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Open AccessArticle

Step by Step Derivation of the Optimum Multistage Compression Ratio and an Application Case

ETSI Industriales, Universidad Politécnica de Madrid (UPM), José Gutiérrez Abascal 2, 28006 Madrid, Spain
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Entropy 2020, 22(6), 678; https://doi.org/10.3390/e22060678
Received: 29 May 2020 / Revised: 12 June 2020 / Accepted: 15 June 2020 / Published: 18 June 2020
(This article belongs to the Special Issue Thermodynamic Optimization of Complex Energy Systems)
The optimum pressure ratio for the stages of a multistage compression process is calculated with a well known formula that assigns an equal ratio for all stages, based on the hypotheses that all isentropic efficiencies are also equal. Although the derivation of this formula for two stages is relatively easy to find, it is more difficult to find for any number of stages, and the examples that are found in the literature employ complex mathematical methods. The case when the stages have different isentropic efficiencies is only treated numerically. Here, a step by step derivation of the general formula and of the formula for different stage efficiencies are carried out using Lagrange multipliers. A main objective has been to maintain the engineering considerations explicitly, so that the hypotheses and reasoning are clear throughout, and will enable the readers to generalise or adapt the methodology to specific problems. As the actual design of multistage compression processes frequently meet engineering restrictions, a practical example has been developed where the previous formulae have been applied to the design of a multistage compression plant with reciprocating compressors. Special attention has been put into engineering considerations. View Full-Text
Keywords: compressors; pressure; multistage; non-equal efficiency; multistage compression; optimisation; optimum compression ratio; Lagrange multipliers; reciprocating compressors compressors; pressure; multistage; non-equal efficiency; multistage compression; optimisation; optimum compression ratio; Lagrange multipliers; reciprocating compressors
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López-Paniagua, I.; Rodríguez-Martín, J.; Sánchez-Orgaz, S.; Roncal-Casano, J.J. Step by Step Derivation of the Optimum Multistage Compression Ratio and an Application Case. Entropy 2020, 22, 678.

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