3060 -- A Procedure for Measuring the Dynamic Thermal Performance of Wall Specimens Using a Calibrated Hot Box PDF

An experimental procedure is developed that permits a calibrated hot box to be used to measure the transient heat-transfer rate through a composite wall specimen. In this procedure, a composite wall specimen is installed between the metering and climatic chambers of a calibrated hot box (CHB), and a time-dependent outdoor climatic condition, such as a sol-air diurnal temperature cycle, is generated in the climatic chamber. The metering chamber is maintained at a typical indoor condition and is used as a calorimeter. The transient heat-transfer rate through the wall specimen at hourly time steps is determined from an energy balance of the metering chamber. In the energy balance, the time-dependent heat-transfer rate through the specimen support frame is predicted using a finite-difference model, and the energy-storage rate within the metering chamber is predicted using a semi-empirical model.

A dynamic calibration test was conducted to investigate the accuracy of this procedure. A masonry wall, comprised of 4-in-thick (0.1 m) polystyrene insulation and 5.6-in-thick (0.14 solid concrete block and having known heat-transfer properties, was installed in the CHB. A sol-air temperature cycle was generated in the climatic chamber. The transient heat-transfer rate through this wall specimen was determined from an energy balance of the metering chamber and compared to the rate predicted using an analytical model using conduction transfer functions. Good agreement was observed between the measured and predicted specimen heattransfer rates, thereby supporting the validity of the energy balance under dynamic conditions. The transient heat-transfer rates associated with the specimen support frame and energy storage within the metering chamber were shown to be important elements in completing the energy balance of the metering chamber under dynamic conditions.

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