Cooling optimization of developing, pulsating, incompressible airflow through a 4-rifled aluminum microtube using statistical approach based on analysis of variance (ANOVA)

In this study, the cooling process of a developing, pulsating, incompressible airflow through a 4-rifled aluminum microtube is optimized. The purpose of the optimization is to reduce the pressure drop and to increase the net rejected heat flux from the inner wall of the microtube to improve cooling. Air, serving as the working fluid, is introduced into the microtube at a temperature of 300 K while the pulsation frequency varies from 1 to 25 Hz and the Reynolds number remains constant at 100. A constant heat flux of 100 W/m² is applied to the outer wall. The governing equations for flow and heat transfer are solved numerically within a cylindrical coordinate system, using the finite volume discretization method. A specialized numerical optimization tool for statistical analysis (Design-Expert®) based on Analysis of Variance (ANOVA) and Response Surface Method (RSM) has also been used to determine the optimal variables. The results show that the amplitude and frequency of the pulsation do not affect the pressure drop. In addition, it is found that by repeating the optimization process with the same model and order while the coefficients of pressure drop and heat flux equations change, the error percentage remain stationary and a more accurate equation cannot be achieved, necessarily. The findings indicate that the proposed design can enhance thermal performance by increasing net rejected heat flux and reducing pressure drop, particularly under optimized flow and geometric condition, which correspond to the highest Thermal Performance Factor (TPF) of 2.5 at frequency of 1 Hz.