Pressure Drop and Heat Transfer of Magnetohydrodynamic Annular Two-Phase Flow in Rectangular Channel

1998 ◽  
Vol 120 (1) ◽  
pp. 152-159 ◽  
Author(s):  
H. Kumamaru ◽  
Y. Fujiwara
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Liquid Flow ◽  
Single Phase ◽  
Two Phase Flow ◽  
Rectangular Channel ◽  
Phase Flow ◽  
Two Phase ◽  
Phase Liquid ◽  
Single Phase Liquid Flow

An annular two-phase flow model has been proposed to predict the pressure drop and heat transfer of magnetohydrodynamic (MHD) gas-liquid metal two-phase flow in a rectangular channel for the case of high void fraction. The model for a rectangular channel, in which the applied magnetic field is perpendicular to the short side of the channel cross-section, nearly predicts Inoue et al.’s experimental data on the MHD pressure drop. For fusion reactor conditions, the model shows calculated results that the MHD pressure drop for two-phase flow can be lowered to 10 percent of that of the single-phase liquid flow and the heat transfer coefficient can be increased by a factor of two or more over that of the single-phase liquid flow.

Modeling Two-Phase Flow in Pipe Bends

2004 ◽  
Vol 127 (2) ◽  
pp. 204-209 ◽  
Author(s):  
Savalaxs Supa-Amornkul ◽  
Frank R. Steward ◽  
Derek H. Lister
Keyword(s):  
Pressure Drop ◽  
Single Phase ◽  
Two Phase Flow ◽  
Cfd Modeling ◽  
Phase Flow ◽  
Water Mixture ◽  
Two Phase ◽  
Candu Reactors ◽  
Phase Liquid ◽  
Visualization Experiments

In order to have a better understanding of the interaction between the two-phase steam-water coolant in the outlet feeder pipes of the primary heat transport system of some CANDU reactors and the piping material, themalhydraulic modelling is being performed with a commercial computational fluid dynamics (CFD) code—FLUENT 6.1. The modeling has attempted to describe the results of flow visualization experiments performed in a transparent feeder pipe with air-water mixtures at temperatures below 55°C. The CFD code solves two sets of transport equations—one for each phase. Both phases are first treated separately as homogeneous. Coupling is achieved through pressure and interphase exchange coefficients. A symmetric drag model is employed to describe the interaction between the phases. The geometry and flow regime of interest are a 73 deg bend in a 5.9cm diameter pipe containing water with a Reynolds number of ∼1E5-1E6. The modeling predicted single-phase pressure drop and flow accurately. For two-phase flow with an air voidage of 5–50%, the pressure drop measurements were less well predicted. Furthermore, the observation that an air-water mixture tended to flow toward the outside of the bend while a single-phase liquid layer developed at the inside of the bend was not predicted. The CFD modeling requires further development for this type of geometry with two-phase flow of high voidage.

Asymptotic Generalizations of the Lockhart-Martinelli Method for Two Phase Flows

2009 ◽  
Author(s):  
Y. S. Muzychka ◽  
M. M. Awad
Keyword(s):  
Pressure Drop ◽  
Single Phase ◽  
Two Phase Flow ◽  
Point Of View ◽  
Phase Flow ◽  
Pressure Gradients ◽  
Two Phase ◽  
Interfacial Pressure ◽  
Phase Liquid ◽  
Flow Pressure

The Lockhart-Martinelli method for predicting two phase flow pressure drop is examined from the point of view of asymptotic modelling. Comparisons are made with the Lockhart-Martinelli method, the Chisholm method, and the Turner-Wallis method. An alternative approach for predicting two phase flow pressure drop is developed using superposition of three pressure gradients: single phase liquid, single phase gas, and interfacial pressure drop. This new approach allows for the interfacial pressure drop to be easily modelled for each type of flow regime such as: bubbly, mist, churn, plug, stratified, and annular, or based on the classical laminar-laminer, turbulent-turbulent, laminar-turbulent and turbulent-laminar flow regimes proposed by Lockhart and Martinelli.

Modelling Two-Phase Flow in Pipe Bends

2004 ◽  
Author(s):  
S. Supa-Amornkul ◽  
F. R. Steward ◽  
D. H. Lister
Keyword(s):  
Pressure Drop ◽  
Single Phase ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Water Mixture ◽  
Cfd Modelling ◽  
Two Phase ◽  
Candu Reactors ◽  
Phase Liquid ◽  
Visualization Experiments

In order to have a better understanding of the interaction between the two-phase steam-water coolant in the outlet feeder pipes of the primary heat transport system of some CANDU reactors and the piping material, themalhydraulic modelling is being performed with a commercial CFD (computational fluid dynamics) code — Fluent 6.1. The modelling has attempted to describe the results of flow visualization experiments performed in a transparent feeder pipe with air-water mixtures at temperatures below 55°C. The CFD code solves two sets of transport equations — one for each phase. Both phases are first treated separately as homogeneous. Coupling is achieved through pressure and interphase exchange coefficients. A symmetric drag model is employed to describe the interaction between the phases. The geometry and flow regime of interest are a 73° bend in a 5.9 cm-diameter pipe containing water with a Reynolds number of ∼105–106. The modelling predicted single-phase pressure drop and flow accurately. For two-phase flow with an air voidage of 5%–50%, the pressure drop measurements were less well predicted. Furthermore, the observation that an air-water mixture tended to flow toward the outside of the bend while a single-phase liquid layer developed at the inside of the bend was not predicted. The CFD modelling requires further development for this type of geometry with two-phase flow of high voidage.

Two-Phase Flow and Heat Transfer in Rectangular Micro-Channels

2003 ◽  
Author(s):  
Weilin Qu ◽  
Seok-Mann Yoon ◽  
Issam Mudawar
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Heat Sinks ◽  
Phase Flow ◽  
Micro Channel ◽  
Two Phase ◽  
Micro Channels

Knowledge of flow pattern and flow pattern transitions is essential to the development of reliable predictive tools for pressure drop and heat transfer in two-phase micro-channel heat sinks. In the present study, experiments were conducted with adiabatic nitrogen-water two-phase flow in a rectangular micro-channel having a 0.406 × 2.032 mm cross-section. Superficial velocities of nitrogen and water ranged from 0.08 to 81.92 m/s and 0.04 to 10.24 m/s, respectively. Flow patterns were first identified using high-speed video imaging, and still photos were then taken for representative patterns. Results reveal that the dominant flow patterns are slug and annular, with bubbly flow occurring only occasionally; stratified and churn flow were never observed. A flow pattern map was constructed and compared with previous maps and predictions of flow pattern transition models. Annual flow is identified as the dominant flow pattern for conditions relevant to two-phase micro-channel heat sinks, and forms the basis for development of a theoretical model for both pressure drop and heat transfer in micro-channels. Features unique to two-phase micro-channel flow, such as laminar liquid and gas flows, smooth liquid-gas interface, and strong entrainment and deposition effects are incorporated into the model. The model shows good agreement with experimental data for water-cooled heat sinks.

Experimental Study on Heat Transfer of Single-Phase Flow and Boiling Two-Phase Flow in Vertical Narrow Annuli

2002 ◽  
Author(s):  
Suizheng Qiu ◽  
Minoru Takahashi ◽  
Guanghui Su ◽  
Dounan Jia
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Two Phase Flow ◽  
Annular Channel ◽  
Phase Flow ◽  
Single Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Narrow Annuli ◽  
Narrow Gaps

Water single-phase and nucleate boiling heat transfer were experimentally investigated in vertical annuli with narrow gaps. The experimental data about water single-phase flow and boiling two-phase flow heat transfer in narrow annular channel were accumulated by two test sections with the narrow gaps of 1.0mm and 1.5mm. Empirical correlations to predict the heat transfer of the single-phase flow and boiling two-phase flow in the narrow annular channel were obtained, which were arranged in the forms of the Dittus-Boelter for heat transfer coefficients in a single-phase flow and the Jens-Lottes formula for a boiling two-phase flow in normal tubes, respectively. The mechanism of the difference between the normal channel and narrow annular channel were also explored. From experimental results, it was found that the turbulent heat transfer coefficients in narrow gaps are nearly the same to the normal channel in the experimental range, and the transition Reynolds number from a laminar flow to a turbulent flow in narrow annuli was much lower than that in normal channel, whereas the boiling heat transfer in narrow annular gap was greatly enhanced compared with the normal channel.

A Multiobjective Parameter Study of Two-Phase Flow Channel Design

2020 ◽  
Author(s):  
Nicholas A. Evich ◽  
Nicholas R. Larimer ◽  
Mary I. Frecker ◽  
Matthew J. Rau
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Two Phase Flow ◽  
Circular Cross Section ◽  
Parameter Study ◽  
Phase Flow ◽  
Two Phase ◽  
Flow And Heat Transfer ◽  
High Heat Transfer ◽  
Manufacturing Techniques

Abstract Advanced manufacturing techniques have improved dramatically in recent years and design freedom for engineered components and systems has never been greater. Despite these advancements, the majority of our design tools for thermal-fluids systems are still rooted within traditional architectures and manufacturing techniques. In particular, the complex nature of two-phase flow and heat transfer has made the development of design methods that can accommodate these complex geometries enabled by new manufacturing techniques challenging. Here, we investigate a new design method for two-phase flow systems. We conduct a multiobjective parameter study considering two-phase flow and heat transfer through a single channel with a circular cross section. To increase our design degrees of freedom, we allow the channel to increase or decrease in cross-sectional area along its flow length, but constrain the channel inlet and outlet to a constant hydraulic diameter. Maximizing heat transfer and minimizing pressure drop are the two design objectives, which we evaluate using two-phase heat transfer correlations and the Homogeneous Equilibrium Model. We find that using small expansion angles can greatly reduce two-phase flow pressure drop and also provide high heat transfer coefficients when compared to straight channel designs. We present a set of feasible designs for varying input heat fluxes, liquid mass flow rates, and channel orientation angles and show how the ideal expansion channel angle varies with these operational conditions.

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