Energy, exergy, and economic (3E) analysis of air bubbles injection into plate heat exchangers

This study aims to experimentally investigate the impact of air bubbles injection on the combined energetic, exergetic, and economic performance characteristics of a plate heat exchanger (P-HEX) with a parallel fluid flow configuration. Cold water, with a fixed volume flow rate of 290 LPH, is mixed with air bubbles (flow rates ranging from 150 to 840 LPH) before entering the P-HEX. The hot water was studied in seven different volume flow rates (280 to 880 LPH) and kept at 50 °C. The results show remarkable increments in the enhancement factors of the number of transfer units and effectiveness, up to 33.17 and 5.5%, respectively, compared to single-phase flow. Furthermore, cold-water side injection boosts the maximum enhancement in the number of transfer units by 2.68 folds, compared to hot water side injection. The maximum entropy generation rate is dampened by 2.45 folds when injecting the cold-water stream instead of the hot one, and the maximum system efficiency is increased from 96.9 to 97.6%. The thermo-economic assessment further highlights the potential of air injection as one of the promising techniques for P-HEXs’ performance, where a maximum specific net profit of 0.45 USD kJ−1 is estimated.