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Real time help-Which has faster thaw time?

  1. Jul 31, 2007 #1
    I am trying discuss steak preparation with another person and an issue has arisen. I do not have time to perform this experiment myself, but thought this might be a good place to find a quicker answer from the gurus.

    Would 1lb of beef (a steak 1" thick) thaw to entirely non frozen faster in a bowl of water that starts at 110 degrees F, or faster in running tap water at 70 degrees F?

    My impression would be in running tap water due to convection, but not sure enough to go out on a limb.

    Also, any way to figure the time for each given that in reality much of the meat is really water?

    Thanks for the help.
     
    Last edited: Jul 31, 2007
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  3. Jul 31, 2007 #2

    chroot

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    There's really no way to answer this question without experiment; there are far too many variables which you've left undefined.

    Examples: How big is the bowl of 110F water? What volume of water is washing over the steak from the 70F tap per unit time? What is the surface area of the steak? How much of that surface area is in good contact with the flow of tap water?

    - Warren
     
  4. Jul 31, 2007 #3
    Yeah, sorry about not thinking about those factors. I guess I will have to put the argument on hold and do this at home. How about your off the hip assumption as I am sure it would hold more value than mine? Assume 1 gallon of hot water and 100% surface area in contact with the water in each circumstance and your best guess for the running water from a kitchen faucet? Steak might be 6 inches in length by 5 inches in height and 1 inch thick.
     
  5. Jul 31, 2007 #4

    chroot

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    If I had to guess, I'd guess the gallon bowl of hot water. The reason I'd guess this is because the entire surface area of the steak is exposed to the water (unlike the tap), and the water in the bowl is always going to be hotter than the water from the tap.

    (A gallon of water has about 10 times the volume of the steak, so the equilibrium temperature of the steak + water is going to be much higher than the 70F water from the tap throughout the entire thaw.)

    - Warren
     
  6. Jul 31, 2007 #5
    In my "mind's eye" I visualize the tap water steak also in a bowl that holds a gallon of water so that there is 100% surface area exposed, but with the tap water running into it and then overflowing, whereas the hot water steak is only in a bowl with no running water (which I realize still has some convection effect as as the water cooled from the steak will sink and the warmer water will replace it).

    Do you think the effect of more "forceful" convection with the tap water would overcome the effect of starting with a higher temperature of water? Again, just looking for an off the cuff answer which I realize probably drives a scientist crazy due to the relative guesswork involved. Sorry.

    I am only asking because if you think there would be a good chance, I am going to pull out some steaks tonight and experiment.:wink:

    Heck, I probably will pull the steaks out regardless:rofl:
     
  7. Jul 31, 2007 #6

    chroot

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    Okay... if you keep changing the story, there's no way I can give you any answer at all.

    What you're describing now is basically two bowls: one with water that begins at 110F and cools, and one with water that is continually replenished and thus maintained at a constant 70F.

    Again, I'd have to go with the 110F bowl, because I don't believe its temperature will fall below 70F during the entire thaw. Before I could answer this exactly, I'd have to know the original temperature of the steak (10F? 20F?), and the desired target temperature (40F?).

    Basically, you want the steak's temperature to rise about 40 or so degrees. The volume of water surrounding it is ten times larger, however, so its temperature is not going to fall nearly as much as 40 degrees (from 110F all the way to 70F).

    The critical metric here is whether or not the water in the 110F bowl will ever go below 70F over the course of the thaw. You can just use basic [itex]Q = m C \Delta T[/itex] heat-transfer concepts to find out which would win.

    - Warren
     
    Last edited: Jul 31, 2007
  8. Jul 31, 2007 #7
    Thanks, I appreciate your help with this. Cheers.
     
  9. Jul 31, 2007 #8

    Danger

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    I don't know the answer, but I do know that exposing the outer layers to really hot water can mess up the cooking later. W always just chucks the steaks into a sink full of cold water and leaves them for a few hours.
     
  10. Jul 31, 2007 #9

    russ_watters

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    One side or the whole thing exposed to running water doesn't matter. The amount of energy contained in a gallon of 110F water is a small fraction of what is required to thaw a reasonable sized steak. The heat of fusion is 80 cal/g-C, but the amount required to change the temp 1 C is 1 cal/g-C. Also, the natural convection of the steak in the gallon of still water is very small.

    The steak would start thawing faster in the 110F water, but in mere seconds would be more thawed by the running 70 F water.
     
  11. Jul 31, 2007 #10

    chroot

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    Russ,

    We're talking a 10:1 ratio of water to steak, and raising the steak temperature perhaps 20F (including heat of fusion), and reducing the water temperature by 40F. I think it might still come down to experiment. I really do think the surface area concern is significant.

    Have you done this kind of experiment before?

    - Warren
     
  12. Dec 7, 2007 #11
    A frozen steak in a bowl of warm water will thaw *slower* than a similar steak in a bowl of water that is being constantly replenished under a tap even with considerably cooler water. This has been shown experimentally. In a still bowl of water, the heat from the layer of water around the steak is transferred to the steak and "insulate" the steak somewhat, slowing the transfer of heat. In the overflowing bowl, convection will allow a more rapid heat transfer. It is analogous to a hot oven (no radiant heating from the coils) vs. a convection oven where the hot air is circulated around the food.

    Of course, I'm sure there is a cross-over point depending on the rate of water flow and the difference in temperature between the water samples (200 degree F still water vs. 33 degree F running water may make a difference, but I'd still vote on the running water.

    On the practical side, this is the method that I always use to thaw meat and it is surprisingly fast.
     
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