Performance evaluation of a triple-effect evaporator with forward feed using exergy analysis

Abstract

SUMMARYThe present study evaluates the performance of a triple-effect evaporator with forward feed (TEEFF) system by using exergy analysis based on actual operational data. The orange juice with a capacity of about 1.222 kg s À1 is concentrated from a dry matter (DM) content of 12 to 65% in this TEEFF, which is situated in an orange juice concentrate line installed in a factory, located in Denizli, Turkey. A Visual Basic 6.0 program was also developed to show how the exergetic performance characteristics of the system vary with the feed flow rates ranging from 1.222 to 1.667 kg s À1. The total exergy efficiency of the TEEEFF is found to be on average 0.85. The largest exergy destruction occurs in the first-effect of the TEEFF system with 48.2% of total, followed by the third and second effects with 32.04 and 19.76% of that. Evaporator performance is also rated on the basis of steam economy, which is obtained to be in the range of 2.05-2.14 under the operation conditions. It is expected that the analysis presented here should provide a designer with a better, quantitative grasp of the inefficiencies and their relative magnitudes in the design, simulation and operation of multiple-effect evaporators.

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“…where Q k is the heat transfer rate through the boundary at temperature T k at location k, W is the work rate, ex tm is the thermo-mechanical flow of exergy, s is the specific entropy, and the subscript zero indicates properties at the temperature and pressure of the environment of the system considered-standard state [27]. Equation (8) can be expanded to the form of Equation (9):…”

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