1/25/2024 0 Comments Heat of compression calculator![]() ![]() The former might be given by economics the latter is a technical issue and will be assessed here. Although it is not ideal, the savings of multistage compression can be huge, depending on the number of stages into which the total compression is split, and how the total pressure ratio, r t = P o u t / P i n, is shared between them. However, this is not possible, so large compressions from a given P i n to a much higher P o u t, are split in smaller stages: one stage compresses the gas at a certain intermediate pressure it is then cooled and sent to the inlet of the next, and the process is repeated until P o u t. The increase in power consumption caused by compressing a gas that is progressively getting hotter, with large mass flows and long operating hours can be economically unsustainable. Special attention has been put into engineering considerations.įor minimum power consumption in industrial applications, gases should ideally be cooled at the same time they are being compressed, maintaining their initial temperature as constant during the whole process. 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. 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. Here, a step by step derivation of the general formula and of the formula for different stage efficiencies are carried out using Lagrange multipliers. The case when the stages have different isentropic efficiencies is only treated numerically. 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 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.
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