This experiment is the survey of liquefied salt flow through graphite pebble channel utilizing jammed bed in the liquefied salt reactor. In this experiment molten salt is used as coolant in the cylindrical type channel because of its high volumetric heat capacity and high temperature. Spherical shaped Graphite pebbles are used as atoms in the channel. The high volumetric heat capacity of the molten salt will cut down the pebble size over gas cooled reactors. This decrease in pebble size will increase in power denseness. The pebble bed advanced high temperature reactor ( PBAHTR ) is the liquid salt cooled, high temperature reactor designed to utilize liquefied salt as its coolant. They are normally used in the industries affecting soaking up and surface assimilation of a solute, distillment, filtration and separation. The operation of the jammed bed is fluxing one or more liquids through a tower with a fixed bed of atoms.
A jammed bed is a perpendicular cylindrical column used in the chemical reactors. The pebble bed reactor construct is based on the reactor nucleus of randomly packed spherical elements incorporating black lead. The experiment is about the survey of force per unit area bead of one fluid flow ( Molten Salt ) through the cylindrical column and compares consequences with the fluent.
Molten salt flow through jammed beds debut:
Packed beds are used to increase the contact between surface country of solid stuff and a fluid ( Molten salt ) fluxing through a column which in bend increases the transmutation between two fluids. When one fluid is used, exchange of ions between the packing stuff and the fluid will happen. Packed beds have many industrial applications where procedure affecting distillment, extraction, contact action, surface assimilation, soaking up, and filtration takes topographic point. The industry applications besides include exhaust scrubbers which are used to take pollutants from waste gases before they allowed back into the environment. The set up of the jammed bed is a cylindrically-shaped column filled with packing stuffs. The cylindrical column has the fluctuation in diameter, tallness and stuff. And the packing stuff fluctuation is in form, raggedness, and atom size. The fluid is so pumped through the column. A jammed bed that is unrestrained can move as a fluid at the higher fluid flow rates. If the infinite between the wadding increases the atoms will hover in the column. Under these conditions the jammed bed is said to hold become fluidization. Fluid flow into the column from underside to exceed, go throughing through the jammed stuffs, there are two force per unit area nodes above and below the wadding that measure the force per unit area bead across the column. The packing stuff surface country will increase if the column ensures unvarying distribution of the fluid. Fig 1 shows the experimental apparatus for flow through liquefied salt. Packed bed is a cylindrical column filled with a packing stuff. Among different types of packing stuffs black lead is the most popular.
Fig 1 Experimental set up for flow through jammed beds [ 1 ]
1.2 Literature Review
The construct of liquefied salt reactor was introduced by the Oak Ridge national research lab in 1940s to develop a atomic engine for a military jet aircraft and support of the aircraft reactor plan for the U.S Air Force. After 30 old ages of research and development followed a design development taking to adoption known as individual fluid, graphite moderated ( MSBR ) . The design of the reactor will be graphite moderated, thermic neutron spectrum reactor that will bring forth extremely efficient electricity and H. The country of progress that made individual fluid black lead moderated popular was that the thought of using an under moderated outer zone of the black lead nucleus.Molten Salt reactor is a atomic fission reactor in which the coolant is liquefied salt mixtures which can run at high temperature. Molten Fluoride salt coolant as uranium tetra fluoride dissolves the atomic fuel in many designs.Molten salt reactor contains fluorides of fissile and fertile elements such as UF, PUFand /or ThFare combined with bearer salts to organize fluids. Single fluid flow designs have both fissionable and fertile combined in one salt.. Whereas the two fluid flow design separate salts for fissile ( UF ) and fertile ( ThF ) . The advantage of the two fluid flow is that, by the absence of Th the treating out fission merchandises from the fuel salt is simplified. Later in 1960 it was determined that black lead is the best stuff for utilizing as atoms in the liquefied salt reactor because it has the capable of long term interaction with the salts. And in the Oak Ridge National Laboratory ( ORNL ) , Molten Salt Reactor experiment was conducted The Molten Salt Reactor Experiment was a trial reactor with 7.4MW imitating the neutronic Kernel of an inherently safe epithermal Th breeder reactor.They used three fuels: Plutonium-239, Uranium-235 and Uranium-233 and the consequence of engendering Th is UFThe big engendering cover of Th salt was obtained in favour of neutron measurings. The heat coming out of the reactor can be cooled by utilizing the air blowers and radiators.
Recent researches shows involvement on the advantages of the high-temperature low force per unit area primary chilling cringle and rely on the ceramic fuel dispersed in the graphite matrix with the molten salt holding high temperature and low force per unit area. These salts have more capacity at taking off the heat from the nucleus, diminishing the demand for pumping, piping, and cut downing the size of the nucleus. Further molten salt reactors research started with U.S Aircraft reactor experiment ( ARE ) .This experiment was designed as a 2.5 MW atomic reactor to derive a high power denseness for usage an engine in a atomic powered bomber. The Aircraft reactor experiment ( ARE ) was ab initio developed by the little size that the design provided. While the Molten salt reactor experiment which was conducted in 1960s is the paradigm of the Th fuel rhythm breeder reactor atomic power works. The advantage of the little nucleus is that it has the fewer stuffs to absorb neutrons.
The advantages of the liquefied salt reactor attract to the 4th coevals international forum and have drawn attending of many researches once more. For the following coevals atomic works the U.S section of energy is carry oning R & A ; D on the Very high temperature reactor ( VHTR ) .
Figure 1 shows the conventional diagram for the flow through jammed beds in the cylindrical column with graphite pebbles.
Fig.1. Design to be analyzed
Figure 1 shows the dimensions of the cylindrical column and the dimensions are listed below.
The design is fundamentally a cylinder with a diameter of 0.3 m, and a tallness of 0.54 thousand high. The pebble bed will incorporate graphite pebbles with a diameter of 0.03 m made out of poco-graphite ( AXF-5Q ) ; therefore there will be 18 or 19 graphite pebbles per bed. Density of the liquefied salt is 2020 Kg/m.Viscosity of the fluid is 0.000296 Kg/s-ft. The cringle will be runing at a temperature of 700A°C, a force per unit area of 0.2 MPa and a mass flow rate of 4.5 kg/s.. The fluid traveling through the trial subdivision will be Flinak ( run salt ) .
1.3 Theoretical computation:
Sabri Ergun conducted many experiments on farinaceous wadding in 1950 ‘s with the hope of happening the correlativity between the force per unit area bead and the fluid. Ergun concluded that force per unit area bead over length of the column depends upon the flow rate, size of the column, surface country of the column and form of the atom ; it depends besides on the intimacy and the orientation of the wadding, the viscousness and the denseness of the fluid besides affairs. Then Ergun developed an equation 1.1 this equation will work until the fluidization point. If the speed of the fluxing fluid is really high that the tightly packed atoms in the column no longer remain stationary, lift along the column and act likewise to the fluid. Then the Fluidization occurs in the jammed beds when the speed of the fluxing fluid is really high Pressure bead through the cylindrical column can be calculated theoretically through the Ergun Equation.
a?†p is Pressure bead, L is the length of jammed bed ( 0.54 m ) , Aµ is the Fluid viscousness with 0.000296 Kg/s-ft, G equals to I?V ( Mass speed ) , V is Superficial speed ( 7.8×10 ) , Iµ is the Inter Particle null fraction ( 0.49 ) , k is the Conversion factor, ( 144 ) , g is the gravitative invariable ( 4.17×10 ) , I? is the Fluid denseness ( 2020 Kg/m ) , D is Effective atom diameter of 0.03 m, Substituting all the deliberate values in Eq 1.1. 0.15 MPa force per unit area bead occurred throughout the trial subdivision.