performance of
Evacuated Tube Solar Collectors,” J. Energy Storage, vol. 30, no.
March 2020, p. 101546, 2020, DOI: 10.1016/j.est.2020.101546.
[20] J. Deng, T. S. O’Donovan, Z. Tian, J. King, and S. Speake, “Thermal
performance predictions and tests of a novel type of flat plate solar
thermal collectors by integrating with a freeze tolerance solution,”
Energy Convers. Manag., vol. 198, no. April, p. 111784, 2019, DOI:
10.1016/j.enconman.2019.111784.
[21] V. Unterberger, K. Lichtenegger, V. Kaisermayer, M. Gölles, and M.
Horn, “An adaptive short-term forecasting method for the energy
yield of flat-plate solar collector systems,” Appl. Energy, vol. 293, p.
116891, 2021. DOI: 10.1016/j.apenergy.2021.116891.
[22] W. Villasmil, M. Troxler, R. Hendry, P. Schuetz, and J. Worlitschek,
“Control strategies of solar heating systems coupled with seasonal
thermal energy storage in self-sufficient buildings,” J. Energy
Storage, vol. 42, 2021. DOI: 10.1016/j.est.2021.103069.
[23] M. M. Ali, O. K. Ahmed, and E. F. Abbas, “Performance of solar
pond integrated with photovoltaic/thermal collectors,” Energy
Reports, vol. 6, pp. 3200–3211, 2020. DOI:
10.1016/j.egyr.2020.11.037.
[24] T. Zhang, G. Lu, X. Zhai, and B. Li, “Structure optimization of a
phase change material integrated solar air collector/storage unit based
upon phase change analysis,” Energy Reports, vol. 7, pp. 1828–1836,
2021, DOI: 10.1016/j.egyr.2021.03.040.
Arly Darío Rincón Quintero was born
in Aguachica, Cesar, Colombia in 1982.
He received the degree in mechanical
engineering from Francisco de Paula
Santander University, Colombia, in 2005
and the degree Master in Energy
Efficiency and Sustainability from the
University of the Basque Country
UPV/EHU, Bilbao, España, in 2013. He is currently pursuing
the Ph.D. degree in Energy efficiency and sustainability in
engineering and architecture with Basque Country
UPV/EHU,Bilbao, España. He is a senior researcher before
MinCiencias, Colombia associate professor at the Unidades
Tecnologicas de Santander, in the Faculty of Natural Sciences
and Engineering.
ORCID: https://orcid.org/0000-0002- 4479-5613
22
Scientia et Technica Año XXVIII, Vol. 28, No. 01, enero-marzo de 2023. Universidad Tecnológica de Pereira
Luis Alfonso del Portillo Valdés. PhD
in Energy and Fluidomechanical
Engineering from the University of
Valladolid, Industrial Engineer from the
Higher Technical School of Engineering
of the UNED (National University of
Distance Education: Madrid ES), and
Industrial Technical Engineer from the
University School of Industrial Technical Engineering of
Bilbao, UPV/EHU and the Research Group ENEDI (Energy
in Building).
ORCID: https://orcid.org/0000-0001-9064-005X
Camilo Leonardo Sandoval Rodriguez
Was born in Bucaramanga, Santander,
on July 24, 1977. Electronic Engineer
from the Industrial University of
Santander, Master in Electronic
Engineering from the Industrial
University of Santander and PhD in
electronics and communications from
the University of the Basque Country
EHU-UPV, Spain. Professor of the Technological Units of
Santander, attached to the Coordination of Electromechanics
and director of the Research Group on Energy Systems,
Automation and Control GISEAC.
ORCID: https://orcid.org/0000-0001-8584-0137
Brayan Eduardo Tarazona Romero. Was
born in Floridablanca, Santander, on
August 21, 1992. Electromechanical
technologist of the Unidades Tecnológicas
de Santander, Colombia in 2013. Ingeniero
Electromecánico de las Unidades
Tecnológicas de Santander, Colombia en el
año 2015. Master in Renewable Energies
and
Energy
Efficiency
from
the
Open
University of Madrid, Spain in 2018 and PhD in Energy
Efficiency and Sustainability in Engineering and Architecture
from the University of the Basque Country EHU-UPV,
Spain. Professor of the Technological Units of Santander,
attached to the Coordination of Electromechanics, the seedbed
Technological Evolution EVOTEC and the Research Group
in Energy Systems, Automation and Control GISEAC.
ORCID: https://orcid.org/0000-0001-6099-0921
Wilmar Leonardo Rondón Romero
was born in Bucaramanga, Santander,
Colombia in 1993. He received the degree
in Electromechanical engineering from
Unidades Tecnológicas de Santander, in
2017. He is a junior researcher before
MinCiencias, Colombia.
ORCID: https://orcid.org/0000-0001-9500-9531