HEAT FLUX MEASUREMENT WITH A FOIL-TYPE

1
HEAT FLUX MEASUREMENT WITH A FOIL-TYPE
GARDON GAGE SENSOR IN THE RADIANT
PANEL TEST SYSTEM


KHANG D. TRAN, Ph.D.

THE MEXMIL COMPANY
SANTA ANA,
CALIFORNIA, USA
International Aircraft Materials Fire Test
Working Group Meeting, March 2004, Atlantic City,
NJ
2
FAR 25.856 (a) flammability test requires a heat
flux value of 1.5 0.075 Btu/sft2 at zero-point
location (1.425 - 1.575).
Calibration data has been recorded and analyzed
to confirm the compatibility of the test system
with the allowed 5 tolerance
3
CALIBRATION CURVE FOR RADIANT PANEL SYSTEM
Heat Flux (Btu/s.ft2)
Zero Point
Position
2 inches
Controller Setting Temperature 1165 F
4
CHAMBER TEMPERATURE (F)
TIME (s)
TEMPERATURE OF RADIANT PANEL CHAMBER AT THE
THERMOCOUPLE 1 LOCATION (11 IN., 2 IN., 11.5 IN.)
5
HEAT FLUX AT ZERO-POINT (BTU/SFT2)
Thermal stability begins
TIME (S)
HEAT FLUX AT ZERO-POINT LOCATION
6
CHAMBER TEMPERATURE AND HEAT FLUX CORRELATION
Thermal stability
7
CHAMBER TEMPERATURE AND HEAT FLUX CORRELATION
HEAT FLUX AT ZERO-POINT (BTU/SFT2)
(560, 1.5)
CHAMBER TEMPERATURE (F)
There exists a linear relationship between the
chamber temperature (at location of interest (11
in., 2 in., 11.5 in.) and the zero-point heat
flux.
8
TEMPERATURE-HEAT FLUX CORRELATION (CEAT LAB)
9
THE ZERO-POINT HEAT FLUX VALUE REQUIRED IN FAA
25.856 (a) 1.5 5 Btu/sft2 (or 1.7 5
Watts/cm2) (1.425 - 1.575) Btu/sft2 or
(1.615 - 1.785) Watts/cm2)
558.7 1.452 559.0 1.452 559.0 1.456 559.3 1.458
559.2 1.454 558.9 1.481 559.3 1.465 559.6 1.4
86 559.6 1.481 559.9 1.481 559.7 1.479 559.8 1
.495
560.2 1.456 560.6 1.481 560.8 1.492 561.4 1.492
561.4 1.474 561.7 1.474 561.8 1.479 561.7 1.4
77 561.8 1.458 562.7 1.456 562.7 1.486 562.0 1
.51
DATA IN 24 SEC. DURATION AFTER THERMAL STABILITY
BEGINS
There is a variation of about 3 F (0.054) of
the chamber temperature at the location of
interest when the heat flux fluctuates in the
range of (1.45-1.51) Btu/sft2
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CIRCULAR FOIL-TYPE GARDON GAGE HEAT FLUX SENSOR
To
Ts
Constantan foil
The center to edge temperature difference is
proportional to the heat flux
Q R2 To - Ts 4k?
?
Copper body
Copper wire
Besides the heat conduction, both heat
convection and heat radiation are present
at least to some extent in virtually all cases.
The foil-type Gardon gage sensor output is
not completely correct because of the
distortion of the temperature profile in the foil
from the assumed radially symmetric, parabolic
profile of heat radiation.
E (Voltage output)
? thickness of the foil R active radius of
the foil k thermal conductivity of the
material.
T. E. Diller, Heat Flux, CRC Press LLC, 2000
and the references cited in this paper