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Comparison of Thermal Buffer Effectiveness
By: CAS Dataloggers
Summary: Experimental data was collected to examine the behavior of RTD probes inserted in various thermal buffers in refrigerator and freezer applications. From the warm-up time vs. temperature curves, a thermal time constant was determined by fitting an exponential line to the data. Also, the behavior of the buffers during typical operation as the refrigeration compressor cycled on and off was observed. Using this data, a comparison of the thermal buffer effectiveness and recommendations on the buffers for refrigerators and freezers are made.
There currently exists a considerable amount of confusion in hospitals, clinics, and the healthcare industry about the use of temperature buffers on probes attached to Digital Data Loggers (DDL) placed in medical refrigerators and freezers. There are no clear indications of which types are most effective due to a lack of published data on the relative performance of the various alternatives. While no official test results have been published, the CDC has recommended the use of glycol bottles in medical refrigerators to provide thermal buffering for probes and most closely approximate the temperature of products for monitoring purposes.
The aim of our study is to give a detailed look at the buffered temperature curves we obtained, to analyze the specific response in both types of units, and provide data that can be used to help select the most appropriate buffer type (or to discern if they were equally effective). We'll compare the response rate of all three buffers, looking for significant differences. Ideally, we want to identify the insulator type that offers the probe a response time to most closely resemble what is happening to the bottle, vaccine, or product under monitoring.
In this paper, we specify our methodologies and equipment in detail so the test is easily reproducible.
Description of Experiment
We conducted this study over the period of several days to acquire the freezer and refrigerator temperature data. All measurements were taken using four (4) identical industry-standard 100-ohm RTD probes. The test involved placing a probe in two (2) bottles, each containing a different temperature buffer with the same immersion. A third probe was placed in a nylon block.
To read more about our test setup, experimental methods, and our conclusion, visit us at https://www.dataloggerinc.com. To find the ideal solution for your application-