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Heat recovery is the reutilization of lavished thermal energy. This paper proposes a hybrid heat recovery system that utilizes exhaust gases of a generator to heat water and produce electricity using thermoelectric generators. The system is composed of a concentric tank with a copper tube passing through it. At the inner surface of the tube, a layer of TEGs is located. The main purpose of the paper is to study the effect of changing the load of the generator on the water temperature and power generated. Knowing that 100 TEGs are utilized, results show that 47 °C hot water and 141 W are produced when load is 10 kW. It increases to 97 °C hot water and 1412 W when the generator load is 38 kW (14.12 W per TEG). Keywords: Heat recovery, Thermoelectric generators, Cogeneration, Domestic hot water, Generators, Exhaust gases

International audience; A two-dimensional numerical simulation of the melting process in a rectangular enclosure for different inclination angles, has been carried out. Galium as a phase change material (PCM) with low Prandtl number is used. A numerical code is developed using an unstructured mesh, finite-volume method and an enthalpy porosity technique to solve for natural convection coupled to solid\textendashliquid phase change. The validity of the numerical code used is ascertained by comparing our results with previously published results. The effect of the inclination angle on the flow structure and heat transfer characteristics is investigated in detail. It is found that the melting rate inside the rectangular cavity increases by decreasing the inclination angle from 90° to 0°.

Abstract Phase change materials (PCM) are attractive candidates for energy storage. They can store large quantities of energy in small volumes at nearly constant temperatures. Despite their advantage, their thermal conductivity is very low with a high-volume change during the melting and solidification process. One way to increase their poor thermal conductivity is to embed them into open cell metallic foams. In this paper, a numerical study is conducted on the effect of the heating and cooling conditions on phase change kinetics of paraffin embedded in a metal foam. Constant heating and sinusoidal heating are similarly investigated. For the constant heat flux, a step function ranging from +1800 W/m2 to −1800 W/m2 is considered, while for the variable heat flux, a sinusoidal function having a similar area as step function is considered at one wall of the container to provide heating and cooling of the PCM/Metal foam composite. A new mathematical model based on the Brinkmann-Forchheimer-extended Darcy equation and the local thermal non-equilibrium model (LTNE) is proposed by applying a two-energy equation. The paraffin phase change is modeled using the enthalpy-porosity method. The numerical results are validated by comparing them with the experimental data. The results showed that at the time of melting it has reduced with sinusoidal heating. The results also showed that the heat losses on the boundary have a greater effect in a sinusoidal heat flux case than in constant heat flux case and this effect is more important on the solidification than on the melting process of the paraffin.

Abstract One of the most promising solution for the current energy crisis is recovering lost energy. Indeed, in many energy systems the percentage of energy loss could exceed 60%. To put it another way, in some applications, recovering energy is as much beneficial as finding new source of energy. Moreover, finding new concepts of energy recovery offers wider horizons to reduce energy consumption. The present work investigates new energy recovery system that combines heat recovery and energy generation using thermoelectric generators (TEG). The proposed system is a triple Thermoelectric-Energy recovery coupled system that from one hand allows to recover the heat of condenser and to reuse the lost energy of exhaust airflow of HVAC all-air system and from the other hand it permits to produce green electricity using TEG. The air of the condenser is considered the heat source, whereas the exhaust air flow is utilized as cooler. To proceed, a mathematical tool is first developed it allows to thermally simulate TEGs for different boundary conditions. The heat and cold source are then modeled where the heat transfer coefficient is determined from the Nusselt number. Furthermore, a parametric analysis is then conducted to evaluate the power generated with the new concept when the air velocity of the exhaust airflow and that of the condenser vary. It is shown that for a space cooling load of 100 kW, a 40×40 cm 2 flat plate is capable to generate 90 W of electrical power.

International audience; A physical model to investigate the melting process around a multiple of heating cylinders in the presence of the natural convection has been carried out. A numerical code is developed using an unstructured finite-volume method and an enthalpy porosity technique to solve for natural convection coupled to solid-liquid phase change. It is found that during the melting process around the cylinders, natural convection circulation around each cylinder interacts with the other cylinders to influence the melt shape. In addition to natural convection, the heat source arrangement is an important factor in determining the melt shape.

Abstract Middle East and North Africa region's abundant solar and wind resources provide a valuable opportunity to diversify energy production and offer a high potential for renewable energies. Thus, the solar water heating systems offer a key element in the deployment of renewable energy throughout the region. To this end, a model was developed and validated to evaluate the performance of these systems with different collectors. Then, an exhaustive energetic, exergetic, environmental and economic analysis of all the region's countries was carried out on the basis of the required meteorological data. Regarding the results for the entire region, the maximum solar fraction values attain 60 % and 83 % for the flat plate and evacuated tube systems, respectively. Under current economic assumptions, propane water heating is cheaper on a life cycle cost basis than electric and diesel heating throughout North Africa. Also, the use of auxiliary electric generators is suitable for all countries in the Middle East region except for Manama-Jordan, Abu Dhabi-UAE and Ankara-Turkey.

The present work deals with the design, implementation and testing of a new heat transfer-based flowmeter. The suggested flowmeter allows the measurement of flow rates in applications involving hot fluid flows, mainly gas flows. The suggested flowmeter operates by circulating a cold fluid (water) of a known flow rate and temperature in a concentric tube heat exchanger in an opposite direction to the main flow of hot fluid of unknown flow rate. The flowmeter enables, from temperature measurements and the energy balance of the exchanger, the determination of the unknown flow rate. It was shown that the suggested flowmeter can reach accuracies greater than 90% depending on different parameters. The flowmeter's precision was shown to be increased with the increase of both cold and hot flow rates. The suggested flowmeter can be enhanced when the fluid temperatures are within the optimal range of operation which are achieved and specified by the design parameters. Keywords: New flowmeter, High temperature, Flow rate, Design, Implementation, Testing

The present work is concerned with the combination of solar energy systems with HVAC systems. Namely, the objective is finding a way of applying green energy concepts to HVAC systems. Particularly, solar concepts are employed to supply electrical power to HVAC systems. Hence, an innovative concept that permits the use of electrical energy provided by parabolic troughs to drive electrical components of the HVAC system is suggested. Thermal modeling along with governing equations of electricity production from parabolic troughs are presented. Calculations of the electrical power needed for HVAC system, showed that an order of magnitude of energy saving is attainable. Finally, the aforementioned concept was applied on a genuine case in Beirut city. It was shown that four mirrors with a 0.5 efficiency of the storage system are capable to drive the pumps of a HVAC system of a 4-floor building all over the year. Keywords: Parabolic trough, HVAC, Energy management, Solar energy, Electrical power, Saving energy

International audience; The transportation impact on pollution and global climate change, has forced the automotive sector to search for more ecological solutions. Owing to the different properties of Fuel Cell (FC), real potential for reducing vehicles’ emissions has been witnessed. The optimization of FC integration within Electric Vehicles (EVs) is one of the original solutions. This paper presents an innovating solution of multi-stack Fuel Cell Electrical Vehicle (FCEV) in terms of efficiency, durability and ecological impact on environment. The main objective is to illustrate the interest of using the multi-stack FC system on the global autonomy, cycling, and efficiency enhancement, besides optimizing its operation performance.

Abstract The aim of this study is to demonstrate the requirement to integrate the urban microclimate to predict the energy needs of buildings. To do this, an integrated approach in TRNSYS software was developed and compared with existing experimental results of a street canyon. Afterwards, a case study was carried out in the case of a street canyon located in the city of Tangier in Morocco. The impact of the aspect ratio on the temperature of the building surfaces and the radiation absorbed by them was examined. The results show that there is greater radiation absorption on the building facades in street canyons than on those of stand-alone buildings. These effects lead to higher surface temperatures in street canyons, resulting in increased cooling energy needs in summer and reduced heating energy needs in winter.