Numerical Simulation on the Boiling Flow Patterns of Al2O3-Water Nanofluid in Micro/Minichannel under Different Hypergravity Levels and Directions

Abstract

Due to the influence of hypergravity that has a significant impact on the performance of heat exchanger in aircraft, which is crucial for electronic equipment on the plane and life safeties of pilots and passengers, a numerical study is conducted using Fluent 20R2 software to investigate boiling flow patterns under different gravity levels and directions. In this study, the thermophysical properties of nanofluids are analyzed, and select the most suitable theoretical model of thermal conductivity, viscosity, and surface tension for present simulations. Choose the grid structure of 122,116 after independence check for grid. The VOF approach is employed for present simulation, and the standard κ − ε turbulence model with nonequilibrium wall function is used. The UDFs for mass and energy source terms and thermophysical properties of nanofluid are developed for calculating the HTC of nanofluid. There are three different gravity directions with gravity levels from 1 g to 9 g. The results show that the flow pattern becomes the stratified flow with the gravity levels increasing when the hypergravity direction is perpendicular to the flow direction, and the HTCs decrease with the increment of gravity levels. The vapor-phase transform to circular when the hypergravity direction is the same as the flow direction, and the HTCs of the second half of the tube are decreasing with the increasing gravity levels. On the contrary, the vapor phase is elongated when the hypergravity direction is opposite to the flow direction, and the HTCs show the enhanced tendency.

Heat transfer and flow characterisation of aircraft heat exchangers considering manufacturing constraints

“…At present, most of the research on thermal management systems focuses on theoretical analysis and node temperature simulation, and less research on heat dissipation and temperature control strategy [9]. At the same time, the hydraulic system thermal analysis method for the calculation of the control body temperature and pressure requires the solution of differential-algebraic equations resulting in complex calculations [10].…”