A study investigating the thawing of the most important meal of the day

by Russell Dibb3/31/2010

How long does it take to thaw foods that come right out of the freezer?

Freeze food items (~267 K)

Allow for free convection

Conduct experiment at room temperature (~295 K)

Record and analyze data

Cylinder in free convection, h_bar = 6.6 W/m^2 K

Bi = 0.11 Longer than expected Errors in measurement

Included peel Approximate k

Temperature

Lumped Capacitanc

e

Transient Conduction

Actual

270 K 7.0 minutes

11.1 minutes

25.5 minutes

Temperature

Location Transient Conduction

Actual

270 K Center 17.7 minutes

22.5 minutes

275 K Surface 3.0 minutes

2.6 minutes

280 K Surface 13.4 minutes

7.5 minutes

Sphere in free convection h_bar = 5.8 W/m^2

K Bi = 0.22 Surface

measurements most realistic

Plate in two-sided free convection h_bar = 6.7 W/m^2 K

Bi = 0.04 Lumped capacitance Approximated k from

weighted average of ingredients

Temperature

Lumped Capacitanc

e

Actual

280 K 4.6 minutes

7.5 minutes

285 K 7.4 minutes

12.7 minutes

Air conditions relatively tranquil Radiation neglected for ease of calculation,

small temperature difference

Models underestimate actual thawing time Exception: bread surface

Heat is very unevenly distributed in bread Do not freeze a banana if you intend to eat it

(they become squishy and less appetizing)