Analysis of a simple Rankine cycle and regenerative Rankine cycle for OTEC applications

초록

In this paper, performance of various working fluids is evaluated for the closed Ocean Thermal Energy Conversion(OTEC) power plant operating on a simple Rankine cycle and regenerative Rankine cycle. The evaporator and condenser are modeled via a UA and LMTD method while the turbine and pump are modeled by specifying isentropic efficiencies. The regenerator is modeled by specifying a heat exchanger effectiveness. HCFC22, Propane(R290), Propylene(R1270), HFC134a, HFC125, HFC143a, HFC32, R410A and ammonia are used as working fluids. Results show that newly developed fluids such as R410A and HFC32 without an ozone depletion potential perform as well as HCFC22 and ammonia. The superheat at the evaporator exit and subcooling at the condenser exit do not affect the performance of the simple OTEC power cycle. Turbine efficiency and heat exchanger size influence greatly the performance of the Rankine cycle. The regenerative Rankine cycle showed a 1.3-2.8% increase in efficiency as compared to the simple Rankine cycle. Since the efficiency of OTEC plants is quite low, this much improvement in efficiency deserves much consideration in the future design and manufacture of closed OTEC plants.