Two methods for calculating the amount of refrigerant required for cyclic temperature testing of insulated packages

This paper describes two calculation methods for estimating the amount of refrigerant required to maintain the temperature inside a small insulating container within a desired range under cyclic temperature conditions. The first calculation method is for a phase change material (PCM) that absorbs and releases heat by melting and solidifying. The PCM used in this study had a phase change temperature of 23.5 degrees C (74.3 degrees F). An equation for estimating the amount of the PCM required under cyclic conditions is shown. Test packages were constructed to meet LISP Controlled Room Temperature (CRT) requirements. Several cyclic tests were conducted with the calculated amount of PCM in the test packages. The results showed that the calculated amount of PCM did maintain the inside temperature within the range 21.4-25.8 degrees C (70.5-78.4 degrees F) throughout the tests. This range met the USP CRT requirement. The second calculation method is for unfrozen gel packs that absorb and release heat by changing temperature. The amount of unfrozen gel pack required to maintain temperature within the USP range was calculated. Several cyclic tests were conducted with the calculated amount of gel packs. The calculated amount was enough to meet the USP requirement. Good agreement between the experimental and calculated temperature profiles was also found. Copyright (c) 2006 John Wiley & Sons, Ltd.