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| | My name is Bennett (44 years old) and my hobbies are Herpetoculture and Trainspotting.<br><br>Also visit my page: [http://medicationseller.com/helminths/index.php?action=profile&u=20008 Fifa 15 coin Generator] |
| The '''Hagen number''' ('''Hg''') is a [[dimensionless number]] used in forced flow calculations. It is the forced flow equivalent of the [[Grashof number]] and was named after the German [[hydraulic]] engineer [[Gotthilf Heinrich Ludwig Hagen|G. H. L. Hagen]].
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| It is defined as:
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| : <math>
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| \mathrm{Hg} = -\frac{1}{\rho}\frac{\mathrm{d} p}{\mathrm{d} x}\frac{L^3}{\nu^2}
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| </math> | |
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| where:
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| *<math>\frac{\mathrm{d}p}{\mathrm{d}x}</math> is the pressure gradient
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| *''L'' is a characteristic length
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| *''ρ'' is the fluid [[density]]
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| *''ν'' is the [[kinematic viscosity]]
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| For natural convection
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| :<math> | |
| \frac{\mathrm{d} p}{\mathrm{d} x} = \rho g \beta \Delta T,
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| </math>
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| and so the Hagen number then coincides with the [[Grashof number]].
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| Awad:<ref>{{cite journal |first=M.M. |last=Awad |title=Hagen number versus Bejan number |journal=[[Thermal Science]] |volume=17 |issue=4 |year=2013 |pages=1245 |doi=10.2298/TSCI1304245A }}</ref> presented Hagen number vs. Bejan number. Although their physical meaning is not the same because the former represents the dimensionless pressure
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| gradient while the latter represents the dimensionless pressure drop, it will be
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| shown that Hagen number coincides with Bejan number in cases where the characteristic
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| length (l) is equal to the flow length (L). Also, a new expression of Bejan
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| number in the Hagen-Poiseuille flow will be introduced. In addition, extending the Hagen number to a general form will be presented. For the case of Reynolds analogy (Pr = Sc = 1), all these three definitions of Hagen number will be the same. The general form of the Hagen number is
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| : <math>
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| \mathrm{Hg} = -\frac{1}{\rho}\frac{\mathrm{d} p}{\mathrm{d} x}\frac{L^3}{\delta^2}
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| </math>
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| where
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| : <math>\delta</math> is the corresponding diffusivity of the process in consideration
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| ==See also==
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| {{NonDimFluMech}}
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| ==References==
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| {{reflist}}
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| {{DEFAULTSORT:Hagen Number}}
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| [[Category:Dimensionless numbers]]
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My name is Bennett (44 years old) and my hobbies are Herpetoculture and Trainspotting.
Also visit my page: Fifa 15 coin Generator