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# Thermodynamics Question, watch

1. Hi:

"A portable high speed drill is driven by a small turbine which uses air drawn from a high pressure air bottle of volume 0.01m^3. The bottle is rigid and heat transfer in both bottle and turbine may be neglected.

The initial bottle pressure is 100bar, and air is used until the pressure falls to 50 bar. During the process the air in the bottle obeys pv^1.4 = constant. The initial temperature was 300k. The air leaves the turbine at a constant temperature of 120K and with negligible velocity."

I can do part a) what is final temp of bottle (=246K)

but part b) What is the work supplied by the turbine to the drill?

Please could someone show me how to get to the final answer of 70.4kJ.

Thanks alot

(Assuming Cp for air = 1.005 KJ/KgK, cp/cv = 1.4)

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Updated: February 8, 2010
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