Diffuser increases the pressure of a fluid at the expense of its:

Explanation:

Diffuser: Ideal Diffuser is a mechanical device that is used to increase the pressure at the expense of kinetic energy.

Kinetic energy is higher at the inlet than that of the outlet. Therefore, the velocity at the exit will be lower than that of the inlet.

Nozzles and diffusers are commonly used in jet engines, rockets, spacecraft, and even garden sprinklers.

From the steady flow energy equation,

\(m\left( {{h_1} + \frac{{{V_1}^2}}{2} + g{Z_1}} \right) + \frac{{dQ}}{{dt}} = \;m\left( {{h_2} + \frac{{V_2^2}}{2} + g{Z_2}} \right) + \frac{{dW}}{{dt}}\)

There is neither heat nor work transfer across the boundary of the system. i.e. δQ = 0 = δW

\({h_1} + \frac{{{V_1}^2}}{2} = \;{h_2} + \frac{{V_2^2}}{2}\)

For the nozzle, V2 ≫V1

For the diffuser, V2 ≪V1

i.e. the velocity of the air at exit is lower than at the inlet of the diffuser.

\({h_1} + \frac{{{V_1}^2}}{2} = \;{h_2} \Rightarrow {h_2} - {h_1} = \frac{{{V_1}^2}}{2}\)

i.e. the specific enthalpy of the air increases from inlet to exit.