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Heat and Mass Transfer

, Volume 46, Issue 11–12, pp 1395–1410 | Cite as

Investigation into the effect of nozzle shape on the nozzle discharge coefficient and heat and mass transfer characteristics of impinging air jets

  • A. B. Etemoglu
  • M. K. Isman
  • M. CanEmail author
Original

Abstract

High velocity impinging air jets are commonly used for heating, cooling and drying, etc. because of the high heat and mass transfer coefficients which are developed in the impingement region. In order to provide data for the designers of industrial equipment, a variety of slot nozzles were tested to determine the effect on heat transfer of both nozzle shape and slot width. A large multi-nozzle rig was also used to measure average heat and mass transfer characteristics under arrays of both slot nozzles and circular holes. As a necessary preliminary to the heat transfer investigation, the discharge coefficients of the nozzles were measured. Then, the experimental results are compared with the simplified flow model. A good agreement was found between the theoretical and experimental results. From the tests, it was also found that the heat transfer results from differently shaped nozzles could be satisfactorily correlated provided that the effective slot width or hole diameter was used to characterize the nozzle shapes.

Keywords

Heat Transfer Heat Transfer Coefficient Mass Transfer Coefficient Stagnation Point Discharge Coefficient 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

As

The surface area (m2)

Af

Free area (%)

B

Slot width (mm)

B′

Effective slot width (mm)

CC

The contraction coefficient (constant)

CD

Discharge coefficient (constant)

Cp

Specific heat (J/kg K)

CV

The velocity coefficient (constant)

D

Diameter of circular nozzle (mm)

D′

Effective diameter of circular nozzle (mm)

DAB

Diffusion coefficient (m2/s)

h

Heat transfer coefficient (W/m2 K)

hfg

Latent heat (J/kg)

hm

The surface mass transfer coefficient (m/s)

\( \dot{m}_{D} \)

The surface mass transfer rate (kg/s)

Nu

Nusselt number (hB/k)

Pr

Prandtl number (μCp/k)

Re

Reynolds number (VEB/υ)

Sc

Schmidt number (υ/DAB)

Sh

Sherwood number (hmL/DAB)

T

Temperature (K)

V

Air jet velocity (m/s)

X

Lateral distance from stagnation point (mm)

Xn

Nozzle to nozzle spacing (mm)

Y

The length of nozzle (mm)

Z

Vertical distance from nozzle outlet to plate (mm)

Greek symbols

δ

The boundary layer thickness (mm)

δ*

The displacement boundary layer thickness (mm)

ρ

Concentration (kg/m3)

υ

Kinematic viscosity (m2/s)

Subscripts

E

Nozzle exit

o

Stagnation point

Superscript

Average value

Notes

Acknowledgments

This work was supported by The Commission of Scientific Research Projects of Uludag University, project number: M-2008/10.

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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  1. 1.Department of Mechanical Engineering, Faculty of Engineering and ArchitectureUludag UniversityBursaTurkey

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