Page 123 - DJJ20063- Thermodynamics 1
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DJJ20063- Thermodynamics 1



                      b )     STEADY FLOW ENERGY EQUATION



                      This equation is a mathematical statement on the principle of Conservation of Energy as

                      applied to the flow of a fluid through a thermodynamic system. The
                      various forms of energy which the fluid can have are as follows:



                      i)      Potential energy

                      If the fluid is at some height Z above a given datum level, then as a result of its mass it
                      possesses potential energy with respect to that datum. Thus, for unit mass of fluid, in the

                      close vicinity of the earth,



                                     Potential energy = g Z

                                                       9.81 Z


                      ii)     Kinetic energy

                      A fluid in motion possesses kinetic energy. If the fluid flows with velocity C, then, for unit
                      mass of fluid,

                                                     C  2
                                     Kinetic energy =
                                                      2

                      iii)    Internal energy

                      All fluids store energy. The store of energy within any fluid can be increased or decreased

                      as a result of various processes carried out on or by the fluid. The energy stored within a

                      fluid  which  results  from  the  internal  motion  of  its  atoms  and  molecules  is  called  its

                      internal energy and it is usually designated by the letter U. If the internal energy of the
                      unit  mass  of  fluid  is  discussed  this  is  then  called  the  specific  internal  energy  and  is

                      designated by u.


                      iv)     Flow or displacement energy

                      In order to enter or leave the system, any entering or leaving volume of fluid must be

                      displaced with an equal volume ahead of itself. The displacing mass must do work on the



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