March 18, 2003
Fluvanna Power Project Main Cooling System Transient Analysis
Bibb & Associates of Kenexa, KS is the EPC contractor for Tenaska's 890MW combined cycle power plant in Fluvanna County, Virginia.
The Fluvanna Generating Station is a dual fuel plant capable of burning both natural gas and No. 2 fuel oil in its three GE gas turbines and Deltak heat recovery steam generator with duct burner. 410MW of the total generating capacity is provided by a GE condensing steam turbine. Cooling for the main condenser and auxiliary heat exchangers is provided by a system including three, 138,000 gpm main circulating pumps supplying cooling water through 78" diameter supply and return lines in conjunction with a 14 cell cooling tower.
Bibb & Associates enlisted AFT's expertise to model the cooling system and analyze its behavior under a variety of pump shutdown and startup scenarios along with associated main discharge valves opening/closing. AFT Impulse 3.0 was used to model the system and included modeling four quadrant pump hydraulics and inertia effects along with the several vacuum breaker/air release valves in the system and partially filled pipes near the pumps at start up. The completed model consisted of 112 pipes plus the 34,140 tubes in the main condenser. A total of nine cases were analyzed with the results clearly illustrating transient liquid flows, air flow through the vacuum breaker/air release valves and, or course, transient pressures.
Fluvanna Generating Station will depend on its main cooling system for reliable operation. Modeling the system with AFT Impulse allows it designers to insure in the design stage this critical system will meet that requirement.
Add custom pipe data to your database
If your like most AFT software users, you probably already use the pipe material database regularly whenever you select one of the eight, built-in pipe materials from within a Pipe Specifications window. Once a material is selected, sizes, types or schedules and roughness values appropriate for the material are automatically made available. What you may not know is how easy it is to add to this selection.
After opening AFT Arrow, AFT Fathom, AFT Impulse or AFT Mercury, select Pipe Material Database from the Database menu. On the left, you'll see the eight standard materials and, as you expand them, you'll see the sizes available for each material and, expanding a size, will display the types or schedules available for that size. Information is organized in the Pipe Material Database as Material, Size, Type (MST). This structure lets you readily add information at the appropriate level.
Let's say you have steel pipe of 4" nominal size but of a custom wall thickness or schedule. To add this to your database, expand Steel, select 4" then click on the New Type button. A window will appear where you can enter the information for this new type of 4" steel pipe (i.e. ID, wall thickness, name).
Another common example would be large diameter fabricated steel pipe made from rolled plate.Nominal sizes, diameters and wall thicknesses are custom, but the thermophysical properties (density, thermal conductivity) can still use the built-in values for steel, so that you want to add these sizes and wall thicknesses to the Steel category of material. Simply select Steel then click on the New Size button. The window that appears will let you specify a nominal size, diameters and wall thickness. If you wanted to create various wall thicknesses for this custom size pipe, you would select the Size then click the New Type button.
Finally, if you want to create a whole new material category, select Pipe Materials then click the New Material button. You'll specify a description or name for the material and a beginning size and wall thickness. Optionally, if you want to do heat transfer with this pipe material, you'll also specify a density and thermal conductivity. Adding sizes and wall thickness to this new material category is the same as described above for any of the built-in materials. Select the new material and click New Size or select a size within the new material and click New Type to add wall thicknesses to a previously created size.
Once you've created your new material, size or type, to use it is as easy as selecting it from within the Pipe Specifications window. You can, of course, specify a custom pipe without adding it to the Pipe Material Database, but if you're going to use it more than once, you might as well add it to your database since doing so will save time and help ensure the correct data is used in the future.