ME EN 340 – Heat TransferFall 2010Eric Peterson and Darrell Skousen

Melting Ice - Convection

Flowing water no

bag Stagnant water no

bag

Flowing water

baggedStagna

nt bagged

Melting Ice

Experimental setup 1/3 kg blocks of ice at -10°C 3 blocks in bags, 3 blocks not in bags Flowing water: Q = 0.05 kg/s at 10°C Stagnant water: V = 5L at T = 10°C and 31°C

Procedure Place each ice block in flowing or stagnant

water and measure time until ice melted

Results

No Bag Plastic Bag10°C Running Water 3.5 min 27.5 min10°C Stagnant Water 75.5 min 105.0 min31°C Stagnant Water 7.5 min 18.75 min

Conclusion

The plastic bag has a large effect on thawing time; between 1.5 and 8 times the rate.

The plastic bag has a more of an effect on running water than stagnant water.

Running water melted the ice much quicker than the stagnant water.

Higher temperature stagnant water can melt the ice at the same rate as running water.

Application

Thermal Properties of water are often used to approximate meat or flesh.

For thawing meats, running cold water thaws much quicker than stagnant cold water.

For meats that can be washed out of the bag, thawing times will be faster (e.g. poultry).