Two-Phase Pressure Drop of CO2 in Mini Tubes and Microchannels

2003 ◽  
Author(s):  
R. Yun ◽  
Y. Kim
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Large Diameter ◽  
Two Phase ◽  
Heating Method ◽  
Pressure Drops ◽  
Direct Heating ◽  
Frictional Pressure Drop ◽  
Phase Pressure

Two-phase pressure drops of CO2 are investigated in mini tubes with inner diameters of 2.0 and 0.98 mm and in microchannels with hydraulic diameters from 1.08 to 1.54 mm. For the mini tubes, the tests were conducted with a variation of mass flux from 500 to 3570 kg/m2s, heat flux from 7 to 48 kW/m2, while maintaining saturation temperatures at 0°C, 5°C and 10°C. For the microchannels, mass flux was varied from 100 to 400 kg/m2s, and heat flux was altered from 5 to 20 kW/m2. A direct heating method was used to provide heat into the refrigerants. The pressure drop of CO2 in mini tubes shows very similar trends with that in large diameter tubes. Although the microchannel has a small hydraulic diameter, two-phase effects on frictional pressure drop are significant. The Chisholm parameter of the Lockhart and Martinelli correlation is modified by considering diameter effects on the two-phase frictional multiplier.

Two-Phase Pressure Drop of Ammonia in a Mini/Micro-Channel

2010 ◽  
Author(s):  
M. Hamayun Maqbool ◽  
Bjo¨rn Palm ◽  
R. Khodabandeh ◽  
Rashid Ali
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Homogeneous Model ◽  
Working Fluid ◽  
Uniform Heat Flux ◽  
Internal Diameter ◽  
Two Phase ◽  
Frictional Pressure Drop ◽  
Phase Pressure

Experiments have been performed to investigate two-phase pressure drop in a circular vertical mini-channel made of stainless steel (AISI 316) with internal diameter of 1.70 mm and a uniformly heated length of 245 mm using ammonia as working fluid. The experiments are conducted for heat flux range of 15 to 350 kW/m2 and mass flux range of 100 to 500 kg/m2s. A uniform heat flux is applied to the test section by DC power supply. Two phase frictional pressure drop variation with mass flux, vapour quality and heat flux was determined. The experimental results are compared to predictive methods available in literature for frictional pressure drop. The Homogeneous model and the correlation of Mu¨ller Steinhagen et al. [14] are in good agreement with our experimental data with MAD of 27% and 26% respectively.

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.

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.

The Numerical Calculation of Two-Phase Pressure Drop During Flow Boiling in the Vertical Annular Channel

2008 ◽  
Author(s):  
Ruosu Wang ◽  
Changhong Peng ◽  
Tao Zhou ◽  
Shichao Wang
Keyword(s):  
Heat Flux ◽  
Numerical Calculation ◽  
Pressure Drop ◽  
Mass Flux ◽  
Flow Model ◽  
Flow Boiling ◽  
Annular Channel ◽  
Phase Flow ◽  
Two Phase ◽  
Phase Pressure

In this paper, according to a separated phase flow model for annular two-phase flow in the vertical annular channel, the liquid film thickness, void fraction and two-phase pressure drop along the flow channel are predicted. The calculated pressure drop values are compared with that measured in experiment in the range of mass flux from 38.8 to 163.1kg/m2s; pressure from 1.5 to 6.0 MPa; and heat flux from 4.9 to 50.7kW/m2 for inside tube and from 4.2 to 78.8kW/m2 for outside tube. It can be found that the model can predict the pressure drop well. With the mass flux increasing and the gap of the annular channel decreasing, pressure drop increases.

Forced Convective Boiling of Refrigerant HCFC123 in a Mini-Tube

2010 ◽  
Author(s):  
Koichi Araga ◽  
Keisuke Okamoto ◽  
Keiji Murata
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Mass Flux ◽  
Pool Boiling ◽  
Constant Heat Flux ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Convective Boiling ◽  
Frictional Pressure Drop ◽  
Heat Transfer Coefficients

This paper presents an experimental investigation of the forced convective boiling of refrigerant HCFC123 in a mini-tube. The inner diameters of the test tubes, D, were 0.51 mm and 0.30 mm. First, two-phase frictional pressure drops were measured under adiabatic conditions and compared with the correlations for conventional tubes. The frictional pressure drop data were lower than the correlation for conventional tubes. However, the data were qualitatively in accord with those for conventional tubes and were correlated in the form φL2−1/Xtt. Next, heat transfer coefficients were measured under the conditions of constant heat flux and compared with those for conventional tubes and for pool boiling. The heat transfer characteristics for mini-tubes were different from those for conventional tubes and quite complicated. The heat transfer coefficients for D = 0.51 mm increased with heat flux but were almost independent of mass flux. Although the heat transfer coefficients were higher than those for a conventional tube with D = 10.3 mm and for pool boiling in the low quality region, they decreased gradually with increasing quality. The heat transfer coefficients for D = 0.30 mm were higher than those for D = 0.51 mm and were almost independent of both mass flux and heat flux.

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.

Two-Phase Pressure Drop and Boiling Heat Transfer in a Single Horizontal Microchannel

2006 ◽  
Author(s):  
Cheol Huh ◽  
Moo Hwan Kim
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Local Flow ◽  
Heat Transfer Coefficients ◽  
Phase Pressure

With a single microchannel and a series of microheaters made with MEMS technique, two-phase pressure drop and local flow boiling heat transfer were investigated using deionized water in a single horizontal rectangular microchannel. The test microchannel has a hydraulic diameter of 100 μm and length of 40 mm. A real time observation of the flow patterns with simultaneous measurement are made possible. Tests are performed for mass fluxes of 90, 169, and 267 kg/m2s and heat fluxes of from 100 to 600 kW/m2. The experimental local flow boiling heat transfer coefficients and two-phase frictional pressure gradient are evaluated and the effects of heat flux, mass flux, and vapor qualities on flow boiling are studied. Both the evaluated experimental data are compared with existing correlations. The experimental heat transfer coefficients are nearly independent on mass flux and the vapor quality. Most of all correlations do not provide reliable heat transfer coefficients predictions with vapor quality and prediction accuracy. As for two-phase pressure drop, the measured pressure drop increases with the mass flux and heat flux. Most of all existing correlations of two-phase frictional pressure gradient do not predict the experimental data except some limited conditions.

Frictional Pressure Drop of Gas-Newtonian and Gas-Non Newtonian Slug Flow in Vertical Pipe

2011 ◽  
Vol 9 (1) ◽  
Author(s):  
Subrata Kumar Majumder ◽  
Sandip Ghosh ◽  
Gautam Kundu ◽  
Arun Kumar Mitra
Keyword(s):  
Pressure Drop ◽  
Slug Flow ◽  
Amyl Alcohol ◽  
Newtonian Liquid ◽  
Vertical Pipe ◽  
Two Phase ◽  
Vertical Column ◽  
Frictional Pressure Drop ◽  
Liquid Systems ◽  
Phase Pressure

Experimental study on two-phase pressure drop in a vertical pipe with air-Newtonian and non-Newtonian liquid in slug flow regime has been carried out within a range of gas and liquid flowrate of 0.5×10-4 to 1.92×10-4 m-3/s and 1.6×10-4 to 6.7×10-4 m3/s respectively. In the present study air and four types of liquids such as water, amyl alcohol, glycerin (two different concentrations), and CMC (Sodium Carboxymethyl Cellulose) are used. The present data were analyzed by two-phase friction method. To predict the two-phase pressure drop, correlations have been developed with Newtonian and non-Newtonian liquid. A general correlation was also developed to predict the two-phase pressure drop in a vertical column of diameter 0.01905 m and 3.4 m height combining both the Newtonian and non-Newtonian liquid systems.

Pressure Drop in a Capillary Tube in Boiling Two-Phase Flow

2003 ◽  
Author(s):  
Fumito Kaminaga ◽  
Baduge Sumith ◽  
Kunihito Matsumura
Keyword(s):  
Pressure Drop ◽  
Vapor Phase ◽  
Mass Flux ◽  
Two Phase Flow ◽  
Capillary Tube ◽  
Flow Boiling ◽  
Phase Flow ◽  
Two Phase ◽  
System Pressure ◽  
Phase Pressure

Two-phase pressure drop is experimentally examined in a flow boiling condition in a tube of diameter 1.45 mm using water in ranges of pressure from 10 to 100 kPa, mass flux from 18 to 152 kg/m2s, heat flux from 13 to 646 kW/m2, and exit quality from 0.02 to 0.77. Also, pressure drop in an adiabatic air-water two-phase flow is measured at atmospheric pressure using the same test section and mass flux ranges of liquid and gas as those in the flow boiling. Decreasing system pressure the pressure drop significantly increases at a given mass flux. Influence of vapor phase on the pressure drop is found to be large both in the adiabatic and the diabatic conditions. The frictional pressure drop correlation for the adiabatic two-phase flow is developed and applied to predict pressure drop in the flow boiling. But it cannot give satisfactory predictions. The Chisholm correlation calculating a two-phase pressure drop multiplier is modified to account the influence of vapor phase in a capillary tube and the modified correlation can predict the pressure drop in the flow boiling within an error of 20%.

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