[StanPH]

Dear all,

I'm doing heat transfer simulations of an in-line tube bank that has cylindrical tubes. When reading articles, some authors compute the Reynolds number based on the tube diameter and maximum velocity between the tubes. Other authors use inlet velocity and some of them compute the Reynolds number based on the inlet hydraulic diameter.

How can I find out if there is "low" or "high" Re to choose appropriate computational model? Re based on the tube diameter and maximum velocity can be "low", while Re based on the inlet parameters can be "high" at the same physical parameters.

Thank you.

[FMDenaro]

Originally Posted by StanPH

Dear all,

I'm doing heat transfer simulations of an in-line tube bank that has cylindrical tubes. When reading articles, some authors compute the Reynolds number based on the tube diameter and maximum velocity between the tubes. Other authors use inlet velocity and some of them compute the Reynolds number based on the inlet hydraulic diameter.

How can I find out if there is "low" or "high" Re to choose appropriate computational model? Re based on the tube diameter and maximum velocity can be "low", while Re based on the inlet parameters can be "high" at the same physical parameters.

Thank you.

All choices produce a congruent non dimensional Re number. The key is to use the correct characteristic lenght and velocity that make the term in the non dimensional equation of O(1).
In principle, the mean inlet velocity and the diameter of the tube would produce the correct Re number.

[StanPH]

Originally Posted by FMDenaro

All choices produce a congruent non dimensional Re number. The key is to use the correct characteristic lenght and velocity that make the term in the non dimensional equation of O(1).
In principle, the mean inlet velocity and the diameter of the tube would produce the correct Re number.

Thank you.
Is the mentioned approach applicable also for a channel with tubes inside?
What if the tubes have different diameters?

[FMDenaro]

Originally Posted by StanPH

Thank you.
Is the mentioned approach applicable also for a channel with tubes inside?
What if the tubes have different diameters?

The flow in the tube inside will produce a Reynolds number that must be estimated by means of the proper velocity and diameter.