rotatable guarded hot box
Researchers use the Rotatable Guarded Hot Box to test full-size wall, fenestration,
roof, and floor systems. The ORNL Rotatable Guarded Hot Box is a unique envelope
testing apparatus available at the Buildings Technology Center. This advanced
thermal testing facility is designed in accordance with ASTM C236, Standard
Test Method for "Steady-State Thermal Performance of Building Assemblies by
Means of a Guarded Hot Box." The RGHB accepts test specimens that are up to
13 ft by 10 ft in cross-section with a metering chamber that is approximately
8 ft by 8 ft. The RGHB is particularly unique because it can accommodate assemblies
up to 24 inches thick, which may be useful in testing projecting or extremely
thick envelope assemblies, a second unique feature is that the test walls can
be rotated and thermal performance measured at any angle from 0 to 180 degrees.
Another unique capability is the ability to conduct dynamic guarded hot box
tests on massive wall systems.
In the above photo, the hot box is show in the open position with a test
wall in place between the hot and cold chambers. To the right of the hot box
is a frame in which another envelope component can be mounted for testing.
The RGHB climate chamber temperature can be controlled from - 10ºF to
140ºF and the air velocity from 0 mph to 15 mph. The RGHB metering chamber
temperature can be controlled from 70ºF to 140ºF and air velocity
from 0 to 1 mph. The instrumentation inventory available consists of 200 Type-T
thermocouple-temperature sensors, 10 thermopile type heat-flux transducers,
two air velocity meters, two pressure transducers and 8 other voltage output
type sensors. The test apparatus is fully automated: the chamber temperatures
and air velocities are computer controlled at steady conditions or in 200 step
cycles. Data collection and processing are performed in real time. The system
was designed for a precision of better than 3 percent and a bias of less than
5 percent. Estimates of the error bands will be generated with all test results.
In the above photos, BTC staff member Andre Desjarlais is shown programming
the controller (left) and inspecting a thermocouple (right).