Rabah Dizene - Academia.edu (original) (raw)

Papers by Rabah Dizene

In this article, we present an experimental study in a wind tunnel of a three-bladed, Rutland 503... more In this article, we present an experimental study in a wind tunnel of a three-bladed, Rutland 503 model, horizontal axis yawed wind turbine. Power measurement and an exploration downstream wake of the turbine using particle image velocimetry measurements are performed. The variation of power coefficient as a function of rotational velocity is presented for different yaw angles. The results show a loss of power from the wind turbine when the yaw angle increases. The velocity field of the downstream wake of the rotor is presented in an azimuth plane, which passes through the symmetry axis of the rotor. The instantaneous velocity field is measured and recorded to allow for obtaining the averaged velocity field. The results also show variations in the wake downstream due to decelerating flow caused by the yawed turbine rotor. Analysis of this data shows that the active control of yaw angles could be an advantage to preserve the power from the wind turbine and that details near rotor wak...

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and ... more is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. This is an author-deposited version published in:

Proceeding of Thermal Sciences 2004. Proceedings of the ASME - ZSIS International Thermal Science Seminar II

Calculation of solar global irradiation on tilted planes from horizontal global one is difficult ... more Calculation of solar global irradiation on tilted planes from horizontal global one is difficult when the time step is small. We used an Artificial Neural Network (ANN) to realize this conversion at a 5-min time step for solar irradiation data of Bouzareah (Algeria). The ANN is developed and optimized on the basis of two years of solar data (1.5 year or training and 0.5 year for test) and the accuracy of the optimal configuration is around 8% for the nRMSE.

Il est inconcevable de dimensionner, de concevoir et de modeliser un systeme energetique solaire ... more Il est inconcevable de dimensionner, de concevoir et de modeliser un systeme energetique solaire sans avoir acces aux donnees meteorologiques et plus particulierement solaires du site d'implantation. Ces donnees sont souvent peu disponibles et il est important de disposer de methodes efficaces pour les estimer. C'est l'objet de cet article qui fait une synthese chronologique des dernieres etudes relatives a l'utilisation des Reseaux de Neurones Artificiels (RNA) appliques a l'estimation du potentiel (...)

This paper deals with the modification of the pressure distributions due to the constraining effe... more This paper deals with the modification of the pressure distributions due to the constraining effects of the walls when a stationary prism is tested in a channel. These constraining effects are often defined as solid and wake blockages. In this paper, attention is then paid to the side wall pressure distributions (partly the source of transverse vibrations since the wake vorticity is organized over the side wall) in the case of two- dimensional rectangular prisms exposed to smooth and grid turbulent flows. Conditions are examined for which similitude is lost and correction techniques are not expected to perform well. An experimental set-up is developed to preserve the additional similitude criteria of grid turbulent flows. This paper deals with the modification of the pressure distributions due to the constraining effects of the walls when a stationary prism is tested in a channel. These constraining effects are often defined as solid and wake blockages. Solid blockage is due to the ...

2018 6th International Renewable and Sustainable Energy Conference (IRSEC), 2018

comparison of a two-dimensional numerical simulation of the instantaneous variation of direction,... more comparison of a two-dimensional numerical simulation of the instantaneous variation of direction, wind speed and the surface roughness of a blade profile S809 of a wind turbine is made with experimental results. Incidence angle profile and the speed variations are in pulsating form (very fast variation in the time), instead of oscillations. The URANS method was used to predict stall and surface roughness influence. Turbulence modeling was carried out by using the standard k−varepsilonk-\varepsilonk−varepsilon and k-omega SST models and FLUENT software for the numerical resolution. The results obtained show the importance of taking into account transient flow behavior and surface roughness effect in operating conditions of wind turbines in order to obtain an accurate aerodynamic load estimation.

This article deals with the case of a house, located in the south Mediterranean coastal region po... more This article deals with the case of a house, located in the south Mediterranean coastal region powered by a hybrid photovoltaic wind power plant. The objective is to satisfy as much as possible the energy demand of this house by renewable electric energy. For the case considered adding to the on-grid 3.2kWp PV system with 12kWh backup a 1kW wind turbine improves the self-sufficiency rate of the house which reaches 81.83%, reduces the energy withdrawn from the grid by 40 %.

Energy

The Darrieus vertical axis wind-turbine (VAWT) has been the subject of numerous recent studies ai... more The Darrieus vertical axis wind-turbine (VAWT) has been the subject of numerous recent studies aimed at improving its aerodynamic performance in order to locate it in urban areas. This article is devoted to the study of an original VAWT with variable-pitch and low tip speed ratio TSR which is favorable to noise reduction and can operate at low velocity wind. The aerodynamic performance of this turbine is studied experimentally in wind tunnel as well as by CFD. In order to obtain the 3D-flow field around the wind turbine rotor, the numerical simulations are performed by means of detached eddy simulation method (DES). The simulation of pitch variation is made possible by using sliding-mesh method. Thus a specially created program adapts the pitch depending on the blade azimuthal position during rotation. The obtained results show that adapted pitch blades are preferable because they permit to obtain a power coefficient Cp that rivals other VAWT in the case of TSR < 1. The maximum torque fluctuation during rotation is lower in the case of adapted variable-pitch compared to fixed-pitch and thus the maximum aerodynamic loads on the structure can be reduced. Moreover, the pitch adaptation leads to lower interaction effects between the upstream-blade wake and downstream blades.

Journal of Applied Fluid Mechanics

Improving the efficiency and suction capability of a multistage centrifugal pump poses a major ch... more Improving the efficiency and suction capability of a multistage centrifugal pump poses a major challenge for the designer of this type of equipment. This paper deals with the optimization of a two stage centrifugal pump using Non-dominated Sorting Genetic Algorithm II (NSGA-II), coupled with three-dimensional Reynoldsaveraged Navier-Stokes (3D-RANS) flow solver. The first stage comprises a suction impeller with a diffuser while the second stage is formed by a second impeller connected to a volute. Both impellers are of different dimensions and are interconnected by a return channel. This arrangement increases the number of varying parameters and thus can add further constraints on the overall optimization process; as a result, a high computational complexity of NSGA-II and a higher computational fluid dynamics (CFD) simulation cost is incurred. In order to save running time, optimization with CFD simulations are performed on each stage separately shall enable to obtain better parameterization flexibility; therefore, permitting to adopt only three objective functions in as well as limiting other geometrical constraints. The objectives of this study are to maximize the head and hydraulic efficiency at a time where the net positive suction head inception (NPSHi) is kept to minimum. The overall efficiency as well as the head of the optimized pump were increased by 9.8% and 15.7%, respectively, at best efficiency point (BEP) (rotational speed N=2600 rpm); the NPSHi of suction impeller was reduced by 13.6%. At N=1450 rpm (BEP), an improvement of 14.9% in the head and 6.52% for the overall efficiency is observed. An important improvement in performance at different operating flow rates was obtained; this was in addition to other enhancements in the volumetric and hydraulic efficiencies. Unsteady CFD simulations were also performed to predict fluctuations in the pressure field, leakage flows and interactions between impellers and collectors. The obtained results were in agreement with experimental data. The head fluctuation of the optimized pump was also reduced by 22.5% in amplitude; this was favored by the presence of a tapered blade towards the trailing edge and the extended radial gap by 4.86% between the second impeller and cutwater, which was caused by the reduction of the impeller diameter.

Journal of Applied Fluid Mechanics

Investigation of the effects blade pitch angle on noise emission from a horizontal axis wind turb... more Investigation of the effects blade pitch angle on noise emission from a horizontal axis wind turbine is the goal of this paper. To understand the flow around blade wind turbine, and to reduce noise emission in order to respect noise regulation, especially a residential area , three different pitch angles 0°, 3°, and 6° are tested, using computational aerodynamic and aero acoustic methods. Three dimensional flow simulations are carried out with two unsteady CFD simulations URANS, DES used to calculate the near-field flow around a HAWT of NREL Phase VI small scale. The far field noise is predicted from the simulated sources by the Ffowcs William and Hawkings analogy, and compared and validated with available test data for a small-scaled model of the NREL Phase VI. The comparison demonstrates a generally good agreement between DES predicted and measured noise levels. It can be seen that the noise emission increases by decreasing pitch angle. Moreover, the pitch angle control has a significant effect on the noise emission especially in the intermediate frequency range. We show that it is possible to reduce the noise level by control pitch angle without losing too much the power.

Renewable Energy

Abstract Investigation of blade tip shape effect on the noise emission from horizontal axis wind ... more Abstract Investigation of blade tip shape effect on the noise emission from horizontal axis wind turbine is the target of this work. To recognize the flow around blade wind turbine, and to minimize the noise emission especially at the tip; three different tip blade configurations are tested by using the aerodynamic and the aero-acoustic computational methods. Three dimensional flow simulations are carried out with two unsteady CFD simulations; Unsteady Reynolds-averaged Naviere-Stokes (URANS) and Detached Eddy Simulation (DES). These methods are used to calculate the near-field flow around a HAWT of NREL Phase VI small scale model with different tip blade shapes. Ffowcs Williams-Hawkings (FW–H) analogy is used to predict the sound generated from the turbine, and then it is validated and compared with available experimental data for small-scaled model of NREL Phase VI. In general, the comparison confirms a good and acceptable agreement between DES results and the experimental measured noise results. Moreover, it is shown that a possibility to reduce or minimize the sound pressure level by using a specific tip shape. The results indicated that the usage of a specific tip shape has an important and significant influence on the noise emission in particular at the high frequency range.

Renewable Energy

Three methods, smart persistence, artificial neural network and random forest, are compared to fo... more Three methods, smart persistence, artificial neural network and random forest, are compared to forecast the three components of solar irradiation (global horizontal, beam normal and diffuse horizontal) measured on the site of Odeillo, France, characterized by a high meteorological variability. The objective is to predict hourly solar irradiations for time horizons from h+1 to h+6. The random forest (RF) method is the most efficient and forecasts the three components with a nRMSE from 19.65% for h+1–27.78% for h+6 for the global horizontal irradiation (GHI), a nRMSE from 34.11% for h+1–49.08% for h+6 for the beam normal irradiation (BNI); a nRMSE from 35.08% for h+1–49.14% for h+6 for diffuse horizontal irradiation (DHI). The improvement brought by the use of RF compared to Artificial Neural Network (ANN) and smart persistence (SP) increases with the forecasting horizon. A seasonal study is realized and shows that the forecasting of solar irradiation during spring and autumn is less reliable than during winter and summer because during these periods the meteorological variability is more important.

Solar Energy

Abstract In the present work, a detailed optical and thermodynamic analysis of the solar Paraboli... more Abstract In the present work, a detailed optical and thermodynamic analysis of the solar Parabolic Trough Collector (PTC) is presented. At first, an optical and 2D thermal modeling of a PTC is developed. This thermal modeling is coupled to an exergy analysis to construct a single model for the PTC’s overall performances prediction. The results are compared to the experimental measurements carried out at Sandia National Laboratories. Then, a parametric study was first performed by using a commercial PTC (Eurotrough ET-150) and a Schott PTR-70 receiver in order to study the effect of some operating and environmental parameters on the PTC’s optical, thermal and exergy efficiencies. The exergy losses and the exergy destruction rates through these parameters are also evaluated. In all cases, the results are in accordance and showed a good agreement with experimental data. The results show that the PTC’s performances are very sensitive to the beam solar radiation and the incidence angle as well as to the PTC’s aperture width, the heat transfer fluid inlet temperature and the mass flow rate. The main deviations in the performances are caused by heat losses from the heat transfer fluid to the surroundings (exergy losses), and/or by the fact of thermal differential through flow direction (exergy destruction) that is the main of the dissipation in the system process. In addition, the simulation of the performance of four Eurotrough ET-150 mounted in series (one loop) under the running conditions of site of Hassi R’Mel (located at the heart of Algerian Sahara) on two typical days is predicted. On summer solstice, the daily maximum energy efficiency and exergy efficiency are 67.91% and 36.08%, respectively. They, however, decrease to 31% and 22.1%, respectively on winter solstice. The overall performance prediction guarantees the real-time evaluation of the PTC with more accuracy.

Http Www Theses Fr, 1993

On etudie experimentalement l'interaction de jets de paroi avec un ecoulement transversal com... more On etudie experimentalement l'interaction de jets de paroi avec un ecoulement transversal compressible uniforme (m=0,7-0,8), pour des taux massiques d'injection faibles (r<1), en vue des applications au refroidissement par jets des aubages de turboreacteurs. Les techniques experimentales mises en uvre donnent une image precise de la physique des interactions, fournissent une importante base de donnees destinees a la validation de codes numeriques et permettent des conclusions preliminaires quant a l'effet de la compressibilite. Pour le premier cas etudie, celui de l'interaction adiabatique avec un jet perpendiculaire, la compressibilite semble reduire le nombre de structures tourbillonnaires autour de l'orifice d'injection tout en augmentant les deficits de vitesse et les extrema de pression. Par contre, il ne remet pas en cause le faible effet de l'epaisseur de couche limite amont ni l'existence d'un battement du sillage du jet. Pour le modele avec cinq jets obliques chauds emergeant d'une paroi egalement chauffee, l'augmentation des nombres de mach, a des taux d'injection semblables, entraine une penetration plus forte des jets dans l'ecoulement transversal avec disparition de l'ecoulement de retour derriere l'orifice et retarde la coalescence des jets. On montre par ailleurs l'existence d'une valeur critique du taux d'injection pour laquelle le transfert thermique parietal est optimal. Cependant, la configuration retenue ne permet pas de realiser un refroidissement par film. Elle peut meme conduire a des points chauds, par entrainement de fluide exterieur vers la paroi

In this article, we present an experimental study in a wind tunnel of a three-bladed, Rutland 503... more In this article, we present an experimental study in a wind tunnel of a three-bladed, Rutland 503 model, horizontal axis yawed wind turbine. Power measurement and an exploration downstream wake of the turbine using particle image velocimetry measurements are performed. The variation of power coefficient as a function of rotational velocity is presented for different yaw angles. The results show a loss of power from the wind turbine when the yaw angle increases. The velocity field of the downstream wake of the rotor is presented in an azimuth plane, which passes through the symmetry axis of the rotor. The instantaneous velocity field is measured and recorded to allow for obtaining the averaged velocity field. The results also show variations in the wake downstream due to decelerating flow caused by the yawed turbine rotor. Analysis of this data shows that the active control of yaw angles could be an advantage to preserve the power from the wind turbine and that details near rotor wak...

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and ... more is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. This is an author-deposited version published in:

Proceeding of Thermal Sciences 2004. Proceedings of the ASME - ZSIS International Thermal Science Seminar II

Calculation of solar global irradiation on tilted planes from horizontal global one is difficult ... more Calculation of solar global irradiation on tilted planes from horizontal global one is difficult when the time step is small. We used an Artificial Neural Network (ANN) to realize this conversion at a 5-min time step for solar irradiation data of Bouzareah (Algeria). The ANN is developed and optimized on the basis of two years of solar data (1.5 year or training and 0.5 year for test) and the accuracy of the optimal configuration is around 8% for the nRMSE.

Il est inconcevable de dimensionner, de concevoir et de modeliser un systeme energetique solaire ... more Il est inconcevable de dimensionner, de concevoir et de modeliser un systeme energetique solaire sans avoir acces aux donnees meteorologiques et plus particulierement solaires du site d'implantation. Ces donnees sont souvent peu disponibles et il est important de disposer de methodes efficaces pour les estimer. C'est l'objet de cet article qui fait une synthese chronologique des dernieres etudes relatives a l'utilisation des Reseaux de Neurones Artificiels (RNA) appliques a l'estimation du potentiel (...)

This paper deals with the modification of the pressure distributions due to the constraining effe... more This paper deals with the modification of the pressure distributions due to the constraining effects of the walls when a stationary prism is tested in a channel. These constraining effects are often defined as solid and wake blockages. In this paper, attention is then paid to the side wall pressure distributions (partly the source of transverse vibrations since the wake vorticity is organized over the side wall) in the case of two- dimensional rectangular prisms exposed to smooth and grid turbulent flows. Conditions are examined for which similitude is lost and correction techniques are not expected to perform well. An experimental set-up is developed to preserve the additional similitude criteria of grid turbulent flows. This paper deals with the modification of the pressure distributions due to the constraining effects of the walls when a stationary prism is tested in a channel. These constraining effects are often defined as solid and wake blockages. Solid blockage is due to the ...

2018 6th International Renewable and Sustainable Energy Conference (IRSEC), 2018

comparison of a two-dimensional numerical simulation of the instantaneous variation of direction,... more comparison of a two-dimensional numerical simulation of the instantaneous variation of direction, wind speed and the surface roughness of a blade profile S809 of a wind turbine is made with experimental results. Incidence angle profile and the speed variations are in pulsating form (very fast variation in the time), instead of oscillations. The URANS method was used to predict stall and surface roughness influence. Turbulence modeling was carried out by using the standard k−varepsilonk-\varepsilonk−varepsilon and k-omega SST models and FLUENT software for the numerical resolution. The results obtained show the importance of taking into account transient flow behavior and surface roughness effect in operating conditions of wind turbines in order to obtain an accurate aerodynamic load estimation.

This article deals with the case of a house, located in the south Mediterranean coastal region po... more This article deals with the case of a house, located in the south Mediterranean coastal region powered by a hybrid photovoltaic wind power plant. The objective is to satisfy as much as possible the energy demand of this house by renewable electric energy. For the case considered adding to the on-grid 3.2kWp PV system with 12kWh backup a 1kW wind turbine improves the self-sufficiency rate of the house which reaches 81.83%, reduces the energy withdrawn from the grid by 40 %.

Energy

The Darrieus vertical axis wind-turbine (VAWT) has been the subject of numerous recent studies ai... more The Darrieus vertical axis wind-turbine (VAWT) has been the subject of numerous recent studies aimed at improving its aerodynamic performance in order to locate it in urban areas. This article is devoted to the study of an original VAWT with variable-pitch and low tip speed ratio TSR which is favorable to noise reduction and can operate at low velocity wind. The aerodynamic performance of this turbine is studied experimentally in wind tunnel as well as by CFD. In order to obtain the 3D-flow field around the wind turbine rotor, the numerical simulations are performed by means of detached eddy simulation method (DES). The simulation of pitch variation is made possible by using sliding-mesh method. Thus a specially created program adapts the pitch depending on the blade azimuthal position during rotation. The obtained results show that adapted pitch blades are preferable because they permit to obtain a power coefficient Cp that rivals other VAWT in the case of TSR < 1. The maximum torque fluctuation during rotation is lower in the case of adapted variable-pitch compared to fixed-pitch and thus the maximum aerodynamic loads on the structure can be reduced. Moreover, the pitch adaptation leads to lower interaction effects between the upstream-blade wake and downstream blades.

Journal of Applied Fluid Mechanics

Improving the efficiency and suction capability of a multistage centrifugal pump poses a major ch... more Improving the efficiency and suction capability of a multistage centrifugal pump poses a major challenge for the designer of this type of equipment. This paper deals with the optimization of a two stage centrifugal pump using Non-dominated Sorting Genetic Algorithm II (NSGA-II), coupled with three-dimensional Reynoldsaveraged Navier-Stokes (3D-RANS) flow solver. The first stage comprises a suction impeller with a diffuser while the second stage is formed by a second impeller connected to a volute. Both impellers are of different dimensions and are interconnected by a return channel. This arrangement increases the number of varying parameters and thus can add further constraints on the overall optimization process; as a result, a high computational complexity of NSGA-II and a higher computational fluid dynamics (CFD) simulation cost is incurred. In order to save running time, optimization with CFD simulations are performed on each stage separately shall enable to obtain better parameterization flexibility; therefore, permitting to adopt only three objective functions in as well as limiting other geometrical constraints. The objectives of this study are to maximize the head and hydraulic efficiency at a time where the net positive suction head inception (NPSHi) is kept to minimum. The overall efficiency as well as the head of the optimized pump were increased by 9.8% and 15.7%, respectively, at best efficiency point (BEP) (rotational speed N=2600 rpm); the NPSHi of suction impeller was reduced by 13.6%. At N=1450 rpm (BEP), an improvement of 14.9% in the head and 6.52% for the overall efficiency is observed. An important improvement in performance at different operating flow rates was obtained; this was in addition to other enhancements in the volumetric and hydraulic efficiencies. Unsteady CFD simulations were also performed to predict fluctuations in the pressure field, leakage flows and interactions between impellers and collectors. The obtained results were in agreement with experimental data. The head fluctuation of the optimized pump was also reduced by 22.5% in amplitude; this was favored by the presence of a tapered blade towards the trailing edge and the extended radial gap by 4.86% between the second impeller and cutwater, which was caused by the reduction of the impeller diameter.

Journal of Applied Fluid Mechanics

Investigation of the effects blade pitch angle on noise emission from a horizontal axis wind turb... more Investigation of the effects blade pitch angle on noise emission from a horizontal axis wind turbine is the goal of this paper. To understand the flow around blade wind turbine, and to reduce noise emission in order to respect noise regulation, especially a residential area , three different pitch angles 0°, 3°, and 6° are tested, using computational aerodynamic and aero acoustic methods. Three dimensional flow simulations are carried out with two unsteady CFD simulations URANS, DES used to calculate the near-field flow around a HAWT of NREL Phase VI small scale. The far field noise is predicted from the simulated sources by the Ffowcs William and Hawkings analogy, and compared and validated with available test data for a small-scaled model of the NREL Phase VI. The comparison demonstrates a generally good agreement between DES predicted and measured noise levels. It can be seen that the noise emission increases by decreasing pitch angle. Moreover, the pitch angle control has a significant effect on the noise emission especially in the intermediate frequency range. We show that it is possible to reduce the noise level by control pitch angle without losing too much the power.

Renewable Energy

Abstract Investigation of blade tip shape effect on the noise emission from horizontal axis wind ... more Abstract Investigation of blade tip shape effect on the noise emission from horizontal axis wind turbine is the target of this work. To recognize the flow around blade wind turbine, and to minimize the noise emission especially at the tip; three different tip blade configurations are tested by using the aerodynamic and the aero-acoustic computational methods. Three dimensional flow simulations are carried out with two unsteady CFD simulations; Unsteady Reynolds-averaged Naviere-Stokes (URANS) and Detached Eddy Simulation (DES). These methods are used to calculate the near-field flow around a HAWT of NREL Phase VI small scale model with different tip blade shapes. Ffowcs Williams-Hawkings (FW–H) analogy is used to predict the sound generated from the turbine, and then it is validated and compared with available experimental data for small-scaled model of NREL Phase VI. In general, the comparison confirms a good and acceptable agreement between DES results and the experimental measured noise results. Moreover, it is shown that a possibility to reduce or minimize the sound pressure level by using a specific tip shape. The results indicated that the usage of a specific tip shape has an important and significant influence on the noise emission in particular at the high frequency range.

Renewable Energy

Three methods, smart persistence, artificial neural network and random forest, are compared to fo... more Three methods, smart persistence, artificial neural network and random forest, are compared to forecast the three components of solar irradiation (global horizontal, beam normal and diffuse horizontal) measured on the site of Odeillo, France, characterized by a high meteorological variability. The objective is to predict hourly solar irradiations for time horizons from h+1 to h+6. The random forest (RF) method is the most efficient and forecasts the three components with a nRMSE from 19.65% for h+1–27.78% for h+6 for the global horizontal irradiation (GHI), a nRMSE from 34.11% for h+1–49.08% for h+6 for the beam normal irradiation (BNI); a nRMSE from 35.08% for h+1–49.14% for h+6 for diffuse horizontal irradiation (DHI). The improvement brought by the use of RF compared to Artificial Neural Network (ANN) and smart persistence (SP) increases with the forecasting horizon. A seasonal study is realized and shows that the forecasting of solar irradiation during spring and autumn is less reliable than during winter and summer because during these periods the meteorological variability is more important.

Solar Energy

Abstract In the present work, a detailed optical and thermodynamic analysis of the solar Paraboli... more Abstract In the present work, a detailed optical and thermodynamic analysis of the solar Parabolic Trough Collector (PTC) is presented. At first, an optical and 2D thermal modeling of a PTC is developed. This thermal modeling is coupled to an exergy analysis to construct a single model for the PTC’s overall performances prediction. The results are compared to the experimental measurements carried out at Sandia National Laboratories. Then, a parametric study was first performed by using a commercial PTC (Eurotrough ET-150) and a Schott PTR-70 receiver in order to study the effect of some operating and environmental parameters on the PTC’s optical, thermal and exergy efficiencies. The exergy losses and the exergy destruction rates through these parameters are also evaluated. In all cases, the results are in accordance and showed a good agreement with experimental data. The results show that the PTC’s performances are very sensitive to the beam solar radiation and the incidence angle as well as to the PTC’s aperture width, the heat transfer fluid inlet temperature and the mass flow rate. The main deviations in the performances are caused by heat losses from the heat transfer fluid to the surroundings (exergy losses), and/or by the fact of thermal differential through flow direction (exergy destruction) that is the main of the dissipation in the system process. In addition, the simulation of the performance of four Eurotrough ET-150 mounted in series (one loop) under the running conditions of site of Hassi R’Mel (located at the heart of Algerian Sahara) on two typical days is predicted. On summer solstice, the daily maximum energy efficiency and exergy efficiency are 67.91% and 36.08%, respectively. They, however, decrease to 31% and 22.1%, respectively on winter solstice. The overall performance prediction guarantees the real-time evaluation of the PTC with more accuracy.

Http Www Theses Fr, 1993

On etudie experimentalement l'interaction de jets de paroi avec un ecoulement transversal com... more On etudie experimentalement l'interaction de jets de paroi avec un ecoulement transversal compressible uniforme (m=0,7-0,8), pour des taux massiques d'injection faibles (r<1), en vue des applications au refroidissement par jets des aubages de turboreacteurs. Les techniques experimentales mises en uvre donnent une image precise de la physique des interactions, fournissent une importante base de donnees destinees a la validation de codes numeriques et permettent des conclusions preliminaires quant a l'effet de la compressibilite. Pour le premier cas etudie, celui de l'interaction adiabatique avec un jet perpendiculaire, la compressibilite semble reduire le nombre de structures tourbillonnaires autour de l'orifice d'injection tout en augmentant les deficits de vitesse et les extrema de pression. Par contre, il ne remet pas en cause le faible effet de l'epaisseur de couche limite amont ni l'existence d'un battement du sillage du jet. Pour le modele avec cinq jets obliques chauds emergeant d'une paroi egalement chauffee, l'augmentation des nombres de mach, a des taux d'injection semblables, entraine une penetration plus forte des jets dans l'ecoulement transversal avec disparition de l'ecoulement de retour derriere l'orifice et retarde la coalescence des jets. On montre par ailleurs l'existence d'une valeur critique du taux d'injection pour laquelle le transfert thermique parietal est optimal. Cependant, la configuration retenue ne permet pas de realiser un refroidissement par film. Elle peut meme conduire a des points chauds, par entrainement de fluide exterieur vers la paroi