THERMOECONOMIC ANALYSIS OF ORGANIC RANKINE CYCLE USING ZEOTROPIC MIXTURES

asme-orc2015 Tracking Number 161

Depletion of fossil fuel resources and their environmental impact have accelerated research work in the area of renewable energy and energy efficiency. Utilization of low temperature renewable energy resources or low grade waste heat can reduce the environmental impact and energy cost. Organic Rankine Cycle (ORC) is a viable option for efficient recovery of medium to low temperature renewable energy and waste heat. Working fluids with lower boiling point enable ORC to recover low grade heat effectively. Selection of the working fluid has a significant impact on ORC system performance. The current study aims to investigate the performance of ORC system using pure working fluids and zeotropic mixtures, based on thermodynamic and thermo-economic parameters of ORC system under different sink and source conditions. Low temperature geothermal water is used as heat source in simulation. Evaporator, expander, condenser and feed pump models are developed in MATLAB. The discretized LMTD method is employed for evaporator and condenser model with appropriate database of heat transfer and pressure drop correlations. The effects of temperature glide and pinch point temperature are analysed on the basis of exergy loss and cost of evaporator and condenser. For comparison, pure working fluids are taken as the base case. The results show that the exergy destruction in evaporator and condenser for zeotropic mixtures is less than pure working fluids. Exergy efficiency of system with zeotropic mixture is higher than pure working fluids. For the same power output, the heat transfer area of evaporator and condenser is reduced considerably and so the cost.