I'm doing some back of the envelope calculations for the potential of a turbine thermal generator using ammonia as a working fluid. I've never done thermodynamics before so I'm looking for a reality check. Isotropic turbine work done by a unit mass is given as h2 - h1 or simply dh between the the state of the fluid before and after the turbine. The temperature of the gas at each state is the temperature at the vaporizer/condenser and the pressure is the vapor pressure of the gas at those temperatures. I'm assuming I can substitute h2 and h1 in my turbine work equation for the specific enthalpy of a saturated gas hg at each temperature from an engineering lookup table for ammonia, and that this will give me the ideal energy per gram for my turbine subsystem.