BEGINNING ESL LESSON. Breakfast is the first meal of the day. We eat breakfast in the morning.
I Eat Heat Transfer for Breakfast
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A study investigating the thawing of the most important meal of the day
by Russell Dibb3/31/2010
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How long does it take to thaw foods that come right out of the freezer?
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Freeze food items (~267 K)
Allow for free convection
Conduct experiment at room temperature (~295 K)
Record and analyze data
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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
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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
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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
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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)