Ahmed A.Y. Al-Waaly

The effect of subcooling inlet has a big effect of the flow patterns for the flow boiling through a microchannel. Higher subcooling lower mass flux will delay the nucleate boiling and vice versa. The water flow boiling inside a microchannel has been analyzed numerically. The microchannel depth was 0.24 mm while the length was 40 mm. The supplied heat fluxes were 500 kW·m-2, 1000 kW·m-2and 1500 kW·m-2 with mass velocities of 400 kg·m-2·s-1 and 800 kg·m-2·s-1. The degrees of subcoooling of inlet water were 5oC, 10oC, 15oC, 20oC, and 25oC. The results showed that the degree subcooling has a considerable impact on both the wall temperature and flow patterns. The rise in the degree of subcooling kept the nucleate flow boiling and retarded the development of convective boiling. In addition, there was a reflection point at which the impact of heat flux on the average of the convective coefficient of heat transfer was altered. The increase in the heat flux may lead to an increase or reduction in the average HTC with respect to the location of the reflection point. The reflection points were 7oC and 5oC for the mass velocities 400 kg·m-2·s-1 and 800 kg·m-2·s-1. Thus, both the degree of subcooling and the heat flux should be simultaneously considered when it comes to the enhancement of HTC during the flow boiling inside the microchannels.

This study is a systematic review of research on heat transfer analysis in cavities and aims to provide a comprehensive understanding of flow and heat transfer performance in various kinds of cavities with or without the presence of fins, obstacles, cylinders, and baffles. The study also examines the effects of different forces, such as magnetic force, buoyancy force, and thermophoresis effect on heat transfer in cavities. This study also focuses on different types of fluids, such as air, water, nanofluids, and hybrid nanofluids in cavities. Moreover, this review deals with aspects of flow and heat transfer phenomena for only single-phase flows. It discusses various validation techniques used in numerical studies and the different types and sizes of mesh used by researchers. The study is a comprehensive review of 297 research articles, mostly published since 2000, and covers the current progress in the area of heat transfer analysis in cavities. The literature review in this study shows that cavities with obstacles such as fins and rotating cylinders have a significant impact on enhancing heat transfer. Additionally, it is found that the use of nanofluids and hybrid nanofluids has a greater effect on enhancing heat transfer. Lastly, the study suggests future research directions in the field of heat transfer in cavities. This study’s findings have significant implications for a range of areas, including electronic cooling, energy storage systems, solar thermal technologies, and nuclear reactor systems.