FIGURE 4-3 Thermocouple installation on the projectile. SOURCE: BPBGT, 2007a.

experiments and the CFD model that is observed. (Figure 4-2 is a typical example.)

The committee originally had concerns that the modeling predictions were inaccurate because the model did not take into consideration the effects of the door openings and closings nor of the purge flows during these transients because the effect was found to be small. The TRRP report indicates that door-opening transients resulted in a “flat spot” of from 1 to 7 minutes in the measured temperature profiles. These were not significant over the 90-105 minute test period. The inlet and exit chamber purge flows of nitrogen are maintained during door openings and enter the MPT and exit through the MPT exhaust headers during door openings (BPBGT, 2007b). The CFD model was modified for prediction of full-scale performance by changing the physical properties and boundary conditions to conform with the full-scale design. The boundary conditions and properties for full-scale analysis are shown in Tables 4-3 and 4-4.

TABLE 4-1 Metal Parts Treater Unit’s Material Properties

Component Materials

 

Tray, fins

ASTMa

Projectiles

Carbon steel

Insulation on MPT doors

CS 85

MPT conveyor, conveyor support, rollers

ASTM

MPT door frames

ASTM

Emissivities

 

Projectiles

0.65

MPT coils and walls

0.9

Conveyor and conveyor support

0.65

Rollers

0.3

MPT doors (insulation)

0.4

Material Properties

 

Steam

 

Density

0.2673 kg/m3

Conductivity

0.0261 J/m-s-°K

Specific heat

2014 J/kg

Expansivity

0.003472 1/°K

Viscosity

0.00005 kg/m-s

ASTM

 

Density

8000 kg/m3

Conductivity

16.3 J/m-s-°K

Specific heat

500 J/kg

CS85

 

Density

85 kg/m3

Conductivity

0.29 J/m-s-°K

Specific heat

1260 J/kg

Carbon Steel

 

Density

7850 kg/m3

Conductivity

51.9 J/m-s-°K

Specific heat

485 J/kg

aAmerican Society for Testing and Materials RA 330 Steel.

SOURCE: BPBG, 2006b.

Finding. The CFD model developed by the BPBGT predicts the trends in temperature behavior over time and space and the location of cold spots within the system.


Finding. The specific heat of the projectile material varies by a factor of two over the temperature range of interest, which may affect the predicted temperature-time profiles.


Recommendation 4-1. For more accurate prediction of temperature heat-up, the dependence of specific heat on temperature should be included in further modeling.

COMPARISON OF TEMPERATURE MEASUREMENTS AND MODELING

Because the experimental data could also be inaccurate, comparisons between the CFD predictions and the data cannot differentiate between errors in the model and



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