Question

After a long, hard week on the books, you and your friend are ready to relax and enjoy the weekend. You take a steak 46 mm thick from the freezer. Assume that the steak is initially at −8°C, that it thaws when the temperature at the center of the steak reaches 4°C, and that the room temperature is 22°C with a convection heat transfer coefficient of 10 W/m²⋅K. Neglect the heat of fusion associated with the melting phase change. Treat the steak as a one-dimensional plane wall having the following properties: ρ = 1000 kg/ m³, c_p = 4472 J/kg⋅K, and k = 0.625 W/m⋅K.

Note: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part.

How long (in seconds) do you have to let the good times roll before the steak has thawed?

The time taken is in seconds

How much energy per unit area (in J/m²) has been added to the steak during this period of thawing?

The amount of energy per unit area is  ×10⁶ J/m².

Answer 1

t = 46mm Tiz- 8°C Tc= 4°C Too = 2200 h = 10w/m²K 3 = 1000kg / m3 CP = 4472 K=0.625 W/m.k ale nie M Tx) - To = e. Ti- Too be has As= 1 mm SVO Assamed for mit area) V = 1x46= 46mm3 (multiplying b= 10x 10-6 m² thickness with Surface area gines 1000x100x 4472 ueline [bz 2.236x10 -3] Sulistituting all values in formula 4 - 22 -8-22 Ob = e-2.2 36 x 103 xt log (0.6) = – 2.236x10²t t = 228. 45 secs -z e-2-236x10'xt ME an uwgy per mit area added to Steak daug Steak thaus from – poc to 4°C energy added - meaT . = SVCO CT₂ -T) = 10008 46 x 70 x 4472 (4-(-8)) = 2.468 J/m2