On the optimization of a vertical twisted tape arrangement in a channel subjected to MWCNT-water nanofluid by coupling numerical simulation and genetic algorithm

摘要

Heat transfer and fluid flow are optimized in a three-dimensional channel under the constant heat flux boundary condition employing a genetic algorithm (GA) coupled with numerical simulation. Multi-wall carbon nanotube (MWCNT)-water nanofluid and vertical twisted tapes are used for heat transfer enhancement. Reynolds (Re) number (5000-25,000), the MWCNT volume fraction of nanoparticles (0-0.16 vol%), the number of vertical twisted tapes (5-10), the angle of attack of the twisted tapes (50 degrees-130 degrees), and their twist angle (180 degrees-720 degrees) are considered as five design parameters. The main objective is to maximize the heat transfer rate and minimize pressure loss. Thirty-five design points are generated by the design of experiment method. Flow at the optimum point that is predicted by the GA is simulated through CFD modeling. Comparing the GA prediction with the CFD results shows excellent consistency between the results. The maximum heat transfer with a minimum pressure loss occurred in the channel with nine twisted tapes (at the twisted angle of 540 degrees and the attack angle of 90 degrees) at Re number of 8000 and solid volume fraction of 0.16 vol %. Relative to the smooth channel at the same condition, in the optimum case, the heat transfer increased by 265%, while the pressure loss increased by 319%.