Stanton number

The Stanton number, St, is a dimensionless number that measures the ratio of heat transferred into a fluid to the thermal capacity of fluid. The Stanton number is named after Thomas Stanton (engineer) (1865–1931).^[1]^[2]^: 476 It is used to characterize heat transfer in forced convection flows.

Formula edit

$St={\frac {h}{Gc_{p}}}={\frac {h}{\rho uc_{p}}}$

where

h = convection heat transfer coefficient
G = mass flow rate of the fluid
ρ = density of the fluid
c_p = specific heat of the fluid
u = velocity of the fluid

It can also be represented in terms of the fluid's Nusselt, Reynolds, and Prandtl numbers:

\mathrm {St} ={\frac {\mathrm {Nu} }{\mathrm {Re} \,\mathrm {Pr} }}

where

Nu is the Nusselt number;
Re is the Reynolds number;
Pr is the Prandtl number.^[3]

The Stanton number arises in the consideration of the geometric similarity of the momentum boundary layer and the thermal boundary layer, where it can be used to express a relationship between the shear force at the wall (due to viscous drag) and the total heat transfer at the wall (due to thermal diffusivity).

Mass transfer edit

Using the heat-mass transfer analogy, a mass transfer St equivalent can be found using the Sherwood number and Schmidt number in place of the Nusselt number and Prandtl number, respectively.

$\mathrm {St} _{m}={\frac {\mathrm {Sh_{L}} }{\mathrm {Re_{L}} \,\mathrm {Sc} }}$ ^[4]

$\mathrm {St} _{m}={\frac {h_{m}}{\rho u}}$ ^[4]

where

$St_{m}$ is the mass Stanton number;
$Sh_{L}$ is the Sherwood number based on length;
$Re_{L}$ is the Reynolds number based on length;
$Sc$ is the Schmidt number;
$h_{m}$ is defined based on a concentration difference (kg s⁻¹ m⁻²);
$u$ is the velocity of the fluid

Boundary layer flow edit

The Stanton number is a useful measure of the rate of change of the thermal energy deficit (or excess) in the boundary layer due to heat transfer from a planar surface. If the enthalpy thickness is defined as:^[5]

$\Delta _{2}=\int _{0}^{\infty }{\frac {\rho u}{\rho _{\infty }u_{\infty }}}{\frac {T-T_{\infty }}{T_{s}-T_{\infty }}}dy$

Then the Stanton number is equivalent to

$\mathrm {St} ={\frac {d\Delta _{2}}{dx}}$

for boundary layer flow over a flat plate with a constant surface temperature and properties.^[6]

Correlations using Reynolds-Colburn analogy edit

Using the Reynolds-Colburn analogy for turbulent flow with a thermal log and viscous sub layer model, the following correlation for turbulent heat transfer for is applicable^[7]

$\mathrm {St} ={\frac {C_{f}/2}{1+12.8\left(\mathrm {Pr} ^{0.68}-1\right){\sqrt {C_{f}/2}}}}$

where

$C_{f}={\frac {0.455}{\left[\mathrm {ln} \left(0.06\mathrm {Re} _{x}\right)\right]^{2}}}$

References edit

^ Hall, Carl W. (2018). Laws and Models: Science, Engineering, and Technology. CRC Press. pp. 424–. ISBN 978-1-4200-5054-7.
^ Ackroyd, J. A. D. (2016). "The Victoria University of Manchester's contributions to the development of aeronautics" (PDF). The Aeronautical Journal. 111 (1122): 473–493. doi:10.1017/S0001924000004735. ISSN 0001-9240. S2CID 113438383. Archived from the original (PDF) on 2010-12-02.
^ Bird, R. Byron; Stewart, Warren E.; Lightfoot, Edwin N. (2006). Transport Phenomena. John Wiley & Sons. p. 428. ISBN 978-0-470-11539-8.
^ ^a ^b Fundamentals of heat and mass transfer. Bergman, T. L., Incropera, Frank P. (7th ed.). Hoboken, NJ: Wiley. 2011. ISBN 978-0-470-50197-9. OCLC 713621645.{{cite book}}: CS1 maint: others (link)
^ Crawford, Michael E. (September 2010). "Reynolds number". TEXSTAN. Institut für Thermodynamik der Luft- und Raumfahrt - Universität Stuttgart. Retrieved 2019-08-26.
^ Kays, William; Crawford, Michael; Weigand, Bernhard (2005). Convective Heat & Mass Transfer. McGraw-Hill. ISBN 978-0-07-299073-7.
^ Lienhard, John H. (2011). A Heat Transfer Textbook. Courier Corporation. p. 313. ISBN 978-0-486-47931-6.

[Hall2018-1] Hall, Carl W. (2018). Laws and Models: Science, Engineering, and Technology. CRC Press. pp. 424–. ISBN 978-1-4200-5054-7.

[Ackroyd2016-2] Ackroyd, J. A. D. (2016). "The Victoria University of Manchester's contributions to the development of aeronautics" (PDF). The Aeronautical Journal. 111 (1122): 473–493. doi:10.1017/S0001924000004735. ISSN 0001-9240. S2CID 113438383. Archived from the original (PDF) on 2010-12-02.

[BirdStewart2006-3] Bird, R. Byron; Stewart, Warren E.; Lightfoot, Edwin N. (2006). Transport Phenomena. John Wiley & Sons. p. 428. ISBN 978-0-470-11539-8.

[Wiley-4] Fundamentals of heat and mass transfer. Bergman, T. L., Incropera, Frank P. (7th ed.). Hoboken, NJ: Wiley. 2011. ISBN 978-0-470-50197-9. OCLC 713621645.{{cite book}}: CS1 maint: others (link)

[Crawford2010-5] Crawford, Michael E. (September 2010). "Reynolds number". TEXSTAN. Institut für Thermodynamik der Luft- und Raumfahrt - Universität Stuttgart. Retrieved 2019-08-26.

[KaysCrawford2005-6] Kays, William; Crawford, Michael; Weigand, Bernhard (2005). Convective Heat & Mass Transfer. McGraw-Hill. ISBN 978-0-07-299073-7.

[Lienhard2011-7] Lienhard, John H. (2011). A Heat Transfer Textbook. Courier Corporation. p. 313. ISBN 978-0-486-47931-6.

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Stanton number

Contents

Formula edit

Mass transfer edit

Boundary layer flow edit

Correlations using Reynolds-Colburn analogy edit

See also edit

References edit