If g is the acceleration of gravity, Vg is the gas velocity, hg is the gas enthalpy per unit mass, z is the elevation with respect to a reference point,ρ is the gas density, and ug is the gas internal energy per unit mass, then the energy-balance equation in its differential form ...
The inlet enthalpy of refrigerant just before the first preheater is estimated with refrigerant’s bulk temperature and pressure. Q is the amount of heat which is supplied by the electricity into the preheaters in direct heating method. G is the mass flux of refrigerant. h′ and h″ are ...
When the heat source temperature is below 130 °C, R1234ze(Z) requires low evaporation pressures, which leads to rather limited enthalpy drops in the turbine which results in a low power output. Figure 5. Net power output and Thermal Efficiency optimization for different heat source temperatures...