A comprehensive criterion for slug-annular flow transition based on flow boiling of R134a in microchannels

2019 ◽  
Vol 105 ◽  
pp. 1-9
Author(s):  
Qiao Yan ◽  
Li Jia ◽  
Zhoujian An ◽  
Qi Peng
Keyword(s):  
Annular Flow ◽  
Flow Boiling ◽  
Flow Transition

scholarly journals Flow Pattern Map of Flow Boiling in a Rectangular Channel Filled with Porous Media

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2440
Author(s):  
Youngwoo Kim ◽  
Dae Yeon Kim ◽  
Kyung Chun Kim
Keyword(s):  
Porous Media ◽  
Flow Pattern ◽  
Flow Regime ◽  
Annular Flow ◽  
Flow Boiling ◽  
Rectangular Channel ◽  
Flow Patterns ◽  
Flow Pattern Map ◽  
Mist Flow ◽  
Churn Flow

A flow visualization study was carried out for flow boiling in a rectangular channel filled with and without metallic random porous media. Four main flow patterns are observed as intermittent slug-churn flow, churn-annular flow, annular-mist flow, and mist flow regimes. These flow patterns are clearly classified based on the high-speed images of the channel flow. The results of the flow pattern map according to the mass flow rate were presented using saturation temperatures and the materials of porous media as variables. As the saturation temperatures increased, the annular-mist flow regime occupied a larger area than the lower saturation temperatures condition. Therefore, the churn flow regime is narrower, and the slug flow more quickly turns to annular flow with the increasing vapor quality. The pattern map is not significantly affected by the materials of porous media.

scholarly journals Annular flow transition model in channels of various shapes.

1988 ◽  
Vol 54 (500) ◽  
pp. 953-958
Author(s):  
Masahiro OSAKABE ◽  
Yuji KAWASAKI ◽  
Kanji TASAKA
Keyword(s):  
Annular Flow ◽  
Transition Model ◽  
Flow Transition

Flow Boiling Visualization of R-134a in a Vertical Channel of Small Diameter

2007 ◽  
Author(s):  
Claudi Marti´n-Callizo ◽  
Bjo¨rn Palm ◽  
Wahib Owhaib ◽  
Rashid Ali
Keyword(s):  
Flow Pattern ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Bubbly Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
R 134A ◽  
Heated Length

The present work reports on flow boiling visualization of refrigerant R-134a in a vertical circular channel with internal diameter of 1.33 mm and 235 mm in heated length. Quartz tube with a homogeneous ITO-coating is used allowing heating and simultaneous visualization. Flow patterns have been observed along the heated length with the aid of a digital camera with close-up lenses. From the flow boiling visualization, seven distinct two-phase flow patterns have been observed: Isolated bubbly flow, confined bubbly flow, slug flow, churn flow, slug-annular flow, annular flow, and mist flow. Two-phase flow pattern observations are presented in the form of flow pattern maps. Finally, the experimental flow pattern map is compared to models developed for conventional sizes as well as to a microscale map for air-water mixtures available in the literature, showing a large discrepancy.

Single-Phase Heat Transfer Enhancement Techniques in Microchannel and Minichannel Flows

2004 ◽  
Author(s):  
Mark E. Steinke ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Electric Fields ◽  
Single Phase ◽  
Flow Boiling ◽  
Swirl Flow ◽  
Flow Transition ◽  
Transfer Enhancement ◽  
Compact Heat Exchangers ◽  
Chip Cooling

The single-phase heat transfer enhancement techniques are well established for conventional channels and compact heat exchangers. The major techniques include flow transition, breakup of boundary layer, entrance region, vibration, electric fields, swirl flow, secondary flow and mixers. In the present paper, the applicability of these techniques for single-phase flows in microchannels and minichannels is evaluated. The microchannel and minichannel single-phase heat transfer enhancement devices will extend the applicability of single-phase cooling for critical applications, such as chip cooling, before more aggressive cooling techniques, such as flow boiling, are considered.

Experimental study of onset of subcooled annular flow boiling

2009 ◽  
Vol 51 (2) ◽  
pp. 361-365 ◽  
Author(s):  
R. Ahmadi ◽  
A. Nouri-Borujerdi ◽  
J. Jafari ◽  
I. Tabatabaei
Keyword(s):  
Experimental Study ◽  
Annular Flow ◽  
Flow Boiling

Heat Transfer and Hydrodynamics of Subcooled Inverted Annular Flow Film Boiling on a Single Rod Heater

2009 ◽  
Author(s):  
Sonny Yi ◽  
Gopinath R. Warrier ◽  
Vijay K. Dhir
Keyword(s):  
Heat Transfer ◽  
Annular Flow ◽  
Flow Boiling ◽  
Film Boiling ◽  
Test Fluid ◽  
Fluid Temperature ◽  
Loss Of Coolant Accident ◽  
Wall Superheat ◽  
Set Up ◽  
Flow Film Boiling

Heat transfer during inverted annular flow boiling of a subcooled liquid was studied in this work. An experiment was set up to simulate flow downstream of a quench front during the reflooding phase of a dried out nuclear core in a loss of coolant accident. Steady-state, subcooled flow film boiling experiments were conducted inside an annular cross section consisting of a single stainless steel rod heater, 71 cm in height and 1.11 cm in diameter, which was placed concentrically within a tube of diameter 1.59 cm. The quench front location was stabilized near the test section inlet using a “hot patch”. The hot patch consisted of a 2.5 cm-long cartridge heater inserted within the inner diameter of the heater tube. All tests were performed with PF-5060 as the test fluid, with mass flux ranging from 200 to 810 kg/m2s, inlet subcooling ranging from 12 to 27 °C, and wall superheat ranging from 200 to 305 °C. The fluid temperature, wall temperature, and pressure were measured at various axial locations. Fluid temperatures in the radial direction were also measured at several axial locations. The data obtained from these experiments were used to determine the wall heat transfer coefficient and liquid side heat transfer rate.

Flow Boiling in Horizontal Tubes: Part 3—Development of a New Heat Transfer Model Based on Flow Pattern

1998 ◽  
Vol 120 (1) ◽  
pp. 156-165 ◽  
Author(s):  
N. Kattan ◽  
J. R. Thome ◽  
D. Favrat
Keyword(s):  
Heat Transfer ◽  
Annular Flow ◽  
Flow Boiling ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Two Phase ◽  
Horizontal Tubes ◽  
High Vapor ◽  
Coefficient Versus ◽  
The Heat Transfer Coefficient

A new heat transfer model for intube flow boiling in horizontal plain tubes is proposed that incorporates the effects of local two-phase flow patterns, flow stratification, and partial dryout in annular flow. Significantly, the local peak in the heat transfer coefficient versus vapor quality can now be determined from the prediction of the location of onset of partial dryout in annular flow. The new method accurately predicts a large, new database of flow boiling data, and is particularly better than existing methods at high vapor qualities (x > 85 percent) and for stratified types of flows.

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