13 September Huawei Seminar (6) (1)
Abstract Two phase thermal passive systems do not have moving parts and are compact, reliable, and cost-effective. Fluid motion in these passive devices could be driven by capillary force, gravity, osmotic pressure, and/or concentration gradient. The fundamental mechanisms and limitations of transport phenomena for passive systems are highlighted, followed by their applications in heat pipes, thermosyphons, vapor chambers, electronic devices, solar cooling, thermal energy storage, and electric transport. The capabilities of the passive systems are limited based on the balance between the driving force and transport resistance. Based on the fundamental understanding of fluid flow and phase change in passive systems, this study proposes associated transport phenomena and quantitative criteria to determine the maximum heat transfer rate, the transport distance, and minimum pore size of wick structures (when relevant) in these passive devices. Boiling and condensation are the key heat-transfer modes with high heat transfer coefficients and widespread applications in various industries and processes. The classical case for boiling is nucleate pool boiling, which started to be investigated at the beginning of the 20th century. Despite a long-term history of research into boiling heat transfer, we still have two groups of scientists who believe that the thermophysical properties of the boiling surface and its microstructure impact the heat transfer coefficient, and another group denies this impact. Therefore, more details and thorough experiments should be performed to extend our knowledge of various parameters impacting basic boiling characteristics. Flow boiling is an even more intense heat-transfer process and is widely used in various heat-transfer devices and equipment, including thermal and nuclear power plants. This type of boiling is more complicated than nuclear pool boiling and contains more characteristics/parameters, which have to be calculated. Condensation is another high-intensity heat-transfer process which is widely used in the Rankine power cycle and other industrial processes. Therefore, it is important to follow up with the latest advances in boiling and condensation.