Throttling Process

The throttling process is defined as a procedure in which there is no alter in enthalpy from state one to state two, h1 =h2; no work is completed, W = 0; and the process is adiabatic, Q = 0. To best understand the theory of the perfect throttling process let us compare what we can examine with the above theoretical suppositions.

An illustration of a throttling process is an ideal gas flowing via a valve in mid-position. From experience we can study that: P_in >P_out, vel_in < vel_out (here P = pressure and vel = velocity). Such observations verify the theory that h_in =h_out . Recall h = u + Pv (v = specific volume), therefore when pressure reduces then specific volume should raise when enthalpy is to stay constant (supposing u is constant). Since mass flow is constant, the change in specific volume is examined as a rise in gas velocity, and this is confirmed by our observations.

The theory also expresses W=0. Our interpretation again verifies this to be true as clearly no "work" has been completed by the throttling process. Lastly, the theory express that an ideal throttling process is adiabatic. This can't clearly be proven by observation as a "real" throttling process is not ideal and will contain some heat transfer.