3 Citations (Scopus)

Abstract

Applications of impingement jets in industry for heating and cooling purposes requires a high convective heat transfer coefficient. Numerous studies have been conducted to improve the convective heat transfer coefficient for a steady impinging jet. A pulsating jet has a very high potential in replacing steady jet after it has been found to be able to increase the heat transfer coefficients at certain localized region and pulsating frequencies. The aims of this study is to determine the velocity profile of a circular pulsating air jet at different pulse frequencies and Reynolds Numbers using a rotating valve pulse jet system. Pulsation of the air jet was produced by a rotating cylinder valve mechanism at frequencies between 10-80 Hz. Flow structures of the heated steady and pulse single circular axisymmetric air jet velocity were measured using a calibrated hot-wire anemometer and presented in non-dimensional form. The measurements were carried out at four different Reynolds numbers which was set at 10000, 16000, 23300 and 32000. The jet exit velocity profile for all the test frequencies are determined by plotting the graph of radial distance against the non-dimensional jet exit velocity. The corresponding Reynolds number in this test is based on time-averaged centre-line velocity. The results of the velocity measurement were plotted side by side using non-dimensional parameters in order to perform direct comparison of the velocity profile at different frequencies and Reynolds numbers. Stagnation point velocities are the same for steady and pulsating jet for all pulse frequencies. As the radial distance from the stagnation point increases, pulsating velocity increases between 20-30% for radial distance of 2-22 mm from stagnation point. Results of the flow structures plotted show a distinctive exit air jet profile which can affect the impingement heat transfer characteristics. This was the result of enhanced turbulence intensities due to pulsating jet produced by the rotating cylinder. From the jet exit velocity profile obtained, it is found that mass flow rate for different test frequencies are slightly different due to the difference in the local velocity measurement affected by the pulses. The jet exit velocity profile data will be used to form a correlation between the pulsating jet velocity and heat transfer data.

Original languageEnglish
Pages (from-to)495-501
Number of pages7
JournalInternational Review of Mechanical Engineering
Volume4
Issue number5
Publication statusPublished - 2010

Fingerprint

Air
Reynolds number
Heat transfer coefficients
Flow structure
Velocity measurement
Heat transfer
Anemometers
Turbulence
Flow rate
Wire
Cooling
Heating
Industry

Keywords

  • Flow structure
  • Jet impingement
  • Pulsating hot air jet
  • Pulse frequency
  • Reynolds number

ASJC Scopus subject areas

  • Mechanical Engineering

Cite this

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title = "Analysis of pulse air jet flow profiles",
abstract = "Applications of impingement jets in industry for heating and cooling purposes requires a high convective heat transfer coefficient. Numerous studies have been conducted to improve the convective heat transfer coefficient for a steady impinging jet. A pulsating jet has a very high potential in replacing steady jet after it has been found to be able to increase the heat transfer coefficients at certain localized region and pulsating frequencies. The aims of this study is to determine the velocity profile of a circular pulsating air jet at different pulse frequencies and Reynolds Numbers using a rotating valve pulse jet system. Pulsation of the air jet was produced by a rotating cylinder valve mechanism at frequencies between 10-80 Hz. Flow structures of the heated steady and pulse single circular axisymmetric air jet velocity were measured using a calibrated hot-wire anemometer and presented in non-dimensional form. The measurements were carried out at four different Reynolds numbers which was set at 10000, 16000, 23300 and 32000. The jet exit velocity profile for all the test frequencies are determined by plotting the graph of radial distance against the non-dimensional jet exit velocity. The corresponding Reynolds number in this test is based on time-averaged centre-line velocity. The results of the velocity measurement were plotted side by side using non-dimensional parameters in order to perform direct comparison of the velocity profile at different frequencies and Reynolds numbers. Stagnation point velocities are the same for steady and pulsating jet for all pulse frequencies. As the radial distance from the stagnation point increases, pulsating velocity increases between 20-30{\%} for radial distance of 2-22 mm from stagnation point. Results of the flow structures plotted show a distinctive exit air jet profile which can affect the impingement heat transfer characteristics. This was the result of enhanced turbulence intensities due to pulsating jet produced by the rotating cylinder. From the jet exit velocity profile obtained, it is found that mass flow rate for different test frequencies are slightly different due to the difference in the local velocity measurement affected by the pulses. The jet exit velocity profile data will be used to form a correlation between the pulsating jet velocity and heat transfer data.",
keywords = "Flow structure, Jet impingement, Pulsating hot air jet, Pulse frequency, Reynolds number",
author = "Rozli Zulkifli and Kamaruzzaman Sopian and Shahrir Abdullah and Takriff, {Mohd Sobri}",
year = "2010",
language = "English",
volume = "4",
pages = "495--501",
journal = "International Review of Mechanical Engineering",
issn = "1970-8734",
publisher = "Praise Worthy Prize",
number = "5",

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TY - JOUR

T1 - Analysis of pulse air jet flow profiles

AU - Zulkifli, Rozli

AU - Sopian, Kamaruzzaman

AU - Abdullah, Shahrir

AU - Takriff, Mohd Sobri

PY - 2010

Y1 - 2010

N2 - Applications of impingement jets in industry for heating and cooling purposes requires a high convective heat transfer coefficient. Numerous studies have been conducted to improve the convective heat transfer coefficient for a steady impinging jet. A pulsating jet has a very high potential in replacing steady jet after it has been found to be able to increase the heat transfer coefficients at certain localized region and pulsating frequencies. The aims of this study is to determine the velocity profile of a circular pulsating air jet at different pulse frequencies and Reynolds Numbers using a rotating valve pulse jet system. Pulsation of the air jet was produced by a rotating cylinder valve mechanism at frequencies between 10-80 Hz. Flow structures of the heated steady and pulse single circular axisymmetric air jet velocity were measured using a calibrated hot-wire anemometer and presented in non-dimensional form. The measurements were carried out at four different Reynolds numbers which was set at 10000, 16000, 23300 and 32000. The jet exit velocity profile for all the test frequencies are determined by plotting the graph of radial distance against the non-dimensional jet exit velocity. The corresponding Reynolds number in this test is based on time-averaged centre-line velocity. The results of the velocity measurement were plotted side by side using non-dimensional parameters in order to perform direct comparison of the velocity profile at different frequencies and Reynolds numbers. Stagnation point velocities are the same for steady and pulsating jet for all pulse frequencies. As the radial distance from the stagnation point increases, pulsating velocity increases between 20-30% for radial distance of 2-22 mm from stagnation point. Results of the flow structures plotted show a distinctive exit air jet profile which can affect the impingement heat transfer characteristics. This was the result of enhanced turbulence intensities due to pulsating jet produced by the rotating cylinder. From the jet exit velocity profile obtained, it is found that mass flow rate for different test frequencies are slightly different due to the difference in the local velocity measurement affected by the pulses. The jet exit velocity profile data will be used to form a correlation between the pulsating jet velocity and heat transfer data.

AB - Applications of impingement jets in industry for heating and cooling purposes requires a high convective heat transfer coefficient. Numerous studies have been conducted to improve the convective heat transfer coefficient for a steady impinging jet. A pulsating jet has a very high potential in replacing steady jet after it has been found to be able to increase the heat transfer coefficients at certain localized region and pulsating frequencies. The aims of this study is to determine the velocity profile of a circular pulsating air jet at different pulse frequencies and Reynolds Numbers using a rotating valve pulse jet system. Pulsation of the air jet was produced by a rotating cylinder valve mechanism at frequencies between 10-80 Hz. Flow structures of the heated steady and pulse single circular axisymmetric air jet velocity were measured using a calibrated hot-wire anemometer and presented in non-dimensional form. The measurements were carried out at four different Reynolds numbers which was set at 10000, 16000, 23300 and 32000. The jet exit velocity profile for all the test frequencies are determined by plotting the graph of radial distance against the non-dimensional jet exit velocity. The corresponding Reynolds number in this test is based on time-averaged centre-line velocity. The results of the velocity measurement were plotted side by side using non-dimensional parameters in order to perform direct comparison of the velocity profile at different frequencies and Reynolds numbers. Stagnation point velocities are the same for steady and pulsating jet for all pulse frequencies. As the radial distance from the stagnation point increases, pulsating velocity increases between 20-30% for radial distance of 2-22 mm from stagnation point. Results of the flow structures plotted show a distinctive exit air jet profile which can affect the impingement heat transfer characteristics. This was the result of enhanced turbulence intensities due to pulsating jet produced by the rotating cylinder. From the jet exit velocity profile obtained, it is found that mass flow rate for different test frequencies are slightly different due to the difference in the local velocity measurement affected by the pulses. The jet exit velocity profile data will be used to form a correlation between the pulsating jet velocity and heat transfer data.

KW - Flow structure

KW - Jet impingement

KW - Pulsating hot air jet

KW - Pulse frequency

KW - Reynolds number

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