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1. The problem statement, all variables and given/known data

Nitrogen at 100°C and specific volume of 0.1846 m^3/kg undergoes a polyprotic expansion process such that pv^(1.2)=const and the final pressure is 100 kPa. A constant pressure compression is then performed to bring the volume back to 0.1846 m^3/kg. Finally a constant volume pressurisation occurs to bring the Nitrogen back to its initial pressure. Nitrogen is a perfect gas with R= 0.297 kJ/kg K and Cv=0.745 kJ/kg K.

i) Determine the initial pressure

ii) Determine T and v at the end of the polyprotic expansion

iii) Sketch 3 processes on a P-V diagram

iv) Calculate the net work done at the conclusion of all three processes

v) Calculate the net heat transfer at the conclusion of all three processes.

2. Relevant equations

p1v1^λ=p2v2^γ

w= Rx(T1-T2)/(n-1)

3. The attempt at a solution

So for the first section I am struggling to keep up with all the processes that are going on. My logic was since the first process is expanding as the volume increases the pressure must decrease therefore our expected initial pressure must be higher than 100 kPa. However I am not entirely sure on how to calculate it. I cannot use the ideal gas law as its not ideal to begin with and the pv^(1.2)=const has limited use as I need the final v for the expansion to be able to use it..

Can someone help me through this question.. I am really struggling with it. Thanks in advance.

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# Homework Help: Polyprotic Expansion HELP

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