Effect of thermal loading on flow distribution in regenerative cooling parallel channels

Abstract

The thermal management system is crucial for protecting combined engines, ensuring vehicle safety at high power levels. Optimizing the heat sink utilization efficiency of heat-absorbing hydrocarbon fuels within this system is therefore critical. This study investigates flow distribution in parallel channels under varying thermal loads and examines the impact of flow inhomogeneity on thermal stress. The flow distribution inhomogeneity (Φ) increased slightly with rising heat flux under low heat load conditions, and showed a 10 % increase as the heat flux rose from 0 to 0.9 MW/m². This is primarily due to the drastic changes in the thermophysical properties of supercritical fluids with temperature. Higher heat flux intensified density difference between fluids in different channels and reduced wall shear stress, with this effect being most pronounced in the central channel. Pyrolysis reactions further aggravated flow distribution inhomogeneity, resulting in an average increase of 33.3 %. The uneven flow distribution caused insufficient flow in edge channels, where conversion rates were most affected by heat flux due to elevated fluid temperatures. Conversely, the central channel was less affected due to higher mass flow. Excessive flow concentration in system corners, combined with inadequate heat absorption, resulted in inefficient heat sink utilization. As flow distribution inhomogeneity increased from 0.237 to 0.307, the maximum thermal stress rose from 187.7 MPa to 195.8 MPa. Channels with lower flow rates were particularly vulnerable to heightened thermal stress, posing an even greater challenge to thermal protection.