Ake a look at the back of a fridge or ac unit. you will see a ‘radiator’ that is used to remove heat from the r134a fluid that circulates within the refrigeration system. using this heat exchanger, the refrigerant-134a at 1 mpa and 90oc is to be cooled to 1 mpa and 30oc by air. the air enters at 100 kpa and 27oc with a volume flow rate of 600 m3/min and leaves at 95 kpa and 60oc. determine the mass flow rate of the refrigerant.[20]

The heater element of a 120 v toaster is a 5.4 m length of nichrome wire, whose diameter is 0.48 mm. the resistivity of nichrome at the operating temperature of the toaster is 1.3 × 10-6 ω·m. the toaster is operated at a voltage of 120 v. (a) what is the power drawn by the toaster? (b) if the cost of electricity is 12 ¢ per kilowatt-hour, and it takes 2 minutes to toast bread, how much does it cost for toasted bread? (c) when the heater element is at room temperature, is the resistivity in the nichrome wire greater than, less than, or equal to it’s resistivity when at operating temperature? explain.