Event Type:

Applied Mathematics and Computation Seminar

Date/Time:

Friday, March 6, 2015 - 12:00 to 13:00

Location:

KEAR 112

Event Link:

Guest Speaker:

Rigel Woodside

Institution:

Thermal Sciences Division, National Energy Technology Laboratory (NETL), U.S. Department of Energy

Abstract:

When developing and applying measurement systems, it is important to consider the

analysis and characterization approaches in the specific context of the measurement

hardware, system to be measured, and the desired outcome. The measurement might

be for determining a physical quantity of interest in the system, or it may be toward

assessing a qualitative state of a system. In advanced systems, multiple measurements

including calibration and characterization routines are usually needed to get results. This

necessitates a propagation of uncertainty analysis. However, all the system variables

which can impact the measurement are rarely all known or even well defined in the real

world. This talk discusses practical considerations in the application of advanced

measurement systems using 2 case studies at NETL with a focus from system analysis

to measurement result.

In the first case, the measurand was the heat flux into a boiler water wall and accuracy

was important. A network of temperature point measurements was implemented and

heat flux was determined based on Fourierâ€™s law of heat conduction. Uncertainty

quantification methodology is discussed and results determined with a typical as-

received device measurement uncertainty of about +/- 30%. A calibration system was

designed and built to characterize and correct for suspected systematic errors with an

expected improvement in heat flux uncertainty to better then +/- 5%. Boiler testing

results showed an improvement in precision for adjacent heat flux pairs close to the

expectation, with a similar improvement in accuracy expected. The measurements also

show interesting drift characteristics during some testing which is thought to have been

caused by uneven ash/slag deposits on the boiler walls.

In the second case, a measurement system was developed and deployed to diagnose

the arc distribution in vacuum arc remelting furnaces. Identifying constricted arc column

conditions at a time scale pertinent to alloy solidification was important. A method based

on the Maxwell-Ampere law and magnetic field measurements external to the system

was used. To characterize system parameters, a 3D Magnetostatic finite element model

(FEM) of the furnace under various arc position states was constructed and

implemented. Then the FEM output data set was fit to a simplified equation based on the

Biot-Savart law in order to decrease computational times in a real time measurement

system scenario. Testing on an industrial furnace showed that significant arc

constrictions persisted during melting and several characteristic arc distributions were

observed. Results also suggested that there were more arcs in the furnace at a given

time then could be uniquely located using the number of sensors deployed.

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