Experimental and numerical analysis on low-temperature off-design organic Rankine cycle in perspective of mass conservation

Experimental and numerical studies on the low-temperature heat recovery organic Rankine cycle operating in off-design conditions are conducted for the in-depth understanding of the system's underlying mechanisms in terms of mass conservation. Experimental data sets were obtained from a 1 kW lab-scale organic Rankine cycle test bed using R245fa as the working fluid. The effects of several boundary conditions, including charged mass, are thoroughly examined under low-temperature heat source within the range of 65–95 °C. Numerical models of the heat exchangers are developed by applying the discretization method to predict the captured mass inside the phase-changing components and validated within 5% error range. By the integration of experimental and numerical methods, unprecedented and critical results covering the pressure formation process, mass distribution, and liquid receiver modeling are derived from the analysis which could not be discovered through previous approaches. The unconventional thermodynamic state of the working fluid inside the liquid receiver is revealed in detail and a passive design is suggested for the liquid receiver model. An improved solver architecture is proposed for the complete development of a fully deterministic off-design organic Rankine cycle simulation model, where the reality-based logics obtained from the key findings are projected into the novel model. •A low-temperature heat recovery off-design organic Rankine cycle is investigated.•The formation of the high- and low-pressure is revealed in terms of mass balance.•The mass distribution is dictated by the liquid holdup effect of heat exchangers.•A passive design is suggested for the modeling of the liquid receiver.•An improved off-design organic Rankine cycle model is newly proposed.