A three-dimensional two-fluid code NEPTUNE_CFD has been validated against the ASU (Arizona State University) [1] and DEBORA [2, 3] boiling flow experiments. Nucleate boiling processes in the subcooled flow boiling regime have been studied on ASU experiments. Within this scope a new wall function is implemented in the NEPTUNE_CFD V1.0.6 code to improve the prediction of flow parameters in the bo...

Flow boiling of 1-methoxyheptafluoropropane (HFE 7000) in 222 m hydraulic diameter channels containing a single row of 24 inline 100 m pin fins was studied for mass fluxes from 350 kg /m2 s to 827 kg /m2 s and wall heat fluxes from 10 W /cm2 to 110 W /cm2. Flow visualization revealed the existence of isolated bubbles, bubbles interacting, multiple flow, and annular flow. The observed flow patte...

This study’s objective was to better understand the CHF condition in microchannels. The effect of different operating parameters – mass flux, inlet subcooling, exit quality, heated length and diameter – were assessed in detail in Part I of the study and compared to the behavior in conventional sized channels. Part II of the study compares the water and R-123 data with existing micro/macrochanne...

A comprehensive review and analysis of prior subcooled flow boiling CHF correlations was conducted to identify those correlations that provide the most accurate predictions for dielectric working fluids and small rectangular flow passages found in electronics cooling applications in both microgravity and Earth gravity. Since most prior correlations were derived from water databases, only those ...

Population balance equations combined with a threedimensional two-fluid model are employed to predict bubbly flows with the presence of heat and mass transfer processes. Subcooled boiling flow belongs to this specific category of bubbly flows is considered. The MUSIG (MUltiple-SIze-Group) model implemented in CFX4.4 is further developed to account for the wall nucleation and condensation in the...

The paper reports pressure drop data for hydrocarbon fluids boiling in vertical upflow in a 8.68 m long, 25.4 mm i.d. tube, heated by direct electrical heating. These data were recorded simultaneously with the boiling heat transfer measurements. The systematic trends of the measured pressure gradient with respect to vapour quality, mass flux and pressure are examined. This provides useful infor...

This study examines the pressure drop characteristics of subcooled two-phase microchannel heat sinks. A new model is proposed, which depicts the subcooled flow as consisting of a homogeneous two-phase flow layer near the heated walls of the microchannel and a second subcooled bulk liquid layer. This model is intended for conditions where subcooled flow boiling persists along the entire microcha...

Critical Heat Flux, or CHF, is an important condition that defines the upper limit of safe operation of heat transfer equipment employing boiling heat transfer in heat flux controlled systems. Although significant research has been conducted in this field, a clear understanding of the basic mechanisms leading to the CHF condition is still lacking. The present article covers the subcooled flow b...