▪ Abstract This review examines recent advances made in predicting boiling heat fluxes, including some key results from the past. The topics covered are nucleate boiling, maximum heat flux, transition boiling, and film boiling. The review focuses on pool boiling of pure liquids, but flow boiling is also discussed briefly.

Boiling heat transfer

Measurement and correlation of critical heat flux in two-phase micro-channel heat sinks

As the scale of devices becomes small, thermal control and heat dissipation from these devices can be effectively accomplished through the implementation of microchannel passages. The small passages provide a high surface area to volume ratio that enables higher heat transfer rates. High performance microchannel heat exchangers are also attractive in applications where space and/or weight constraints dictate the size of a heat exchanger or where performance enhancement is desired. This survey article provides a historical perspective of the progress made in understanding the underlying mechanisms in single-phase liquid flow and two-phase flow boiling processes and their use in high heat flux removal applications. Future research directions for (i) further enhancing the single-phase heat transfer performance and (ii) enabling practical implementation of flow boiling in microchannel heat exchangers are outlined.

History, Advances, and Challenges in Liquid Flow and Flow Boiling Heat Transfer in Microchannels: A Critical Review

Geometrical effects of MEMS-based microfabricated inlet orifices on the suppression of parallel channel and upstream compressible volume in stabilities commonly exhibited during flow boiling in parallel microchannels have been investigated. The heat fluxes at the onset of unstable boiling have been obtained over effective heat fluxes ranging from 9 to 614 W/cm 2 and mass fluxes from 115 to 389 kg/m 2 s. A dimensionless parameter M, which accounts for the pressure drop increase imposed by the inlet restrictors, has been used to correlate the extent of flow instability suppression. It has been shown that the onset of unstable boiling asymptotically increases with M. At sufficiently high M values, parallel channels and upstream compressible volume instabilities are completely eradicated although it gives way to another instability to develop, namely, the critical heat flux conditions. A correlation has been developed in terms of M to predict the conditions leading to unstable boiling.

Suppression of Boiling Flow Oscillations in Parallel Microchannels by Inlet Restrictors

Providing a comprehensive introduction to the fundamentals and applications of flow and heat transfer in conventional and miniature systems, this fully enhanced and updated edition covers all the topics essential for graduate courses on two-phase flow, boiling, and condensation. Beginning with a concise review of single-phase flow fundamentals and interfacial phenomena, detailed and clear discussion is provided on a range of topics, including two-phase hydrodynamics and flow regimes, mathematical modeling of gas-liquid two-phase flows, pool and flow boiling, flow and boiling in mini and microchannels, external and internal-flow condensation with and without noncondensables, condensation in small flow passages, and two-phase choked flow. Numerous solved examples and end-of-chapter problems that include many common design problems likely to be encountered by students, make this an essential text for graduate students. With up-to-date detail on the most recent research trends and practical applications, it is also an ideal reference for professionals and researchers in mechanical, nuclear, and chemical engineering.

/pdf/two-phase-flow-boiling-and-condensation-in-conventional-and-5aink3qfmk.pdf

Hironobu Ohno

Papers

An improved version of the generalized correlation of critical heat flux for the forced convective boiling in uniformly heated vertical tubes.