Suppose that you want to freeze 1 kg of water for a party, and only have 5 minutes to do it. Relying on nothing but your keen physical abilities, a dixie cup, duct tape and a piece of string, you manage to build a refrigerator unit which can do the job.(adsbygoogle = window.adsbygoogle || []).push({});

The temperature inside the refrigeration unit is 273 K, and the temperature outside is 350 K. Since you are a brilliant UW student, assume that your refrigerator has the maximum possible efficiency. The Latent Heat of Fusion of water is 3.33×105 J/kg. Assume that the initial temperature of the water is 273 K.

a. What is the change in entropy in the water per second in J/K s?

HELP: Change in entropy = Change in energy/ Absolute Temperature.

b. What is the heat flow ( Q_hot/time ) into the hot well per second in J/s?

HELP: Use the entropy flux calculated in part b, 350 K, and use

c. How much POWER must you provide to drive your refrigerator in Watts? (That is, work done per second?)

HELP: Q(hot) = Q(cold) + Work. Remember, power is work/time.

Entropy = Energy transfer / Temperature.

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# Homework Help: Efficiency of refrigerator unit

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