Thermal Performance Analysis of Plaster Reinforced with Raffia Vinifera Particles for Use as Insulating Materials in Building

The present study focuses on the formulation of new composite consisting of plaster and raffia vinifera particle (RVP) with the purpose to reducing energy consumption. The aim of this study is to test this new compound as an insulating eco-material in building in a tropical climate. The composites samples were developed by mixing plaster with raffia vinifera particles (RVP) using three different sizes (1.6 mm, 2.5 mm and 4 mm). The effects of four different RVP incorporations rates (i.e., 0wt%, 5wt%;10wt%;15wt%) on physical, thermal, mechanicals properties of the composites were investigated. In addition, the use of the raffia vinifera particles and plaster based composite material as building envelopes thermal insulation material is studied by the habitable cell thermal behavior instrumentation. The results indicate that the incorporation of raffia vinifera particle leads to improve the new composite physical, mechanical and thermal properties. And the parametric analysis reveals that the sampling rate and the size of raffia vinifera particles are the most decisive factor to impact these properties, and to decreases in the thermal conductivity which leads to an improvement to the thermal resistance and energy savings. The best improvement of plaster composite was obtained at the raffia vinifera particles size between 2.5 and 4.0 mm loading of 5wt% (C95P5R) with a good ratio of thermo-physical-mechanical properties. Additionally, the habitable cell experimental thermal behavior, with the new raffia vinifera particles and plaster-based composite as thermal insulating material for building walls, gives an average damping of 4°C and 5.8°C in the insulated house interior environment respectively for cold and hot cases compared to the outside environment and the uninsulated house interior environment. The current study highlights that this mixture gives the new composite thermal insulation properties applicable in the eco-construction of habitats in tropical environments.

Influence of Heavy Fuel Oil on the Thermo-Physical and Erodibility Properties of Earthen Materials

This study focuses on the use of heavy fuel oil in construction material in Burkina Faso. Its mixture with silty or clayey soil is used as a coating to reinforce the walls of raw earth constructions which are very sensitive to water. The interest of this study is to determine erodibility, water content, while highlighting the influence of the porosity accessible by water on thermal diffusion in construction material containing heavy fuel oil. The heavy fuel oil was mixed with a silty-clayey soil, in different proportions, and water to make bricks samples on which tests were carried out. At the end of the experimental tests, it appears that the water content increases gradually, but not significantly with the addition of heavy fuel oil, which causes a slight increase in the speed of heat propagation through the material with reduced porosity, particularly those containing higher quantities of heavy fuel oil. Conversely, we note a good performance of heavy fuel oil in terms of water resistance properties such as porosity accessible by water and erodibility. This allows us to conclude that the mixture of heavy fuel oil and silty-clayey soil used as a coating material could greatly reduce water infiltration into the walls of housing constructions with raw earthen materials.

Numerical Assessment of the Thermal Efficiency of a Concentrated Photovoltaic/Thermal (CPV/T) Hybrid System Using Air as Heat Transfer Fluid

In this paper, we propose a thermal model of a hybrid photovoltaic/thermal concentration system. Starting from the thermal balance of the model, the equation is solved and simulated with a MATLAB code, considering air as the cooling fluid. This enabled us to evaluate some of the parameters influencing the electrical and thermal performance of this device. The results showed that the temperature, thermal efficiency and electrical efficiency delivered depend on the air mass flow rate. The electrical and thermal efficiencies for different values of air mass flow are encouraging, and demonstrate the benefits of cooling photovoltaic cells. The results show that thermal efficiency decreases air flow rate greater than 0.7 kg/s, whatever the value of the light concentration used. The thermal efficiency of the solar cell increases as the light concentration increases, whatever the air flow rate used. For a concentration equal to 30 sun, the thermal efficiency is 0.16 with an air flow rate equal to 0.005 kg/s;the thermal efficiency increases to 0.19 with an air flow rate equal to 0.1 kg/s at the same concentration. An interesting and useful finding was that the proposed numerical model allows the determination of the electrical as well as thermal efficiency of the hybrid CPV/T with air flow as cooling fluid.

Contribution of Satellite Observations in the Optical and Microphysical Characterization of Aerosols in Burkina Faso, West Africa

In this work, we proceed to an optical and microphysical analysis of the observations reversed by the MODIS, SeaWiFS, MISR and OMI sensors with the aim of proposing the best-adapted airborne sensor for better monitoring of aerosols in Burkina Faso. To this end, a comparison of AOD between satellite observations and in situ measurements at the Ouagadougou site reveals an underestimation of AERONET AOD except for OMI which overestimates them. Also, an inter-comparison done based on the linear regression line representation shows the correlation between the aerosol models incorporated in the airborne sensor inversion algorithms and the aerosol population probed. This can be seen through the correlation coefficients R which are 0.84, 0.64, 0.55 and 0.054 for MODIS, SeaWiFS, MISR and OMI respectively. Furthermore, an optical analysis of aerosols in Burkina Faso by the MODIS sensor from 2001 to 2016 indicates a large spatial and temporal variability of particles strongly dominated by desert dust. This is corroborated by the annual and seasonal cycles of the AOD at 550 nm and the Angström coefficient measured in the spectral range between 412 nm and 470 nm. A zoom on a few sites chosen according to the three climatic zones confirms the majority presence of mineral aerosols in Burkina Faso, whose maxima are observed in spring and summer.

Experimental Evaluating of the Physical, Mechanical and Durability Properties of Natural, Recycled and Both Combined Aggregates Based Concretes

This experimental study aims at the reuse of recycled aggregates (RA), resulting from the demolition of concrete, cement block and cement mortar, in the manufacture of common construction in Burkina Faso. The RA can readily replace natural aggregates in concrete. Then five formulations of natural and recycled aggregates based concrete for characteristic strength of 25 Mpa were prepared in addition to the natural aggregates base concrete named reference concrete (BN): two types of recycled aggregates concrete (BR), three types of recycles and natural combined aggregates base concrete (BC). The properties of natural and recycled aggregates were characterized and the physical, mechanical strength and durability properties were also evaluated for all concrete specimens. All the studied concrete formulation present a density between 2000 kg/m3 ≤ ρ ≥ 2600 kg/m3 and an average slump of 4.9 ± 0.1 cm. The obtained results indicate that the recycled aggregates are suitable for current concrete. Two out of the five combinations studied, such as the natural (BN) and combined aggregate (BC2) based concretes satisfy the mechanical characteristics (Rc28 > 25 MPa) at 28 days of age and an average absorption coefficient of 2.93% and 3.98%. The recycled aggregate based concrete (BR1, BR2) and combined aggregate based concrete (BC1), gave respective average compressive strength of 21.55 MPa, 20.50 MPa and 20.30 MPa, i.e. a difference of 13.80% to 18.80% under the characteristic strength (25 MPa) aimed at 28 days of age. Thus, the recycled aggregates are in conformity with the normative prescriptions and their use for standard concrete gives adequate physical, mechanical and durability properties for the production of the C20/25 concrete series in the common civil engineering applications.

Experimental Study of the Evolution of Temperatures in Pavement Structures and Influence of Traffic on the RN1 in Burkina Faso in a Hot and Dry Climate

Asphalt concrete pavements in hot and dry climates deteriorate prematurely some time after their construction. This degradation is accelerated under the effect of heavy vehicle traffic pressure and high temperatures after the bitumen has softened. A study was conducted on the RN1 in Burkina Faso in order to analyze the evolution of temperature and traffic in the process of degradation of asphalt concrete pavements. It consisted on the one hand in recording the temperatures at different points inside the layers of asphalt concrete pavements and the layer of laterite. These results were compared with the values of the softening temperatures of the bitumen obtained in the laboratory. On the other hand, this study is supplemented by the daily counting of heavy goods vehicles passing through the RN1 during the month of April in order to study the influence of the evolution of heavy goods vehicle traffic on the degradation of pavements in hot and dry climatic conditions. The results obtained for temperatures and the frequency of heavy goods vehicle traffic favor pavement deterioration under certain conditions.

Numerical Study of Heat Transfer in a Differentially Heated Cavity

Laminar natural convection is studied in a square cavity filled with air whose two vertical sides are subject to a temperature difference, while the other two horizontal sides are adiabatic. The hot and cold wall temperatures are kept constant. We have presented a dynamic and thermal study of pure natural convection for different values of the Rayleigh number. The numerical simulation was carried out for Rayleigh numbers ranging from 102, 103, …, 105 and the Prandtl number is Pr = 0.71. We used the COMSOL Multiphysic 5.1 software, which allows us to simultaneously solve the coupled physical phenomena in a square enclosure containing air under the Boussinesq approximation. For the coupling of natural convection with radiation from radiative surfaces, both horizontal faces are subjected to radiative flux, and the emissivity of the surfaces varies from ε = 0.1 to 0.8. We have seen that a circulation process is involved. The fluid that is subjected to a high temperature near the hot wall rises to the ceiling and the fluid near the cold wall sinks. This movement continues until the fluid reaches thermal equilibrium. In a natural convection-surface radiation coupling, simulation results indicate that radiative exchange decreases as a function of the Rayleigh number. Surface radiation reduces the flow in the cavity.

Experimental Study and Modeling of a Convective Dryer for Fruits and Vegetables

The present work deals with the study of the thermal performances of a convective dryer for fruits and vegetables. This dryer, operating with energy generated from the combustion of biomass in a boiler connected to a water/air heat exchanger could be a solution to the problematic of energy related to drying. An experimental and theoretical study is carried out on the temperature profile inside the dryer. For this purpose, 10.3 kg of tomatoes were dried on the experimental setup. The operation lasted about 16 hours and reduced the moisture content from 93.8% to 12% in wet basis. The overall thermal efficiency of the convective dryer during the trial is 10.76%. For the theoretical study, the dryer components (boiler, water/air exchanger and drying chamber) are first modeled individually;the different sub-programs are then coupled to form the convective dryer program. The method of global heat balances combined with the one called “ε-NUT” is used. The set of equations is discretized using the implicit method of finite differences, then solved with the Gauss algorithm in Fortran 90. The theoretical results obtained are in good agreement with those measured.

Investigation of the Behavior of a Photovoltaic Cell under Concentration as a Function of the Temperature of the Base and a Variable External Magnetic Field in 3D Approximation

The photovoltaic (PV) cell performances are connected to the base photogenerated carriers charge. Some studies showed that the quantity of the photogenerated carriers charge increases with the increase of the solar illumination. This situation explains the choice of concentration PV cell (C = 50 suns) in this study. However, the strong photogeneration of the carriers charge causes a high heat production by thermalization, collision and carriers charge braking due to the electric field induced by concentration gradient. This heat brings the heating of the PV cell base. That imposes the taking into account of the temperature influence in the concentrator PV cell operation. Moreover, with the proliferation of the magnetic field sources in the life space, it is important to consider its effect on the PV cell performances. Thus, when magnetic field and base temperature increase simultaneously, we observe a deterioration of the photovoltage, the electric power, the space charge region capacity, the fill factor and the conversion efficiency. However the photocurrent increases when the base temperature increases and the magnetic field strength decreases. It appears an inversion phenomenon in the evolution of the electrical parameters as a function of magnetic field for the values of magnetic field B> 4×10-4 T.

Thermal Study and Modeling of the Cold Room of a Solar Adsoption Refrigerator

In this work, we are interested in the study of the thermal exchanges which take place at the evaporator of an adsorption refrigerator. Due to the cost of designing experimental devices and the impossibility of studying the influence of certain parameters experimentally, an alternative would be simulation. The aim is to provide a model for predicting the thermal behavior of the various elements in the cold room of an adsorption solar refrigerator. A dynamic modelling of the refrigerator taking into account fluid flow, heat and mass transfer phenomena in the cold room was made. The calculation code obtained using COMSOL 5.1 software makes it possible to analyze and study the influence of the various parameters on the performance of the system. In a second step, the theoretical results obtained were compared with the experimental results in order to validate the model. The analysis of the influence of the physical-thermal properties of the insulating material on the temperature of the chamber makes it possible to conclude that a material having a low density ρ, a low thermal conductivity λ and a low specific heat capacity offers better performance to the cold room. Better thermal insulation also implies having a reasonable insulation thickness.

Establishment of a Model for the Calculation of the COP of a Solar Adsorption Refrigerator

This paper deals with the evaluation of the Coefficient of Performance (COP) of solar adsorption refrigeration. In the literature, simulation models to predict the thermal behaviour and the coefficient of performance of these systems are uncommon. This is why we suggest a model to simulate the operation of the machine in a typical hot and dry climate of the city of Ouagadougou. The objective is to provide a model for calculating the COP from the measurement of the ambient temperature and the irradiation of a given site. Starting from mathematical modelling, a resolution and simulation were made with COMSOL software based on the Dubinin-Astakhov adsorption model, the heat transfer balance equations, and the Linear Driving Force (LDF) model to describe the thermal behaviour of the system. A one-week measurement sequence on the adsorption solar refrigerator at the Albert Schweitzer Ecological Centre (CEAS) validated the numerical results. The measurement shows that for the days with high sunshine, the temperature of the reaction medium reaches 110°C, and the pressure reaches 500 mbar. This leads to a production of cold that allows it to reach the temperature of -5°C at the evaporator. Under these conditions, the COP is worth 14%. These results are obtained both by numerical simulation using the COMSOL 5.1 software and after a measurement session on the solar refrigerator available to the CEAS. We obtained an experimental and theoretical coefficient of performance varying between 9% and 14% with a difference of between 0% and 3%. We conclude that our model is suitable to estimate the COP of any device based on its thermal properties, the ambient temperature and the irradiation of a given site.

Numerical Study of a Cylindro-Parabolic Cooker “Blazing Tube”

The objective of this work is to numerically determine the thermal performance of the parabolic cylinder cooker commonly “blazing tube”. These performances were determined by establishing heat balances at the different levels of the system. The equations obtained have been discretized;simplifying assumptions have been made to facilitate their resolution. We adopted Gauss Seidel’s method using MATLAB software to solve these equations. The temperatures of the coolant, the glass and the absorber were determined as a function of time and along the tube. The thermal efficiency was also determined. It emerged that the different temperatures evolve linearly as a function of the length of the tube. Yield and temperatures depend on the amount of sunshine.

Comparative Study of the Thermal and Mechanical Properties of Foamed Concrete with Local Materials

Living in a habitat with comfort is requested by all. Cinder block bricks have poor thermal properties, leading people to use fan heaters and air conditioners to regain comfort. To overcome this problem of thermal discomfort in buildings, we used lightweight concrete such as foamed concrete which is a material that has improved thermal properties for thermal comfort. In addition, this material was compared with local materials used for the construction of buildings such as BTC, adobe and BLT mixed with binders. The results showed that foamed concrete is a material that has good thermal and mechanical properties compared to local materials mixed with binders. The foamed concrete having acceptable thermo-mechanical properties was that having a density of 930 kg/m3. It has a thermal resistance of 0.4 m2·K/W for a thickness of 20 cm. The foamed concrete having acceptable thermo-mechanical properties was that having a density of 930 kg/m3. It has a thermal resistance of 0.4 m2·K/W for a thickness of 20 cm. For sunshine on a daily cycle equal to 12 hours, the characteristic thickness achieved by this material is 7.29 cm. It also has a shallow depth of heat diffusion having a lower thickness than other materials. This shows that foamed concrete is a promising material for the construction of buildings.

Impact of the Thicknesses of the p and p+ Regions on the Electrical Parameters of a Bifacial PV Cell

The present paper is about a contribution to the bifacial PV cell performances improvement. The PV cell efficiency is weak compared to the strong energy demand. In this study, the base thickness impacts and the p+ zone size influence are evaluated on the rear face of the polycrystalline back surface field bifacial silicon PV cell. The photocurrent density and photovoltage behaviors versus thickness of these regions are studied. From a three-dimensional grain of the polycrystalline bifacial PV cell, the magneto-transport and continuity equations of excess minority carriers are solved to find the expression of the density of excess minority carriers and the related electrical parameters, such as the photocurrent density, the photovoltage and the electric power for simultaneous illumination on both sides. The photocurrent density, the photovoltage and electric power versus junction dynamic velocity decrease for different thicknesses of base and the p+ region increases for simultaneous illumination on both sides. It is found that the thickness of the p+ region at 0.1 μm and the base size at 100 μm allow reaching the best bifacial PV cell performances. Consequently, it is imperative to consider the reduction in the thickness of the bifacial PV cell for exhibition of better performance. This reduced the costs and increase production speed while increasing conversion efficiency.

Effect of the Orientation on the Comfort of a Building Made with Compressed Earth Block

Thermal comfort is one of the most important requirements that scientists and building designers must meet to ensure the indoor air quality knowing its importance on productivity and the health of occupants. However, it has never been of great concern for architects and architectural historians and seldom explores it. Buildings are the large consumer of the most energy consumption (around 40% worldwide) and generate around 35% of GHGs like CO2 that leads to extreme climate change. Hence, general and specific eco-friendly solutions in the field of building construction are required. Analysis of this study shows that air conditioning consumption can be significantly reduced thanks to the compressed earth bricks and by taking into account the climate and the orientation of the facades. However, this paper establishes viable low-cost option of building energy consumption while maintaining the thermal comfort and good indoor air quality. This work explains the effect of a single residential room orientation, by reducing the thermal amplitude, and improving the thermal phase shift in Ouagadougou climate conditions in April. Internal temperature was modelled with 8 cardinal orientations. The result corresponds to a decrease of thermal amplitude damping greater than 4°C between East-West and North-South sides and, with a thermal phase shift of 4 hours 30 minutes between the Nord and West walls.