Calculating Work Energy Input for Compressing Air in a Piston-Cylinder Assembly

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To calculate the work energy input for compressing air in a piston-cylinder assembly, the specific internal energy must be converted to total internal energy by multiplying the specific internal energy by the mass of the air. The initial specific internal energy is 28 KJ/kg, and the final specific internal energy is 65 KJ/kg for 20 kg of air. Additionally, a heat loss of 3.2 KJ during the process must be accounted for. The discussion emphasizes the importance of distinguishing between specific and total internal energy in energy calculations. Understanding this concept is crucial for accurately determining the work required for the compression process.
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A piston-cylinder assembly contains 20kg of air with a specific internal energy of 28K J/kg. It is compressed to a high pressure and the final specific internal energy is 65K J/kg. During the process there is a heat loss of 3.2K J. Determine the work energy input needed for the compressor.


Just want to ask how come I need to use the mass times the internal energy? What's the concept behind?



Thanks.
 
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You have been given the "specific internal energy". This is different to the "internal energy". And the question asks for a calculation of energy. So you need to calculate the internal energy by using the specific internal energy. I think you have already guessed how to do that.
 
oops... why didn't i see that haha... anyway thank you Mr Brucew :)
 
ha, no worries. It is easy to miss.
 

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