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...
This paper deals with experimental investigations of flow boiling in tubular ducts of selected refrigerants—R134a, R507A, and R600a—under near-critical pressures. Near-critical boiling is characterised by low specific enthalpy of evaporation. The positive effect of this feature is the fact that ...