33
Figure 5: Simulated temperature distribution in a 100% MWV FluidX 1.0ml tube removed from cryostorage and exposed to RT conditions. Over time, the temperature is highly uniform throughout the entire sample volume.
Figure 2: Vial warm-up rate sensitivity to H₂O volume in RT, interior sensor. Vials warmed to above Tg,H₂O at times ranging from 24 – 40 seconds. Initial temperature plateau detected in the -173°C to -169°C range is due to the short interval where vials sit inside the cryorack and cryobox when fi rst extracted from the freezer. All vial interior sensors show comparable warm-up rate sensitivity to H₂O.
Figure 6: Simulated absorbed heat from the FluidX 1.0ml tube when warming from -173°C to -1°C. Convective heat transfer is responsible for the greatest contribution of energy transferred from the environment to the tube whereas conduction through the TC wires was negligible and thus not simulated.
Equation 1. Q=h•A•(Tenv−Tvial)•t Handling vials in environments < −150°C reduces absorbed heat by >90%.
Figure 3: Vial warm-up rate sensitivity to H₂O volume in dry ice, interior sensor. Vials warmed to above Tg,H₂O at times ranging from 9 – 45 seconds. All vial interior sensors show comparable warm-up rate sensitivity to H₂O.
Equation 1: Calculation demonstrating how convective heat transfer into a vial can be greatly reduced by decreasing the environment temperature. For instance, handing a cryogenic vial in an environment below -150°C reduces the heat absorbed by the vial by more than 90%.
Simulation Insights
• Convective heat transfer dominated over conductive or radiative modes. • Conductive heat through thermocouple wires was negligible. • Simulated and measured warm-up profi les showed excellent agreement.
• Total absorbed energy could be reduced by >90% by maintaining handling environments below −150°C.
Discussion
The rapid approach to Tg,H₂O during even brief exposure to warmer environments underscores the need for stringent cryogenic handling protocols. Notably, dry ice environments may pose greater thermal risks than ambient air below −90°C due to conductive heat from direct contact and enhanced convection from CO₂ sublimation. Cryoboxes with lids signifi cantly reduce exposure rates and should be used whenever possible. Handling time should be minimised, and, ideally, all manipulations should occur within environments maintained below −150°C.
Conclusion
Cryovials removed from LN₂ storage are at high risk of exceeding Tg,H₂O within seconds during handling. Warm-up rate is most strongly infl uenced by environmental temperature and vial exposure method, with minimal infl uence from vial volume or geometry. Cryogenic best practices should include:
Figure 4: H₂O fi lled FluidX vial temperature distribution when extracted from cryostorage and exposed to RT. At any given time, the maximum spatial ice temperature variation is within 4°C due to greater thermal diffusivity (α) of ice compared to polypropylene (PP) (e.g. αIce (T -150°C) = 1.07e-5 mm2/s vs. αPP (T 22 °C) = ~1.29e-7 mm2/s. Data indicates that H₂O temperature increase inside the vials is highly uniform with limited point-to-point spatial variations.
• Keeping samples in cryoboxes with lids during handling. • Limiting exposure time outside LN₂ environments. • Performing handling operations in environments ≤ −150°C.
These steps help preserve biological sample integrity by preventing transient crossings above Tg,H₂O.
Read, Share and Comment on this Article, visit:
www.labmate-online.com
WWW.LABMATE-ONLINE.COM
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60
