Joule-Brayton cycle efficiency

For an irreversible gas turbine cycle (the irreversible Joule-Brayton (UB) cycle of Fig. 1.9), less than unity) and < 1 so that the thermal efficiency is... 

If, in the heat pumps, the energy of compression is not recovered but is wasted in letdown valves (as the pressure of the working fluid is reduced to the low pressure of the evaporator (Joule-Thomson cycle), the liquefaction efficiency will be low (35-60%). This range of efficiencies is a function of the liquefier size and refrigerant used. If the letdown valves are replaced by turbo expanders (Brayton cycle), which recover some of the compression energy during pressure letdown, and if helium or neon refrigerants are used, the efficiency can theoretically reach 80-90%. 

Brayton (or Joule) Cycle Efficiency, itip. Percent ... 

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