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gfd43tg
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Homework Statement
Air at 100 F is flowing through a packed bed of spheres having a diameter of 0.5 inches. The void fraction (ε) of the bed is 0.38 and the bed diameter is 2 feet. The bed height is 8 feet. If the air enters at 16.2 psia at a rate of 47.5 lb / min calculate the pressure drop of the bed in psi.
Homework Equations
Ergun Equation
http://en.wikipedia.org/wiki/Ergun_equation
The Attempt at a Solution
For this problem, I want to use the Ergun equation. In our lecture slide, it said that for gases, the ergun equation can be used if the average density of the gas is used in the density term (slide attached). I have a couple questions about this problem. First, do I assume that the gas is isothermal and remains at 100 F upon entry and exit? Second, I don't think I can use the density of the air at the inlet as the density term, but I did it anyway because I didn't know what to do. If I don't know the pressure at the outlet, then how can I find the average density? This is twofold because the air density can be affected by the temperature, which is uncertain right now if its 100 F at the outlet, as well as the pressure at the outlet.
The viscosity of air was found online
http://www.lmnoeng.com/Flow/GasViscosity.php