Calculate the ratio in thawing time for packaged frozen blood in two scenarios.

Question

Calculate the ratio in thawing time for packaged frozen blood in two scenarios. One package has

the bottom surface on styrofoam that can be considered as insulated. The second package has the

bottom surface on a wire mesh such that the same convection occurs over the bottom surface as over

the top surface. The thermal conductivity of the blood material is 0.55 W/mK and the surface heat

transfer coefficient is 20 W/m2K. The thickness of the package is equal to 2.5 cm and the other two

dimensions of the packages are much greater than the thickness, so that the heat transfer can be

considered as one-dimensional along the thickness.

Explanation / Answer

As the both packages have same thermal conductivity and surface heat transfer coefficient. But package one has one surface insulated so it can lose heat only through one surface and takes double the time of second package which has both surfaces conducting and loosing heat.

So Thawing Time Ratio=t1/t2=2

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