The Experts below are selected from a list of 885 Experts worldwide ranked by ideXlab platform
Rui Zhuan - One of the best experts on this subject based on the ideXlab platform.
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simulation of boiling Flow in evaporator of separate type heat pipe with low heat flux
Annals of Nuclear Energy, 2015Co-Authors: Yiwu Kuang, Wen Wang, Rui ZhuanAbstract:Abstract The separate type heat pipe heat exchanger is considered to be a potential selection for developing passive cooling spent fuel pool – for the passive pressurized water reactor. This paper simulates the boiling Flow behavior in the evaporator of separate type heat pipe, consisting of a bundle of tubes of inner diameter 65 mm. It displays two-phase characteristic in the evaporation section of the heat pipe working in low heat flux. In this study, the two-phase Flow model in the evaporation section of the separate type heat pipe is presented. The volume of fluid (VOF) model is used to consider the interaction between the ammonia gas and liquid. The Flow patterns and Flow behaviors are studied and the agitated bubbly Flow, churn bubbly Flow are obtained, the slug bubble is likely to break into churn slug or churn Froth Flow. In addition, study on the heat transfer coefficients indicates that the nucleate boiling is the dominant mechanism in large pipes at low mass and heat flux, with the heat transfer coefficient being less sensitive to the total mass flux.
Yeung H. - One of the best experts on this subject based on the ideXlab platform.
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Two Phase Flow Patterns in Large Diameter Vertical Pipes
'Wiley', 2013Co-Authors: Ali S., Yeung H.Abstract:An experimental investigation of adiabatic upward co-current air-water two phase Flow has been carried out to determine the Flow patterns in a 12.2m high and 250mm nominal diameter vertical pipe. The visual observations of Flow patterns were supplemented by statistical analysis of the time-averaged void fraction determined by pressure drop method. Five Flow patterns were identified in the vertical test section namely – dispersed bubbly, bubbly, agitated bubbly, churn/Froth Flow within the experimental superficial velocity range (ja = 0.18-2.2m/s and jw = 0.18-1.2m/s). Conventional slug Flow consisting of smooth bullet shaped bubbles (Taylor bubble) and liquid slugs was never observed, instead agitated bubbly Flow was the most dominant Flow pattern in relevant superficial velocity range. Based on the visual and statistically extracted information, a Flow pattern map was developed and compared to the existing Flow pattern maps. Available Flow regime transition models compared against the present experimental data yielded poor agreement with none of the existing models predicting the transitions as a whole. A satisfactory agreement was obtained with other large diameter studies with inconsistencies mainly attributable to confusion in the identification of the Flow patterns
Karolos Grigoriadis - One of the best experts on this subject based on the ideXlab platform.
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Low Pressure Experimental Validation of Low-Dimensional Analytical Model for Air–Water Two-Phase Transient Flow in Horizontal Pipelines
'MDPI AG', 2021Co-Authors: Hamdi Mnasri, Amine Meziou, Matthew A. Franchek, Wai Lam Loh, Thiam Teik Wan, Nguyen Dinh Tam, Taoufik Wassar, Yingjie Tang, Karolos GrigoriadisAbstract:This paper presents a low-pressure experimental validation of a two-phase transient pipeline Flow model. Measured pressure and Flow rate data are collected for slug and Froth Flow patterns at the low pressure of 6 bar at the National University of Singapore Multiphase Flow Loop facility. The analyzed low-dimensional model proposed in comprises a steady-state multiphase Flow model in series with a linear dynamic model capturing the Flow transients. The model is based on a dissipative distributed parameter model for transient Flow in transmission lines employing equivalent fluid properties. These parameters are based solely on the Flowing conditions, fluid properties and pipeline geometry. OLGA simulations are employed as an independent method to validate the low-dimension model. Both low-dimensional and OLGA models are evaluated based on the estimated two-phase pressure transients for varying gas volume fraction (GVF). Both models estimated the two-phase Flow transient pressure within 5% mean absolute percent error of the laboratory data. Additionally, an unavoidable presence of entrained air within a pipeline is confirmed for the case of 0% GVF as evidenced by the pressure transient estimation. Thus, dampened oscillations in the simulated 0% GVF case exists owing to an increase in the fluid compressibility
Dee Bradshaw - One of the best experts on this subject based on the ideXlab platform.
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A critical analysis of Froth transportation models in flotation
2014Co-Authors: Saeed Farrokhpay, Kym Runge, Dee BradshawAbstract:It is well known that Froth phase has a controlling influence on the overall flotation performance. Froth recovery is expected to be affected by Froth transportation behaviour. The latter has been represented by different volume balance and energy balance based models. In Froth transportation models based on a volume balance, the Froth phase is divided into different zones. The total Froth residence time is the sum of the time spent in each zone and is dependent on the cell geometry, bubble burst rate and the position that bubbles enter into the Froth phase. Alternatively, the Froth transportation model based on an energy balance treats the Froth phase as a block. In this model, Froth height above the concentrate lip is being predicted by minimising the energy of the system which is dependent on the Froth geometry, Froth stability and Froth rheology. The Froth height can be used to calculate the Froth efficiency of delivering mineralized bubbles from the pulp to the concentrate lip. This paper critically analyses the current models of Froth transportation in flotation, and examines the limitations of these models. The importance of Froth rheology, which is the resistance to the Froth Flow towards the discharging weir, in determining Froth transportation, is also highlighted.
Yiwu Kuang - One of the best experts on this subject based on the ideXlab platform.
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simulation of boiling Flow in evaporator of separate type heat pipe with low heat flux
Annals of Nuclear Energy, 2015Co-Authors: Yiwu Kuang, Wen Wang, Rui ZhuanAbstract:Abstract The separate type heat pipe heat exchanger is considered to be a potential selection for developing passive cooling spent fuel pool – for the passive pressurized water reactor. This paper simulates the boiling Flow behavior in the evaporator of separate type heat pipe, consisting of a bundle of tubes of inner diameter 65 mm. It displays two-phase characteristic in the evaporation section of the heat pipe working in low heat flux. In this study, the two-phase Flow model in the evaporation section of the separate type heat pipe is presented. The volume of fluid (VOF) model is used to consider the interaction between the ammonia gas and liquid. The Flow patterns and Flow behaviors are studied and the agitated bubbly Flow, churn bubbly Flow are obtained, the slug bubble is likely to break into churn slug or churn Froth Flow. In addition, study on the heat transfer coefficients indicates that the nucleate boiling is the dominant mechanism in large pipes at low mass and heat flux, with the heat transfer coefficient being less sensitive to the total mass flux.
