Optimization of a Two-stage Compressor

by Christian Muneton

Submitted : Fall 2008

In this project the problem that was presented was to compress nitrogen through a two-stage compressor. The gas was said to be ideal and the compressors were said to be adiabatic with an isentropic efficiency of 0.7. I was asked to find the values of temperatures and pressures for all streams, the power requirement for each compressor as well as the minimal amount of power to optimize the design, and the amount of cooling water required for the heat exchanger. The limitations were that the outlet temperatures of the compressors may not exceed 550 K, the outlet temperature of the heat exchanger may not exceed 295 K, and the outlet temperature of the heat exchanger must be at least 5 K cooler than temperature 2. The approach I took was to find the equation for work and take the derivative to optimize the design so I could find the pressures and temperatures for all the other paths. I concluded that an optimal design will have the same amount of work for each compressor.

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