Absorbed Radiation

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O A Jaramillo - One of the best experts on this subject based on the ideXlab platform.

  • optimization of a linear fresnel reflector applying computational fluid dynamics entropy generation rate and evolutionary programming
    Renewable Energy, 2020
    Co-Authors: Oscar A Lopeznunez, Arturo J Alfaroayala, J J Ramirezminguela, J M Belmanflores, O A Jaramillo
    Abstract:

    Abstract This work presents an optimization of a Linear Fresnel Reflector based on the Computational Fluid Dynamics, the Entropy Generation Rate and the Evolutionary Programming method. The objective function of the optimization process takes into account the maximization of the Absorbed Radiation solar flux on the receiver tube and the minimization of the total Entropy Generation Rate. A set of design equations were used to build the Linear Fresnel Reflector geometries of each one of the individuals per generation. The design equations consider, among others, a coupling between the angles and distances of the mirrors and the required geometrical parameters for the construction of the CPC secondary reflector. The Evolutionary Programming considers a small population of six individuals per generation and takes into account a search space for geometric parameters such as the aperture area, the width and the length of the mirrors. The mutation operator is applied to generate the individuals and the selection operator is applied to find the best individuals for the next generation. Seven generations were needed to find the optimal Linear Fresnel Reflector. The optimal Linear Fresnel Reflector (NN individual) presents an increase of 2.48% for the average Absorbed Radiation flux on the absorber tube and a decrease of 20% for the total Entropy Generation Rate, both in comparison with a prototype of a Linear Fresnel Reflector. For the Absorbed Radiation flux, both individuals presents the minimum values on the top side of the absorber tube (1,386 W m-2 and 1,982 W m-2 for the prototype and NN individual respectively), while the maximum values are located at the lower part of the absorber tube (7,180 W m-2 and 8,199 W m-2 for the prototype and NN individual respectively). In terms of local Entropy Generation Rate, the NN individual has a decrease of 14.6%, 60% and 36.8% of Entropy Generation Rate due to viscous dissipation, heat transfer and Radiation respectively at the CPC zone in comparison with the prototype of a Linear Fresnel Reflector. Finally, the NN individual has an increase of 16.4% and 23.8%. for the thermal efficiency and the exergy efficiency, respectively.

  • a numerical analysis of the energy and entropy generation rate in a linear fresnel reflector using computational fluid dynamics
    Renewable Energy, 2020
    Co-Authors: Oscar A Lopeznunez, Arturo J Alfaroayala, J J Ramirezminguela, Carlos J Castro, O A Jaramillo, Cesar E Damianascencio, Sergio Canoandrade
    Abstract:

    Abstract This work presents an energy and entropy generation analysis of a Linear Fresnel Reflector using the Computational Fluid Dynamics. It consists of 25 mirrors oriented to a receiver tube, which is located inside a Compound Parabolic Concentrator. The formulation of the entropy generation rate considers the phenomena of viscous dissipation, heat transfer and Radiation, it is performed in a local and global way and implemented by user-defined functions. Results of the incident Radiation, Absorbed Radiation, Radiation temperature, temperature gradients, air velocity contours, Nusselt number and optical efficiency, are presented. Results show that the maximum values of the Absorbed Radiation (7800 W m−2), incident Radiation (30,000 W m−2) and Radiation temperature were located at the receiver tube. Also, the maximum value of the temperature gradient (39,000 K m−1) was obtained on the lower half of the receiver tube and the upper part of the secondary receiver. Moreover, the highest values of the entropy generation rate were located at the upper part of the secondary receiver for each phenomenon considered. It is concluded that the entropy generation rate due to heat transfer phenomenon is the most dominant (97.4% of the total), followed by Radiation (2.59%) and then by viscous dissipation (negligible).

Oscar A Lopeznunez - One of the best experts on this subject based on the ideXlab platform.

  • optimization of a linear fresnel reflector applying computational fluid dynamics entropy generation rate and evolutionary programming
    Renewable Energy, 2020
    Co-Authors: Oscar A Lopeznunez, Arturo J Alfaroayala, J J Ramirezminguela, J M Belmanflores, O A Jaramillo
    Abstract:

    Abstract This work presents an optimization of a Linear Fresnel Reflector based on the Computational Fluid Dynamics, the Entropy Generation Rate and the Evolutionary Programming method. The objective function of the optimization process takes into account the maximization of the Absorbed Radiation solar flux on the receiver tube and the minimization of the total Entropy Generation Rate. A set of design equations were used to build the Linear Fresnel Reflector geometries of each one of the individuals per generation. The design equations consider, among others, a coupling between the angles and distances of the mirrors and the required geometrical parameters for the construction of the CPC secondary reflector. The Evolutionary Programming considers a small population of six individuals per generation and takes into account a search space for geometric parameters such as the aperture area, the width and the length of the mirrors. The mutation operator is applied to generate the individuals and the selection operator is applied to find the best individuals for the next generation. Seven generations were needed to find the optimal Linear Fresnel Reflector. The optimal Linear Fresnel Reflector (NN individual) presents an increase of 2.48% for the average Absorbed Radiation flux on the absorber tube and a decrease of 20% for the total Entropy Generation Rate, both in comparison with a prototype of a Linear Fresnel Reflector. For the Absorbed Radiation flux, both individuals presents the minimum values on the top side of the absorber tube (1,386 W m-2 and 1,982 W m-2 for the prototype and NN individual respectively), while the maximum values are located at the lower part of the absorber tube (7,180 W m-2 and 8,199 W m-2 for the prototype and NN individual respectively). In terms of local Entropy Generation Rate, the NN individual has a decrease of 14.6%, 60% and 36.8% of Entropy Generation Rate due to viscous dissipation, heat transfer and Radiation respectively at the CPC zone in comparison with the prototype of a Linear Fresnel Reflector. Finally, the NN individual has an increase of 16.4% and 23.8%. for the thermal efficiency and the exergy efficiency, respectively.

  • a numerical analysis of the energy and entropy generation rate in a linear fresnel reflector using computational fluid dynamics
    Renewable Energy, 2020
    Co-Authors: Oscar A Lopeznunez, Arturo J Alfaroayala, J J Ramirezminguela, Carlos J Castro, O A Jaramillo, Cesar E Damianascencio, Sergio Canoandrade
    Abstract:

    Abstract This work presents an energy and entropy generation analysis of a Linear Fresnel Reflector using the Computational Fluid Dynamics. It consists of 25 mirrors oriented to a receiver tube, which is located inside a Compound Parabolic Concentrator. The formulation of the entropy generation rate considers the phenomena of viscous dissipation, heat transfer and Radiation, it is performed in a local and global way and implemented by user-defined functions. Results of the incident Radiation, Absorbed Radiation, Radiation temperature, temperature gradients, air velocity contours, Nusselt number and optical efficiency, are presented. Results show that the maximum values of the Absorbed Radiation (7800 W m−2), incident Radiation (30,000 W m−2) and Radiation temperature were located at the receiver tube. Also, the maximum value of the temperature gradient (39,000 K m−1) was obtained on the lower half of the receiver tube and the upper part of the secondary receiver. Moreover, the highest values of the entropy generation rate were located at the upper part of the secondary receiver for each phenomenon considered. It is concluded that the entropy generation rate due to heat transfer phenomenon is the most dominant (97.4% of the total), followed by Radiation (2.59%) and then by viscous dissipation (negligible).

Josua P Meyer - One of the best experts on this subject based on the ideXlab platform.

  • combining ray tracing and cfd in the thermal analysis of a parabolic dish tubular cavity receiver
    SOLARPACES 2015: International Conference on Concentrating Solar Power and Chemical Energy Systems, 2016
    Co-Authors: K J Craig, Justin Marsberg, Josua P Meyer
    Abstract:

    This paper describes the numerical evaluation of a tubular receiver used in a dish Brayton cycle. In previous work considering the use of Computational Fluid Dynamics (CFD) to perform the calculation of the Absorbed Radiation from the parabolic dish into the cavity as well as the resulting conjugate heat transfer, it was shown that an axi-symmetric model of the dish and receiver absorbing surfaces was useful in reducing the computational cost required for a full 3-D discrete ordinates solution, but concerns remained about its accuracy. To increase the accuracy, the Monte Carlo ray tracer SolTrace is used to perform the calculation of the Absorbed Radiation profile to be used in the conjugate heat transfer CFD simulation. The paper describes an approach for incorporating a complex geometry like a tubular receiver generated using CFD software into SolTrace. The results illustrate the variation of CFD mesh density that translates into the number of elements in SolTrace as well as the number of rays used in the Monte Carlo approach and their effect on obtaining a resolution-independent solution. The conjugate heat transfer CFD simulation illustrates the effect of applying the SolTrace surface heat flux profile solution as a volumetric heat source to heat up the air inside the tube. Heat losses due to convection and thermal re-Radiation are also determined as a function of different tube absorptivities.

  • 3 d cfd modeling of a slanted receiver in a compact linear fresnel plant with etendue matched mirror field
    Energy Procedia, 2015
    Co-Authors: A E Rungasamy, K J Craig, Josua P Meyer
    Abstract:

    Abstract Compact linear Fresnel receivers can be modified to include an etendue conserving mirror field as opposed to a flat field. Etendue can be used as an indicator of the losses within the system and therefore the optical optimization of the mirror field seeks to conserve incoming etendue. This can be done once for peak conditions and subsequently fixed with mirrors rotating throughout the day; or the mirror axis points can also be allowed to move up and down throughout the day, creating new etendue conservation curves. Radiation is modeled using discrete ordinates with no conduction in a two-dimensional and the Absorbed Radiation flux profiles are subsequently patched onto a three-dimensional slanted receiver as a heat source. The commercial software package ANSYS Fluent v15.0 was used together with the Matlab toolset to study the influence of different mirror fields on the amount of Radiation transferred to the collector pipes.

  • computational fluid dynamics analysis of parabolic dish tubular cavity receiver
    2015
    Co-Authors: K J Craig, Josua P Meyer, Willem Gabriel Le Roux
    Abstract:

    The paper describes the Computational Fluid Dynamics (CFD) analysis of a parabolic dish tubular cavity receiver. The analysis uses the geometry of an experimental setup and considers experimental conditions as well as ideal conditions linked to a Brayton cycle microturbine implementation. The CFD analysis comprises of two parts. First, the Radiative Transfer Equation (RTE) is solved with a Finite Volume (FV) method using the Discrete Ordinates (DO) method for the optical performance of the dish and receiver to obtain the Absorbed Radiation on the receiver tube. In this method both an axi-symmetric model with a ring-like receiver is considered utilizing a 2-D mesh as well as a 3-D model with the spiraling tubular receiver. The former is much less computationally intensive because of the extra dimension but simplifies the receiver shape. The result of this FV simulation is an Absorbed Radiation distribution that is patched as volumetric heat source in the second CFD simulation. This simulation is a conjugate heat transfer model that evaluates the heat transfer to the heat transfer fluid as well as the losses from the cavity insulation and due to thermal re-Radiation. The method is evaluated for an ambient lower pressure experimental test at the University of Pretoria as well as a theoretical implementation at Brayton cycle conditions.

Alex Lazarian - One of the best experts on this subject based on the ideXlab platform.

  • polarization of absorption lines as a diagnostics of circumstellar interstellar and intergalactic magnetic fields fine structure atoms
    The Astrophysical Journal, 2006
    Co-Authors: Huirong Yan, Alex Lazarian
    Abstract:

    The relative population of the fine-structure sublevels of an atom's ground state is affected by radiative transitions induced by an anisotropic Radiation flux. This causes the alignment of atomic angular momentum. In terms of observational consequences for the interstellar and intergalactic medium, this results in the polarization of the absorption lines. In the paper we consider the conditions necessary for this effect and provide calculations of polarization from a few astrophysically important atoms and ions with multiple upper and lower levels for an arbitrary orientation of magnetic fields to the (1) source of optical pumping, (2) direction of observation, and (3) Absorbed source. We also consider an astrophysically important degenerate case, in which the source of optical pumping coincides with the source of the Absorbed Radiation. We present analytical expressions that relate the degree of linear polarization and the intensity of absorption to the three-dimensional orientation of the magnetic field with respect to the pumping source, the source of the Absorbed Radiation, and the direction of observations. We discuss how all these parameters can be determined via simultaneous observations of several absorption lines and suggest graphical means that are helpful in practical data interpretation. We prove that studies of absorption line polarization provide a unique tool to study three-dimensional magnetic field topology in various astrophysical conditions.

  • polarization of absorption lines as a diagnostics of circumstellar interstellar and intergalactic magnetic fields fine structure atoms
    arXiv: Astrophysics, 2006
    Co-Authors: Huirong Yan, Alex Lazarian
    Abstract:

    The relative population of the fine structure sublevels of an atom's ground state is affected by radiative transitions induced by an anisotropic Radiation flux. This causes the alignment of atomic angular momentum. In terms of observational consequences for the interstellar and intergalactic medium, this results in the polarization of the absorption lines. In the paper we consider the conditions necessary for this effect and provide calculations of polarization from a few astrophysically important atoms and ions with multiple upper and lower levels for an arbitrary orientation of magnetic fields to the a) source of optical pumping, b) direction of observation, c) Absorbed source. We also consider an astrophysically important ``degenerate'' case when the source of optical pumping coincides with the source of the Absorbed Radiation. We present analytical expressions that relate the degree of linear polarization and the intensity of absorption to the 3D orientation of the magnetic field with respect to the pumping source, the source of the Absorbed Radiation, and the direction of observations. We discuss how all these parameters can be determined via simultaneous observations of several absorption lines and suggest graphical means that are helpful in practical data interpretation. We prove that studies of absorption line polarization provide a unique tool to study 3D magnetic field topology in various astrophysical conditions.

J J Ramirezminguela - One of the best experts on this subject based on the ideXlab platform.

  • optimization of a linear fresnel reflector applying computational fluid dynamics entropy generation rate and evolutionary programming
    Renewable Energy, 2020
    Co-Authors: Oscar A Lopeznunez, Arturo J Alfaroayala, J J Ramirezminguela, J M Belmanflores, O A Jaramillo
    Abstract:

    Abstract This work presents an optimization of a Linear Fresnel Reflector based on the Computational Fluid Dynamics, the Entropy Generation Rate and the Evolutionary Programming method. The objective function of the optimization process takes into account the maximization of the Absorbed Radiation solar flux on the receiver tube and the minimization of the total Entropy Generation Rate. A set of design equations were used to build the Linear Fresnel Reflector geometries of each one of the individuals per generation. The design equations consider, among others, a coupling between the angles and distances of the mirrors and the required geometrical parameters for the construction of the CPC secondary reflector. The Evolutionary Programming considers a small population of six individuals per generation and takes into account a search space for geometric parameters such as the aperture area, the width and the length of the mirrors. The mutation operator is applied to generate the individuals and the selection operator is applied to find the best individuals for the next generation. Seven generations were needed to find the optimal Linear Fresnel Reflector. The optimal Linear Fresnel Reflector (NN individual) presents an increase of 2.48% for the average Absorbed Radiation flux on the absorber tube and a decrease of 20% for the total Entropy Generation Rate, both in comparison with a prototype of a Linear Fresnel Reflector. For the Absorbed Radiation flux, both individuals presents the minimum values on the top side of the absorber tube (1,386 W m-2 and 1,982 W m-2 for the prototype and NN individual respectively), while the maximum values are located at the lower part of the absorber tube (7,180 W m-2 and 8,199 W m-2 for the prototype and NN individual respectively). In terms of local Entropy Generation Rate, the NN individual has a decrease of 14.6%, 60% and 36.8% of Entropy Generation Rate due to viscous dissipation, heat transfer and Radiation respectively at the CPC zone in comparison with the prototype of a Linear Fresnel Reflector. Finally, the NN individual has an increase of 16.4% and 23.8%. for the thermal efficiency and the exergy efficiency, respectively.

  • a numerical analysis of the energy and entropy generation rate in a linear fresnel reflector using computational fluid dynamics
    Renewable Energy, 2020
    Co-Authors: Oscar A Lopeznunez, Arturo J Alfaroayala, J J Ramirezminguela, Carlos J Castro, O A Jaramillo, Cesar E Damianascencio, Sergio Canoandrade
    Abstract:

    Abstract This work presents an energy and entropy generation analysis of a Linear Fresnel Reflector using the Computational Fluid Dynamics. It consists of 25 mirrors oriented to a receiver tube, which is located inside a Compound Parabolic Concentrator. The formulation of the entropy generation rate considers the phenomena of viscous dissipation, heat transfer and Radiation, it is performed in a local and global way and implemented by user-defined functions. Results of the incident Radiation, Absorbed Radiation, Radiation temperature, temperature gradients, air velocity contours, Nusselt number and optical efficiency, are presented. Results show that the maximum values of the Absorbed Radiation (7800 W m−2), incident Radiation (30,000 W m−2) and Radiation temperature were located at the receiver tube. Also, the maximum value of the temperature gradient (39,000 K m−1) was obtained on the lower half of the receiver tube and the upper part of the secondary receiver. Moreover, the highest values of the entropy generation rate were located at the upper part of the secondary receiver for each phenomenon considered. It is concluded that the entropy generation rate due to heat transfer phenomenon is the most dominant (97.4% of the total), followed by Radiation (2.59%) and then by viscous dissipation (negligible).