Question

What is throttling process preferred over isentropic expansion process?

Answer 1

i don't know sorry plz ……………………………

Answer 2

Hey.

Here is your answer.

Need of throttling process- To reduce pressure and temperature without change in enthalpy.

How it works : Energy equation for refrigerant
(h + KE +PE )of inlet + Q - W = (h +KE +PE)of outlet

KE= Kinetic energy 
PE=Potential energy
h=enthalpy
Q=heat transfer 
W=work transfer

Throttling process can be done by capillary tube.Working fluid is flow through capillary tube.
- capillary tube is isolated .so Q =0
 - Work transfer W=0
 - ∆KE= 0 ( velocity will change but it is negligible)
 -∆PE=0
 
So we can say 
(h)inlet =(h)outlet
h1=h2

Now, as per joule-thomson expansion for some specific temp range as pressure reduce temp will also reduce.

How pressure reduce ?
As fluid flow through capillary its velocity increase as per continuity eqation (AV=const).hence conversion of pressure energy into kinetic energy takes place. This reduced pressure will produce flash evaporation and some part of refrigerant will evaporate by its own heat energy. This will reduce its temperature.

Whereas icentropic expansion is also called Adiabatic expansion.

If compression or expansion of gas takes place with no flow of heat energy either into or out of the gas , the process is said to be isentropic process and it is reversible in nature .

So, During the throttling process, heat absorption capacity at a cons. pressure of a unit mass of refrigerant remains the same, ie,
                                             h1=h2.
hence it is preferred over icentropic expansion.

Thanks.