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Air Recirculation

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Telma Teixeira Franco – One of the best experts on this subject based on the ideXlab platform.

  • development of operational strategies to remove carbon dioxide in photobioreactors
    Chemical Engineering Journal, 2009
    Co-Authors: Eduardo Jacoblopes, Sergio Revah, Sergio Hernandez, Keiko Shirai, Telma Teixeira Franco
    Abstract:

    Abstract The objective of this work was to evaluate different operational strategies for photobioreactors to remove carbon dioxide using the cyanobacteria, Aphanothece microscopica Nageli. Two types of reactor configuration, bubble column and Airlift were evaluated under three different operational conditions to treat Air containing 15% carbon dioxide: simple operation, Air Recirculation and two sequential reactors. The results obtained showed that the reactor configuration and the operational mode were both determinant criteria for the performance of photobioreactors in the biological conversion of carbon dioxide. Operations with Air Recirculation showed possibilities for use in small-scale operations, but two-stage sequential photobioreactors (elimination capacity and removal efficiency of 12,217 gcarbon/m3reactor day and 52.5%, respectively) were shown to be the operational mode with greatest potential for application on an industrial scale by the increased removal efficiency.

Kaveh Tajbakhsh – One of the best experts on this subject based on the ideXlab platform.

  • Reducing temperature stratification using heated Air Recirculation for thermal energy saving
    Energy and Buildings, 2011
    Co-Authors: Mostafa Rahimi, Kaveh Tajbakhsh
    Abstract:

    Abstract Using discrete heat sources such as a radiator or a gas heater, a large amount of heated Air is accumulated under the ceiling surface where it is usually far enough from the occupancy zone. The idea of transferring this heated Air into the occupancy zone has been the subject of the present study. A full length-scale model of a compartment was constructed and equipped with a radiator and an Air circulating mechanism. Temperature distribution on the symmetry plane was specified for the two cases of usual heating and heating with Air circulation. Heat loss from the surfaces of the enclosure was also determined using thermal maps of both the internal and the external surfaces of the enclosure. In order to examine the effect of circulating Air on the thermal energy saving quantitatively, a numerical model was developed and validated using experimental results. The input heat rate of the enclosure was compared for the two cases of usual heating and heating with Air circulation considering different heights for a typical heating space. Based on the results, having the same mean Air temperature within the occupancy zone, the input heat rate of a compartment could be moderated using circulating Air criterion.

M.a. Said – One of the best experts on this subject based on the ideXlab platform.

  • Effect of CRAC units layout on thermal management of data center
    Applied Thermal Engineering, 2017
    Co-Authors: Sameh A. Nada, M.a. Said
    Abstract:

    Abstract Comprehensive numerical studies of thermal management of data centers were presented by several investigators for different geometric and operating conditions of data centers. In the present work, a technical note regarding the effect of the computer room Air conditioning (CRAC) units layout arrangements is presented. Two arrangements of CRAC units layouts are investigated; namely locating CRACs units in line with the racks row and locating the CRACs units perpendicular to the rack row. Temperature distributions, Air flow characteristics particularly Air Recirculation and bypass and thermal management in data centers are evaluated in terms of the measureable overall performance parameters: supply/return heat indices (SHI/RHI) and return temperature indices (RTI). The results showed that locating CRAC units perpendicular to the racks row has the following effects: (i) enhances the uniformity of the Air flow from the perforated tiles along the rack row, (ii) reduces the hot Air Recirculation at the ends racks of the row and the cold Air bypass at the middle rack of the row and (iii) enhances the data center performance parameters RTI, SHI and RHI.

  • Numerical investigation and parametric study for thermal and energy management enhancements in data centers’ buildings
    Applied Thermal Engineering, 2016
    Co-Authors: Sameh A. Nada, M.a. Said, Mohamed Rady
    Abstract:

    Abstract A CFD numerical investigation of Air flow and temperature distribution in data centers is presented for different operating and geometric conditions. Numerical experiments were conducted to parametrically study the effects of perforated tiles opening ratio, data center power density and locations of Computer Room Air Conditioning (CRAC) on the data center performance. Temperature distribution especially hot spot points, Air flow characteristics particularly Air Recirculation and bypass and thermal management in data centers are evaluated in terms of the measureable overall performance parameters: supply/return heat indices (SHI/RHI), return temperature indices (RTI) and return cooling indices (RCI). Techniques of using cold aisle containments for enhancing the cooling effectiveness of data centers are investigated and evaluated. The results showed that (i) increasing the perforation ratio of perforated tails decreases the Recirculation and bypass of Air flow around the rack, (ii) increasing data centers’ power density and supplied Air flow rates increases the Air bypass and Air re-circulation, (iii) changing the spacing between the CRAC units and cold aisle slightly changes of Air Recirculation and bypass around the racks, and (iv) using appropriate cold aisle containment improves the performance of cooling of data centers, especially at high power density.

Sameh A. Nada – One of the best experts on this subject based on the ideXlab platform.

  • Effect of CRAC units layout on thermal management of data center
    Applied Thermal Engineering, 2017
    Co-Authors: Sameh A. Nada, M.a. Said
    Abstract:

    Abstract Comprehensive numerical studies of thermal management of data centers were presented by several investigators for different geometric and operating conditions of data centers. In the present work, a technical note regarding the effect of the computer room Air conditioning (CRAC) units layout arrangements is presented. Two arrangements of CRAC units layouts are investigated; namely locating CRACs units in line with the racks row and locating the CRACs units perpendicular to the rack row. Temperature distributions, Air flow characteristics particularly Air Recirculation and bypass and thermal management in data centers are evaluated in terms of the measureable overall performance parameters: supply/return heat indices (SHI/RHI) and return temperature indices (RTI). The results showed that locating CRAC units perpendicular to the racks row has the following effects: (i) enhances the uniformity of the Air flow from the perforated tiles along the rack row, (ii) reduces the hot Air Recirculation at the ends racks of the row and the cold Air bypass at the middle rack of the row and (iii) enhances the data center performance parameters RTI, SHI and RHI.

  • Numerical investigation and parametric study for thermal and energy management enhancements in data centers’ buildings
    Applied Thermal Engineering, 2016
    Co-Authors: Sameh A. Nada, M.a. Said, Mohamed Rady
    Abstract:

    Abstract A CFD numerical investigation of Air flow and temperature distribution in data centers is presented for different operating and geometric conditions. Numerical experiments were conducted to parametrically study the effects of perforated tiles opening ratio, data center power density and locations of Computer Room Air Conditioning (CRAC) on the data center performance. Temperature distribution especially hot spot points, Air flow characteristics particularly Air Recirculation and bypass and thermal management in data centers are evaluated in terms of the measureable overall performance parameters: supply/return heat indices (SHI/RHI), return temperature indices (RTI) and return cooling indices (RCI). Techniques of using cold aisle containments for enhancing the cooling effectiveness of data centers are investigated and evaluated. The results showed that (i) increasing the perforation ratio of perforated tails decreases the Recirculation and bypass of Air flow around the rack, (ii) increasing data centers’ power density and supplied Air flow rates increases the Air bypass and Air re-circulation, (iii) changing the spacing between the CRAC units and cold aisle slightly changes of Air Recirculation and bypass around the racks, and (iv) using appropriate cold aisle containment improves the performance of cooling of data centers, especially at high power density.

Shuai Yan – One of the best experts on this subject based on the ideXlab platform.

  • Quantitative effects of supply Air and contaminant sources on steady contaminant distribution in ventilated space with Air Recirculation
    Building and Environment, 2020
    Co-Authors: Xiaoliang Shao, Shukui Liang, Chao Liang, Shuai Yan
    Abstract:

    Abstract Identifying the contributions of different influencing factors to indoor Air environment is beneficial for seeking measures to improve environmental quality. The independent effect of supply Air and contaminant source can be quantified using accessibility index; however, for ventilated rooms with Air Recirculation devices, the effects of supply Air and contaminant source cannot be described directly owing to the effect of Air Recirculation. In this study, a concise linear expression is derived to establish a correlation between steady contaminant distribution and each of independent supply Air and contaminant sources with Air Recirculation, based on which index of revised accessibility is defined to evaluate the effects of supply Air and contaminant sources. The reliability of the proposed method is verified by comparing with simulation result. Two numerical cases, i.e., two Air Recirculation devices with cleaning efficiency and a recirculated Air curtain, are analyzed to study the quantitative effects of supply Air and contaminant source. It is discovered that Air Recirculation devices change the Airflow field considerably, and that the purification effect of Air Recirculation devices with cleaning efficiencies of 0.2 and 0.3 reduces the effects of supply Air and contaminant source. The recirculated Air curtain reduces the dominant area of Air supply inlet, with regional revised accessibility decreasing from 0.69 to 0.54. Air curtain at an appropriate Airflow rate significantly reduces the effect of contaminant source at distant areas, with regional revised accessibility decreasing from 1.03 to 0.64. The proposed method is beneficial for evaluating Air Recirculation in establishing indoor environment.