Multi-objective optimisation of VCR systems by applying TOPSIS to the single-objective solutions obtained with Excel Solver

Multi-objective optimisation analyses using Microsoft Excel

Abstract

This paper describes two methods for using the single-objective solver that comes with Microsoft Excel and the TOPSIS decision-making technique for multi-objective optimisation of a two-stage vapour-compression refrigeration (VCR) system. The Excel-aided model developed for analysing the exergetic and economic performance of the system was first used to obtain six optimised solutions by using the two solution methods provided by Solver that separately maximised the system’s exergetic efficiency (ε) and minimise its total cost-rate (Ctotal) and equipment cost rate (Cequip). A dual-objective optimised solution that simultaneously maximises ε and minimises Ctotal was also obtained by using the MIDACO solver. The first method applies TOPSIS to rank the seven optimised solutions by using five weighting schemes. As should be expected, the results of this method show that MIDACO’s dual-objective solution achieved the first rank, while the two Solver solutions that minimised the equipment cost rate occupied the lowest two ranks. According to this method, the two Solver solutions that maximised the exergetic efficiency closely satisfy the dual objective of the 2E optimisation. The second method applies TOPSIS in an active manner by using Solver to adjust the relevant design variables so that the parameter Ci that measures the closeness of the base design to the ideal dual-objective target is maximised. The results obtained show that this method cannot only produce a multi-objective solution, but that its solution is closer to the ideal dual-objective target than MIDACO’s 2E solution.

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