Cylinder¶

class pychemengg.heattransfer.externalflow.Cylinder[source]¶

Bases: object

Models a circular cylinder.

Parameters

`None_required`‘None’: This class takes no parameters for instance creation.

Examples

First import the module externalflow.

>>> from pychemengg.heattransfer import externalflow as extflow 
>>> cyl = extflow.Cylinder
# This will create an instance of the class 'Cylinder'.
# Methods of the class 'Cylinder' can then be called like so :-
# cyl.method(kwarg1=x, ...)

Attributes

`None_required`‘None’: This class does not expose any instance attributes.

__init__(*args, **kwargs)¶

Methods

`Nu_churchill_bernstein`([Re, Pr])	Average Nusselt number for flow over circular cylinder.
`Nu_hilpert_knudsen_katz`([Re, Pr])	Average Nusselt number for flow over circular cylinder.
`__init__`(args, *kwargs)

Nu_churchill_bernstein(Re=None, Pr=None)[source]¶

Average Nusselt number for flow over circular cylinder.

Parameters

Reint or float: Reynolds number for fluid flow over the cylinder.
Print or float: Prandtl number for the fluid.

Returns

Nuint or float: Average Nusselt number for turbulent flow on circular cylinder.

Warning

A Nusselt number is returned based on the equation even if parameters (such as Re, Pr) do not fall in their respective allowable range limits (see above under ‘Notes’). However, if this happens, a warning is issued.

Notes

The following formula is used:

\[Nu = 0.3 + \cfrac {0.62 Re^{1/2} Pr^{1/3}} {\left[ {1 + (\frac{0.4}{Pr})^{2/3}} \right]^{1/4}} \left[ 1 + \left( \frac {Re} {282000} \right)^{5/8} \right]^{4/5}\]

where:

\(Re Pr > 0.2\)

Fluid properties are at film temp (\(T_{film}\)):

\(T_{film} = (T_{infinity} + T_{surface})/2\)

\(T_{infinity}\) = temperature of fluid away from surface

\(T_{surface}\) = temperature of surface

References

[1] Yunus A. Cengel and Afshin J. Ghajar, “Heat And Mass Transfer Fundamentals and Applications”, 6th Edition. New York, McGraw Hill Education, 2020.

Examples

First import the module externalflow.

>>> from pychemengg.heattransfer import externalflow as extflow 
>>> cyl = extflow.Cylinder()
# This will create an instance of the class 'Cylinder'.
# Then call the method like so :-
>>> cyl.Nu_churchill_bernstein(Re=4.219e4, Pr=0.7202)
124.44556447378223

Nu_hilpert_knudsen_katz(Re=None, Pr=None)[source]¶

Average Nusselt number for flow over circular cylinder.

Parameters

Reint or float: Reynolds number for fluid flow over the cylinder.
Print or float: Prandtl number for the fluid.

Returns

Nuint or float: Average Nusselt number for laminar/turbulent flow on circular cylinder.

Warning

A Nusselt number is returned based on the equation even if parameters (such as Re, Pr) do not fall in their respective allowable range limits (see above under ‘Notes’). However, if this happens, a warning is issued.

Notes

The following formula is used:

\[Nu = C Re^{m} Pr^{1/3} \]

where:

C, m : depend on Re

\(0.4 \eqslantless Re \eqslantless 400000\)

\(Pr \eqslantgtr 0.7\)

Fluid properties are at film temp (\(T_{film}\)):

\(T_{film} = (T_{infinity} + T_{surface})/2\)

\(T_{infinity}\) = temperature of fluid away from surface

\(T_{surface}\) = temperature of surface

References

[1] Yunus A. Cengel and Afshin J. Ghajar, “Heat And Mass Transfer Fundamentals and Applications”, 6th Edition. New York, McGraw Hill Education, 2020.

Examples

First import the module externalflow.

>>> from pychemengg.heattransfer import externalflow as extflow 
>>> cyl = extflow.Cylinder()
# This will create an instance of the class 'Cylinder'.
# Then call the method like so :-
>>> cyl.Nu_hilpert_knudsen_katz(Re=4.219e4, Pr=0.7202)
127.97991118302727