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Engineering, 24.10.2019 20:43 manuellopez1981

It is commonly recommended that hot foods be cooled first to room temperature by simply waiting a while before they are put into the refrigerator to save energy. despite this common sense recommendation, alex keeps cooking a large pan of stew twice a week and putting the pan into the refrigerator while it is still hot, thinking the money saved is probably too little. however, being pretty stingy, a money-based argument would surely change alex’s behavior. determine how much money alex would save in a year, by letting the pan of food cool before putting it in the refrigerator. assume the mass of the pan and its content is 5 kg, the average temperature of the kitchen is 20 oc, and the average temperature of the food is 95 oc when it is taken off the stove. the refrigerated space is maintained at 3 oc, and the average specific heat of the food and the pan can be taken to be 3.9 kj kg-1 oc -1 . the refrigerator has a coefficient of performance of 1.2 and the cost of electricity is 10 cents/kwh.

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