Refrigerated Thawing Time

Thawing carries the same latent heat and the same two resistances as freezing, but two things change and both push the same direction: the driving temperature difference is now the cooler ABOVE the thaw point instead of the freezer below it, and conduction happens through the THAWED outer layer, whose conductivity is roughly a third of frozen product's. A 38 F cooler gives a driving difference near 10 F where a -10 F freezer gave 38 F, so thawing takes several times longer than freezing did. A 12 lb turkey treated as a 0.7 ft sphere at 64 lb/ft3 and 106 BTU/lb, thaw point 28 F, walk-in at 38 F, h = 2.0 and unfrozen k = 0.28 gives a driving term of 6784 / 10 = 678.4, a surface term of 0.0583 and an internal term of 0.0729, so about 89 hr, which is 3.7 days. That brackets the USDA rule of thumb of roughly 24 hours per 4 to 5 pounds a little long, which is the safe direction. Note that the internal term now EXCEEDS the surface term, the reverse of the frozen slab: in thawing, thickness usually controls and blowing more air at a frozen turkey does very little. An engineering estimate; the FDA Food Code's permitted methods and a measured product temperature govern.

thaw_time_hr = (density_pcf x latent_heat_btu_lb / (cooler_temp_f - thaw_point_f)) x (P x a_ft / h_coeff + R x a_ft^2 / k_unfrozen); thaw_time_days = thaw_time_hr / 24.

Plank's equation applied to thawing, with the ASHRAE Handbook Refrigeration shape constants cited by name and not reproduced, reported against the four thawing methods permitted by FDA Food Code section 3-501.13, cited by section; the Food Code method and a measured product temperature govern.

The conduction relation is public physics and the Food Code methods are cited by section, not mirrored. The product's dimension, density, latent heat, thaw point, cooler temperature, and conductivities are the user's values.

Estimate. AHJ and licensed professional govern.

Field names used by the API: a_ft, shape, density_pcf, latent_heat_btu_lb, thaw_point_f, cooler_temp_f, h_coeff, k_unfrozen, thaw_time_hr, thaw_time_days, surface_term, internal_term

• Unfrozen conductivity conduction is through the THAWED outer layer, whose k is roughly a third of the frozen valuefood refrigeration practice
• Permitted methods FDA Food Code section 3-501.13: refrigeration at 41 F or below; running water at 70 F or below reaching 41 F within four hours; microwave immediately followed by cooking; or as part of cookingFDA Food Code section 3-501.13
• Cross-check USDA rule of thumb, roughly 24 hours of refrigerator thawing per 4 to 5 poundsUSDA Food Safety and Inspection Service