Old Radiator, New Radiator
The radiator of a car is a type of heat exchanger. Hot fluid coming from the car engine, called the coolant, flows through aluminum radiator tubes of thickness that release heat to the outside air by conduction. The average temperature gradient between the coolant and the outside air is about 130 .
The term is called the temperature gradient, which is the temperature difference between the coolant inside and the air outside per unit thickness of tube.
The radiator of an old car is no longer performing satisfactorily. The average temperature gradient between the coolant flowing through its tubes and the outside air is 195 , causing the engine to overheat.
If the old radiator is replaced with a new one that has longer tubes made of the same material and same thickness as those in the old unit, what should the total surface area available for heat exchange be in the new radiator to achieve the desired cooling temperature gradient?
a)twice that of the old unit
b)three-halves that of the old unit
c)same as that of the old unit
d)two-thirds that of the old unit
e)one-half that of the old unit