Low-Grade Waste Heat Recovery for Power Production using an Absorption-Rankine Cycle

An investigation of heat recovery for power generation using an absorption-Rankine cycle with a low temperature waste heat source was conducted. In such a cycle, the condenser and boiler of a conventional Rankine system are replaced with an absorber and desorber. A recuperative solution heat exchanger is also incorporated between the absorber and desorber to minimize the external heat input. An ionic liquid-refrigerant pair is used as the working fluid, for which fluid properties were developed using the Peng-Robinson equation of state for a binary mixture. A detailed thermodynamic model of the system was developed to understand the potential of this cycle and working fluid combination. It was shown that the system is capable of achieving 15 percent conversion efficiencies using waste heat in the 130-160C range. A parametric study also shows that the system can operate over a range of source and sink temperatures. The effects of solution heat exchanger efficiency and turbine efficiency on system performance are also investigated.