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Entropy 2009, 11(4), 702-712; doi:10.3390/e11040702

Determination of the Real Loss of Power for a Condensing and a Backpressure Turbine by Means of Second Law Analysis

Helsinki University of Technology, Department of Energy Technology, P.O.box 4400, Fin-02015 TKK, Finland
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Received: 19 August 2009 / Accepted: 27 October 2009 / Published: 30 October 2009
(This article belongs to the Special Issue Exergy: Analysis and Applications)
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Abstract

All real processes generate entropy and the power/exergy loss is usually determined by means of the Gouy-Stodola law. If the system only exchanges heat at the environmental temperature, the Gouy-Stodola law gives the correct loss of power. However, most industrial processes exchange heat at higher or lower temperatures than the actual environmental temperature. When calculating the real loss of power in these cases, the Gouy-Stodola law does not give the correct loss if the actual environmental temperature is used. The first aim of this paper is to show through simple steam turbine examples that the previous statement is true. The second aim of the paper is to define the effective temperature to calculate the real power loss of the system with the Gouy-Stodola law, and to apply it to turbine examples. Example calculations also show that the correct power loss can be defined if the effective temperature is used instead of the real environmental temperature.
Keywords: Gouy-Stodola law; entropy generation rate; exergy; effective temperature Gouy-Stodola law; entropy generation rate; exergy; effective temperature
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Holmberg, H.; Ruohonen, P.; Ahtila, P. Determination of the Real Loss of Power for a Condensing and a Backpressure Turbine by Means of Second Law Analysis. Entropy 2009, 11, 702-712.

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