The George W. Woodruff School of Mechanical Engineering
Georgia Institute of Technology, Atlanta GA 30332­0405
Undergraduate Instructional Laboratories

TO: Dr. Yogendra Joshi, Undergraduate Laboratory Instructor

March 25th, 2015

FROM: ME 4056 Section B­8
SUBJECT: Blackbody Radiation Lab INTRODUCTION

This lab was conducted on March 11th, 2015 in a thermal­fluids instructional lab located at the Georgia Institute of Technology. An experiment involving blackbodies and the Stefan­
Boltzmann law of blackbody radiation was conducted where the radiant power from a blackbody cavity was experimentally determined using a thermopile sensor and was compared to theoretical
4
values which are dependant on T
.The experiment was then repeated for varying aperture size,

distance, and temperature and the results were compared.

APPARATUS AND PROCEDURE
Apparatus. In this experiment, an Infrared Systems Development Corp. IR­564 blackbody cavity and an IR­301 temperature controller were used. The blackbody cavity features an aperture adjustment mechanism, which allowed the hole diameter to be adjusted to 2.54 cm and 1.02 cm. The maximum allowable operating temperature of the blackbody cavity was
1200°C, which was more than adequate for the purposes of this experiment. The heat flux detector that was used was a Coherent Inc. PM3 high sensitivity thermopile with a 1.12 cm diameter sensor. In order to take measurements of the resulting radiant power, the thermopile was moved with respect to the stationary blackbody along an optical rail. There was a discrepancy regarding the distance between the thermopile mount and the thermopile sensor such that the actual distance was 4.4 cm greater than the distance at which the reading was taken. The thermopile was surrounded by a thermally­isolating piece of foam in order to protect it from any unintended radiation. A FieldMaxII­TO laser power meter was then used to display the resulting heat flux based on the manufacturer’s calibration specifications.

1

Uncertainty. The generic and commercial IDs of each apparatus used in this lab and the associated uncertainty values
U
,
U
, and
U
U
A
B
C are shown in Table 1. All
C values were calculated using Equation 1,

(1)

where any negligible
U
or
U
values were considered to be zero.
A
B
The blackbody cavity has a
U
of 0.1 °C by inspection, and a
U
of 0.5 °C for
A
B temperatures ranging from 0 to 600 °C and an uncertainty of 0.7 °C for temperatures ranging from 600 to 1100 °C. The resulting
U
C of the blackbody is 0.51 °C for the 0 to 600° C range and
0.71°C for the 600 to 1100°C range. The blackbody aperture has a
U
of 0.01 cm, by inspection
A
and a negligible
U
U identical to the
U
of 0.01 cm. According to the
B making the
C value A value manufacturer’s catalog, the
U
A value for Coherent Inc.’s laser power meter is 0.1% of the FS value and the
U
is 1% of the reading. The FS value is 30 mW resulting in a
U
of 0.3
B value A mW. The power meter’s
U
was 0.26 mW, resulting in a
U
of
0.40 mW. Error propagation
B
C analysis for the laser power meter’s
U
is shown later. The detector diameter has a
U
of
C value A
0.01 cm, as determined by S. Kommandur, and a negligible
U
U of 0.01 cm.
B value resulting in
C
The ruler which was used has a
U
of 0.5 mm due to difficulty in alignment, a negligible
U
, and
A
B a concluding
U
of 0.5 mm. The thermometer has a
U
of 0.5 °C by inspection and a
U
of 1 °C
C
A
B
according to the H­B