Besides being a quantity to express a system's capacity???

Try to understand what is enthalpy since if you put such a question you did not understand what it is.

Enthalpy increases steam velocity through the turbine nozzles, so in a reheat turbine you can increase its output by returning steam to the boiler to be reheated and back to the turbine to do more work.

Regards JD.

Hi my friend

Your main field possibly is not a branch of mechanical engineering.

Anyhow ,if we write the 1st law of thermodynamics for a turbine(steam or gas) the effect of entalpy is clear .I write and make it simple for you:

Power =turbine mass flow rate * (h1-h2)

h1=entalpy of turbine inlet fluid

h2=entalpy of turbine outlet fluid

Of course the computation of entalpy depending on situation can be very coplicated or easy and simple.

Good luck