Now let us go to the other extreme and consider a large roast in an oven. If
you have done any roasting, you must have noticed that the temperature distribution
within the roast is not even close to being uniform. You can easily
verify this by taking the roast out before it is completely done and cutting it in
half. You will see that the outer parts of the roast are well done while the center
part is barely warm. Thus, lumped system analysis is not applicable in this
case. Before presenting a criterion about applicability of lumped system
analysis, we develop the formulation associated with it.