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Annular Space

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Ahmad Arabkoohsa – One of the best experts on this subject based on the ideXlab platform.

  • a new version of a low concentration evacuated tube solar collector optical and thermal investigation
    Solar Energy, 2019
    Co-Authors: Mavd De Paula Ribeiro Teles, K. A.r. Ismail, Ahmad Arabkoohsa

    Abstract:

    Abstract This work is focused on investigating the performance of a new version of evacuated tube solar collector with and without solar tracking system. The evacuated tube solar collector is composed of an absorbing copper tube positioned eccentrically inside a transparent glass cover tube which has a reflective film insert on its inner surface and vacuum in eccentric Annular Space. Modeling of the proposed evacuated tube collector is based on the conservation equations of mass, momentum and energy and discretized by using the finite volumes method. A home-built numerical code is developed, tested and its grid size optimized. This code is validated against available experimental and numerical results. Effects of the tilt angle and tracking systems are also evaluated. The results showed maximum and minimum daily efficiencies of the collector of about 73% and 42%, respectively. The annual efficiency of this collector was evaluated as 61.5% for the city of Sao Luis, Brazil. The new contributions from the present work include the reflective film, the eccentricity of the absorber and the presence of vacuum in the Annular Space. The reflective film helps to keep the absorber at uniform temperature and reduce thermal induced stress. The eccentricity is introduced to create concentration effect which helps to increase the outlet temperature of the working fluid and reduce the mass of the collector system. The presence of vacuum in the eccentric Annular Space reduces effectively the thermal losses, improves the efficiency.

Mavd De Paula Ribeiro Teles – One of the best experts on this subject based on the ideXlab platform.

  • a new version of a low concentration evacuated tube solar collector optical and thermal investigation
    Solar Energy, 2019
    Co-Authors: Mavd De Paula Ribeiro Teles, K. A.r. Ismail, Ahmad Arabkoohsa

    Abstract:

    Abstract This work is focused on investigating the performance of a new version of evacuated tube solar collector with and without solar tracking system. The evacuated tube solar collector is composed of an absorbing copper tube positioned eccentrically inside a transparent glass cover tube which has a reflective film insert on its inner surface and vacuum in eccentric Annular Space. Modeling of the proposed evacuated tube collector is based on the conservation equations of mass, momentum and energy and discretized by using the finite volumes method. A home-built numerical code is developed, tested and its grid size optimized. This code is validated against available experimental and numerical results. Effects of the tilt angle and tracking systems are also evaluated. The results showed maximum and minimum daily efficiencies of the collector of about 73% and 42%, respectively. The annual efficiency of this collector was evaluated as 61.5% for the city of Sao Luis, Brazil. The new contributions from the present work include the reflective film, the eccentricity of the absorber and the presence of vacuum in the Annular Space. The reflective film helps to keep the absorber at uniform temperature and reduce thermal induced stress. The eccentricity is introduced to create concentration effect which helps to increase the outlet temperature of the working fluid and reduce the mass of the collector system. The presence of vacuum in the eccentric Annular Space reduces effectively the thermal losses, improves the efficiency.

Jian Zhang – One of the best experts on this subject based on the ideXlab platform.

  • studies on strongly swirling flows in the full Space of a volute cyclone separator
    Aiche Journal, 2005
    Co-Authors: Liyuan Hu, Lixing Zhou, Jian Zhang

    Abstract:

    The three-dimensional (3-D) strongly swirling turbulent flows in the full Space of a volute cyclone separator was measured using laser Doppler velocimetry (LDV), and was simulated using an improved Reynolds stress equation model by modifying the empirical constants in the isotropization of production and convection model (IPCM) + wall pressure–strain term of the Reynolds stress equation, incorporated into the platform of FLUENT 6.0. Predicted Reynolds stress model (RSM) velocities are more reasonable than those obtained previously. The specific features of turbulent flows in the separation Space, dust hopper, Annular Space, and the outlet tube are different. The results show that the time-averaged tangential velocity profiles in the separation Space have a typical Rankine-vortex structure. In some regions, such as the entrance, the vicinity of the top of the Annular Space, the inner vortex-flow region, the vicinity of the discharge port, the vicinity of the wall, the intersection part between the upward and downward flows, the turbulent intensity is very large and changes sharply; the turbulence is anisotropic in most regions, but the magnitudes of three RSM velocity components are of the same order of magnitude. The distribution of time-averaged tangential velocity is asymmetric in the Annular Space. The longitudinal secondary vortexes exist near the top of the dust hopper and the top of the cyclone. The distribution of time-averaged axial velocity in the exit tube is entirely different from that in the separation Space. © 2005 American Institute of Chemical Engineers AIChE J, 51: 740–749, 2005