An isoperibol calorimeter is one where the surrounding jacket is maintained at a constant temperature while the temperature of the bomb and bucket rise as heat is released by the combustion. The Model 6400, 6300, 1271, and 6200 Calorimeters are true isoperibol calorimeters. In these implementations, a water jacket, maintained at a fixed temperature, completely surrounds the combustion bomb and its 'bucket'. A microprocessor-based controller monitors both the temperature of the bucket and the jacket and performs the necessary heat leak corrections that result from differences in these two temperatures. These corrections are applied continuously throughout a test rather than as a final correction base on pre and post test measurements.

Continuously Compensated Calorimetry

The Parr 6100 Calorimeter takes advantage of the real time, continuously corrected method developed by Parr in its implementation of the isoperibol method. No attempt is made in the Model 6100 Calorimeter to establish the constant jacket temperature required for isoperibol calorimetry. Instead, the temperature of the jacket is continuously monitored and real time heat leak corrections are applied based upon the temperature difference between the bucket and the actual temperature of the jacket. While this method is not truly an isoperibol method, its real time correction procedure achieves the same purpose with nearly equal results. What it can not do is match the temperature uniformity of a circulating water jacket.

Compensated Calorimetry

The Parr 6772 Calorimetric Thermometer, serving as a controller for the 1341 or 6725 Calorimeters, uses yet another approach to emulate the isoperibol calorimetric method. In these calorimeter systems, the heat leak is precisely measured during the calorimetric pre-period. This evaluation results in an estimate of the effective, average temperature of the calorimeter surroundings. This temperature value is then used throughout the test interval to provide the calorimeter heat leak correction. While not as robust as either of the other two methods outlined above, it harnesses the computing power of the controller, with no additional hardware costs, to provide heat leak correction capability that is almost identical to the approach used when non-electronic thermometry and manual calorimetric techniques are employed.

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Isoperibol Calorimetry Methods and Modes

    Calorimetry Methods and Modes    
Today's Date: 03 September 2010
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