Diphenyl-diphenyl oxide eutectic mixture for high temperature waste-heat valorization by a partially evaporated cycle cascade

Abstract

Organic Rankine Cycle power production plants are very promising heat-to-power systems. High-temperature waste-heat valorization presents a great potential for the development of this technology. However, the operating limit of usual organic working fluids is close to 300 °C. To increase this limit, Diphenyl-Diphenyl Oxide mixtures could be used as high-temperature working fluids thanks to their thermal stability limit of 400 °C. This work presents an original cascade of a Diphenyl-Diphenyl Oxide Partially Evaporated Cycle and an Organic Rankine Cycle. This solution can help in increasing the power output of an ORC system used for high temperature sensible waste-heat valorization. The paper presents first an original state of the art of Diphenyl Oxide used in Rankin Cycles. Then, a single stage Diphenyl-Diphenyl Oxide Partially Evaporated Cycle is explored to analyze its thermodynamic particularities before the presentation of the cascade system optimization. Besides, a comparison to a simple Organic Rankine Cycle system is done to assess the performance improvement achieved by the proposed cascade. This is done for various bottom cycle fluids and hot source temperatures. The power production can be increased by 4%–17% for source temperatures ranging between 400 °C and 500 °C. The proposed Diphenyl-Diphenyl Oxide cycle could be used as a plug-in system in heat recovery and transport oil loops.