Search

The proposed work uses the CFD commercial flow solver Ansys CFX. This solver is a finite volume-based method. Ansys CFX is used to compute heat transfer at the fluid-solid interface using its CHT module to improve the efficiency of the cooling PV system. The cooling PV system proposed by Wilson is the best-chosen design since it uses a confined water flow and then no water is lost or evaporated also it uses the hydraulic head of water from a tank without the use of a circulating pump. According to the last studies of a confined flow, the k-w turbulent model of Wilcox is selected to study heat transfer inside a 3D geometry proposed by Wilson. The recirculation area effect on heat transfer lowers the wall heat flux at the solid-fluid interface so this recirculation area must be avoided. To achieve the recirculation area, different cooling PV systems geometries can be investigated in future studies.

This research offers a numerical study of steady and laminar mixed convection flow in a circular pipe as part of a flat plate solar collector, which is crossed by nanofluids. The pipe is kept at a constant wall temperature and then at a constant heat flux, which represents the solar radiation received by the pipe. The governing coupled equations are solved with the finite volume approach. Computations are carried out using an in-house computer code, which has been satisfactorily validated by comparison to previous investigations. Empirical relations are used to predict the effective thermal conductivity and viscosity of nanofluids. The results are investigated using dynamic and thermal fields, with a special emphasis on the Nusselt number calculated along the active wall. They demonstrate that increasing the volume fraction of nanoparticles and Reynolds number improves heat transfer.

The aim of this short review is to present the progress made in wildland fire modelling during the last 50 years and the intellectual track followed by wildland fires models, from fully empirical models in the 60s, to semi-empirical ones in the 70s, to fully physical models at the end of the 90s. During the last period, the large diffusion of HPC methods substantially contributed to the development of multiphase formulations applied to wildland fire modelling. Many studies have particularly focused on the effects of various parameters (vegetation, topography, atmosphere) affecting the behaviour of a fire front propagating through a forest fuel layer.

The three-dimensional numerical simulation of laminar mixed convection heat transfer with and without porous medium in a cylindrical duct was carried out in this study. The cylinder is divided into three parts. The first and the third parts are adiabatic, while the central part is subjected to a constant heat flux. The effects of Darcy number, porosity, permeability and Nusselt number on heat transfer were considered. This problem is modeled by the Navier-stokes equations in the fluid region and by the Darcy-Brinkman-Forchheimer equation in the porous region, and for the thermal field the energy equation is used. The resolution of these equations was performed by the computational fluid dynamics code Ansys15.2 software using finite volume approach. The obtained results showed an accumulation of the hot fluid with stratification in the upper part of the pipe while the lower region of the pipe remained at practically constant temperature. The effect of the porous matrix is very noticeable on the velocity profile. The insertion of a porous high permeability medium significantly improves heat transfer.

Solar stills are typically used to use solar energy to extract clean and fresh water from salt water sources. Considering that solar energy is the primary energy source utilized. This technology is incredibly cost-effective. The effectiveness of solar stills is affected by a multitude of factors which includes location, height, wind speed, inclination angle of the glass, and glass thickness. The solar still performance at different time period of the year will be examined. Results are taken into account for the location of Islamabad on March 22, June, September, and December after every hour of operation from 10 am to 4 pm. The heat transport within the solar still has also been determined, based on theoretical calculations of the total radiation falling on the still. Maximum solar distillate output after 6 hours of operation was found on 22nd June and minimum result was found on 22nd December.

The environment (Winter cold) affects both the individual and the equipment and communications needed to support workflow or general communication. Therefore, the issue of providing thermal conditions in which the communication device is located while a person stays in the cold is relevant. To protect such devices from premature cooling, they are placed in special parts of clothing. Model-ling and research of thermal insulation properties of garment parts for protection from cold of mobile communication devices will allow to establish effective parameters of thermal insulation structure. Such parameters will allow to develop and manufacture warm clothes with special details, which will maintain the performance and increase the time of stable operation of mobile communication devices necessary for a person in cold conditions. The geometrical model and the model mesh were developed. According to the results of numerical model-ling, the dependence of temperature in the thermal pocket on the ambient temperature was obtained, taking into account the presence or absence of the heating plate. The results of numerical modelling of model calculations al-lowed to theoretically justify by zoning and heating power the system of artificial thermoregulation in thermal protective clothing with integrated electronic devices.

The efficiency of a Parabolic Trough (PT) Solar Power Plant heavily relies on its thermal performance. Modern technology has allowed for the creation of more efficient methods of producing steam and of collecting solar energy for thermal power generation. Ministry of New & Renewable Energy (MNRE) built and tested an 11.1 m2 parabolic trough concentrator (PTC). A system that generates steam indirectly by using concentrating solar power (CSP) is examined. The study examined absorbers' thermal properties, thermal efficiency of combined thermal exchangers, concentration ratio, heat efficiency, and steam generation to determine their influence on energy efficiency. The experimental findings display that 557.85 watts of energy are absorbed by the PTC receiver. The PT solar plant system has a thermal energy efficiency of 25 to 29 % and a concentration factor of about 200 on average. The parabolic trough concentrator generates a maximum of 9.1 kg.h-1 of steam.

The study introduces Malikov's two-fluid methodology along with the RSM turbulence model for simulating turbulent heat transfer phenomena. It elucidates that temperature fluctuations within turbulent flows arise from temperature differentials between the respective fluids. Leveraging the two-fluid paradigm, the researchers develop a mathematical framework to characterize turbulent heat transfer dynamics. This resultant turbulence model is then applied to analyze heat propagation in turbulent flows around a flat plate and in scenarios involving submerged jets. To validate the model's efficacy, numerical outcomes are juxtaposed against established RSM turbulence models and experimental findings. The comparative analysis reveals that the two-fluid turbulent transport model aptly captures the thermodynamic behaviors inherent in turbulent flows with exceptional precision.

One of the most significant groups of thermal energy handling equipment utilized in industries is heat exchangers. Their particular uses include chemical processing, waste heat recovery, space heating and air conditioning, and power generation. Most people consider heat exchangers to be complicated machines. Double-pipe heat exchangers are easy to build and analyze. However, given their extensive usage in industries, their significance is unquestionable. They have undergone several improvements to impact energy, reduce material costs, and thereby mitigate environmental deterioration. In industry, heat exchangers are commonly utilized for both heating and cooling purposes. Heat passes via the dividing walls of a recuperator, a form of heat exchanger that has distinct flow routes for each fluid along its tubes. Typically, the base fluid is water, ethylene glycol or oil, and the nano-particles are composed of metals, oxides or carbides. Nanofluid's ability to increase the rate of exchanging the heat in a variety of heat devices is experimentally assessed since adding nanoparticles to the base fluid improves its thermophysical characteristics. The use of inserts and nanofluids together significantly improves heat transmission.

We conducted, in this work, a three-dimensional numerical study of forced convection heat transfer of a laminar flow of water passing through micro-channels with and without longitudinal vortex generator, using the CFD code “Ansys- Fluent”. This work aimed to elucidate the effect of vortex generators on the dynamic and thermal behavior of the micro-fluidic flow. The results obtained show that the increase in the Reynolds number leads to an improvement in the quality of heat transfer in both cases of the study. Rectangular micro-channel with LVG can improve heat transfer compared to smooth rectangular micro-channel while consuming more pressure drop. In the range of Reynolds numbers between 200 and 1200, a 2-21% increase in the mean Nusselt number was observed for micro-channels with LVG compared to smooth micro-channels. This occurs through better mixing of the fluid, reduction in the thickness of the thermal boundary layer, and increased heat transfer area. In addition, the friction factor has been increased by more than 50% compared to smooth micro-channels, due to the local resistance of LVGs and the presence of secondary flows.

A transient two-dimensional numerical simulation using the COMSOL-Multiphysics software, is carried out for an experimental structure (Minnesota Experiment), and using the same thermo-physical properties of the soil and the same indoor and outdoor climatic conditions. The general heat transfer equation in unsaturated porous media has been used to simulate energy losses. A mathematical approach has also been developed in order to calculate the thermal conductivity of different materials with the aim of making them closer to real values. The main goal is to compare the results of the simulated temperatures with the values measured in-situ. An excellent correlation between the simulated temperatures and those resulting from the experimental structure was obtained. At the same time, the exhaustive analysis of heat fluxes crossing the soil-structure interface has enabled us to propose practical solutions for reducing losses through the slab-on-ground.

The Sabatier reaction is a key element of power-to-gas development. For this reason, even though the process is known since more than one century, the Sabatier reaction is currently the object of important research efforts towards the development of new catalysts for performance improvement. However, the industrial exploitation of the Sabatier reaction depends on the development of reactors that match the best catalyst with an appropriate heat management. For this reason, this paper develops a methodology for the contemporary optimization of the reactor concept and the catalysts. It is observed that the reactor can be divided into three sections with contrasting requirements. In the first section, the main requirement concerns the reach of the reaction activation conditions. Hence, an adequate match between catalyst and reactor is needed, for example with an appropriate pre-heater. Once the reaction is activated, a reaction hotspot is formed, so that the cooling becomes determining and the main requirement for the catalyst is the resistance to poisoning and sintering. In the last section of the reactor, the low temperature activity of the catalyst is determining, so that a high-performing catalyst is needed. This paper indicates a strategy for the rational design of this catalyst, based on mechanistic evidences.

A complete description of the thermodynamic behavior of an Otto cycle engine is obtained in terms of shaft rotation angle by a Python code. From results, indicators of high technical relevance are calculated, including effective pressure, specific break power, specific fuel consumption and volumetric efficiency. The proposed transient model solves transient mass and energy balances including compressible flow through the valves and combustion speed. The implemented code is validated by comparing numerical results with experimental measurements of an engine operating without combustion stage and at constant angular speed. By using the developed method, more conservative and realistic results are found for, among other indicators, thermal efficiency, volumetric efficiency and effective average pressure, and it is possible to predict the thermodynamic behavior of Otto cycle engines in an accurate and efficient way. [ABSTRACT FROM AUTHOR]

There’s a lot of hope for phase change material (PCM) in applications like sustainable energy generation and retrieval of heat loss. Latent heat thermal energy storage (LHTES) systems containing hydrated salt (HS) at minimum-temperature have been the topic of much study, particularly with regards to their thermal behavior and charging-discharging properties. The PCM was prepared by adding sodium acetate trihydrate (SAT), a nucleation agent, and a thickness agent to the test tube. We monitored PCM’s temperature behavior and analyzed its thermal characteristics. Natural convection was the dominant way of heat transmission while the phase change material temperature was over the fusion threshold, whereas conduction was the dominant mode when liquid phase change material formed during the phase transition progression. Heat storage and release efficiency as a function of tube diameter and flow rate was analyzed. Internal stainless-steel fins and aluminium fins of varying thicknesses were added to the tube to increase heat transmission. The shape of the storing tube and fins was shown to have a significant impact on the heat transmission among the thermal fluid and the phase change material. Charging and discharging duration may be cut by 28 % and 25 %, respectively, because to the revised fins shape. Our findings from this study can serve as an experimental foundation for using the minimum-temperature hydrated salt LHTES system.

The energy collected from various renewable resources, such as sunlight, geothermal warmth, wind, and water, is referred to as renewable power. The sun is the ultimate source of vitality. Solar radiation vitality can be utilized in many functions, such as heating buildings and dusty foliage crops, dying chicken, wood taste, and treating modern elements. All the energy patterns in nature asking them are the origin of the sun. The solar air heater (SAH) is very common along with commonly applied sun-oriented heating apparatus. Perhaps, SAH is utilized for a wide range of applications, from residential to commercial. Improving the SAH efficiency is done by applying rib elements on the bottom side of the roughness element ribs, grooves, fins, baffles, twisted tapes, deflectors, etc., and improved Thermo-hydraulic performance (THP). Various investigators have prepared several practices in their research work to obtain a greater transfer of thermal energy between these solar collector heaters by applying various rib elements to the absorbent surface. The objective of that study is obliged to describe and conclude tests on the impact of modest rib element height and face projection upon absorber plate along duct surface as artificial rib elements of different shapes on heat transfer along friction factor. The research on artificially roughened SAH ducting is thoroughly analyzed in this paper. The purpose of this paper is to summarize several studies on the thermal and hydraulic performance of synthetically roughened SAH ducting. For the analyzed range of parameters, it was discovered that the usage of arc-shaped-shaped rib geometry and metal grit ribs has the maximum THP parameters in comparison to often roughness geometry. For the tested range of parameters, the use of broken arc ribs has the highest Nu compared to the plain arc-shaped rib roughness. Arc configuration of roughness element exhibits fewer ranges pressure diminishes than the V form design because the produced secondary flow has a curved structure and is rougher.

Icing of the injection layer in underground tunnels and ventilation shafts leads to wear, destruction of supporting structures and flooding. In St. Petersburg the air temperature in winter can drop to -25 ° C, what can lead to these phenomena in the subway facilities. The article presents the modeling results of a viscous three-dimensional air flow, heat and mass transfer of a metro ventilation shaft in the Ansys CFX program. A numerical model of the ventilation shaft and the surrounding soil consisting of five layers has been developed: air; foam glass concrete; prefabricated cast-iron tubing lining; injection layer; soil massif. The parameters of the computational grid and the boundary conditions of the problem are specified. Two models of the ventilation shaft with an axial length of 1 m and 10 m were built. Temperature plots are constructed for three tasks, where the injection layer consists of water, wet clay soil and average between water and wet clay soil. The choice of overall thermal and technical characteristics of the thermal insulation material during the reconstruction of the existing ventilation shafts in three different sealing space conditions is confirmed.

In this article, an analysis of the integration of nanofluids and their applications in the field of solar energy has been discussed. Practically, several factors affect the physical properties of nanofluids. The use of nanofluids as an absorbent fluid is an effective approach to improve heat transfer in solar-powered devices. The main objective of this review is to examine and categorize all existing formulas and correlations on the physical properties and physical models of nanofluids, including thermal conductivity, viscosity, density, and specific heat, and to summarize the research carried out in recent years on the applications of nanofluids in solar energy systems. This article also identifies future research opportunities in the field of solar energy

The paper deals the problem of pool boiling heat transfer on the surface produced by the modification with the laser beam. The laser enabled to produce grooves and roughness which have a positive impact on heat transfer. The distilled water and ethanol boiling performance of a horizontally located specimen is discussed and the test results are compared with the model of boiling heat transfer selected from the literature. The laser technique proved to be a valuable tool for producing surfaces that improve thermal performance during pool boiling.

One of the major reasons, why nanosatellites are still in a state of vulnerability, is the increase of their thermal temperature, which in many cases leads to the failure of the missions they were originally designed for. In order to maintain the quality of the thermal management system, while keeping the electronic equipment in reliable working conditions. This paper presents a research on the thermal environment and the passive thermal control systems (PTC) of nanosatellites, based on a CFD computational fluid dynamics tool. The idea of this work is to provide a PTC to nanosatellites at a specific altitude in low earth orbit in order to determine their temperature values. From the results collected, the temperatures of the nanosatellites change drastically depending on the presence or absence of heat dissipation. This also depends on the type of the considered coating. It was also noticed that the temperature inclined with the choice of surface coating which was stipulated by the α/ε ratio. Therefore, it would be wise to choose the right surface coating at the very beginning of the design.

Heat pipes have applications in several areas of thermal engineering, including electronic components to spacecraft thrust chamber exchangers. Although they can transfer large amounts of heat over a spatially restricted interval, they exhibit several operating limitations. The properties of the working fluid, the capillary structure, the orientation of the pipe, the length and the diameter of the pipe, are parameters that affect these limits. The present study aims to numerically evaluate the heat transfer capacity of a heat pipe. A one-dimensional model is developed considering water, ammonia and sodium as working fluids. The capillary structure is taken to be a wire mesh wick or a square groove, for which several operating thermal ranges are investigated. A comparative study for different properties of heat pipes has been performed using the Matlab® software. [ABSTRACT FROM AUTHOR]

This study presents a comparison between two solar power tower receivers. Selecting the optimum location of thousands of heliostats, the most profitable tower height, receiver size and geometric shape remains a challenge. In our case, we are interested in the geometric shape of the receiver. Two solar receivers connected in series and the other in parallel with different cross-sections and identical internal surface areas were studied. We performed a comparison to find the right pipe connection that gives us the good thermal capacity and solar tower efficiency. The heat transfer fluids used are water vapor and molten salts (NaNO3-NaNO2 - KNO3/NaNO3 - KNO3/LiF - NaF - BeF2), the software used for this study is ANSYS CFX with an unstructured grid with 825 300 cells and standard turbulent model and the flow of heat imposed on the receiver tubes 0.5 MW. We have been assumed that heat transfer occurs only by conduction and convection. The simulation results show the influence of parameters on the temperature field between the input and output of the receiver. The numerical simulation was done by the ANSYS CFX calculation software and using a Z620 Workstation computing machine. The objective of this work is to define the performance geometry for receivers in solar towers.

Turbulent flow and heat transfer characteristics were studied and analyzed numerically for a constant property Newtonian fluid flowing through a two-dimensional horizontal rectangular cross section channel with staggered, transverse cascaded rectangular-triangular fins (CRTFs) and a constant temperature along both walls. The governing equations based on model used to describe the turbulence phenomenon, are solved by the finite volume method using the SIMPLEC-algorithm. Computations were carried out in the fully-developed regime for different Reynolds numbers, and geometric locations. In particular, velocity and temperature fields, skin friction coefficient, and local and average Nusselt numbers were obtained. This study can be a real application in the field of heat exchangers and air plane solar collectors.

Coolant plays important characteristic in automobile industry to prevent failure and damage by balancing the temperature. Due to this approach, coolants are being used as new thermal fluid to study the heat transfer coefficient performance. This study consists of an experimental investigation of internal convective heat transfer of 50:50 Water-Ethylene Glycol based Nano-fluid through a copper tube of 18mm external diameter and 16.5mm internal diameter and a test section of 1m in a fully turbulent regime. Total convective heat transfer coefficient of Nano fluid at three different volumetric concentrations of nanoparticles is estimated. Local convective heat transfer at eight different points along the tube at varying Reynolds number is also determined. At 0.15% volumetric concentration of SiO2 Nanoparticles (NPS) 29% increment in convective heat transfer coefficient (CHT) is observed. The decrease in the heat transfer rate is observed with changing distance axially. Particles disorganized movement of NPs and undulation in the fluid and increased in thermal conductivity of Nano fluid can be possible reason for extra ordinary change in heat transfer.

The building envelope is an important element that influences energy performance, both in terms of gains and losses. Indeed, much research has focused on improving and optimizing this element. The façade represents the main component of the envelope; it plays a crucial role lying in the protection of the internal environment of the building from external climate variations, by providing thermal comfort to its occupants. In order to gain in energy efficiency, a numerical investigation (CFD) on the influence of the geometric shape of façades on heat exchange in the building is carried out in this work. More particularly, the study will be established on double skin façades (DSF) representing the most commonly used facade typology on high-rise buildings. The simulations will be carried out taking into account the climate in Paris region. The first part will be dedicated to the definition of the basic model, which will be considered as a reference case with plan surfaces on the outside and inside of the building. In the second part, the influence of the shape of the external façade on heat exchange will be discussed.

Solar refrigerator machines based on solid adsorption present a highly interesting solution to the Industry of Cooling Production. In one hand, they are significantly attractive economy ways because of the abundance of the solar energy resources. In the other hand, they are environment friendly. As a result, these machines could present one of the most competitive solutions to the improvement of this very industry. The aim of this paperwork is to provide an accurate study on how to design, seize and build a prototype of an adsorption solar refrigerator using activated-carbon/ammonia pair: Firstly, we used a static model, which is based on the use of state equations (vapor/liquid) at thermodynamic equilibrium. This model computes the cycled mass and the cycle coefficient of performance (COPc) for each four characteristic temperatures of the cycle. Secondly, we develop a dynamic simulation program based on conservation equations of energy and mass in the reactor, this program allow the calculation of the temperature, the pressure inside the reactor, the adsorbed mass and the solar coefficient of performance (COPs). Finally, in the light of our results, we design this prototype, it would consist of the reactor: a solar panel, size 1 m2contain tubes with a diameter of 10cm, an air condenser, and a cold chamber containing an air evaporator.

The current advances and problems of medical cryoexposure thermal simulation are considered. Recommendations on improving geometric models, thermophysical properties, boundary conditions, and for parameterizing of the computational domain are proposed. These recommendations can be applied to most modern FEA software packages (tested in Ansys CFX 19.2). Examples of cryoablation and cryotherapy simulation are presented.

One of the most promising applications of highly effective computer technology (supercomputers) is numerical simulation of complex physical and thermophysical proccesses occuring in vast areas of concert halls and sport arenas while heating, ventilating and air conditioning. According to Russian technical standarts for building construction, numerical modeling of these systems should be carried out on the stage of their design. The variety of problems and demands, lack of understanding of the physical process involved and the necessity to make genuine decisions are encountered while conducting such a work. The experience in modeling of ventilation and air conditioning systems of Bolshoi Krenlevskyi Palace concert halls and the Moscow Conservatory named after P.I. Chaikovskyi, Zaryadie Park Philarmony concert hall and a covered ice rink arena is described.

The paper discusses a dynamic model of coil-wound heat exchanger and its implementation in the MathWorks SimulinkTM computer simulation system. As a simulation object was chosen a coil-wound heat exchanger with wire-finned tubes of a commercial low-capacity air separation unit. The methods for obtaining experimental data has been described, the non-steady heat exchange process has been simulated, and the obtained results have been analyzed.

In the present work, an unsteady analysis is carried out for the thermal characterisation of a fire-fighter protective clothing. Coupled radiative and conduction heat transfers are considered within the clothing with a focus on the first skin layer. The protective clothing is modelled as a 1D solid medium, featuring three layers of tissues, separated by several air-gaps. A parametric analysis is performed in the aim to predict the effect of conductive and radiative tissue properties fluctuation on the first skin's layer temperature. The obtained results using the finite element software COMSOL Multiphysicsare compared with stationary 2-D calculations, and faced to unsteady simulations based on the finite volume method. A relative reduction of 50% in the absorptivity of the skin, (in the case of wearing a fine knitted fabric) makes it possible to reduce the temperature of the first skin's layer to a tolerable value. [ABSTRACT FROM AUTHOR]

Micro-scale catalytic combustion characteristics and heat transfer processes of preheated methane-air mixtures (φ = 0.4) in the plane channel were investigated numerically with detailed chemical kinetic mechanisms. The plane channel of length L = 10.0 mm, height H =1.0 mm and wall thickness δ = 0.1 mm, which inner horizontal surfaces contained Pt/γ-Al2O3 catalyst washcoat. The computational results indicate that the presence of the gas phase reactions extends mildly the micro-combustion stability limits at low and moderate inlet velocities due to the strong flames establishment, and have a more profound effect on extending the high-velocity blowout limits by allowing for additional heat release originating mainly from the incomplete CH4 gas phase oxidation in the plane channel. When the same mass flow rate (ρin × Vin) is considered, the micro-combustion stability limits at p: 0.1 MPa are much narrower than at p: 0.6 MPa due to both gas phase and catalytic reaction activities decline with decreasing pressure. Catalytic micro-combustor can achieve stable combustion at low solid thermal conductivity ks < 0.1 W∙m-1•K-1, while the micro-combustion extinction limits reach their larger extent for the higher thermal conductivity ks = 20.0-100.0 W∙m-1•K-1. The existence of surface radiation heat transfers significantly effects on the micro-combustion stability limits and micro-combustors energy balance. Finally, gas phase combustion in catalytic micro-combustors can be sustained at the sub-millimeter scale (plane channel height of 0.25 mm).

Morocco is considered as a water-stressed country and is among the countries that face fresh water scarcity. However Morocco has an important solar energy and a significant amount of seawater and ocean. Therefore converting saline water to fresh water using solar energy is the perfect and the cleanest solution. Solar still is the simplest, cleanest and cheapest technology of solar desalination. In this paper a novel solar still with stepped-slope absorber plate and baffles was proposed and developed in order to enhance the thermal performance of the conventional solar stills. In order to validate the performance of the developed technology a comparative study were elaborated. A mathematical model was developed. The energy balance equations for the various elements of the solar still are formulated and numerically solved using the dynamic simulation program Matlab/SimulinkTM and the Euler explicit method programmed by C++. Also, the experimental process of the new construction was evaluated and validates the new pattern performance. The thermal performance was investigated and shows considerable improvement through the new construction.

3D printing is an intersting process in the context of creating original objects. Selective laser sintering printers use a laser to fuse polyamide particles together with specific resin and heat. The difference in temperature between the different areas in the process causes the appearance of deformations, the objective of this work is the modeling of the thermal SLS phenomenona, by following the evolution of the temperature as a function of time.This model is based on the resolution of the heat conduction equation coupling with convection and radiation conditions with a distribution heat source and constant thermal coefficients by the meshless method based on radial basis function , the result of this study,will be presented and compared with other works.

Mixed convection within a shallow rectangular cavity of aspect ratio, A = 12, confining a Newtonian fluid (Pr = 7), is studied analytically and numericallyin the case where the horizontal walls, whose upper one is moving, are adiabatic, whereas those vertical are submitted to uniform density of flux. The obtained results show the validity of the parallel flow approximation and the considerable effect of the Richardson (0.1 ≤ Ri ≤ 105) and Reynolds (0.1 ≤ Re ≤ 10) numbers on the flow intensities and the heat transfer. [ABSTRACT FROM AUTHOR]

This work is a study of coupled charges and heat transfers phenomena on a low temperature PEMFC single cell. A one-dimensional steady state model was developed to compute current and temperature distributions in a PEMFC single cell whatever the operating conditions. The work comprises of three parts: Firstly, a literature survey was conducted to describe the principle of a PEMFC and the fundamental operations. A state of the art of the previous modeling works on the PEMFC was also presented in this part. Secondly, the developed model using the basic relations to describe heat and charges transfer phenomena occurring in the single PEM cell was presented. Finally, a simple simulation tool called FCvb was performed and optimized using Visual Basic Excel and referring to the previous relations in the developed model. To finalize this study, a conclusion and perspectives were presented in the last part of this work.

Energy consumption in oil mills is a major item of costs and a sensitive point in the production of biofuels. To improve their performance, industrials can recover lowtemperature heat thanks to a new technology of heat exchangers suitable for treating granular solid materials. Information about the energy requirements of the rapeseed crushing being not readily available, the article gives a detailed assessment of consumption items (per ton of seed: 263 MJ for preparation operations and 284 MJ for solvent extraction). These exchangers used as pre-conditioners saves about 55 MJ.t−1 of heat by use of steam condensates. We could go further in use of these devices on the one hand to recover heat from press cake and meal, and secondly to use recovered energy to dry and warm up the seeds before pre-pressing. In this configuration, the energy savings could reach 38% of current needs.

Opportunity to take the grain internal transfers into account in the context of the modelization of the fixed bed drying of corn: a review. The fixed-bed drying is a preservation technique widely used in food industries. Its control and optimization require to know the distributions of temperature and water content in the bed depending on the operating conditions used. This information is obtained through modeling of the heat and mass transfers involved. Models of fixed bed drying have two components. The first one is the model at the product level. This model can predict how temperature and water content of the product change at each point of the bed according to local conditions of temperature and humidity. The second component is the model for the entire bed, which describes how heat and water are conveyed by the drying air through the bed. In this literature review, the main models of fixed bed drying are presented, with particular emphasis on the models used for corn drying. In this review, these two components are presented separately. The goal is to idendify the advantages and disadvantages of each approach, and opportunities for future research in this field.

Due to global warming and the high toxic gas emissions of traditional power generation methods, renewable energy has become a very active topic in many applications. This study focuses on one versatile type of solar energy: Hybrid Photovoltaic Thermal System (hybrid PV/T). Hybrid PV/T combines both PV and thermal application and by doing this the efficiency of the system will increase by taking advantage of the temperature loss from PV module. The solar radiation and heat will be harnessed to deliver electricity and hot water simultaneously. In the present study a solar system is designed to recycle the heat and improve the temperature loss from PV module in order to supply both electricity and domestic hot water. The project was tested twice in Zouk Mosbeh - Lebanon; on May 18, 2016, and June 7, 2016. The average electrical efficiency was around 11.5% with an average electrical power output of 174.22 W, while with cooling, the average electrical efficiency reaches 11% with a power output of 200 W. The temperature increases by about 7 degrees Celsius from the inlet. The 1D conduction model is also performed in order to design the hybrid PV/T system.

In the present experimental study, the influence of Opening ratio on the chamber temperature in case of vented triangular enclosure with hot base plate has been undertaken. Due to more flow passage, the average air temperature in the enclosure decreases by 12% for OR of 0.25 and 13% for OR of 0.5 compared to OR of 0.125. Similar trend is observed for Rayleigh number with a rise of 73% in OR 0.5 compared to OR of 0.125. Further, the influence of radiation heat transfer in the natural convection based enclosure is also studied. This kind of investigation is useful in the design and analysis of electronic cooling systems.

The task of improving the buildings energy efficiency is one of the most important tasks in the design of buildings. The buildings energy efficiency can be improved by rational choice of building structures and reduction of the heat transfer. Significant heat transfer of a building occurs through the windows. At the design stage of a building, it is necessary to estimate the magnitude of a heat transfer of different windows. Currently the designers are increasingly using the technology of building information modeling (BIM). 3D-model of the building consists of models of structural elements, which contain information about the different geometric, physical, technological and other characteristics of the structure. The aim of this work is to develop a parametric information model of the window taking into account its heat transfer resistance. In this paper the design of window units with one, two and three sashes are discussed. The value of window-reduced resistance to a heat transfer is calculated inside the window information model and is presented in the table. The method can be applied to different window design. Thermophysical parameter of the window information model can be used to assess the energy costs of operating the building.

The intention of this study is to give an idea about the influence of water-spray cooling on the solidification process of the liquid metal which enables to locate the shear region. The effect of spray heat transfer coefficient (hspray) during the liquid-to-solid transition through the cooled zone temperature and the metal latent heat of solidification are highlighted. A gray iron continuous casting process subjected to water-sprays cooling was simulated using the commercial code COMSOL MULTIPHYSICS 5.2. The obtained results show the great influence of hspray on the location of transition region as well as the relationship between hspray, wall outer temperature, latent heat dissipation, and the solidification time.

Intensifying electronic component power dissipation levels, shortening product design cycle times, and greater than before requirement for more compact and reliable electronic systems with greater functionality, has heightened the need for thermal design tools that enable accurate solutions to be generated and quickly assessed. The present numerical study aims at developing a computational tool in OpenFOAM that can predict the heat dissipation rate and temperature profile of any electronic component in operation. A suitable computational domain with defined aspect ratio is chosen. For analyzing, “buoyant Boussinesq Simple Foam“ solver available with OpenFOAM is used. It was modified for adapting to the investigation with specified initial and boundary conditions. The experimental setup was made with the dimensions taken up for numerical study. Thermocouples were calibrated and placed in specified locations. For different heat input, the temperatures are noted down at steady state and compared with results from the numerical study.

The article deals with the heat transfer solution in the fluid flow inside a pipe, the small tube is inserted into the pipe and its axis is perpendicular to the axis of the pipe. The fluid is water, the regime of the fluid flow is turbulent. The small tube is loaded by the internal source of the heat, the power of the source is constant and homogenous over the small tube surface and the cold water cools down the small tube. The analysis of the described problem helps to design the experimental model (the heat source above all) to validate the CFD results. The work included the numeric and analytic method. The model was prepared with the aim to investigate large amount of the variants of the geometric set up (the tube and pipe diameters ratio, the geometrical aspect ratio, corresponding stabilization length of the pipe for given diameter), the flow properties (variation of the velocity values, Reynolds number) and the power of the heat source (ensuring the measurable differences of the temperatures on the tube surface, large Nusselt number). The effect of the constrained space has been observed and described, compare to the free fluid flow.

The dimensioning of the heating systems equipping new and existing buildings, in the case of their energy-related upgrading is an extremely important activity in the context of reaching the targets of the European Directive 31 /2010 / UE concerning the Buildings Energy Performance (PEC). The accurate determination, phenomenological based, of the buildings thermal response leads to determining the climatic parameters representative for the climatic zones and for the buildings structure.Unlike the EN 12831: 2003 European Regulation, the design outdoor temperature in the conditions of Romania’s various zones was determined by the identification of the thermal response specific to the transient conditions of the heat transfer through the composite structures of the opaque and glazing closing components with the thermal response in idealized, steadystate conditions; thus, the design outdoor temperature was determined, which is conditioned by an acceptable discomfort during the coldest pentads of a 48 years climatic statistics (1961-2008). The climatic parameter which generates the modeling similitude is the virtual outdoor temperature which allows the use of the steady-state conditions mathematical formalism in issues of heat transfer in transient conditions. A dependency relation between the design indoor temperature, identical to the resulting indoor temperature (different from the operational temperature) and the air volume average temperature is emphasized.Special attention is given to the heat transfer at the building-soil boundary, in the form of various practical solutions (buildings the basement of which is not directly heated, equipped or not with heating systems, directly heated and occupied, as well as buildings on plinths); in all the cases, the solutions approached are specific to the envelope which is or not thermally insulated.

Comparison of two drying models applied to corn drying in fluidized bed. In this article, two predictive models of the temperature and water content of corn grains during their drying in a fluidized bed are compared. The first model is a simplified one, where the physical phenomena implied in the process are not described. It can be solved using freewares available on Internet. The second is a more complex model, based on the basic physical laws governing the phenomena of heat and mass transfer within the product. It requires the use of commercial finite element software to solve it. The two models are parameterized with four dryings where the temperature remains constant during the process, then validated on dryings with variable temperature and an intermittent drying. The two models are able to describe with an acceptable precision the evolutions of water content during continuous dryings, and to predict the evolutions of water content during dryings with variable temperature and the intermittent drying. The dynamic model is however not able to describe the evolution of the grains temperature during dryings at variable temperature with a precision lower than one degree Celsius. If this precision is sufficient, the use of the dynamic model will reduce considerably the costs in time and license of software for the modeling of the corn drying in a fluidized bed.

Efficient, cost effective, and stable high-temperature heat storage material systems are important in applications such as high-temperature industrial processes (metal processing, cement and glass manufacturing, etc.), or electricity storage using advanced adiabatic compressed air energy storage. Incorporating phase change media into heat storage systems provides an advantage of storing and releasing heat at nearly constant temperature, allowing steady and optimized operation of the downstream processes. The choice of, and compatibility of materials and encapsulation for the phase change section is crucial, as these must guarantee good and stable performance and long lifetime at low cost. Detailed knowledge of the material properties and stability, and the coupled heat transfer, phase change, and fluid flow are required to allow for performance and lifetime predictions. We present coupled experimental-numerical techniques allowing prediction of the long-term performance of a phase change material-based high-temperature heat storage system. The experimental investigations focus on determination of material properties (melting temperature, heat of fusion, etc.) and phase change material and encapsulation interaction (stability, interface reactions, etc.). The computational investigations focus on an understanding of the multi-mode heat transfer, fluid flow, and phase change processes in order to design the material system for enhanced performance. The importance of both the experimental and numerical approaches is highlighted and we give an example of how both approaches can be complementarily used for the investigation of long-term performance.