Power Requirement for Compression of Air

by Scott Lyon

Submitted : Fall 2008

The problem for this project wished to adiabatically compress air from 1 bar and 300 K to a higher pressure, and asked us to calculate the outlet temperature and work per unit mass required by the compressor. Using basic thermodynamic equations and calculus knowledge, I began to understand what needed to be done in order to solve this problem. I started by integrating the equation for the heat capacity of air, and then setting up the equation so that Cp(heat capacity) was being divided by T(temperature in K). Then using Microsoft Excel, I solved for the ideal temperature for the compressor to work at different pressures. Once I had all of these ideal temperatures, I was able to calculate the ideal work of the compressor using more integration. After finding the ideal work for the system, calculating the actual work was as simple as dividing the ideal work by the isentropic efficiency of the compressor, which happened to be 0.7. Finally, I was able to use the goal seek program on Excel to calculate the actual temperature of the compressor at different pressures (P). The most noticeable conclusion that I withdrew from my results, was that as the pressure increased, so did the temperature and work. Also, the ideal temperature and ideal work were much lower than the actual temperature and work, showing that the compressor was actually less efficient.

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