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Air-Cooled Heat Exchangers

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Detlev G. Kröger – One of the best experts on this subject based on the ideXlab platform.

  • Numerical investigation of the effect of fan performance on forced draught Air-Cooled Heat exchanger plenum chamber aerodynamic behaviour
    Applied Thermal Engineering, 2003
    Co-Authors: Chris J. Meyer, Detlev G. Kröger

    Abstract:

    The primary purposes of this numerical investigation is to determine to what extent the performance characteristics of a particular axial flow fan affects the plenum chamber aerodynamic behaviour of a forced draught Air-Cooled Heat exchanger. An axial flow fan and Heat exchanger model is implemented within a commercially available computational fluid dynamics code and combined to resolve the flow field through a range of forced draught Air-Cooled Heat Exchangers. It is found that a change in the angle at which the fan blades are set in the fan hub as well as the volume flow rate at which the fan operates affects the plenum chamber aerodynamic behaviour. It is further shown that the maximum possible recovery of kinetic energy within the plenum chamber does not necessarily coincide with the point of maximum fan static efficiency.

  • Plenum chamber flow losses in forced draught Air-Cooled Heat Exchangers
    Applied Thermal Engineering, 1998
    Co-Authors: Chris J. Meyer, Detlev G. Kröger

    Abstract:

    The primary objective of this experimental investigation is to determine the influence that different fan and Heat exchanger characteristics as well as the plenum chamber geometry have on the flow losses in the plenum chamber of a forced draught Air-Cooled Heat exchanger (ACHE). The effect of air flow maldistribution on the Heat exchanger thermal performance is also investigated. A series of model tests are conducted employing different fans and Heat Exchangers. It is found that there is a critical minimum distance between the outlet of the fan and the Heat exchanger. The Heat exchanger loss coefficient and its inlet geometry have a relatively strong influence on plenum losses as well as on the air velocity distribution at the outlet of the Heat exchanger. Other variables, including the position of the fan in the fan casing, fan-to-Heat exchanger area ratio and fan characteristics, have a lesser effect on plenum performance. A plenum chamber recovery coefficient is defined and expressed in terms of measured parameters. This coefficient can be employed in the design of practical ACHEs. It is further found that air flow maldistribution only has a small influence on the Heat exchanger thermal performance.

  • Flow distortions at the fan inlet of forced-draught Air-Cooled Heat Exchangers
    Applied Thermal Engineering, 1996
    Co-Authors: K. Duvenhage, Chris J. Meyer, J.a. Vermeulen, Detlev G. Kröger

    Abstract:

    The effect of inlet flow distortions on fan performance in forced-draught Air-Cooled Heat Exchangers (ACHEs) is investigated numerically and experimentally. By varying the distance between the ACHE fan platform and the ground level, significant changes in air volume flow rate are observed. Three different fan inlet shrouds are considered and recommendations towards designing and evaluating the performance of an ACHE are made. The effect of different lengths of a cylindrical fan inlet shroud, as well as the effect of cylindrical sections as part of a conical and a bell-mouth inlet shroud, is also investigated. The results show that a critical length for both the cylindrical inlet shroud and the cylindrical sections of the conical and bell-mouth inlet shrouds can be obtained for optimal fan performance.

Chris J. Meyer – One of the best experts on this subject based on the ideXlab platform.

  • Numerical investigation of the effect of inlet flow distortions on forced draught Air-Cooled Heat exchanger performance
    Applied Thermal Engineering, 2005
    Co-Authors: Chris J. Meyer

    Abstract:

    Forced draught Air-Cooled Heat Exchangers (ACHEs) are often arranged into banks consisting of multiple rows of fan-Heat exchanger combinations. Fans on the outer edge of the banks are subject to severe cross-flow conditions as the air is swept past en route to fans located deeper within the banks. The cross-flow conditions give rise to increased inlet flow losses. The current investigation seeks to develop a better understanding of the nature of these increased inlet flow losses through the numerical resolution of flow fields associated with systems comprising a single and two banks of ACHEs. For installations comprising two banks of ACHEs it is found that the inlet flow losses of the periphery fan are dominated by flow separation occurring around the inlet lip of the fan inlet section. These flow losses can be reduced by the installation of a walkway at the edge of the fan platform or by the removal of the periphery fan inlet section. For a system comprising of a single bank of ACHEs it is found that the numerical models used accurately reflect the experimentally determined differences in inlet flow losses experienced by systems using either bell-mouth, conical or cylindrical fan inlet sections.

  • Numerical investigation of the effect of fan performance on forced draught Air-Cooled Heat exchanger plenum chamber aerodynamic behaviour
    Applied Thermal Engineering, 2003
    Co-Authors: Chris J. Meyer, Detlev G. Kröger

    Abstract:

    The primary purposes of this numerical investigation is to determine to what extent the performance characteristics of a particular axial flow fan affects the plenum chamber aerodynamic behaviour of a forced draught Air-Cooled Heat exchanger. An axial flow fan and Heat exchanger model is implemented within a commercially available computational fluid dynamics code and combined to resolve the flow field through a range of forced draught Air-Cooled Heat Exchangers. It is found that a change in the angle at which the fan blades are set in the fan hub as well as the volume flow rate at which the fan operates affects the plenum chamber aerodynamic behaviour. It is further shown that the maximum possible recovery of kinetic energy within the plenum chamber does not necessarily coincide with the point of maximum fan static efficiency.

  • Plenum chamber flow losses in forced draught Air-Cooled Heat Exchangers
    Applied Thermal Engineering, 1998
    Co-Authors: Chris J. Meyer, Detlev G. Kröger

    Abstract:

    The primary objective of this experimental investigation is to determine the influence that different fan and Heat exchanger characteristics as well as the plenum chamber geometry have on the flow losses in the plenum chamber of a forced draught Air-Cooled Heat exchanger (ACHE). The effect of air flow maldistribution on the Heat exchanger thermal performance is also investigated. A series of model tests are conducted employing different fans and Heat Exchangers. It is found that there is a critical minimum distance between the outlet of the fan and the Heat exchanger. The Heat exchanger loss coefficient and its inlet geometry have a relatively strong influence on plenum losses as well as on the air velocity distribution at the outlet of the Heat exchanger. Other variables, including the position of the fan in the fan casing, fan-to-Heat exchanger area ratio and fan characteristics, have a lesser effect on plenum performance. A plenum chamber recovery coefficient is defined and expressed in terms of measured parameters. This coefficient can be employed in the design of practical ACHEs. It is further found that air flow maldistribution only has a small influence on the Heat exchanger thermal performance.

Y.p. Yang – One of the best experts on this subject based on the ideXlab platform.

  • impacts of tower spacing on thermo flow characteristics of natural draft dry cooling system
    International Journal of Thermal Sciences, 2016
    Co-Authors: Hangtao Liao, Xiaoze Du, Liu Yang, Xiaodan Wu, Y.p. Yang

    Abstract:

    Abstract Multi-towers are widely introduced to the natural draft dry cooling system in power plants, and the geometrical layout of dry-cooling towers is a key issue to the thermo-flow characteristics of natural draft dry cooling system. Based on a representative two-tower design with vertically arranged Heat exchanger bundles around the circumference, the air-side flow and Heat transfer models of natural draft dry cooling system at the tower spacing to diameter ratios from 0.1 to 3 are developed and the velocity, pressure and temperature fields of cooling air in the absence and presence of ambient winds are presented. The mass flow rate and Heat rejection of the two Air-Cooled Heat Exchangers at various wind speeds and in various wind directions are calculated. The correlations between the Heat rejection of each tower and the tower spacing, wind speed and angle are obtained. The results show that the impacts of tower spacing on thermo-flow characteristics of natural draft dry cooling system depend on the wind speed and the arrangement of towers. The towers arranged in line are superior to those arranged in other patterns. When the tower spacing to diameter ratio is lower than unity, the conspicuous interaction between two towers will deteriorate the thermo-flow performances of natural draft dry cooling system. The results can contribute to the dry-cooling tower layout of natural draft dry cooling system in power plants.

  • influences of height to diameter ratios of dry cooling tower upon thermo flow characteristics of indirect dry cooling system
    International Journal of Thermal Sciences, 2015
    Co-Authors: Hangtao Liao, Lijun Yang, Xiaoze Du, Y.p. Yang

    Abstract:

    Abstract Ambient winds may reduce the cooling efficiency of a nature draft dry-cooling tower, so it is of benefit to the design and operation of indirect dry cooling system to determine the preferred tower shape to restrain the adverse impacts of ambient winds. Based on the dry-cooling tower with vertically arranged Heat exchanger bundles around the circumference, air-side flow and Heat transfer models are developed for three typical height to diameter ratios of tower. The velocity, pressure and temperature fields of cooling air in the absence and presence of ambient winds are presented, and the mass flow rate, Heat rejection and outlet water temperature of each sector and Air-Cooled Heat Exchangers are calculated. The results show that the dry-cooling tower with a low height to diameter ratio is superior to that with a high ratio in thermo-flow performances of indirect dry cooling system at high wind speeds on condition that the Air-Cooled Heat Exchangers have the same Heat transfer surface areas. At low wind speeds, the mass flow rate and Heat rejection of Air-Cooled Heat exchanger vary little with height to diameter ratios of tower due to almost the same buoyancy forces. It is recommended to take a low height to diameter ratio of tower, especially at strong ambient winds for better thermo-flow performances of indirect dry cooling system.