Department of Chemical and Biological Engineering

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HEAT TRANSFER - ChE 306

Question of the Day

08/18/10: How much thermal energy is required to heat up 1 scoop of ice cream to body temperature? (find answer in calories). How much energy is listed for the nutritional value of 1 scoop of ice cream? Compare the two values. Why are they different? Answer
08/31/10: Which will cool faster: A cup of black coffee, or a similar cup of coffee with a small bit of cream added (assume the cream added does not drop the temperature significantly)? Why? Answer
09/03/10 One particular late-night infomercial sells "Fast-Thaw" plates made of a metal (perhaps steel) with grooves cut in the top surface. They claim that placing frozen foods on this plate will decrease the time that it takes for the food to thaw out. Will this device work? Why or why not? Answer
09/22/10 You are familiar with the wind chill factor (especially on cold winter days). It is due to the effect of wind convection on heat loss from your body. Will the wind chill be colder with dry air or humid air? Answer
09/30/10 It has been reported that heating water in a microwave can result in an explosion of steam and water as soon as someone touches the vessel used to heat the water. Can this occur, and how does the heating differ from heating water in a pan on the stove? Answer

10/14/10 In a question posed in the Parade Section to Marilyn vos Savant, a reader asked: Why can you reach with your bare hand inside a 500 oF oven briefly, but not into a pot of boiling water at 212 oF without getting burned? Answer

11/05/10 A conventional oven for a home kitchen has burners at the bottom (used for regular baking) and at the top (used for broiling). Which set of burners will heat up an oven more efficiently? PART 2. Compared to a conventional oven, a convection oven uses a fan to blow air over the burners. Which oven will cook food more evenly? Which one will cook food faster?
11/06/10 Which of these methods will cool a canned beverage faster? placing the can in a refrigerator at 40 oC or water at 40 oC? placing in ice cubes or in crushed ice? placing in subcooled ice cubes at -20 oC or in ice water at 0 oC? placing in ice cubes or ice cubes with added salt?
 
 

 

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