is the shaft- work, for example, due to a turbine or a pump or blower, which delivers energy to the fluid or vice-versa. if the machine is turbine
if the machine is pump or blower
can also be written as
Note that is zero if
(inviscid fluid)
(tangential velocity) = 0
(choice of CS)
The general energy-balance equation can be re-arranged to obtain the following expression for a CV:
The terms of the equation are accumulation, conduction, shaft-work, viscous work, and energy efflux across CS, including pressure-energy .
For most engineering applications of steady-state, two–port system (one inlet and one outlet), uniform flow over the ports (1-D flow), and being perpendicular to CS (by a suitable choice), one can obtain the following expression for energy- conservation:
(stagnant fluid) there is no surface work, 
is the shaft- work, for example, due to a turbine or a pump or blower, which delivers energy to the fluid or vice-versa. 
if the machine is turbine 
if the machine is pump or blower 
can also be written as 
is zero if 
(inviscid fluid)
(tangential velocity) = 0
(choice of CS) 
being perpendicular to CS (by a suitable choice), one can obtain the following expression for energy- conservation: 
