Moreover, if the flow is under isothermal condition without exchange of heat with surrounding (insulated system) and
Note: unit of each term is or
If (no pump or turbine)
over two ports system, for example, in a tube or pipe or a tank:
(Fig. 19b)
The above conservation equation is also known as mechanical energy balance, consisting of KE, PE, and pressure-energy. Each term is also known as ‘head’. We re-note the assumptions made in obtaining the above ME balance equation.
(1) SS (2) isothermal (3) No shaft work (4) negligible viscous work, .
It is important to note that viscous work can be neglected if the fluid is inviscid or a suitable choice of CS so that is perpendicular to CS.
and 
or 
(no pump or turbine)
over two ports system, for example, in a tube or pipe or a tank: 
(4) negligible viscous work, 
. 
is perpendicular to CS. 
