Modeling and combined application of the modified NSGA-II and TOPSIS to optimize a refrigerant-to-air multi-pass louvered fin-and-flat tube condenser

In the present work, the performance of a refrigerant-to-air multi-pass louvered fin-and-flat tube condenser is optimized without changing the condenser dimensions include length, width and depth. In order to achieve this aim, a one dimensional finite element model is developed to predict the condenser performance. The developed model is then used for optimization procedure after validating by the experimental data. The modified NSGA-II approach is applied to maximize heat transfer rate (Q) and minimize entropy generation number (Ns), refrigerant pressure drop (ΔPref) and air pressure drop (ΔPair) as the objective functions. The non-dominated optimum design points are then plotted and trade-off optimum points are obtained using the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) and Nearest to the Ideal Point (NIP) method. Comparing the results of four-objective optimization with the results of separately run three and two-objective optimization problems reveals that Q and Ns can be used interchangeably. An independent two-objective optimization of Q and ΔPref results in heat transfer rate increase of about 4% and refrigerant pressure drop reduction of about 85%. In addition, the calculations show that in this case the effectiveness of the optimized condenser increases 3.3% in comparison with the base line condenser. Also, the results of sensitivity analysis of change in the optimum heat transfer rate and refrigerant pressure drop with change in the decision variables are reported.