Volume 15, Issue 3 (May 1987)
Calibration of the NBS Calibrated Hot Box
A series of calibration tests were conducted in the laboratory in order to determine the overall experimental error and uncertainty for the NBS calibrated hot box. For these tests, 10 cm (4 in.) and 20 cm (8 in.) thick polystyrene wall specimens having independently measured thermal resistances were installed in a support frame and sandwiched between the metering and climatic chambers. The metering chamber was operated at a typical indoor condition for a residence, while the climatic chamber was operated at selected steady outdoor winter conditions. For each of the tests, an energy balance was performed on the metering chamber. The heat transfer that flanks the wall specimen and passes through the support frame was predicted using a finite-difference model. The other heat losses and gains for the energy balance were measured. The residual energy loss for the energy balance of the metering chamber represents the overall experimental error and uncertainty.
The maximum observed residual energy loss for all of the calibration tests without the metering chamber cooling coil operated was 1.9 W. This value occurred when the 10 cm (4 in.) wall specimen was exposed to a 23 K (41°F) temperature difference. This value, however, comprised only 1.8% of the net energy input to the metering chamber.