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https://www.sciencedirect.com/search?qs=physical%20meaning%20of%20Prandtl%20number&show=25&sortBy=relevance

The Prandtl number (Pr) or Prandtl group is a dimensionless number named after the German physicist Ludwig Prandt defined as the ratio of momentum diffusivity to thermal diffusivity. ... In heat transfer problems, the Prandtl number controls the relative thickness of the momentum and thermal boundary layers. When Pr is small, it means that the heat diffuses quickly compared to the velocity (momentum). This means that for liquid metals the thickness of the thermal boundary layer is much bigger than the velocity boundary layer. The mass transfer analog of the Prandtl number is the Schmidt number.

So the physical meaning of Prandtl number is:

1) ratio of momentum to thermal diffusivity

2) ratio of momentum to thermal boundary layer

Anything else?

Please give your idea.

Thank you

Prandtl number is mostly constant for gases, mostly between 0.7 to 1, which is why you will be able to find thermal conductivity of gases at a high temperatures, which is otherwise difficult because of convection currents. Prandtl number is a measure of exactly what phenomenon dominates.

Prandtl number is the ratio of kinematic viscosity to thermal diffusivity. It takes into account three physical properties at time (absolute viscosity, specific heat and thermal conductivity) and also is the ratio of two constants in molecular transportation (momentum transport through molecular friction and heat energy transport through conduction). It also signifies the relative speed with which momentum and energy propagates through fluid.

It is a ratio of kinematic viscosity and thermal diffusivity.

Dear respected colleagues and scholars. Please participate in the discussion and give your comments.

Thank you very much.

The following link and article can be useful based on your enquiry:

https://www.researchgate.net/post/What_are_implication_of_high_Prandtl_number_thermal_diffusivity_and_thermal_conductivity_of_a_particular_fuel_in_a_diesel_engine_or_IC_engine

Silva, W. C., Rocha, A. M., Castro, M. P. P., Sthel, M. S., Vargas, H., David, G. F., & Perez, V. H. (2014). Unconventional characterization of biodiesel from several sources by thermal lens spectroscopy to determine thermal diffusivity: Phenomenological correlation among their physicochemical and rheological properties. Fuel, 130, 105-111.

Hope it is useful?

O.D. Samuel, Ph.D

Dear Olusegun D. Samuel ,

Thank you very much for your valuable reply. Do you have any other meaning of the Prandtl number?

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Prof. Nazaruddin Sinaga ,

Please, find attached the Article entitled, " Prandtl number of optimum biodiesel from food industrial waste oil and diesel fuel blend for diesel engine Fuel ( IF 5.578 ) Pub Date : 2020-10-03 , DOI: 10.1016/j.fuel.2020.119049 Olusegun David Samuel; M. Adekojo Waheed; A. Taheri-Garavand; Tikendra Nath Verma; Olawale U. Dairo; Bukola O. Bolaji; Asif Afzal " for other meaning of the Prandtl number.

Regards,

O.D. Samuel

Thank you very much dear Olusegun D. Samuel for your reply and valuable contribution.

Best regards,

Nazar

In heat transfer problems, the Prandtl number controls the relative thickness of the momentum and thermal boundary layers. When Pr is small, it means that the heat diffuses quickly compared to the velocity (momentum). This means that for liquid metals the thermal boundary layer is much thicker than the velocity boundary layer.

Thanks dear Debajyoti Bose for your kind reply.

Have a good time.

Best regards.

See also:

https://www.researchgate.net/post/Prandtl_Number_physical_significance

The Prandtl number is a dimensionless quantity that puts the viscosity of a fluid in correlation with the thermal conductivity.

Significance -

Source:

1. https://www.sciencedirect.com/topics/chemistry/prandtl-number#:~:text=The%20Prandtl%20number%20is%20a,transport%20capacity%20of%20a%20fluid.

2.https://www.researchgate.net/post/Prandtl_Number_physical_significance

Dear Md. Estabrak Ahammod Sakib ,

Thank you for your reply....

The Prandtl numbers of fluids range from less than 0.01 for liquid metals to more than 100,000 for heavy oils. Note that the Prandtl number is in the order of 10 for water.The Prandtl numbers of gases are about 1, which indicates that both momentum and heat dissipate through the fluid at about the same rate. Heat diffuses very quickly in liquid metals (Pr1) relative to momentum. Consequently the thermal boundary layer is much thicker for liquid metals and much thinner for oils relative to the velocity boundary layer.