This case study highlights IST's use of Flownex to model the pneumatic conveying system of the Pebble Bed Modular Reactor, incorporating sphere kinematics via user coding. Flownex predicts interactions between helium gas and 60mm graphite fuel spheres, enabling accurate simulation of sphere velocities, pressure pulses, heat transfer, and system behavior, optimizing design for safety, performance, and durability.
CUSTOMER PROFILE
As a diversified engineering solution business, IST has extensive experience in the nuclear, energy, telecommunications, and defense industries. In addition to being a niche supplier to South African industries, IST applies its technologies across a range of markets in Africa and internationally.
IST successfully uses Flownex as an engineering tool in there day to day business, and as seen in this case study, they were able to incorporate sphere kinematics through the powerful equation element within Flownex.
CHALLENGE
In a pneumatic conveying system, the interaction between the gas and the particles being conveyed is very important for control and performance prediction. This is also the case for the Fuel Handling System of the Pebble Bed Modular Reactor, where the fuel (in the form of 60mm graphite spheres) is pneumatically conveyed with Helium (±11m vertically). The Helium accelerates the pebbles in the feed line and then pneumatically breaks the pebbles before they are deposited back into the bed or storage container. The challenge is to model/predict the sphere kinematics, and to determine the interaction of the sphere on the flow velocities/distribution in the system.
BENEFITS
In this case study, the endless possibilities within Flownex are highlighted by the application of user coding and the versatility it adds to the tool.
SOLUTION
By being able to introduce user coding to the transient simulation, the sphere kinematics (interaction between sphere and gas flow) can be incorporated in the simulation to predict the exact overall system behavior. The maximum pebble velocity being conveyed (a critical design restriction) can be predicted and designed for.
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INTRODUCTION
As a diversified engineering solution business IST has extensive experience in the nuclear, energy, telecommunications and defence industries. In addition to being a niche supplier to South African industries, IST applies its technologies across a range of markets in Africa and internationally.
IST successfully uses Flownex as an engineering tool in there day to day business and as seen in this case study they were able to incorporate sphere kinematics through the powerful equation element within Flownex.
In this case study the endless possibilities within Flownex are highlighted by the application of user coding and the versatility it adds to the tool.
CHALLENGES
In a pneumatic conveying system, the interaction between the gas and the particles being conveyed is very important for control and performance prediction. This is also the case for the Fuel Handling System of the Pebble Bed Modular Reactor, where the fuel (in the form of 60mm graphite spheres) is pneumatically conveyed with Helium (±11m vertically). The Helium accelerates the pebbles in the feed line and then pneumatically brakes the pebbles before they are deposited back into the bed or storage container. The challenge is to model/predict the sphere kinematics, and to determine the interaction of the sphere on the flow velocities/distribution in the system.
SOLUTION
Being able to introduce user coding to the transient simulation, the sphere kinematics (interaction between sphere and gas flow) can be incorporated in the simulation to predict the exact overall system behavior. The maximum pebble velocity being conveyed (a critical design restriction) can be predicted and designed for.
RESULTS
With the sphere kinematics incorporated with the compressible gas and solid gas heat transfer models in Flownex, it is very easy to see the interaction of the sphere on the gas flow velocities, temperatures and sphere velocities at the feed and brake lines. One can clearly see the pressure pulses caused by a sudden introduction of a sphere in the conveying stream, as well as bypass and leak flow changes due to the additional flow loss caused by the sphere. Flownex can model the pressure pulses in the conveying stream due to its ideal gas and compressible gas models. By designing the valve positions with the designer functionality, one can make sure that the sphere stays below its maximum allowable velocity throughout the conveying route. The design philosophy of controlling the mass flow distributions through the different pneumatic lines in the system can also be investigated.
Heat transfer from the pebbles to the pneumatic gas simulated in Flownex can be used to determine at which temperature the pebbles are deposited in the storage container. The sphere cooling rate to the pneumatic gas is used to determine if there are any thermal stresses on the pebble.
It is also possible to see the effect of a second sphere introduced a few seconds after the first, and determine if they would catch each other on route. This knowledge can then be used to determine the maximum possible transfer rate of the pebbles without damage. The maximum transfer rate is essential in determining the amount of pebbles that can be moved through the fuel handling system, analyzed, sorted and stored within any given day. With this knowledge from Flownex it can be evaluated whether the pebble analyzer or the pebble pneumatic transport is the limiting factor in the sphere transport system.
Damaging the pebbles due to excessive speed, collision of pebbles or congestion in the transport of the pebbles is critical design parameters with unwanted results if these parameters were exceeded. Being able to simulate the transport of the pebbles in an integrated fashion allows the system as a whole (transport, control, valve sizing, blower sizing, insulation, operating temperatures, etc.) to be designed, analyzed and optimized for performance, safety and durability.