Thermodynamic Analysis of Organic Rankine Cycle Using Dry Working Fluids

摘要

Utilization of waste heat is not economically incentive to the industry once the temperature of the waste heat drops to a certain level. This is primarily due to a low efficiency when converting the energy of the waste hat to some forms of useful power. A Rankine cycle using organic fluids as working fluids, called organic Rankine cycle (ORC), is potentially feasible in recovering low-enthalpy containing heat sources. Nevertheless, an efficient operation of the ORC depends heavily on two factors: working conditions of the cycle and the thermodynamic properties of the working fluids. The main objective of this study is to investigate the effects of these two factors on the performance of the ORC. The working fluids under investigation are: Benzene (C_6H), Toluene (C_7H_8), p-Xylene (C_8H_10), R113 and R123. Irreversibility of a system using various working fluids was studied since it represents the energy balance in recovering the waste heat. The study shows that the system efficiency increases as the inlet pressure of the turbine increases regardless of the working fluid used. Among the working fluids under investigation, p-Xylene shows the highest efficiency while Benzene the lowest. The study also shows that irreversibility depends on the type of heat source. Generally speaking, p-Xylene has the lowest irreversibility in recovering a high temperature waste heat while R113 and R123 have a better performance in recovering a low temperature waste heat. In addition, an economic feasibility of ORC using various working fluids was given for ORC's with commercial capacities.