A Study of Non-Equilibrium Two-Phase Pressure Drop in Converging Channels Supplied With Atomized Liquid

2006 ◽  
Author(s):  
J. D. Schwarzkopf ◽  
C. T. Crowe ◽  
B. Q. Li
Keyword(s):  
Numerical Model ◽  
Pressure Drop ◽  
Phase Change ◽  
Heat Fluxes ◽  
Two Phase ◽  
Converging Channel ◽  
Mini Channels ◽  
Phase Pressure ◽  
Good Agreement ◽  
Non Equilibrium

Two-phase pressure drop measurements are very difficult to make while the fluid is in non-equilibrium condition (i.e. while phase change is occurring). This is further complicated by the fact that supplying the channels with an initial quality comprised of atomized liquid and entrained gas changes the presupposed trends. The purpose of this paper is to present methods of measurement for fluctuating two-phase pressure drop in converging mini-channels with phase change (i.e. in the heat acquisition zone), an initial quality, and varying heat fluxes. The inlet and exit hydraulic diameters of the converging channel are 1.55mm and 1.17mm respectively and the fluid was PF5050. A numerical model was developed to understand the parameters contributing to the trends identified in the data. The numerical model includes the momentum effects of droplets from entrainment and atomization. The model shows good agreement with the experimental data.

High Heat Flux Subcooled Flow Boiling of Methanol in Microtubes

2015 ◽  
Author(s):  
Farzad Houshmand ◽  
Hyoungsoon Lee ◽  
Mehdi Asheghi ◽  
Kenneth E. Goodson
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Flow Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Two Phase ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
Inner Diameter ◽  
Phase Pressure

As the proper cooling of the electronic devices leads to significant increase in the performance, two-phase heat transfer to dielectric liquids can be of an interest especially for thermal management solutions for high power density devices with extremely high heat fluxes. In this paper, the pressure drop and critical heat flux (CHF) for subcooled flow boiling of methanol at high heat fluxes exceeding 1 kW/cm2 is investigated. Methanol was propelled into microtubes (ID = 265 and 150 μm) at flow rates up to 40 ml/min (mass fluxes approaching 10000 kg/m2-s), boiled in a portion of the microtube by passing DC current through the walls, and the two-phase pressure drop and CHF were measured for a range of operating parameters. The two-phase pressure drop for subcooled flow boiling was found to be significantly lower than the saturated flow boiling case, which can lead to lower pumping powers and more stability in the cooling systems. CHF was found to be increasing almost linearly with Re and inverse of inner diameter (1/ID), while for a given inner diameter, it decreases with increasing heated length.

Analysis of Two-Phase Pressure Drop Fluctuation Characteristics in a Single Mini-Channel

2016 ◽  
Vol 366 ◽  
pp. 151-156
Author(s):  
Bei Chen Zhang ◽  
Qing Lian Li ◽  
Yuan Wang ◽  
Jian Qiang Zhang
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Flow Boiling ◽  
Circular Cross Section ◽  
Low Frequency ◽  
Amplitude Fluctuation ◽  
Heat Fluxes ◽  
Two Phase ◽  
Phase Pressure

Two-phase pressure drop fluctuations during flow boiling in a single mini-channel were experimentally investigated. Degassed water was tested in circular cross section mini-channels with the hydraulic diameter of 1.0 mm at liquid mass fluxes range of 21.19-84.77 kg m-2 s-1 and heat fluxes of 0~155.75 kW m-2. Effects of heat flux and mass flux on pressure drop fluctuations were discussed based on the time and frequency domain analysis of the measured pressure drop. Two types of fluctuations were identified, which are the incipient boiling fluctuation (IBF) and the explosive boiling fluctuation (EBF) respectively. The IBF is a low frequency low amplitude fluctuation, which relates to the bubble dynamics when incipient boiling occurs. It is sensitive to the thermal and flow conditions. With the increase of heat flux and mass flux, the IBF is suppressed. The EBF is a low frequency high amplitude fluctuation, which occurs near the critical heat flux.

F221 Two-Phase Pressure Drop through Return Bend in Micro- and Mini-channels

2015 ◽  
Vol 2015.20 (0) ◽  
pp. 373-376
Author(s):  
Akimaro KAWAHARA ◽  
Michio SADATOMI ◽  
Shinichi MIYAGAWA
Keyword(s):  
Pressure Drop ◽  
Two Phase ◽  
Mini Channels ◽  
Phase Pressure

On the Operational Parameters Effects on Two-Phase Pressure Drop Characteristics of Reentrant Copper Microchannels

2016 ◽  
Author(s):  
Daxiang Deng ◽  
Qingsong Huang ◽  
Yanlin Xie ◽  
Wei Zhou ◽  
Xiang Huang ◽  
...  
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Heat Sink ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Two Phase ◽  
Cooling Systems ◽  
Phase Pressure

Two-phase boiling in advanced microchannel heat sinks offers an efficient and attractive solution for heat dissipation of high-heat-flux devices. In this study, a type of reentrant copper microchannels was developed for heat sink cooling systems. It consisted of 14 parallel Ω-shaped reentrant copper microchannels with a hydraulic diameter of 781μm. Two-phase pressure drop characteristics were comprehensively accessed via flow boiling tests. Both deionized water and ethanol tests were conducted at inlet subcooling of 10°C and 40°C, mass fluxes of 125–300kg/m2·s, and a wide range of heat fluxes and vapor qualities. The effects of heat flux, mass flux, inlet subcoolings and coolants on the two-phase pressure drop were systematically explored. The results show that the two-phase pressure drop of reentrant copper microchannels generally increased with increasing heat fluxes and vapor qualities. The role of mass flux and inlet temperatures was dependent on the test coolant. The water tests presented smaller pressure drop than the ethanol ones. These results provide critical experimental information for the development of microchannel heat sink cooling systems, and are of considerable practical relevance.

Experimental Study on Two-Phase Pressure Drop of Air-Water in Horizontal Mini Channel

2014 ◽  
Author(s):  
Ravi S. Engineer ◽  
Hemant B. Mehta
Keyword(s):  
Pressure Drop ◽  
Single Phase ◽  
Water Mixture ◽  
Two Phase ◽  
New Correlation ◽  
Flow Test ◽  
Mini Channels ◽  
Glass Tubes ◽  
Straight Flow ◽  
Phase Pressure

The new correlation for two-phase pressure drop for mini channel is developed by performing experiment on adiabatic two-phase pressure drop in mini channel with 3.1 mm diameter. Air-water mixture is used as the working substance. 180°-90°-90° (straight flow) test sections made of transparent glass tubes of 3.1 mm diameter with lengths of 900 mm. The superficial velocity varies from 0.2238 m/s to 1.1876 m/s for liquid (UL) and air (UG). Two phase flow pressure drop experiment is divided into two parts. First single phase pressure drop for air and water is experimented. The diameter is verified by measuring pressure drop of the air. Single phase pressure drop for air and water is experimented first which is followed by two phase pressure drop in the same mini channel. The existing correlations for macro and mini-channels are compared with the experimental data. Using Matlab & Minitab; a new correlation has been developed to predict two-phase pressure drop in horizontal mini channels.

scholarly journals Experimental study on two-phase pressure drop of air-water in small diameter tubes at horizontal orientation

2014 ◽  
Vol 18 (2) ◽  
pp. 521-532 ◽  
Author(s):  
Arun Autee ◽  
Srinivasa Rao ◽  
Ravikumar Puli ◽  
Ramakant Shrivastava
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Mass Flux ◽  
Small Diameter ◽  
Water Mixture ◽  
Two Phase ◽  
Horizontal Orientation ◽  
Mini Channels ◽  
Total Mass Flux ◽  
Phase Pressure

Experimental results of adiabatic two-phase pressure drop in small diameter tubes are presented in this work. Air-water mixture is used as the working substance. Four test sections made of transparent acrylic tubes of different internal diameters ranging from 3.0 mm to 8.0 mm are used with different test section lengths from 150 mm to 400 mm. The investigation is carried out within the range of mass flux of water 16.58 -3050 kg/m2s, mass flux of air 8.25-204.10 kg/m2s and total mass flux 99.93-3184.69 kg/m2s. Some of the existing correlations for macro and mini-channels are compared with the experimental data. Based on the experimental data; a new correlation has been developed to predict two-phase pressure drop in horizontal channels.

Single and two-phase pressure drop in serpentine mini-channels

2011 ◽  
Vol 50 (8) ◽  
pp. 877-884 ◽  
Author(s):  
Adam A. Donaldson ◽  
Deepak M. Kirpalani ◽  
Arturo Macchi
Keyword(s):  
Pressure Drop ◽  
Two Phase ◽  
Mini Channels ◽  
Phase Pressure
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