Pressure Drop of Two-Phase Flow in a Pipeline with Longitudinal Variations in Heat Flux

1995 ◽  
pp. 378-381
Author(s):  
P. S. Shen ◽  
Y. W. Jao
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Longitudinal Variations

Experimental Investigation and Flow Visualization of the Two-Phase Flow Instability at Low Vapor Quality in a Vertical Narrow Channel

2018 ◽  
Author(s):  
Liqiang Pan ◽  
Yang Liu ◽  
Weihua Li ◽  
Yefei Liu
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Test Section ◽  
Two Phase Flow ◽  
Flow Instability ◽  
Narrow Channel ◽  
Bubble Nucleation ◽  
Phase Flow ◽  
Vapor Quality ◽  
Two Phase

The two-phase flow instability of forced convection has been experimentally investigated in a vertical narrow channel with the hydraulic diameter of 2.857mm and aspect ratio of 20. Transparent, metallic and conductive films on external surfaces of the test section can provide visualization and uniform heating for deionized water. The heat flux is 6–18.2 kW · m−2. When the instability occurs at low vapor quality, a series of parameters are measured and visualized images are obtained by a high-speed camera. The results show that the large amplitude of pressure drop between the inlet and outlet in the test section is due to the elongated bubble, and the value of pressure drop is positively correlated with the volume of the bubble. The oscillation period of pressure drop decreases with the increase of heat flux, and the period can be determined by the method of the Fast Fourier Transform. The backflow phenomenon is analyzed, which has a greater effect on the oscillation of pressure drop than bubble nucleation, bubble growth, bubble coalescence and recoiling of bubble boundary.

Characteristics of Two-Phase Flow Pressure Drop of Propane in Horizontal Circular Small Tube

2016 ◽  
Vol 819 ◽  
pp. 371-375
Author(s):  
Agus Sunjarianto Pamitran ◽  
Sentot Novianto ◽  
T.A. Simanjuntak ◽  
Nasruddin ◽  
Muhammad Idrus Alhamid
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Two Phase Flow ◽  
Saturation Temperature ◽  
Experimental Result ◽  
Phase Flow ◽  
Two Phase ◽  
Small Tube ◽  
Flow Pressure

This study experimentally investigated two-phase flow pressure drop of propane as refrigerant in horizontal small tube. Inner diameter and length of the tube were 7.6 mm and 1.07 m, respectively. In order to get pressure drop data, the experiment was conducted in various conditions of 10 to 25 kW m-2 heat flux, 200 to 628 kg m-2 s-1 mass flux, and 4.0 to 11.7°C saturation temperature. This study clearly showed the effect of heat flux, mass flux, and saturation temperature on the pressure drop of propane. This study also investigated which fluid properties gave higher effect on the frictional pressure drop due to its change over the process based on the recent experiment data. The existing pressure drop correlations were evaluated against the experimental result.

scholarly journals A Separated-Flow Model for Predicting Flow Boiling Critical Heat Flux and Pressure Drop Characteristics in Microchannels

2012 ◽  
Author(s):  
Tie Jun Zhang ◽  
Siyu Chen ◽  
Evelyn N. Wang
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Critical Heat Flux ◽  
Flow Model ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Separated Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Microchannel Cooling

Two-phase microchannel cooling promises high heat flux removal for high-performance electronics and photonics. However, the heat transfer performance of flow boiling microchannels is limited by the critical heat flux (CHF) conditions. For variable heat inputs and variable fluid flows, it is essential to predict CHFs accurately for effective and efficient two-phase microchannel cooling. To characterize the CHF and pressure drop in flow boiling microchannels, a separated-flow model is proposed in this paper based on fundamental two-phase flow mass, energy, momentum conservation and wall energy conservation laws. With this theoretical framework, the relationship among liquid/vapor interfacial instability, two-phase flow characteristics and CHF is further studied. This mechanistic model also provides insight into the design and operational guidelines for advanced electronics and photonics cooling technologies.

Pressure Drop of Two-Phase Flow Boiling with R-22 and R-290 in 7.6 mm Diameter Tube

2016 ◽  
Vol 818 ◽  
pp. 23-27
Author(s):  
Agus Sunjarianto Pamitran ◽  
Nasruddin ◽  
Helmi Dadang Ardiansyah ◽  
Muhammad Idrus Alhamid
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Phase Flow ◽  
Lower Mass ◽  
Two Phase ◽  
Experimental Pressure

The characteristics of two-phase flow boiling of R-290 are required for replacing R-22 that has been phased-out. The present study focuses on experimental pressure drop for R-22 and R-290. The experiment was run with heat flux of 5.09 kW/m2 to 19.03 kW/m2, mass flux of 114.91 kg/m2s to 751.74 kg/m2s and saturation temperature of 4.77°C to 18.12°C. The present result showed that pressure drop was affected by heat flux, mass flux and saturation temperature. Lower mass flux, heat flux and saturation temperature results in lower pressure drop. The pressure drop of R-290 is lower than that of R-22. Among the existing pressure drop prediction methods, Lokhart-Martinelli (1949) gives the best prediction for the present pressure drop data.

Experimental Study of Flow Boiling in Microchannel

2007 ◽  
Author(s):  
S. G. Singh ◽  
S. P. Duttagupta ◽  
A. M. Kulkarni ◽  
B. P. Puranik ◽  
A. Agrawal
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Flow Rate ◽  
Heat Input ◽  
Boiling Heat Transfer ◽  
Two Phase Flow ◽  
Phase Region ◽  
Phase Flow ◽  
Two Phase

With the reduction in size of electronic devices, the problem of efficient cooling is becoming more and more severe. Boiling heat transfer in microchannels is fast emerging as a promising solution to the problem. In the present work, microchannels were fabricated on a silicon wafer. A chrome-gold micro-heater was integrated and characterized on the other side of the wafer. The change in resistance of the micro-heater in the temperature range of 20 °C – 120 °C was found to be within 10%. Deionized water was used as working fluid in microchannel. The single-phase pressure drop across the microchannel was found to increase linearly with increasing flow rate in confirmation with conventional laminar flow theory. Also, the pressure drop decreases with an increase in heat input due to a reduction in viscosity. The study was extended to two phase flow with flow rate and heat flux as the control parameters. The onset of two phase flow, at a given heat flux, with a decrease in flow rate, can be identified by the departure of linear pressure drop to non-linearity; this point was also confirmed through visual observation. In two-phase region of flow, pressure drop was found to increase initially, passes through a maximum and then decreases, with a decrease in flow rate. The experiments are performed for several heat fluxes. Both the onset of two phase and maximum pressure drop in the two phase region shifts to higher flow rates with an increase in heat input. Such detailed experimental results seem to be missing from the literature and are expected to be useful for modeling of boiling heat transfer in microchannels. Another pertinent observation is presence of instability in two-phase flow. It was found that at higher flow rate and heat flux instability in two-phase flow was more. An attempt to record these instabilities was made and preliminary data on their frequency will be presented. This study may help to choose suitable operating conditions for a microchannel heat sink for use in electronics cooling.

scholarly journals X-ray Imaging-Based Void Fraction Measurement in Saturated Flow Boiling Experiments with Seawater Coolant

2021 ◽  
Vol 5 (4) ◽  
pp. 31
Author(s):  
Seth Eckels ◽  
Zayed Ahmed ◽  
Molly Ross ◽  
Daniel Franken ◽  
Steven Eckels ◽  
...  
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Void Fraction ◽  
Test Section ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Tap Water ◽  
Phase Flow ◽  
Two Phase ◽  
X Ray

Recent studies have shown that the presence of dissolved salts in water can exhibit peculiar flow boiling and two-phase flow regimes. Two-phase flow and convective flow boiling are typically characterized with the help of void fraction measurements. To quantitatively improve our understanding of two-phase flow and boiling phenomenon with seawater coolant, void fraction data are needed, which can not be obtained from optical imaging. In this paper, we present experimental void fraction measurements of saturated flow boiling of tap water and seawater using X-ray radiography. X-rays with a maximum energy level of 40 KeV were used for imaging the exit region of the heated test section. At lower heat flux levels, the two phase flow in seawater was bubbly and homogeneous in nature, resulting in higher void fractions as compared to tap water. With an increase in heat flux, the flow regime was similar to slug flow, and void fraction measurements approached similarity with tap water. The predicted pressure drop using the measured void faction shows good agreement with the measured total pressure drop across the test section, demonstrating the validity of the measurement process.

Study on Flow Boiling Heat Transfer and Two-Phase Flow Pressure Drop in Flat Mini-Channel

2009 ◽  
Author(s):  
Yasuo Koizumi ◽  
Hiroyasu Ohtake ◽  
Ken Sato
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Cross Section ◽  
Boiling Heat Transfer ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Wide Cross ◽  
Flow Pressure

Flow and the heat transfer characteristics of boiling two-phase flow of water in flat mini-rectangular-channels were examined. The cross-sections tested were 1.0×10 to 0.2×10 mm and the flow channel length was 250 mm. Single phase flow pressure drop was well expressed by the method for the usual size in the present experimental range. Boiling heat transfer of 0.5 mm high and 10 mm wide cross section was similar to that of the usual size. However, that 0.2 mm high and 10 mm wide cross section was a little different from that of the usual size. An increase in the heat flux after the onset of nucleate boiling on the boiling curve is milder than that of the usual size. Thus, the critical heat flux was lower than that of the usual size. Flow patterns observed in the present experiments were a little different from the Baker flow pattern chart. Consistent agreement was not obtained between the present results of the two-phase flow pressure drop and predictions by the methods for the usual size and also for a mini tube. Subcooled boiling was observed widely in the test section. This made it difficult to determine the local conditions such as quality that was necessary to calculate the Lockhart-Martinelli parameter for the two-phase flow pressure drop prediction.

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