Studying thermodynamics I face this following text from Cengel's book.
Throttling valves are usually small devices, and the flow through them may be assumed to be adiabatic (q = 0) since there is neither sufficient time nor large enough area for any effective heat transfer to take place. Also, there is no work done (w=0), and the change in potential energy, if any, is very small (pe=0). Even though the exit velocity is often considerably higher than the inlet velocity, in many cases, the increase in kinetic energy is insignificant (ke=0). Then the conservation of energy equation for this single-stream steady-flow device reduces to **h2>h1 (kJ/kg)*
Previously, I thought that enthalpy meant internal energy + work energy (PV). So If the book says throttling valves have no work involved, how is energy equation about enthalpy (u + PV)?