Enhanced flow boiling in microchannels using auxiliary channels and multiple micronozzles (II): Enhanced CHF and reduced pressure drop

Enhancing critical heat flux (CHF) of flow boiling without escalating pressure drop is highly desirable in thermal management of high power-density electronic devices. Usually, an improved CHF can be achieved by restricting flow or at a higher mass velocity, leading to a higher pressure drop. In this study, compared to the two-nozzle microchannel configuration, the improved microchannel configuration as detailed in the Part (I) of this study can enhance CHF without sacrificing pressure drop. In this part, CHF is experimentally evaluated together with the pressure drop with mass flux ranging from 120 kg/m2 s to 600 kg/m2 s. Compared to the two-nozzle configuration, our study shows that CHF can be enhanced up to 32% with a ∼53% reduction of pressure drop at a mass flux of 325 kg/m2 s. The bubble collapse-removal process is significantly improved because more micronozzles are integrated. The enhanced pumping effect, which is created by rapid bubble collapse processes in the entire main channels, enables a more sustainable liquid supply and hence delays the CHF conditions. Moreover, two-phase flow in terms of pressure drop fluctuations is more stable owing to the effective management of bubble confinement in the entire channel.