Steady-state Flow Processes

Many of the engineering devices like turbines, compressors, pumps, nozzles, condensers, heat exchangers etc. operate at steady state conditions. The general expression developed for the control volume in the earlier lecture can be simplified if steady flow conditions are assumed.

These are:

• The mass flows into the control volume at a constant rate and leaves the control volume at the same rate. Therefore, there is no accumulation of mass inside the control volume. Thus, .

or,

(13.1)

• The state of the matter at the inlet, exit and at any given point inside the control volume does not change with respect to time. Therefore,

(13.2)

• The rate of energy transfer as heat and work across the control surface is a constant. constant; constant

With these, the first law for the control volume reduces to the form

(13.3)