Flow maldistribution and its effect on the thermal performance of miniaturized devices: A perspective from thermal boundary condition

Abstract

Owing to their high compactness, high-pressure resistance and superior heat transfer capability, compact heat exchangers and microchannel heat sinks are an integral part and play an important role in advanced hydrogen energy systems. In such miniaturized devices, numerous unit channels are typically installed in the core region between the inlet and outlet manifolds, resulting in fluid flow maldistribution which affects the thermal performance of the device. This review focuses on single-phase flow maldistribution and its effects on the thermal performance of miniaturized devices under typical thermal boundary conditions. An exhaustive literature review reveals that a popular belief within this research field is that lower flow maldistribution improves thermal performance. As a result of this belief, a large number of experimental studies were conducted under adiabatic condition. Further, methods developed to mitigate maldistribution were used regardless of the thermal boundary conditions. However, quantitative comparisons between these studies reveal that the relationship between maldistribution and thermal performance is non-linear, as maldistribution does not invariably cause negative effects and can even enhance the thermal performance under certain circumstances if properly utilized. None of the existing parameters adequately reflect this complex relationship. Finally, countermeasures against maldistribution are recommended depending on the specific thermal boundary conditions, and future research needs are outlined.

Keywords

• Hydrogen energy
• Compact heat exchanger
• Microchannel heat sink
• Flow maldistribution
• Thermal performance
• Thermal boundary condition