ABSTRACT
One term in our overall energy balance is "heat" and was defined as energy transferred across the boundary of the system as a result of temperature difference. The overall energy balance tells us only that the sum of all the terms in the equation must remain constant - that a balance be maintained - that is, that energy be a conserved quantity. We can, therefore, calculate rate of transfer of any of the various forms of energy directly from the overall energy balance only if we know the total of the remaining terms. The overall energy balance by itself (or even when combined with the overall momentum and mass balances) is therefore seldom sufficient to determine the state of our system.
