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Introduction | Details of Test Section Construction
Instrumentation and Test Procedures |
Test Results | Conclusion
Instrumentation and Test Procedures
Each test assembly was lifted by crane into the LSCS. A sketch of the LSCS is shown in Fig. 3 to illustrate the placement of an assembly with the climate chamber above it and the metering and guard chambers below it. Each assembly was fully instrumented with the same set of
thermocouples on the upper and lower surfaces. Within the vertical projection of the metered area, nine thermocouples were fixed to the upper surface and another nine to the lower surface. An additional four thermocouples on the upper surface and four on the lower surface were placed outside the vertical projection of the metered area near the corners of the metering chamber walls. An array of 21 thermocouples measured metering chamber air temperature about 3 in. below the top of the metering chamber. Nine thermocouples in the air 3 in. below the bottom surface of each assembly corroborated these data. They were placed at the locations of the thermocouples in the metered area on the bottom surface. An array of 25 thermocouples measured the air temperature in the climate chamber about 3 in. above the roof surface.
The purpose of the metering chamber is to obtain the energy flow through the 64 ft2 of open area at its top as a result of the temperature difference imposed between the climate and metering chambers and across the test section. This energy flow is obtained by measuring all other energy flows into the metering chamber in accordance with ASTM C-1363, Standard Test Method for the Thermal Performance of Building Assemblies by Means of a Hot Box Apparatus. The energy flows include the amount across the metering chamber walls and floor due to any imbalance between the metering and guard chamber air temperatures. This energy flow was determined as a function of the temperature imbalance by previous use of a calibration panel. The energy flow through the metering chamber walls and floor is given by the sum over each face. On each wall and the floor, the average temperature difference measured by nine differential thermocouples is multiplied by the component’s area and divided by its R-value. The same calibration panel is used periodically to establish the overall accuracy and precision of energy balances for the metering chamber (1). The accuracy is generally of the order of ±10%. The precision is generally of the order of ±1% as a result of excellent control of imposed conditions by the control system.