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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Response of a slotted plate flow meter to horizontal two phase flow

Muralidharan, Vasanth 17 February 2005 (has links)
The slotted plate flow meter has been widely tested as an obstruction flow meter during the past several years. It has been tested for both single-phase flows as well as for two-phase flows. Previous studies have revealed that the slotted plate flow meter is always better in performance and accuracy than the standard orifice plate flow meter. This study is primarily based on how a slotted plate responds to horizontal two-phase flow with air and water being used as the working fluids. The plates under consideration are those with beta ratios of 0.43 and 0.467. Experiments have been performed with six different configurations of the slotted plate test sections. The performances of the slotted plate flow meters will be compared to that of a standard orifice plate flow meter and then with a venturi. The effects of varying the upstream quality of the two-phase flow on the differential pressure and the coefficient of discharge of the slotted plates, the standard orifice plate and the venturi will be evaluated. Response characteristics at low differential pressures will be investigated. Tests for repeatability will be performed by studying the effects of the gas Reynolds number and the upstream quality on the differential pressure. The differential pressures across the slotted plates, the standard orifice plate and the venturi will be compared. Reproducibility will be evaluated by comparing the data obtained from all six different configurations. One of the main objectives of this study is to arrive at the best suitable procedure for accurately measuring the flow rate of two-phase flow using the slotted plate flow meter.
72

Reduced gravity Rankine cycle system design and optimization study with passive vortex phase separation

Supak, Kevin Robert 10 October 2008 (has links)
Liquid-metal Rankine power conversion systems (PCS) coupled with a fission reactor remain an attractive option for space power applications because system specific power and efficiency is very favorable for plant designs of 100 kW(e) or higher. Potential drawbacks to the technology in a reduced gravity environment include two-phase fluid management processes such as liquid-vapor phase separation. The most critical location for phase separation is at the boiler exit where only vapor must be sent to the turbine because blade erosion occurs from high velocity liquid droplets entrained by vapor flow. Previous studies have proposed that rotary separators be used to separate the liquid and vapor from a two phase mixture. However these devices have complex turbo machinery, require kilowatts of power and are untested for high vapor flow conditions. The Interphase Transport Phenomena (ITP) laboratory has developed a low-power, passive microgravity vortex phase separator (MVS) which has already proven to be an essential component of two-phase systems operating in low gravity environments. This thesis presents results from flight experiments where a Rankine cycle was operated in a reduced gravity environment for the first time by utilizing the MVS for liquid and vapor phase separation. The MVS was able to operate under saturated conditions and adjust to system transients as it would in the Rankine cycle by controlling the amount of liquid and vapor within the device. A new model is developed for the MVS to predict separation performance at high vapor flow conditions for sizing the separator at the boiler, condenser, and turbine locations within the cycle by using a volume limiting method. This model factors in the following separator characteristics: mass, pumping power, and available buffer volume for system transients. The study is concluded with overall Rankine efficiency and performance changes due to adding vortex phase separation and a schematic of the Rankine cycle with the integration of the MVS is presented. The results from this thesis indicate the thermal to electric efficiency and specific mass of the cycle can be improved by using the MVS to separate the two phases instead of a rotary separator.
73

An experimental investigation of the countercurrent flow limitation

Solmos, Matthew Aaron 10 October 2008 (has links)
A new correlation for the prediction of the Countercurrent Flow Limitation (CCFL) in a large diameter tube with a falling water lm is proposed. Dierent from previous correlations, it predicts the onset of ooding by considering the relative velocities of the working uids and the lm thickness of the liquid layer. This provides a more complete accounting of the physical forces contributing to CCFL. This work has been undertaken in order to provide a better estimate of CCFL for reactor safety codes such as MELCOR, MAAP, and SCDAP/RELAP. Experiments were conducted to determine the CCFL for a 3-inch inner diameter smooth tube with an annular liquid lm and air injection from the bottom. The size of the test section and the range of working uid ow rates were based on a scaling analysis of the surge line of a PressurizedWater Reactor pressurizer. An experimental facility was designed and constructed based on this analysis in order to collect data on the CCFL phenomenon. In order to capture some of the physical phenomena at the onset of ooding visual pictures were taken at high speed. These pictures provided a new understanding of the process of transition to ooding. The facility also produced a new set of ooding data. This can also lead to a more comprehensive mechanistic model.
74

An experimental study of vertically upward air-water two-phase slug flow using hot-film anemometry /

Wang, Guanjun, January 2001 (has links)
Thesis (Ph.D.)--Memorial University of Newfoundland, 2002. / Bibliography: leaves169-179.
75

Numerical Solvers for Transient Two-Phase Flow

Du, Xiaoju January 2013 (has links)
Certain numerical methods have been well developed for solving one-dimensional two-phase flow (e.g. gas and liquid) problems in the literatures during the last two decades. Based on the existing methods, the present work compares the computational efficiency, accuracy, and robustness of various numerical schemes by predicting the numerical solutions of fluid properties for a specific case to find the proper numerical method. One of the numerical schemes introduced in this work is a practical, semi-implicit upwind method used for fluid flow simulations in different flow patterns,stratified flow and slug flow. This method implements the iterative and non-iterative schemes using a two-fluid model that consists of sets of non-hyperbolic equations. A numerical error term is applied in the pressure equation to maintain the volume balance of the two-phase flow model. If the temperature varies, the discretised energy equations use similar error terms as in the pressure equation. In some cases, the small values of the numerical errors are negligible and do not influence the numerical results. These errors are, however, important factors to consider when maintaining the stability and robustness of the above numerical schemes for strong non-linear cases. The computational efficiency ofthe non-iterative scheme, where the inner iterations are deactivated, is better than the iterative scheme. Different grid arrangements are compared with respect to computational accuracy and efficiency. A staggered structured grid implements the same semi-implicit upwind method as in the non-iterative scheme; the non-staggered grid arrangement uses an existing flux-splitting scheme (Evje and Flåtten, 2003) as a reference. All the above schemes produce numerical solutions with a single precision that normally satisfy the requirements of computational accuracy of industrial two-phase pipe flows. However, if one pursues a higher-order accuracy scheme, e.g. a Roe-averaged algorithm, the governing equations should be strictly a hyperbolic system of partial differential equations, which is achieved by introducing the nonviscous force terms in the two-fluid model (LeVeque, 2002).By properly incorporating the non-conservative terms in the formulation of the numerical fluxes, the capability of the Roe-averaged algorithm is demonstrated by capturing shock waves. Results from the present research include the following. A one-dimensional scheme that solves a system of discretised equations with the staggered semi-implicit upwind method is presented and validated for its computational efficiencyand robustness. This scheme can be widely used in the industry with sufficient accuracy. The other first-order semi-implicit numerical schemes producestable numerical results, especially in the dynamic cases of two-phase flow, except when the gas phase nearly disappears or appears in pipes. The Roe-averaged algorithm is recommended due to the high-resolution numerical results obtained, but at the costs of computational time and effort.
76

Downward two phase flow in vertical tubes

Chase, Sherwin January 1971 (has links)
In the present work, experimental data is obtained for the amount of air entrained by water and sugar solutions, of viscosities 3.6 and 4.7 centipoises, flowing down pipes of diameters 1.0, 1.5 and 2.0 inches. The dynamics of vapour entraining flow is discussed, and a method for calculating liquid flow rate at which pipe flows full is suggested. The experimental results have been presented in terms of some of the common dimensionless groups used in fluid mechanics in an attempt to develop an overall correlation scheme.
77

Interphase transfer processes in cocurrent two phase channel flow

Stinson, Michael J. 12 1900 (has links)
No description available.
78

Onset of flow instability in uniformly-heated microchannels

Kennedy, Jonathan Edward 12 1900 (has links)
No description available.
79

Flow visualization within a seven-rod micro-bundle

Narrow, Taryn Lea 08 1900 (has links)
No description available.
80

Combined heat and mass transfer in gas-liquid two-phase systems

Eghbali, Davoud A. 12 1900 (has links)
No description available.

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