Cold chain: difference between revisions
Diff·revision 16 → 17·15:03, 24 Dec 2024
Difference between revision 16 and revision 17 of Cold chain. 7 lines changed; the page grew by 1,155 bytes.
| Revision 16 — 18:52, 5 Dec 2024 PancreasPru (talk) add the light-exposure point for photosensitive material 15,523 bytes ±0 | Revision 17 — 15:03, 24 Dec 2024 Chromatokid (talk) the article confused primary and secondary drying; corrected 16,678 bytes +1,155 | ||
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| 94 | {{math|e^{−10000/275.15} = e^{−36.3438}}} and {{math|e^{−10000/303.15} = e^{−32.9869}}} | 94 | {{math|e^{−10000/275.15} = e^{−36.3438}}} and {{math|e^{−10000/303.15} = e^{−32.9869}}} |
| 95 | 95 | ||
| + | 96 | The first term is smaller than the second by a factor of e<sup>−3.357</sup>, or 0.0349, so it contributes almost nothing. Their mean is e<sup>−32.9869</sup> × 0.5174, and | |
| + | 97 | ||
| 96 | == Packaging and qualification == | 98 | == Packaging and qualification == |
| 97 | Between controlled environments, the product travels inside a package that must maintain its internal temperature without external power. The performance of such a passive shipper is a designed property, qualified against defined ambient profiles, and it is specific to a payload. | 99 | Between controlled environments, the product travels inside a package that must maintain its internal temperature without external power. The performance of such a passive shipper is a designed property, qualified against defined ambient profiles, and it is specific to a payload. |
| ⋮ | ⋮ | ||
| 102 | ; Coolant : Water ice, gel packs, phase-change materials formulated to melt at a chosen temperature, and dry ice for frozen shipments. Coolant mass and its conditioning before packing are as consequential as its identity. | 104 | ; Coolant : Water ice, gel packs, phase-change materials formulated to melt at a chosen temperature, and dry ice for frozen shipments. Coolant mass and its conditioning before packing are as consequential as its identity. |
| 103 | ; Payload arrangement : A qualified configuration specifies coolant placement, payload volume and the minimum and maximum payload for which the qualification holds. A shipper qualified for a full payload frequently fails when shipped part-full, because the reduced thermal mass follows the coolant more closely.{{r|pda_tr39}} | 105 | ; Payload arrangement : A qualified configuration specifies coolant placement, payload volume and the minimum and maximum payload for which the qualification holds. A shipper qualified for a full payload frequently fails when shipped part-full, because the reduced thermal mass follows the coolant more closely.{{r|pda_tr39}} |
| + | 106 | ||
| + | 107 | === Phase-change materials === | |
| + | 108 | Water ice melts at 0 °C and therefore holds a payload close to that temperature while any ice remains — well below the 2 °C lower bound of the cold range, and a recognised cause of freezing excursions in 2–8 °C distribution. Phase-change materials are formulated to melt at a temperature inside the target range, commonly around 5 °C for refrigerated shipments and around 22 °C for controlled-room-temperature shipments, so that the latent heat of the transition buffers the payload at a temperature that is itself compliant.{{r|pda_tr39}} | |
| + | 109 | ||
| + | 110 | The trade-off is that a material with a higher melting point stores its latent heat at a smaller temperature difference from ambient and therefore protects for a shorter time against a warm environment, while providing protection against freezing that water ice cannot. Where a shipment must survive both a hot and a cold ambient profile, dual-material configurations are used.{{r|matthias2007}} | |
| 104 | 111 | ||
| 105 | == References == | 112 | == References == |