Chapter 3 Material and Energy Balance

Accumulation

=in-out + generation - comsumption

For total mass of the system, = in - out

Two types: time dependent, and time independent

Energy Balance

Accumulation= in - out

energy can be transferred to or from the system in the forms of heat and work

Accumulation term

reflects changes in the total energy (internal, kinetic, and potential) contained within the system

In and out terms

reflect the internal, kinetic, and potential energy of matter entering and leaving. They must also reflect the flow work done on the system as material enter or leaves the system

Energy Balance Equation

work and heat are the two forms without accompanying mass flows

each term can either be positive or negative. If energy is added to the system the sign is positive, if energy is removed from the system then sign is negative

Ws = V dp

For a pump, a compressor, a turbine, or any other process involving shaft work

when there are liquids volumes: constant with respect to T and P Ws= V( Pout- Pin)

Common Chemical Process Equipment

Valve, Nozzle, pump, turbine, compressor, heat exchanger

steady state processes only

single piece of equipment is the system

no Wec in any equipment at steady state