Energy Balances on Single-Phase Nonreactive Processes

3 ENERGY BALANCES ON SINGLE-PHASE NONREACTIVE PROCESSES 

Suppose sys(f) is the total energy (internal + kinetic + potential) of a system, and ihm and /hout are the mass flow rates of the system input and output streams. (If the system is closed, these quantities each equal zero.) Proceeding as in the development of the transient mass balance equation, we apply the general energy balance equation (11.3-1) to the system in a small time interval from t to t + 1st, during which time the properties of the input and output streams remain approximately constant. The terms of the equation are as follows (see Section 7,4)  

If we now substitute the given expressions for accumulation, input, and output into Equation 11.3-1, divide by Ar, and let At approach zero, we obtain the general differential energy balance  

If there are several input and output streams, a term of the form 

It is quite difficult to solve Equation 11.3-2 unless a number of simplifications are made. We will restrict our consideration to systems that satisfy the following conditions  

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Energy Balances on Single-Phase Nonreactive Processes 555... 

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