Advances in Thermal Science and Energy

In this work, we combined the homogenization and finite volume methods to predict the solid fraction and the effective thermal conductivity from 3D real morphologies of wood, namely spruce and poplar. High resolution scans performed by a nano-tomograph, together with image processing are two steps of great importance to obtain the digital representation of the real morphology suitable for computation. These tools allow the generation of the 3D mesh of the thresholded sample. The stationary diffusion model is directly considered to gain in performance. Numerical results revealed that several minutes of CPU time are enough to predict the values of the thermal conductivity on the representative volumes. Compared to some of our recent works, the present methodology is not only efficient, but also more accurate.

This paper presents 2D simulations of Direct Carbon Fuel Cells (DCFC) performance. The impact of the operating parameters, such as porosity of the cathode and gas inlet concentration (dioxygen), on the latter performance is investigated. The in-house numerical code based on the Lattice-Boltzmann technic with the Multiple Relaxation Time (MRT) scheme was utilized to calculate the gas flow field inside the various components of the fuel cell. The conservation equations for species were solved using finite differences. Specifically, on the cathode side, dioxygen and carbon dioxide diffused from the cathode gas channel through the cathode towards the cathode/electrolyte interface. At the three-phase boundaries, the oxygen and carbon dioxide react by consuming electrons provided by the external circuit, resulting in the generation of carbonate ions. The results of the present simulations demonstrate that a high cathode porosity and high dioxygen concentration have a direct and positive effect on the overall performance of the DCFC.

Natural double diffusive convection in a square cavity employing variable thermal conductivity and viscosity of Al2O3 water based nanofluid was investigated numerically by means of the lattice Boltzmann method with the BGK operator with three distribution functions. The enclosure is subjected to constant temperatures and concentrations on its side walls while the horizontal ones are kept impermeable and adiabatic. This study presents and discusses the findings on the effects of nanoparticles volume fraction (φ = 0 and 0.05), buoyancy ratio (N = 1 and 2), and Lewis number (10−3 ≤ Le ≤ 10) on temperature, concentration, and stream function distributions, as well as the maximum stream function, and Nusselt and Sherwood numbers. The outcomes exhibit that the heat transfer rate and the mass transfer rate, respectively, increases and declines with the nanoparticles volume fraction. The opposite trend of this latter is observed with the Lewis number, while the heat and mass transfer rates increment with the buoyancy ratio.

This paper studies mixed double-diffusive convection inside a sliding top-wall rectangular enclosure submitted along the vertical walls to constant thermal and solutal fluxes and containing a Newtonian fluid. The paper put forward two approaches for solving the problem at hand, a numerical one based on the finite difference method and an analytical approach using the parallel flow approximation. The investigation shows that the convection main controlling parameters are: thermal Rayleigh number $${\text{Ra}}_{T} ,$$ Ra T , buoyancy ratio $$N,$$ N , Lewis number $${\text{Le}},$$ Le , and Peclet number $${\text{Pe}}$$ Pe with both approaches showing perfect agreement for wide ranges of governing parameters. To shed further light on the effects of mentioned parameters on convection phenomena, an acceptable criterion is adopted to delineate natural, mixed, and forced convections dominance regions, and that separately for heat transfer and mass transfer. The parameters $${\text{Pe}}$$ Pe and $${\text{Ra}}_{T}$$ Ra T significantly impact the shift from one convective regime to another. As for $${\text{Le}},$$ Le , varying it affects the main mechanism driving heat and mass transfer; thus, strongly influences transfer rates. Further, increasing $${\text{Le}}$$ Le enhances forced regime contribution in overall convection while stretching the range for which mixed regime occurs. Unexpectedly though, heat and mass diffusion rates difference $$\left( {{\text{Le}}\, \ne \,1} \right)$$ Le ≠ 1 have no significant effect on boundaries delimiting mixed regime for heat and mass transfer separately.

A multiphysics model based on coupling heat transfer and phase field problems for simulating the thermal and microstructural behavior of the solid-state sintering process was presented. The coupling problem between the heat conduction and phase field models was solved by using the finite element method. The thermal and microstructural behaviors of the solid-state sintering process are presented in this work. It was found that the thermal field leads to the activation of the microstructural field through the mechanisms of mass transport, while the evolution of the phase field variables influences the thermal properties of the material. The convergence of the thermal field is much faster than the microstructural field, so simulations at constant temperature produce almost the same result as at variable temperature for the simulated cases.

A sessile drop evaporates when it is deposited on a heated or non-heated substrate. Then, as the three phases solid, liquid, and gas interact, several effects can occur. These include thermo-capillarity, strong evaporation near the triple line and thermal buoyancy that may induce the liquid motion inside the drop, and thermo-solutal buoyancy that causes motion in the surrounding gas. The combination of all these effects generates complex flow patterns, which affect heat and mass transfer phenomena. In the present study, all these effects are taken into account for developing a numerical model which allows analyzing the contribution of each one to the evaporation of the drop. The numerical predictions show an important increase of heat and mass transfer at the drop edge due to thermo-capillarity and thermo-solutal buoyancy in the surrounding air. Furthermore, the cooling effect resulting from evaporation depends much more on the thermal compensation provided by the substrate. The kinetics of evaporation is highly influenced by the wall temperature and the substrate thermal conductivity rather than by the variation of the drop surface area and the fluid motion.

In this study, a simple method for measuring the thermal conductivity of a compressed earth brick is presented. The principle of the method is based on the measurement of the temperature on one side of the brick while the opposite side is subject to a constant density of heat flux. Five thermocouples were placed on each side to monitor the temperatures on both sides of the brick. A numerical model of heat transfer by single-dimensional conduction at transient speed is developed to calculate the temperature at any point in the brick. The estimation of thermal conductivity is carried out by an inverse technique to reduce the difference between the measured and calculated temperature profiles respectively. The proposed method is validated by direct measurement of thermal conductivity by the hot disk technique TPS 1500. The obtained results showed that the developed device enables the measurement of the thermal conductivity with good precision.

In the present paper, a three-dimensional natural convection induced by a heat generating block placed in the lower adiabatic surface of a cubical cavity is studied numerically. The upper surface of the cavity is maintained cold at a constant temperature, while the other surfaces are considered adiabatic. The cooling fluid is air $$\left( {{\text{Pr}}\, = \,0.72} \right)$$ Pr = 0.72 and the solid block to the fluid thermal conductivity ratio, $$\left( {k^{*} \, = \,{{k_{s} } \mathord{\left/ {\vphantom {{k_{s} } {k_{a} }}} \right. \kern-0pt} {k_{a} }}} \right),$$ k ∗ = k s / k a , covers the range 0.1 to 200. The generated power and considered domain dimension correspond to values of the Rayleigh number ranging between $$10^{4}$$ 10 4 and $$10^{6} .$$ 10 6 . The block’s dimension (height and width) is one of the important controlling parameters of the present problem. The three-dimensional flow structures and the corresponding heat transfer rates are illustrated for different combinations of the governing parameters. The study focuses on the analysis of the effect of three-dimensionalities with the aim of ruling on the conditions of validity of the two-dimensional approach in terms of Rayleigh number. This goal is achieved for various sizes of the block and thermal conductivity ratios.

This paper concerns the modelling of the thermal evolution of a multi-disc aircraft brake during the aircraft’s stopping phase. An experimental set up using flywheels to simulate realistic aircraft braking is used to measure temperatures in the different components of the system using thermocouples. Therefore, based on the measurements taken under these experimental conditions, the heat fluxes due to the friction dissipation have been identified.Based on the identified heat fluxes at the interfaces, the calculated temperatures are in accordance with the measurements taken on the experimental test bench. Furthermore, the determined parameter values exhibit physical consistency. The heat energy that has been identified corresponds to the level of mechanical energy degradation measured during different tests, thus affirming the validity of the obtained results.

A commercial multi-orifice diffuser (OD) is compared under the same experimental conditions to a previously validated innovative lobed diffuser (LD). The OD head is a cylindro-spherical surface pierced with 20 orifices arranged in three rows leading to efficient jet diffusion. The jet analysis reveals that the flow from the closest two orifice-rows to the ceiling attach to it by Coanda effect whereas the orifice jets from the lower orifice-row are directed towards the occupied zone. Thermal comfort analysis reveals less satisfactory conditions for OD than for LD. In the former case, higher velocities in the occupied zone are responsible of a slightly cold sensation. The recorded pressure loss is higher in OD than in LD, whereas no significant difference was observed in terms of sound pressure level in the occupied zone.

The combined impact of a Lorentz force and volumetric heat generation on natural convection heat transfer and fluid flow in a square cavity are investigated numerically using MRT-LBM. The cavity is filled with a non-Newtonian fluid and submitted to a partial heating from below. The main physical parameters controlling the problem are the Hartmann number ( $$0 \le Ha \le 50$$ 0 ≤ H a ≤ 50 ), the external Rayleigh number ( $$Ra_{E} = 10^{5}$$ R a E = 10 5 ), the parameter characterizing the intensity of heat generation ( $$R = 0$$ R = 0 and $$1$$ 1 ), and the power-law index ( $$0.8 \le n \le 1.2$$ 0.8 ≤ n ≤ 1.2 ). The findings of the present study are illustrated by presenting streamlines, isotherms, and mean Nusselt numbers.

Li-ion cells (LIC) are regarded as a very promising technology for energy storage systems due to their high energy density and good cycling stability. However, they still have several shortcomings, especially in terms of safety. Under off-nominal conditions, LIC can experience thermal runaway that can lead to fire and explosion hazards. To understand the triggering conditions of thermal runaway, as well as its consequences, thermal abuse tests on fully charged high-capacity LIC were carried out. Three types of LIC, namely lithium-nickel-manganese-cobalt, super lithium-iron-phosphate, and lithium-nickel-cobalt-aluminum, with nominal capacities of 28, 39, and 42.2 Ah respectively, were selected. Measurements included cell mass loss, gas temperature, vent bursting and thermal runaway delays. The test results showed that the effects of runaway are all the more important as the capacity (energy stored) of the cell is high. With increasing capacity, thermal runaway occurs earlier, and different failure modes can be observed: a slow combustion with diffusion flame, aggressive jet flame containing molten metal particles, up to a fireball ejecting all the contents of the cell.

This paper analyses numerically (by Large Eddy Simulation) the natural ventilation effect by a duct exhaust system on smoke thermal stratification with increasing duct section and duct height in a tunnel fire. The flow pattern behavior in the tunnel with duct is described first. Then an application method for the stratification parameter « S» is presented. For the larger duct section, results show that exist a strong disturbance within the smoke layer under the ceiling with severe instability occurrence between the hot and the cold layers. However, in case of the higher duct, the stack effect appears and increases to a critical condition in which the smoke area thickness beneath vent decreases to 0, leading to the occurrence of the plug-holing phenomenon. In these cases, the stratification was purely destroyed. Result show also that the stratification was obtained where the stratification parameter seems to be greater than 1 and a correlation criterion to characterize the smoke flow stratification is predicted.

In the present work, the thermal and kinetic characteristics of bio-epoxy composites under an oxidative atmosphere are investigated. The main objective is to evaluate the thermo-mechanical behavior of such materials for heat exchange purposes in aggressive/corrosive media. To this end, two parameters have been selected to describe the effect of (1) the fire-retardant coating as fire protection, and (2) the SiC powder as a filler for thermal conductivity improvement. Several samples were first manufactured by Vacuum Bag Resin Transfer Molding (VBRTM) process and then analyzed by thermogravimetric analysis under oxidative atmosphere. Comparison results highlight the proposed fire-retardant has a beneficial effect in terms of fire protection. In addition, the SiC powder charge has great potential for thermal conductivity enhancement without impacting the mass loss rates.

The present research aims to study, on the one hand, rice husks from the Kovié rice fields in Togo and those from the Camargue in France and, on the other hand, rice husk concrete, a biobased material, from the triple angle of microscopic analysis, characterization of thermal properties and experimental evaluation of the behavior under climatic loads through reduced models under similar exposure conditions. The objective is to observe the microscopic topography and the chemical composition, to evaluate the thermal conductivity and the specific heat and to judge the evolution of two parameters of comfort (air temperature and relative humidity of the studied models) within the framework of a follow-up of measurements mobilizing the use of thermo-hydric sensors. The analysis of the obtained results reveals a very interesting potential of the studied biobased materials, regarding indoor comfort in built environments, in connection with the microstructural contents.

In this study, laminar mixed convection flow in a lid-driven cavity with two embedded rotating cylinders maintained at a hot temperature is examined. The upper wall of the enclosure is in motion and maintained at a cold temperature when the vertical walls are insulated. In this paper, the numerical method used is the lattice Boltzmann method (LBM). The numerical simulations are performed to investigate the Richardson number's effect on temperature/velocity fields and the rate of heat transfer. The immersed boundary method (IBM) is used to deal with the boundary conditions in complex geometries. It is found that for low Richardson number values, the natural convection mode is dominated by forced convection mode. In addition, increasing the Richardson number leads to a decrease in the rate of heat transfer.

This paper uses a combination of the discrete ordinate method and finite volume method to numerically study surface radiation and natural convection in a square cavity with a partially heated inner rectangular block. The system under investigation consists of an air-filled cavity, with symmetrical cooling provided by vertical sidewalls at a cold temperature $${\text{T}}_{{\text{C}}}$$ T C . The study aims to analyze the hydrodynamic and thermal behavior of the fluid, as well as the convective and radiative heat transfers, by varying the Rayleigh numbers and surface emissivities. To carry out the research, a custom CFD code developed in FORTRAN is utilized. The findings reveal that the presence of surface radiation enhances the flow intensity within the cavity.

In a previous work, we developed methods based on the Pulsed Flying Spot (PFS) to estimate the thermal diffusivity on the plane of (an)isotropic materials. This thermal property is dependent on temperature or water content. In this work, we propose the device be used in transient temperature conditions to estimate the thermal diffusivity of 304L stainless steel. The first measurement in transient conditions makes it possible to simply and rapidly characterize many materials for temperature conditions other than the ambient. In the second step, we carry out transient thermal diffusivity measurements as a function of water content. We show, for a particularly heterogeneous material (a stoneware tile), that the thermal diffusivity is clearly dependent on the water content. Imbibition, for stoneware, leads to an increase in thermal diffusivity while drying leads to a decrease in the same value. This preliminary work can lead to contactless measurement of water content for different types of materials (food matrix, building materials, etc.).

In this chapter, the slip flow and viscous dissipation effects on the Graetz problem in microchannels are investigated. The developed velocity profile and the temperature distribution are analytically calculated using an original method. At the inlet, a non-uniform temperature profile satisfying the energy equation in the entrance section is imposed. The Nusselt number is determined in terms of the Knudsen and Brinkman numbers and some known values of the fully developed Nusselt number are validated using the literature. It is found that for a constant pressure drop, the Nusselt number increases as the Knudsen number increases. With viscous dissipation for the no-slip flow, the value of the Brinkman number has no influence on the fully developed Nusselt number. However, the fully developed Nusselt number value increases as the Knudsen number increases. The different values of the Brinkman number change the Nusselt number only in the thermal entrance region before reaching the constant independent value at different lengths.

This paper considers a study of thermomechanical coupling. Through a study in a 1D configuration, a thermomechanical transfer function using analytical technique was performed. This function links the mechanical deformation and the temperature. The goal of this research is to propose an inverse thermoelastic approach for determining this excitation temperature and the thermomechanical properties of materiel from experimental measurements. In the first phase, we made a computational study to evaluate the efficiency of our technique by investigating the sensitivity to thermoelastic parameters as well as the influence of measurement noise on all experimental measurements. The use of the Tikhonov regularization technique and truncated singular value decomposition (TSVD) is demonstrated to effectively apply the inversion using noised measurements. Temperature and deformation measurements are used to estimate the coefficient of thermal expansion (CTE) and thermal diffusivity by minimizing an objective function using a least squares criterion. Experimentally, a strain gauge is used to measure this deformation and then apply a deconvolution product to those measurements to determine the temperature of the heated surface. As a result, it is no longer necessary to know the temperature distribution to solve the thermomechanical problem. To identify the two-thermoelastic properties, both temperature measurement mechanical deformation are used in the same experimental bench.

The authors examine the influence of a uniform magnetic field on the characteristics of thermal and dynamic behaviors of non-Newtonian fluid generated by natural convection in a tilted square cavity. The MRT-LBM is employed to elucidate the main physical parameters’ effect, namely, the Hartmann number $$Ha$$ Ha (from 0 to 50) and the power-law index $$n$$ n (from 0.6 to 1.4), for fixed inclination angle ( $$\gamma = 45^\circ$$ γ = 45 ∘ ) and Rayleigh number ( $$Ra = 10^{5}$$ R a = 10 5 ). According to the findings of this study, the flow intensity and the heat transfer are negatively affected by rising either the power-law index or the Hartmann number.

This paper studies mixed double-diffusive convection both numerically and analytically within a double lid-driven rectangular cavity with imposed constant thermal and solutal fluxes on the vertical boundaries while the horizontal walls are considered insulated and impermeable. The opposing flow case is considered where the applied fluxes and moving walls work in opposing directions. To numerically solve the problem governing equations, the finite volume method is adopted, while the parallel flow approximation is used to derive the analytical solution. It is found that the convection main governing parameters are: thermal Rayleigh number $$Ra_{T}$$ R a T , buoyancy ratio $$N$$ N , Lewis number $$Le$$ Le , and Peclet number $$Pe$$ Pe . The two established solutions display perfect agreement for the considered wide ranges of controlling parameters. For a mixed convection regime, increasing $$Ra_{T}$$ R a T reduces flow strength and the rates of heat and mass transfer due to the opposing nature of applied boundary conditions, while for a dominant natural regime, increasing $$Ra_{T}$$ R a T does the opposite resulting in a more pronounced convective regime. As for the effect of the buoyancy ratio, it promotes the contribution of natural regime in the overall convection as it increases.

Optimization is one of the most attractive topics for researchers who aim to improve energy systems performance. This work presents a mathematical analysis of entropy generation and exergy destruction in a microchannel of hexagonal section. A new theoretical model was developed based on Bejan equation, to perform entropy generation numbers, exergy loss and exergy efficiency of various nanofluids flow with different heat fluxes. The results shows that increasing heat flux cause an increase in both entropy and exergy loss due to heat dissipation. Frictional entropy has the highest contribution of total entropy rate. The best exergy efficiency is obtained for certain heat fluxes and it reaches its maximum for pure water.

A mathematical model and a 3D computer code simulating the evaporation of a sessile water droplet placed on a solid substrate have been developed. The numerical results are compared and validated, on the one hand with the literature and on the other hand with experimental results, for the case of a sessile water droplet evaporating at ambient temperature. Good agreement was observed in these comparisons. The experimental results show that the droplet follows the pinned mode during evaporation, therefore this hypothesis will be considered in the numerical simulation. When the substrate is heated, its nature (glass or PTFE) influences the evaporation kinetics and modifies the behavior of thermal fields in the solid substrate.

Numerical simulations were performed using the Lattice Boltzmann Method to investigate natural convection heat transfer in an annulus system. The system consisted of an air-filled square cavity, with differential heating, and contained circular-shaped isothermal pairs serving as heat sources/sinks. The study examined the influence of various Rayleigh numbers ( $$10^{3}$$ 10 3 to $$10^{6}$$ 10 6 ) and different arrangements of cylinders within the cavity on heat transfer characteristics. The code's accuracy was confirmed by validating it with various instances of natural thermal flows. These included scenarios such as natural convection in a triangular cavity with a heated circular cylinder, natural convection in a concentric annulus, and natural convection in a square cavity with a heated circular or elliptical cylinder. The findings emphasize the notable influence of cylinder arrangement on heat transfer within the enclosure.

The present work is dedicated to a numerical investigation of natural convection in a differentially heated square enclosure with a solid partition attached to the heated wall and a heating block freely positioned in the cavity. In this study, the length of the solid wall, the position of the heating block, and the Rayleigh numbers of 103, 104, and 105 are investigated for seven different positions of the heating block and three different lengths of the solid partition. The finite difference method through the concept of vorticity-stream function formulation has been applied. The results clearly show that when the heated block is moved towards the cold wall, the average value of the Nusselt number decreases. For high Rayleigh numbers, the average value of the Nusselt number varies proportionally and inversely with the length of the solid partition when the heated block is positioned after or before position 4 respectively. The positive influence of the heated block on the average Nusselt number can be seen when the heated block is moved to the upper heated part of the cavity. The entropy generation is maximum at position 4 for all scenarios.

Heat storage using phase change materials is an interesting way to improve the energy efficiency of a building. In this regard, we conduct a numerical study in order to analyze the thermal behavior of two samples of microencapsulated PCMs embedded in plasterboard, the first with a single PCM and the second with a hybrid PCM. While the phase change occurs at a given temperature level for the single PCM, it occurs at two different melting temperatures within a small temperature range for the hybrid PCM, which increases storage performance and storage time. A new mathematical model that handles the phase change at two different melting temperatures based on the enthalpy method is used. The phenomenon is solved numerically by means of the finite volume method. A computer code is implemented utilizing a fully implicit scheme. Simulation results show that the use of a hybrid PCM improves stored energy by 12% and increases storage time by 56%.

Among the most attractive alternatives to parabolic trough solar power plants (PTC) is direct steam generation (DSG). The environmental problems related to the use of thermal oil can be minimized, as well as the investment and maintenance charges. However, the instability of the fluid flows generated in the solar field and the difficulty in controlling the process make this new technology still challenging. The receiver tubes can be damaged due to high-temperature gradients. For this purpose, it is necessary to examine the working conditions of the DSG-PTCs system. The water feed mass flow rate is the most important parameter that strongly influences the flow pattern and the process operating. Therefore, the present work focuses on the investigation of the feed mass flow rate impact on the steam production process in a row of PTCs. The outcomes of the numerical simulation indicate that, in order to prevent the stratification phenomenon, it is desirable to select a feed water flow rate more than 0.5 kg/s and to regulate it in accordance with solar flux to ensure a relatively high steam quality production.

Perovskite photovoltaics have emerged as a cost-effective, fast developing technology with interesting light harvesting properties allowing for impressive breakthroughs in the field photovoltaic solar energy conversion. Charge selective layers are crucial to achieving optimal performances in this kind of solar cells. This conference paper presents preliminary results exploring the potential of carbon nanotubes in improving the performance of perovskite solar cells. The optimization of the dispersion of commercially available carbon nanotubes is first examined, where acid functionalized carbon nanotubes in chlorobenzene are found to allow for a visibly better dispersion. Considering their renown charge transport properties, the potential of introducing carbon nanotubes in conventional perovskite solar cells (PSCs) is then studied. This demonstrated a visible increase in performance, highlighted by an improved fill factor and photovoltage. Though as conventional PSCs are prone to metal oxidation induced losses, carbon electrodes are introduced as an alternative. This work thus puts the perovskite/carbon interface under the spotlight as it is identified as a major loss channel in carbon electrode PSCs due to the absence of compatible hole selective layers. Accordingly, carbon nanotubes are introduced at this interface, leading to an enhanced device performance with a recorded fill factors approaching 70%.

In order to improve the cooling of electronic devices, in this paper we investigate the performance of a passive cooling system of electronic equipment. The effect of adding nanoparticles to phase change material (PCM) on the performance of the system has been studied. In addition, the effects of the number of fins and their thickness on the phase change heat transfer process and the optimal configuration parameters of the PCM-based heat sink are evaluated. An optimal configuration of a rectangular enclosure with fins and a phase change material (PCM) based heat sink is determined to extend the safe operation time and keep the temperature of the electronic device in a safe range. The results show that the addition of fins has a significant impact on the heat transfer during the phase change of PCM. Moreover, the four-finned heat sink has a lower base temperature compared to the other cases with a high enhancement rate. On the other hand, compared to the case of PCM alone, the addition of copper nano-particles in the PCM has a little significant effect on the heat sink base temperature.

In this chapter, an experimental investigation is carried out to study the characteristics of the pressure-composition isotherms (P-C-T) of the LaNi4Mn0.5Co0.5 alloy. These isotherms provided important information about the phase transitions, thermodynamic properties and stability of the alloy under different conditions. The effects of feed pressure and cooling, as well as heating temperature on the rate of hydrogen uptake/desorption by the alloy were analyzed. The effects of the partial substitution of Ni by the elements Mn and Co on the phase structure and hydrogen storage properties of LaNi4Mn0.5Co0.5 alloy are studied. It is known that the Mn, Co elements decrease the plateau pressure of hydrogen absorption and desorption of LaNi4Mn0.5Co0.5 alloy. For that, the substitution of these elements improve kinetic velocity of hydrogen storage capacity. The LaNi4Mn0.5Co0.5 alloy also shows excellent plateau performance with very small hysteresis and sloping which is attributed to the interstitial size effect.

The sub-Sahara is one of the regions of the world with the greatest lack of access to energy and clean water. However, this area has a great solar potential. In this work, we propose a sizing model for a Solar Pumping System according to the available energy and the identified uses. This sizing is based on the cost criterion that we wish to minimize under a few constraints. The objective of this study is to optimise the pumping system to ensure the availability of energy as close as possible to the needs so that the isolated areas benefit from it in line with their resources. We illustrate the validation of the proposed method by three scenarios. As a result, the usage profile has a major impact on the optimal design of a Solar Pumping System and therefore on the final cost of the installation.

Metal foams possess high porosity, high strength-to-weight ratio, and excellent thermal conductivity, making them suitable for a range of engineering applications, including thermal heat exchange and energy storage systems. In this study, we focused on investigating the application of mixed convection in a three-dimensional heated channel filled with metallic foam to enhance solar radiation absorption. The Darcy-Brinkman model and the two-equation energy model, assuming local thermal non-equilibrium (LTNE), were utilized to conduct numerical simulations using the finite volume method (FVM) and iterative SIMPLE algorithm. We analyzed the dynamic and thermal fields for various thermal conductivity ratios $$\left( {\tilde{\lambda }} \right)$$ λ ~ and observed that incorporating two blocks of metal foam into the channel improves heat transfer and achieves thermal mixing at the channel output, particularly for high thermal conductivity ratios $$\left( {\tilde{\lambda }} \right)$$ λ ~ .

Direct steam generation is considered as a potential substitute for conventional power generation technologies, for its advantageous characteristics. It can be directly powered by solar radiation by concentrating it on a specific point, besides eliminating heat exchangers and fluid refrigerant, which allows to reduce operating costs. It is crucial, to properly grasp the two-phase flow involved in these technologies. In this paper, we numerically explore the effect of flow strength and wall-driven position on the flow structure and dynamic behavior of bubbles in a square enclosure, through employing the Boltzmann pseudopotential lattice method. The terminal position of the bubble reflects the concurrence between the existing forces. When the value of the Reynolds number exceeds 600, the fluid flow strength overcomes buoyancy and pushes the bubble towards the center of the primary vortex, regardless of the wall-driven configuration. In terms of flow structure, wall-driven flow structures dominate the square cavity in all studied cases. The wall motion configuration affects the bubble trajectory, especially the left wall-driven case where the bubble only reaches the second quarter of the cavity height before being driven toward the center of the primary vortex. Note that the wall configuration has a strong impact on bubble trajectory for equal Reynolds values.

A dynamic model of the PVT solar system is presented in this article coupled to a heat storage tank, a heat exchanger, and pump controllers. To predict the instantaneous system efficiencies, the working fluid temperature at the collector’s output, and the tank temperature with inlet temperature fluctuations, a Matlab/Simulink-based model has been developed. The findings show that in the summer, heat storage temperatures can rise to 55 ℃. The results show also that the annual average overall PVT system efficiency is increased by about 21.83% when considering a controlled coupled PVT collector. We may infer that increasing the PVT system by considering a storage tank coupled with pump controllers is a good option. The simulation’s output may be used as a research basis for dynamic simulation for predicting coupled PVT solar collector performance.

This work was focused into the exploitation and the application of solar thermal energy for the desalination of saltwater or wastewater. It was an experimental study of three single-slope solar stills designed and manufactured at ISSAT Kairouan in the center of Tunisia. The purpose of this study was to improve the freshwater productivity of the systems presented by implementing some modifications and improvements. In fact, the first distiller was conventional; the other two systems are equipped with external reflectors to concentrate the captured solar radiation as well as internal mirrors on the internal faces of the distillers. The particularity of this study was the use of some local materials available free of charge (from the Kairouan region) to store sensible heat during the hot period of the day and to diffuse this energy in the cold period of the day, in order to maximize fresh water production. The obtained results was promising: the daily production of pure water increased by 20% and it reached 5.8 L/m2 day.

It is anticipated that fuel cells technologies will have a considerable role in the sustainable and productive energy system in the future owing to their elevated energy efficiency and fuel flexibility. Recently, the progress for fuel cells has gone quickly. However these technologies are in their early development stage, although, the potential is huge. A three-dimensional numerical model based on the finite element method is developed to assess the performance of the planar SOFC. The governing equations for momentum, species, charges are solved by a segregated solver. The model is operated at a steady state, to observe polarization curves, concentration profiles, and current density profiles. It has been validated by showing good agreement with experimental data at an operating temperature of 1000 K. The effect of the electronic phase volume fraction in the active layer is investigated using a parametric sweep study. This study admits to a good understanding of the relation between the performance of SOFC and the microstructure.

Currently, energy storage is becoming a real challenge in the face of this industrial and economic technological transition. The orientation toward the strategy of use of phase change materials represents a sustainable and efficient alternative to reduce energy consumption in terms of heating during the period of intermittence and increase the thermal comfort of the occupants. This work is devoted to carrying out a set of experimental tests to study the storage capacity of two types of phase change materials in order to test the feasibility of integrating them into building elements. The results obtained show that the increase in heating power at 80 W/m2 causes a significant phase shift of about 8.59 ℃ between the inside and outside surfaces of the plaster wall and the paraffin wax (2). In addition, this type of phase change material can store a significant amount of heat during the charging phase, which leads to an increase in wall temperature of approximately 4 ℃ during the intermittent period compared to the reference case. Finally, the results of the phase change material thermal conductivity measurements obtained by the box method are in accordance with the values given by the manufacturer.

The investigation of the sludge fermentation procedure used to generate biogas is presented in this paper. Actually, this study focuses on the examination of a mesophilic anaerobic digestion of textile wastewater using numerical modeling. To prevent any thermal losses during the fermentation process, the modeling of thermal and mass exchanges is done in the initial phase. The mathematical model used is established on that presented by Guo et al. The results show that the heat losses through the digester's walls are the most crucial factor to control. In the second phase, the progression of the pressure and methane concentration within the digester are examined. The simulation method is based on the general two-film theory model of mass transfer. The results demonstrate that the amount of biogas progress decreases with the organic matters in the sludge. In addition, as it is proved by the literature, the pressure of the generated biogas does not surpass 4 bars during the fermentation process.

The energy performance of a building and its environmental impact are strongly influenced by its interactions with surrounding buildings. Therefore, in order to evaluate its energy performance, it is necessary to study the inter-building longwave radiative exchanges and the shading effect from surrounding buildings. This study aims to evaluate the energy demand of BESTEST building using TRNSYS software including microclimatic interactions and shading of surrounding buildings. We studied the effect of shading and longwave radiative exchange between buildings for different cases. The study shows a significant difference of about 2.4 ℃ in summer between the outdoor temperatures of the facades (i.e., east facing wall) of the reference case building and the other cases and an increase/decrease of about 40% (for cooling) in the energy demand of the building. These results show how to take into consideration thermal interactions buildings in an urban context to help urban design and planning.

In this experimental study, we evaluate the heat transfer performance of a flat copper heat pipe filled with water incorporating a capillary structure composed of cubic orthogonal grooves (Flat Orthogonally Grooved Heat Pipe, FOGHP). Under a cold source temperature equal to 40 ℃, it is shown that the FOGHP dissipates heat input powers up to 60 W, which corresponds to a heat flux of nearly 10 W/cm2 with evaporator temperatures lower than 100 ℃ for the horizontal and thermosyphon orientations, and 110 ℃ for the anti-gravity orientation. The effective thermal conductivity of the FOGHP reaches 2.6, 2.8, and 2.2 times that of copper for the horizontal, thermosyphon, and antigravity positions respectively. Compared to a flat copper plate, the FOGHP allows reductions in the maximum evaporator temperature of 58 ℃, 63 ℃, and 51 ℃ for the horizontal, thermosyphon, and anti-gravity orientations, respectively. The capillary limit is found to be 30 W whatever the FOGHP orientation, and the evaporation heat transfer coefficients are higher than those of condensation.

The present work deals with a 2D numerical modelling of the Steam Methane Reforming (SMR) process in Micro Channel Reactors (MCR). A calculation code solving laminar flow, heat balance, and species equations was developed in the basis of OpenFOAM (Open Field Operation and Manipulation) platform. First, the developed numerical model was validated against experimental data from literature, and then used to explore the hydrodynamic, thermal, and mass behavior of SMR reaction within a MCR plane configuration. Strong methane conversion has been noticed and the MCR first half leading to a maximal hydrogen production at this zone. Given the importance of this observation, a sensitivity analysis using Design of Experiment method has been carried out to investigate the effect of the most influential parameters (operational pressure and temperature, and inlet velocity). Finally, the most optimal parameter values giving the highest H2 production yield are identified.

Membrane distillation combines thermal and membrane techniques for freshwater preparation that can be an important solution to the shortage of fresh water in some regions of the world. The objective of this work is (1) to develop a concept of AGMD (air gap membrane distillation) using a flat plate type separator to limit inside heat loss, (2) to find the adequate coupling with a heat pump for the heat requirement and for the use with solutions highly concentrated in salts and (3) to look for paths towards the optimal configuration of this unit. Heat and mass transfers were modelled with EES (Engineering Equation Solver). The effect of operating parameters including the evaporator inlet temperature (hot channel Th), condenser inlet temperature (cold channel Tc) and the number of stage on the permeate flux were investigated. The simulation analysis revealed that flow of permeate increases significantly if the difference between the inlet temperature of the hot channel Th and the inlet temperature of the cold channel Tc and if the number of stages increases. Based on these simulations, a 3D model was built with SolidWorks. This multilayer AGMD unit will be fabricated and tested at the laboratory.

This paper treats the moisture-related characteristics of bio-based construction materials. Experiments were conducted using the wet cup method and the isothermal adsorption method. This last method provided information on the amount of absorbed moisture by each material, while the wet cup method measured the amount of moisture vapor crossing the material and the moisture resistance of the material. Two different samples were studied and compared: the first one is from a lightweight earth material having a good thermal insulation property. The second one is the cob material characterized by its durability and mechanical structures. By assuming that the absorbed moisture flux is equivalent to the flux passing through the material under steady state conditions, the study was able to calculate transfer coefficients such as water vapor permeability, moisture diffusion coefficient, and ambient transfer coefficient.

The building stock and the construction industry together represent the most energy-consuming sector in the world. Indeed, existing building retrofit is a real challenge. The energy needs estimation of these buildings requires particular attention to the thermophysical proprieties of the envelope composition. The majority of efforts have been focused on analyzing the energy needs of existing buildings and their actual energy consumption measurement using dynamic thermal simulation and only some studies have evaluated in situ the thermal performance of the existing building envelope. Therefore, this study explores the potential of non-destructive methods, such as the heat fluxmeter method and infrared thermography, to assess the difference in expected and measured building Heat transfer coefficient (U-value), particularly for buildings with low U-values. Consequently, this paper discusses the potential of non-destructive approaches, including heat-fluxmeter methods and quantified thermography, to evaluate all differences arising from predicted and measured buildings heat transfer coefficient (U), particularly those with low values. Following the procedure described in this article, the value of the fluxmeter method could be approximated between 33.92 and 3.36% of the design U-value, compared to about 30% for quantitative infrared thermography. The obtained results will then help the experts to select the best method according to ambient conditions, implementation of the method and specific data analysis.

The main goal of this study is to investigate numerically the thermal performances of thermal management systems (TMSs) for an electric vehicle battery pack. Three different TMSs were considered i.e. natural convection TMS mode, passive TMS using phase change material (PCM) and hybrid liquid coolant-PCM TMS mode. A lumped thermal dynamic model is developed based on transient energy balances and then validated with measured data from the literature. An in-depth parametric study is carried out where the influence of several design and operation parameters on the TMS’s performances is presented and analyzed. When compared to passive PCM and natural convection, the results demonstrate that combining PCM with liquid cooling for battery thermal management reduces the maximum battery temperature by around 38 and 4.5℃, respectively.

Today, the building and construction industries account for over 30% of both direct and indirect CO2 emissions, rendering them significant contributors to environmental pollution. Additionally, an overwhelming 70% of the energy consumption in buildings can be attributed to the operation of air conditioning systems, serving the purpose of indoor cooling and heating. Within Morocco, the building sector emerges as a highly energy-intensive domain, encompassing a substantial share of the overall energy consumption, reaching up to 33% in the year 2017. This energy utilization is further distributed between residential buildings, accounting for 26%, and tertiary buildings, contributing to 7% of the total energy consumption. Bioclimatic design strategies stand out as highly promising and effective approaches in enhancing the energy efficiency of buildings. In light of this, the primary aim of this research is to assess the influence exerted by exterior wall vegetation on the energy requirements of buildings within a Mediterranean climate. The study model encompasses various mechanisms of heat transfer, encompassing radiative and convective exchanges between the vegetation layer and the surrounding environment, alongside the consequential impact of evapotranspiration. It was programmed using Python programming software, and then integrated into TRNSYS 18 software. The results show that the impact of vegetated walls is more important during the summer period (compared to the winter period) since they reduce 56.68% of the cooling loads in the Mediterranean climate.

The use of insulation materials made from biomass waste is becoming increasingly popular, and the specific fiber morphology of Posidonia Oceanica leaves (POL) makes them a promising candidate for producing eco-friendly composite insulation materials based on a mortar matrix. This study investigates the effects of chemical and boiling treatments on the physical and thermal properties of the composite material, and compares the quality and performance of fiber-reinforced cement mortar matrix structures with non-reinforced ones that lack fiber addition. The results show that POL requires appropriate treatment, with the alkali treatment being the most effective option. Boiling treatment has a negative effect on POL fibers. Measurements demonstrate that cement mortar reinforced with POL fibers is a highly resistant material, especially when treated with alkali. When the alkali treatment is applied to POL, the resulting thermal conductivity, thermal diffusivity, heat capacity, and thermal effusivity values are 0.15 Wm−1K−1, 2.13 × 10–7 m2s−1, 457.23 JKg−1K−1, and 325 Jm−2K−1s−0.5, respectively.

In this work, we present a methodology to estimate the water diffusion coefficient of a clay slab during convective drying by hot air. This parameter was determined using a numerical method by minimizing the difference between the points of the experimental and simulated drying kinetics. The resolution of the transfer equations of the solid and liquid phase was done using the finite volume method, which takes into account the shrinkage rate of the clay during drying. The diffusion coefficient, as a function of temperature and water content, varies from 1.33 × 10−11 to 5.95 × 10−11 m2/s. The Arrhenius relationship with an activation energy value of 683.73 J/mol clearly shows this effect of temperature on the diffusion coefficient. A predictive correlation of diffusivity as a function of temperature and water content was determined for the type of clay studied.

In order to reduce the effect of climate change on our environment, multiple energy efficient solutions have been developed in all energy-consuming sectors around the world, especially the building sector. Improving the envelope performance of our buildings with bio-based construction materials has been proven to be an effective way of improving the thermal comfort, acoustic insulation capacity and reducing the cooling and heating loads of buildings. The objective of this paper is to present a review of the recent biomaterials that have been developed and proposed in literature as potential construction and insulation materials for buildings, like concrete reinforced with natural fibers (straw, hemp, date palm wood alfa, cellulose…) and biobased phase change materials. Their hygrothermal performance was discussed detailing the effect of their porous aspect on their density, thermal conductivity, water vapor absorption, diffusion, thermal resistance and hygric buffering capacity. Furthermore, their acoustic insulation potential and actual challenges compared to conventional materials were discussed.

This work deals with the drying kinetics of myrtle fruits (Myrtus Communis) initially dried and treated by the Instant Controlled Pressure-Drop DIC as a preservation method of aromatic and medicinal plant. The thermo-mechanical DIC treatment consists in putting a partially dried Myrtle fruit in a high saturated steam pressure (P = 100–500 kPa) for a short period (t = 10–30 s) just before instantly dropping pressure to an absolute pressure vacuum of 5 kPa. The drying experiments carried out airflow of 50 ℃ and a constant velocity of 2 m/s before and after DIC texturing. Statistical analysis of the results shows that this treatment significantly changes the physical and structural properties and generally improves the effective diffusivity for drying.

In a complex environment, such as an urban area, the built elements that make up the urban fabric strongly modify the microclimatic conditions by disturbing the wind and heat flow distribution between the different surfaces. Indeed, studying the urban microclimate has become a necessity for a better assessment of the building's energy performance and the guarantee of indoor thermal comfort. The objective of this study is to demonstrate the necessity of considering the urban microclimate in the prediction of the building energy needs. To this end, an integrated approach in the TRNSYS software validated in previous studies was used. The findings show firstly that the assessment of the building indoor thermal comfort requires to consider the microclimate close to the building, given its effect not only on the building energy needs but also on the indoor comfort of the occupants. Neglecting the urban microclimate can lead to inappropriate decisions for improving the thermal comfort in buildings. From the perspective of understanding the order in which the street canyon parameters affect the building energy needs, we performed a sensitivity study using Sobol's method, which provides the importance of considering the different street canyon parameters on the building energy needs.

This research aims at investigating the effects of thermal insulation made of date palm fibers (DPF) in maintaining comfortable thermal conditions of a building in a semi-arid climate. Based on a numerical simulation with TRNSYS software, the effects of this passive technique on indoor comfort and cooling/heating loads are examined. This technique is evaluated compared to a non-insulated house reference case built with conventional building materials. The results reveal an improvement in the indoor thermal situation and a reduction of 11% for the heating and 15% for the cooling load for the building insulated with date palm fibers.

This paper reports on an investigation of the impacts of the urban microclimate and reduced solar access potentials in modifying the urban energy balance and, hence, the energy demand of office buildings. The building construction itself is considered as well, for it affects the outdoor-indoor thermal exchanges through the built envelope as shared interface. Combined urban and building numerical modelling (TEB, TRNSYS) is used to perform extensive parametric studies for the Mediterranean warm-humid location of Algiers. The simulation plans as well as the results rely on the statistical design of experiments (DOE). The investigated variables: thermal insulation, thermal inertia, window ratio, and aspect ratio, revealed to be decisive; yet differently for outdoors and indoors and for heating and cooling. The cooling energy demand is found to be higher (34.8%) and the heating energy demand lower (17.2%) under urban microclimate conditions as direct consequence of a prevailing in-canyon warming.