Performance Modelling and Exergy-Economic Analysis of Thermal Driven
Multiple Effect Distillation System for Brackish Water Treatment
Abstract
Multi-effect distillation shines as a thermal desalination technique due
to its economic viability and broad range of application. It effectively
tackles desalination for seawater and brackish water, regardless of
capacity, using a low-temperature (below 70°C) evaporation and
distillation process. This study employs exergy analysis to identify the
components within a six-effect Multiple Effect Distillation (MED) system
where exergy destruction occurs, followed by an exergy-economic analysis
to evaluate the system’s overall performance. Exergy, representing the
maximum obtainable work from a substance, is examined for both feed
water and distillate in the context of their chemical potential
differences. The calculated exergy values for different system states
are presented, revealing the exergy destruction attributed to
irreversibility such as friction and heat transfer. The system’s overall
exergy efficiency is determined to be 74.47%, indicating that only this
portion of feed water exergy is converted into useful distillate exergy.
The remaining exergy is lost due to irreversibility. An exergy balance
for the 6-effect MED system is provided, showing that 25.53% of the
energy input is lost as exergy destruction. Three different economic
model are used to estimate the distillate cost for different feedwater
temperature and distillate cost found to be 3.63, 1.9, 2.45 $/m
3 respectively.