Sensitivity analysis of nanofluid flow over different flat tubes confined between two parallel plates using Taguchi method and statistical analysis of variance

Abstract

In this research, the effect of simultaneous use of nanofluids and flat tubes to evaluate the efficiency of heat exchangers in the fluid flow over tandem tubes between two parallel plates is investigated and analyzed. The use of effective methods to reduce the number of numerical experiments and achieve accurate and reliable analysis with statistical techniques as well as the use of passive methods to improve the performance of tube heat exchangers are investigated in this study. The focus of the research is to achieve the optimal values of controlling factors, determine the effectiveness of each variable and evaluate the hydraulic and thermal behaviors of the flow structure. For this purpose, nanofluid containing aluminum oxide nanoparticles with volume fractions of 0–8%, flat tubes with 1.5, 2, 2.5 axial ratios, and square sections in comparison with circular tubes are used. Constant temperature boundary conditions are applied on the confining plates and the surface of the tubes. To perform sensitivity analysis, the Taguchi method with L25 orthogonal array and statistical analysis of variance (ANOVA) are utilized. The obtained results show that by changing the cross-section and further flattening, heat transfer and pressure drop decrease concurrently. Moreover, with increasing the volume fraction of nanoparticles, both parameters related to heat transfer rate and flow pressure drop increase. Examining the combination of the two output parameters of the flow and obtaining the efficiency evaluation criterion, it is determined that flattening the tubes, in contrast to increasing the volume fraction of nanoparticles, increases the efficiency of the heat exchanging modules. One of the important results obtained in utilizing the Taguchi method with ANOVA analysis, in addition to reducing the numerical calculations by 80%, is accurate and reliable findings that are confirmed by comparison with the full factorial method.