### Abstract

The study was carried out to determine the Nusselt number at stagnation point and at radial distance away from stagnation point for steady and pulsating flow of circular air jet. A heat transfer of heated steady and pulsating air jet at frequencies of 10, 30, 50 and 70 Hz impinging on a flat aluminium plate 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 radial distance away from the stagnation point. The radial distance is 2, 4, 6, 8, 10 and 12 cm away from stagnation point. The heat flux of the heated air jet impinging on the plate was measured using a heat flux microsensor located on the plate. Measurement of the heat flux 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 16000. Results obtained show that the stagnation point Nusselt number is higher for steady jet compared to pulsating jet at all frequencies. However, local Nusselt number calculated for pulsating jet were higher than the local Nusselt number for steady jet at radial distance 4 cm and above. The higher Nusselt number obtained at localized radial positions can be due to the higher instantaneous velocity at these locations. The relationship between the Nusselt number and the radial distance for each of the pulsating frequencies were plotted. The polynomial equations used to relate these parameters were listed in the table. Pulsating frequency of 10 Hz shows the highest increases of 166% compared to steady jet Nusselt number while at 30 Hz the maximum increases is 103%, at 50 Hz the increases is at 66% and at 70 Hz the increases is at 23%. Percentage increases is higher at low pulsating frequencies.

Original language | English |
---|---|

Pages (from-to) | 369-378 |

Number of pages | 10 |

Journal | European Journal of Scientific Research |

Volume | 29 |

Issue number | 3 |

Publication status | Published - 2009 |

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### Keywords

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

### ASJC Scopus subject areas

- General

### Cite this

**Comparison of local nusselt number for steady and pulsating circular jet at Reynolds number of 16000.** / Zulkifli, Rozli; Sopian, Kamaruzzaman; Abdullah, Shahrir; Takriff, Mohd Sobri.

Research output: Contribution to journal › Article

}

TY - JOUR

T1 - Comparison of local nusselt number for steady and pulsating circular jet at Reynolds number of 16000

AU - Zulkifli, Rozli

AU - Sopian, Kamaruzzaman

AU - Abdullah, Shahrir

AU - Takriff, Mohd Sobri

PY - 2009

Y1 - 2009

N2 - The study was carried out to determine the Nusselt number at stagnation point and at radial distance away from stagnation point for steady and pulsating flow of circular air jet. A heat transfer of heated steady and pulsating air jet at frequencies of 10, 30, 50 and 70 Hz impinging on a flat aluminium plate 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 radial distance away from the stagnation point. The radial distance is 2, 4, 6, 8, 10 and 12 cm away from stagnation point. The heat flux of the heated air jet impinging on the plate was measured using a heat flux microsensor located on the plate. Measurement of the heat flux 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 16000. Results obtained show that the stagnation point Nusselt number is higher for steady jet compared to pulsating jet at all frequencies. However, local Nusselt number calculated for pulsating jet were higher than the local Nusselt number for steady jet at radial distance 4 cm and above. The higher Nusselt number obtained at localized radial positions can be due to the higher instantaneous velocity at these locations. The relationship between the Nusselt number and the radial distance for each of the pulsating frequencies were plotted. The polynomial equations used to relate these parameters were listed in the table. Pulsating frequency of 10 Hz shows the highest increases of 166% compared to steady jet Nusselt number while at 30 Hz the maximum increases is 103%, at 50 Hz the increases is at 66% and at 70 Hz the increases is at 23%. Percentage increases is higher at low pulsating frequencies.

AB - The study was carried out to determine the Nusselt number at stagnation point and at radial distance away from stagnation point for steady and pulsating flow of circular air jet. A heat transfer of heated steady and pulsating air jet at frequencies of 10, 30, 50 and 70 Hz impinging on a flat aluminium plate 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 radial distance away from the stagnation point. The radial distance is 2, 4, 6, 8, 10 and 12 cm away from stagnation point. The heat flux of the heated air jet impinging on the plate was measured using a heat flux microsensor located on the plate. Measurement of the heat flux 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 16000. Results obtained show that the stagnation point Nusselt number is higher for steady jet compared to pulsating jet at all frequencies. However, local Nusselt number calculated for pulsating jet were higher than the local Nusselt number for steady jet at radial distance 4 cm and above. The higher Nusselt number obtained at localized radial positions can be due to the higher instantaneous velocity at these locations. The relationship between the Nusselt number and the radial distance for each of the pulsating frequencies were plotted. The polynomial equations used to relate these parameters were listed in the table. Pulsating frequency of 10 Hz shows the highest increases of 166% compared to steady jet Nusselt number while at 30 Hz the maximum increases is 103%, at 50 Hz the increases is at 66% and at 70 Hz the increases is at 23%. Percentage increases is higher at low pulsating frequencies.

KW - Heat transfer coefficient

KW - Jet frequency

KW - Nusselt number

KW - Pulsating air jet

KW - Reynolds number

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M3 - Article

AN - SCOPUS:67449088228

VL - 29

SP - 369

EP - 378

JO - European Journal of Scientific Research

JF - European Journal of Scientific Research

SN - 1450-202X

IS - 3

ER -