FUEL OIL ADIMENSIONAL NUMBERS (PRANDTL & GRASHOF) 1

[santiagooo]

does anyone know where i could find the prandtl and grashof numbers for the fuel oil?????

 

[25362]

Santiago,

These dimensionless numbers depend on a variety of thermophysical fuel properties all of which vary with temperature and fuel oils are of various specifications. Besides, the Gr also depends on physical dimensions whether plates, pipes, etc., and the [Δ]T between surface and bulk, or a given heat flux, and the gravitational constant.

For example take a fuel, within a 6" (Sch 40) pipe and an internal [Δ]T of 10^oC, kept at ~100^oC with the following properties:

[β] = 7[×]10^-4/K
[ν] = 30[×]10^-6 m²/s
[κ] = 0.14 W/m.K
C_p = 2,2 kJ/(kg.K)
g = 9.8 m/s²

The resulting values would be:

Pr ~ 420
Gr ~ 8[×]10⁸.

As[í] que no creo que puedas encontrar dichos valores publicados y tendr[á]s que calcularlos por ti mismo.

 

[santiagooo]

Gracias 25326 por tu respuesta,

so, according to your response, in order to calculate Pr and Gr I need the thermophysical fuel properties, in my case of fuel oil. Ive been searching for the latter, but unfortunaty I could'nt find them. Do you know any source where to find them?

thanks again for your answer, its been of great help.

 

[IRstuff]

Given that there are probably dozens of "fuel oils," don't you think that you might want to volunteer what specifics you actually know about the "fuel oil?"

Is this for school?

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[25362]

IRstuff is right. There are many types of fuel oils.
If this is just a school exercise, I think you"ll find a useful example of thermophysical properties at various temperatures for an unused engine oil in table A-4 on Heat Transfer by J.P. Holman, McGraw-Hill International Student Edition.
Chapter 7 of the same book deals with natural-convection systems.
Don't forget Gr requires also (geometrical) dimensions in its calculations.

 

[santiagooo]

thanks again 25362,

Actually, its not for school. Anyway, youre right, i didnt specified the fuel oil. Its Fuel Oil Nº6, and ill be needing as you said before, the following thermophysical properties,

?, Cp, ?, ?

So, do you know where i could find them?

 

[25362]

Even HFO No.6 has a wide range of viscosities, for example, from 15 to 50 cSt at 100^oC. Therefore, it seems to me there are no tabulated values for these properties of HFO No.6.

I still suggest you exploit the data given in Holman's book (probably available in any technical library) to get some "approximate" figures.

 

[25362]

BTW, thread481-196761 may help you to understand the problem.

 

[FeX32]

santiagooo stugatsa


Fe

 

[bolmeteus]

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