Validation of a Mechanical Freezer Used for the Cryopreservation of Fresh Frozen Plasma: Thermodynamic and Heat Transfer Evaluations

Plasma for clinical use should be frozen and stored in this state until use. In this study we revised our standard procedure for the cryopreservation of plasma to verify its compliance to Italian, European, and American norms, which require a specific cooling rate. To this aim, we performed three tests. In test 1 we recorded the temperature of the freezing chamber of our mechanical blast freezer; in tests 2 and 3 we recorded and certified with thermocouples the freezing curve of plasma units frozen without and with protective packaging (soft polyethylene bag and cardboard box). In test 2 the freezer was loaded in a single operation, whereas in test 3 we simulated the ordinary loading operation that requires the opening of the loading door on two occasions, which decreases thermal efficiency. The validation of the cooling system, which included a thermal analysis, allowed us to characterize the critical steps of the plasma freezing process. The thermal analysis was conducted under ideal conditions in order...