Correlations of percentage increases in local nusselt number with radial distance for steady and pulsating jet

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Abstract

This study was carried out to determine the correlations between percentage increases in local Nusselt number at different radial distance between steady and pulsating flow of circular air jet. A heat transfer of heated steady and pulsating air jet at frequencies between 10 to 80 Hz was measured in the study. The set-up was used to measure the heat flux at the stagnation point and the local Nusselt number at different radial distance. The radial distance is at 2, 4, 6, 8, 10 and 12 cm away from stagnation point. Measurement of the heat flux using a RdF heat flux microsensor was used to calculate the local heat transfer coefficient and local Nusselt number for steady air jet and for pulsating jet at Reynolds number of 32000. Results obtained show that the stagnation point Nusselt number is higher for steady jet compared to pulsating jet at all frequencies except at 70 Hz. At pulsating frequency of 70 Hz, the local Nusselt number is higher than the steady jet at all local positions. Percentage increases in local Nusselt number calculated for pulsating jet were higher than the local Nusselt number for steady jet starting from radial distance of 1 cm and above for pulsating frequencies of 20, 30 and 60 Hz. For pulsating frequency of 40, 50 and 80 Hz, the increases starts at radial distance of 2 cm. The relationship between the Nusselt number and the radial distance for each of the pulsating frequencies were determined for each pulsating frequency.

Original languageEnglish
Pages (from-to)613-618
Number of pages6
JournalInternational Review of Mechanical Engineering
Volume3
Issue number5
Publication statusPublished - 2009

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Nusselt number
Heat flux
Air
Microsensors
Heat transfer coefficients
Reynolds number
Heat transfer

Keywords

  • Heat transfer coefficient
  • Jet frequency
  • Nusselt number
  • Pulsating air jet
  • Reynolds number

ASJC Scopus subject areas

  • Mechanical Engineering

Cite this

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title = "Correlations of percentage increases in local nusselt number with radial distance for steady and pulsating jet",
abstract = "This study was carried out to determine the correlations between percentage increases in local Nusselt number at different radial distance between steady and pulsating flow of circular air jet. A heat transfer of heated steady and pulsating air jet at frequencies between 10 to 80 Hz was measured in the study. The set-up was used to measure the heat flux at the stagnation point and the local Nusselt number at different radial distance. The radial distance is at 2, 4, 6, 8, 10 and 12 cm away from stagnation point. Measurement of the heat flux using a RdF heat flux microsensor was used to calculate the local heat transfer coefficient and local Nusselt number for steady air jet and for pulsating jet at Reynolds number of 32000. Results obtained show that the stagnation point Nusselt number is higher for steady jet compared to pulsating jet at all frequencies except at 70 Hz. At pulsating frequency of 70 Hz, the local Nusselt number is higher than the steady jet at all local positions. Percentage increases in local Nusselt number calculated for pulsating jet were higher than the local Nusselt number for steady jet starting from radial distance of 1 cm and above for pulsating frequencies of 20, 30 and 60 Hz. For pulsating frequency of 40, 50 and 80 Hz, the increases starts at radial distance of 2 cm. The relationship between the Nusselt number and the radial distance for each of the pulsating frequencies were determined for each pulsating frequency.",
keywords = "Heat transfer coefficient, Jet frequency, Nusselt number, Pulsating air jet, Reynolds number",
author = "Rozli Zulkifli and Kamaruzzaman Sopian and Shahrir Abdullah and Takriff, {Mohd Sobri}",
year = "2009",
language = "English",
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AU - Zulkifli, Rozli

AU - Sopian, Kamaruzzaman

AU - Abdullah, Shahrir

AU - Takriff, Mohd Sobri

PY - 2009

Y1 - 2009

N2 - This study was carried out to determine the correlations between percentage increases in local Nusselt number at different radial distance between steady and pulsating flow of circular air jet. A heat transfer of heated steady and pulsating air jet at frequencies between 10 to 80 Hz was measured in the study. The set-up was used to measure the heat flux at the stagnation point and the local Nusselt number at different radial distance. The radial distance is at 2, 4, 6, 8, 10 and 12 cm away from stagnation point. Measurement of the heat flux using a RdF heat flux microsensor was used to calculate the local heat transfer coefficient and local Nusselt number for steady air jet and for pulsating jet at Reynolds number of 32000. Results obtained show that the stagnation point Nusselt number is higher for steady jet compared to pulsating jet at all frequencies except at 70 Hz. At pulsating frequency of 70 Hz, the local Nusselt number is higher than the steady jet at all local positions. Percentage increases in local Nusselt number calculated for pulsating jet were higher than the local Nusselt number for steady jet starting from radial distance of 1 cm and above for pulsating frequencies of 20, 30 and 60 Hz. For pulsating frequency of 40, 50 and 80 Hz, the increases starts at radial distance of 2 cm. The relationship between the Nusselt number and the radial distance for each of the pulsating frequencies were determined for each pulsating frequency.

AB - This study was carried out to determine the correlations between percentage increases in local Nusselt number at different radial distance between steady and pulsating flow of circular air jet. A heat transfer of heated steady and pulsating air jet at frequencies between 10 to 80 Hz was measured in the study. The set-up was used to measure the heat flux at the stagnation point and the local Nusselt number at different radial distance. The radial distance is at 2, 4, 6, 8, 10 and 12 cm away from stagnation point. Measurement of the heat flux using a RdF heat flux microsensor was used to calculate the local heat transfer coefficient and local Nusselt number for steady air jet and for pulsating jet at Reynolds number of 32000. Results obtained show that the stagnation point Nusselt number is higher for steady jet compared to pulsating jet at all frequencies except at 70 Hz. At pulsating frequency of 70 Hz, the local Nusselt number is higher than the steady jet at all local positions. Percentage increases in local Nusselt number calculated for pulsating jet were higher than the local Nusselt number for steady jet starting from radial distance of 1 cm and above for pulsating frequencies of 20, 30 and 60 Hz. For pulsating frequency of 40, 50 and 80 Hz, the increases starts at radial distance of 2 cm. The relationship between the Nusselt number and the radial distance for each of the pulsating frequencies were determined for each pulsating frequency.

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