ME EN 340 – Heat Transfer Fall 2010 Eric Peterson and Darrell Skousen

Melting Ice - Convection Flowing water no bag Stagnant water no bag Flowing water bagged Stagnant 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 BagPlastic Bag 10°C Running Water 3.5 min27.5 min 10°C Stagnant Water 75.5 min105.0 min 31°C Stagnant Water 7.5 min18.75 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).