In a nuclear reactor core, fuel rods are supported by grid structures referred to as spacer grids. These spacer grids provide support to the fuel rods maintaining them at a fixed distance from each other, reducing the vibrations that would occur if the rods were not supported. As one of the major flow obstructions in the core, spacer grids have been found to affect the coolant flow hydrodynamics and heat transfer characteristics. There have been studies in regards to a single phase coolant traveling along the fuel rods and through the spacer grids; Mizutani et al (2007), Zhang (2008), however there is a need for enhanced information of what occurs when two phases travel through the spacer grid. Under certain conditions, the coolant may become a mixture of two phases along the rod bundle leading to the creation of interfaces between the different phases. The interaction between these two phases is critical in understanding the flow hydrodynamics and heat transfer characteristics.
When analyzing the thermal-hydraulics of two-phase flow, it is expressed in terms of macroscopic field equations and constitutive relations using a continuous formulation. This has been incorporated in classic formulations including the homogeneous flow model, drift flux model (Zuber and Findley, 1965), and the two-fluid model (Ishii, 1975). The formulation considered the most accurate is the two-fluid model developed by Ishii due to its treatment of the interfacial interaction terms. It considers the phases separately in terms of two sets of equations that govern the mass, momentum and energy. These equations represent the macroscopic field of each phase, and are not independent of each other but have phase interaction terms that couple the transp...
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...he grid causes breakup and coalescence of the two-phase flow structure, however this study does not include that happens to the flow as it travels further downstream of the grid.
1.4 Thesis Objective
The object of the current study is to an investigation into the fundamental effect of a spacer grid flow restriction in a scaled 3x1 fuel rod bundle on single and two-phase flow structures. This study consists of three major components:
Investigate the effects of the spacer grid on flow regime transition before and after the spacer grid, developing a flow regime map for the facility.
Investigate the effects of the spacer grid on local two-phase flow parameters, by measuring around the center rod, at four axial locations 7Dh before, & 7, 16, 45 Dh after grid.
To investigate single phase velocities using laser Doppler anemometer before, after and inside the grid.
The data which was collected in Procedure A was able to produce a relatively straight line. Even though this did have few straying points, there was a positive correlation. This lab was able to support Newton’s Law of Heating and Cooling.
"As a rule of thumb R< ~2000 laminar flow and R> ~3000 turbulent flow" Anything in between 2000 and 3000 is unstable and may go back and forth between laminar and turbulent flow.
...i, E.G., Smith, R.V., 1964, “Nucleate and Film Pool Boiling Design Correlations for O2, N2, H2, and He,” T-1, Plenum Press New York, K.D. Timmerhaus, eds., Cryogenic Engin. Conference, Boulder,
From the graph 2, it is seen clearly that the relationship between purity and boil-up rate is inversely proportional to each other. In order to achieve a good separation and high purity between the liquid and the vapour must be brought to an intimate contact by counter-current flow. Increasing the vapour flow actually means decreasing the interaction time between the down flowing liquid and up flowing vapour inside the column. Hence, if ...
Located at about 81 miles north of Kiev, Ukraine, and about 12 miles south of the border to Belarus, the Chernobyl plant consisted of four RBMK-1000 (Reactor Bolshoy Moshchnosty Kanalny) nuclear reactors. Reactors one and two were constructed from 1970 to 1977, while reactors three and four were completed in 1983. Before the nuclear accident occurred two more reactors were being constructed to have better energy production. An artificial lake of some 236,808,000 square feet was located just southeast of the plant where a tributary was constructed to run cooling water for the four reactors. The RBMK-1000 is a Soviet-designed and built graphite moderated pressure tube type reactor. It is designed to slow down neutrons and make them more effective in producing fission in the fuel surrounding the pressure tubes. The power production of this reactor is 3200 MW (megawatts) thermal. Many safety systems such as the emergency core cooling system were integrated into the design of the reactor. One of the most important features of the RBMK reactor is that it can hold a 'positive void coefficient'. This is w...
Ordinary fluid flow is different from granular flow so study of every particle’s behavior is necessary. Different physical phenomena, like interaction between particles and
In order to study the aspects of fluid mechanics that need to be taken into account when constructing our cooling tower, a breakdown of different behaviours of fluids under different conditions must be performed and tested against the flow rate. The experimental design would have to explore the influence of the length of the flow pipe as well as the density and temperature on the flow rate of the fluid.
Consider the parallel flow of two viscous fluids in an infinite, fully saturated, uniform, homogeneous and isotropic two porous media with the Darcy's coefficients and . The statically stable situation was considered, so the upper fluid is assumed the lighter (vapor) while the lower one is assumed to be the heaver (liquid). The two fluids are incompressible and have uniform densities and viscosities for the liquid and for the vapor. The interface between the two fluids is assumed to be well defined and is initially flat to form the plane y = 0. Also, we consider that the two fluids are streaming with uniform horizontal velocities and throughout the two superposed porous media. The subscripts (1) and (2) refer to the lower and upper fluid, respectively. The acceleration due to gravity
Refrigeration, the production of cold, is an essential practice for present-day living. It is used in a many place like the processing and preservation of food, conditioning of air for comfort, manufacture of chemicals and other materials, cooling of concrete, medical applications etc. Refrigeration is defined as the science of maintaining the temperature of a particular space lower than its surrounding space. Refrigeration and air conditioning involves various processes such as compression, expansion, cooling, heating, humidification, de-humidification, air purification, air distribution etc. In all these processes, there is an exchange of mass, momentum and energy. All these exchanges are subject to certain fundamental laws. Hence to understand and analyses the refrigeration and air conditioning systems, a basic knowledge of the laws of thermodynamics, fluid mechanics and heat transfer is essential.
The basic design of the Greenfield Naturals Water Structuring Unit was inspired by implosion technology first developed by Viktor Schauberger based on his observations of water flowing in mountain streams. He realized that the flow dynamics of water followed a three dimensional vortex pattern – a pattern that occurs at every stage of the hydrologic cycle.
Numerical investigation has been carried out to study about the temperature distribution of the reactor channel under LOCA with fuel rods deformed and undeformed under high temperature heat transfer. The numerical work of simulation would be done in commercial CFD software ANSYS 14.0.
... temperature of 112 0C also and a pressure 2.5 bar. Cooling water is used to condense the vapor exiting column. Remaining methane and hydrogen are separated in reflux drum where the vapor stream is combined with other gases streams. The overhead of first and second separator are combined to form fuel gas. The liquid stream exiting in the bottoms of the reflux drum is pumped at pressure of 3.3 bar for discharging pressure. The pump stream is separated in two streams. One stream is to feed to tray one of the column and the other one stream is cooled down to 38 0C in heat exchanger. Then, the cooled product stream is sent to storage.
On a more scientific note I am interested in mechanics of fluids. This interest was enforced last year when I had the opportunity to attend a lecture on fluid mechanics at P&G. At the conference I greatly expanded my knowledge regarding the physical aspect of fluids and their properties. In last year's AS course we have met a topic in this field. I will be applying ideas and knowledge gathered from last year for this investigation.
Cross model produces Newtonian viscosities at very low and shear rates compared to the Power Law model (Kim, 2002).
In present study; pressure base approach was chosen because of the flow of air in wind tunnel is incompressible.