Constructal thermodynamic optimization for dual-pressure organic Rankine cycle in waste heat utilization system

In this study, a novel system comprising of a two-stage organic Rankine cycle, driven by geothermal energy and coupled with a proton exchange membrane electrolyser, is investigated and optimized from thermodynamic and exergoeconomic viewpoints. Various working fluids are considered so as to ascertain the effects of thermophysical properties on the performance of the system. The electricity output from the two-stage organic Rankine cycle is employed to produce hydrogen through electrochemical reactions in the proton exchange membrane electrolyser. The effects are assessed on key parameters of variations in geothermal water temperature and the pressure ratio of high-pressure organic Rankine cycle turbine. Considering three distinct cases, a thorough optimization is performed utilizing a genetic algorithm. It is concluded that a 2-3 percent-point improvement in energy efficiency, as well as a 35% to 41% increase in hydrogen production and a 9.5% to 12% reduction in cost per unit exergy of hydrogen can be achieved via optimization. R123 is shown in the optimization to perform the best among the considered working fluids, with isopentane performing second best.

Evaluation and optimization of a novel geothermal-driven hydrogen production system using an electrolyser fed by a two-stage organic Rankine cycle with different working fluids

Analysis and optimization of a fuel cell integrated with series two-stage organic Rankine cycle with zeotropic mixtures

Performance analysis of a dual-loop bottoming organic Rankine cycle (ORC) for waste heat recovery of a heavy-duty diesel engine, Part I: Thermodynamic analysis

Energy, exergy and economic analyses and performance assessment of a trigeneration system for power, freshwater and heat based on supercritical water oxidation and organic Rankine cycle

Improvement in performance of Organic Rankine Cycle (ORC) systems, particularly in the context of dual heat sources such as IC engines, leads to better return on investments. However, the choice of architecture to achieve the best performance is not evident from available literature. When two separate heat sources are present concurrently at different temperature levels with heat contents such as in IC engines, single stage pre-heated ORC and dual loop ORC are the two commonly deployed ORC architectures. In this study, two stage architectures: Series two stage ORC (STORC) and Parallel two stage ORC (PTORC) are analysed and their performance is compared against a single stage pre-heated ORC at sub-critical conditions in the utilization of high temperature (primary) exhaust gases (573–773 K) and low temperature (secondary) jacket water (353–393 K) representing IC engine waste heat conditions. Results show that STORC and PTORC are able to achieve the maximum net power output for an intermediate utilization of secondary heat source. The power output gains from two stage layouts improves significantly with a reduction in heat source temperature difference and for lower ratios of the heat available between the primary to secondary heat source. For a 2.9 MW natural gas IC engine operating at its design point, STORC delivers 8.5% more power output whereas PTORC delivers 0.3% less power output than pre-heated ORC. Compared to a dual–loop ORC, STORC presents a less complex and improved cycle architecture with a 13.1% increased power output and a 27.9% reduced heat exchanger requirements.

Performance investigation of two stage Organic Rankine Cycle (ORC) architectures using induction turbine layouts in dual source waste heat recovery

Design and performance analysis of a novel Transcritical Regenerative Series Two stage Organic Rankine Cycle for dual source waste heat recovery

The Transcritical Regenerative Series Two-stage Organic Rankine Cycle (TR-STORC) was shown to deliver improved performance than Series Two-stage ORC (STORC) and single-stage ORC for dual-source heat recovery applications. However, TR-STORC utilizes partial evaporation for regeneration which requires precise control of two-phase flows. In real-time operations involving dual/multiple heat sources, this is difficult to achieve due to fluctuating heat inputs, leading to liquid carryover and subsequent corrosion of turbine blades. This study explores a novel Transcritical Ejector Regenerative STORC (TER-STORC), which replaces the need for two phase flows with a avapor-vapor regeneration via an ejector operating entirely with fully evaporated vapor (FE mode). Partial evaporation (PE) mode of TER-STORC requiring two-phase flows is also analyzed for comparison. Results indicate that the FE mode of TER-STORC can achieve performance comparable to PE mode and TR-STORC. FE mode of ejector operation is less sensitive to variations in ejector pressure drop than PE mode while delivering 0.2–4% lower power outputs with lower heat exchanger requirements than TR-STORC by up to 18%.At the engine design point, only a 2% drop in power output is seen for FE mode compared to TR-STORC. TER-STORC presents a robust system with reduced complexity for multisource heat recovery. 

Anandu Surendran

Papers

Performance investigation of two stage Organic Rankine Cycle (ORC) architectures using induction turbine layouts in dual source waste heat recovery

Design and performance analysis of a novel Transcritical Regenerative Series Two stage Organic Rankine Cycle for dual source waste heat recovery

An ejector based Transcritical Regenerative Series Two-Stage Organic Rankine Cycle for dual/multi-source heat recovery applications

An ejector based Transcritical Regenerative Series Two-Stage Organic Rankine Cycle for dual/multi-source heat recovery applications

A novel transcritical-recuperative two-stage Organic Rankine Cycle for dual/multi-source heat recovery applications