(c)  Nozzle:

A nozzle is primarily used to increase the flow velocity.

Figure 13.2

The first law reduces to

(13.6)

or,

(13.7)

If the inlet velocity is negligible and then otherwise, .The velocity is increased at the cost of drop in enthalpy. If an ideal gas is flowing through the nozzle, the exit velocity can be expressed in terms of inlet and outlet pressure and temperatures by making use of the relations: and .

Therefore,

(13.8)

From the relations governing adiabatic expansion,

(13.9)

We get,

(13.10)