THE STEAM POWER CYCLE,  a brief overview. Water possesses three phases; solid, liquid and gas.  At most temperatures, adding heat to any of these phases produces a proportional temperature rise termed “sensible heat”.  Sensible heat is heat added to a process that is measured by a rise in temperature or, as JP Joule put it, heat “indicated by the thermometer”. GENERATION is the act of creating steam in boilers or steam generators. Water isn’t always ‘sensible’ (That’s a joke, son).  Under normal sea level conditions, ice can’t exceed 32 degrees F and water can’t pass 212 F even though heat is added.  Energy never disappears, it must go somewhere or do something; ice uses the absorbed energy to change into the water phase at 32F while water assumes the steam phase at 212 F.   The English word latent comes from Latin latens, meaning “lying hid”.  Temperatures that remain constant until all the ice has melted or water evaporated are thus referred to as “latent heat”. The above suggests: *    All sensible heat applied in superheating is available for conversion into work by the engine. *    All sensible heat applied to bring the water to the boiling temperature is lost. *    Part of the latent heat is available for conversion to work and part is lost to the cooling medium. Limits to the Rankine Cycle can be understood by examining the roles latent and sensible heat play in the four steam cycle elements: GENERATION *   Adding sensible heat raises pressurized temperature to the boiling point. *   Adding latent heat transforms the water into pressurized steam. *   Adding more sensible heat raises the steam temperature, superheating it. EXPANSION *   Superheat extracted from the steam in the engine does work. *   Latent heat extracted from the steam in the engine does work. CONDENSATION *   Latent heat extracted from the exhaust steam, transforming it into condensate, does no work. *   Sensible heat extracted from the exhaust steam, cooling it below condensation temperature, does no        work FEED *   Heat is neither added or extracted. The amount of energy required to melt ice and vaporize water are respectively called the latent heats of fusion and vaporization.  “Saturation temperature” describes the temperature at the boiling point; at this temperature steam can be saturated with (carry) an unspecified amount of water of identical temperature.  “Superheated steam” describes the condition at which steam has absorbed sensible heat beyond the latent heat, warming the steam beyond saturation temperature.