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Organic Rankine Cycles

September 2015

September 2015

Publisher: University of Tabriz
ISBN: 600720431-6

Authors:

Mortaza Yari

University of Tabriz

Farzad Mohammadkhani

Urmia University-Engineering Faculty of Khoy

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September 2015

Mortaza Yari · Farzad Mohammadkhani

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Article

Multi-objective optimization of low-temperature waste-heat ORC power generation systems

May 2013 · Dongli Gongcheng Xuebao/Journal of Chinese Society of Power Engineering

Owing to the limitations of single-objective optimization on existing organic Rankine cycle (ORC) power generation system, a multi-objective optimization design was conducted for the low-temperature waste-heat ORC power generation system from the point of view of thermodynamic and economic aspects, by taking maximum exergy efficiency and minimum investment of system as the objective functions, ... [Show full abstract] selecting 5 key thermal parameters as the decision variables, such as turbine inlet temperature, turbine inlet pressure, pinch temperature difference, approach temperature difference and condenser temperature difference, etc., optimizing the ORC power generation system with working fluids R123, R245fa and isobutane using non-dominated sorting genetic algorithm (NSGA-II), and subsequently Pareto optimal solutions were obtained, from which the optimum design solution with optimal combinations of system thermal parameters was selected with the aid of an ideal point. Results show that under the given waste heat conditions, R245fa is the optimal working fluid in consideration of both the thermodynamic performance and the economic efficiency. The optimum solution shows an optimal exergy efficiency of 10.37% and a minimum investment of 4558400 Yuan.

Article

The discussion of composition shift in organic Rankine cycle using zeotropic mixtures

May 2017 · Energy Conversion and Management

Zeotropic mixtures have been important candidates for working fluids in the organic Rankine cycle (ORC) because of the temperature glide characteristic. “Composition shift” is a widespread phenomenon for zeotropic mixtures’ application in thermodynamic systems and certainly needs to be considered in ORC. In this paper, the evaporator, condenser, expander and pump models are respectively developed ... [Show full abstract] and then the circulating composition is calculated. Based on that, the forming reasons of “composition shift” are well illuminated. The influences of composition shift on the system net power output and heat transfer process are presented and analysed. The influence factors including pressure, two-phase zone area, total charge mass and velocity difference between liquid and vapor phase are also carefully discussed. Besides, the inner relation between temperature glide and composition shift is also revealed at last. The results showed that the optimal charge concentration of the low boiling point component in practice should be a bit lower than the optimal concentration without considering composition shift. Besides, the local composition shift characteristic will affect the heat transfer process by altering the temperature along the heat exchanger. Reducing the two-phase zone area, increasing the total charge mass, increasing the evaporation pressure and reducing the slip ratio can mitigate the effect of composition shift. The simulation also reveals that the magnitudes of temperature glide and composition shift show a good linear relation by just altering the charge composition.

Conference Paper

Full-text available

Technoeconomic analysis of internal combustion engine-organic Rankine cycle cogeneration systems in...

August 2018

Organic Rankine cycle (ORC) systems are a promising technology for converting heat to useful power, especially in combined heat and power (CHP) applications with significant quantities of surplus heat that would otherwise be wasted. Beyond the technical performance of these systems, their economic feasibility is crucially important for their wider deployment. In this study, a technoeconomic ... [Show full abstract] optimisation of CHP systems is performed in which ORC engines convert heat recovered from internal combustion engines (ICEs), and specifically from both the ICE hot-water output and exhaust-gas stream. The overall aim is to evaluate the impact of the ORC power output and of the components' design and capital cost on the financial viability of a relevant project, while evaluating a range of candidate working fluids. Results indicate that ORC designs optimised for maximum power output correspond to higher specific investment cost (SIC), with the best performing fluids achieving a SIC of £2100 per kW. In contrast, optimisation for minimum SIC returns values as low as £1700 per kW, or 20% lower. For systems designed and optimised for maximum power, a large fraction of jacket water heat is recovered, while for minimum SIC the utilisation drops to minimise the size and cost of the heat exchangers. The best-performing ORC designs for minimum SIC have discounted payback periods (DPPs) of 4-5 years, while those optimised for power output have DPPs of 6-7 years, however, the net present values (NPVs) of the latter designs are up to 27% higher than the former. Therefore, there is a trade-off to consider over the project life between high-capacity ORC engines with a high SIC and longer DPP, and designs with minimal SIC but lower power output, shorter DPP and lower NPV. The effect of increasing the amount of hot water required by the building is also analysed, and the ORC engine is shown to be sensitive to this factor for some working fluids.

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Article

Full-text available

A novel geothermal system combined power generation, gathering heat tracing, heating/domestic hot wa...

July 2014 · Geothermics

Oil wells in the high water-cut period become geothermal wells, thereby increasing the recoverable reserve. A novel geothermal system involving organic Rankine cycle (ORC), absorption refrigeration, gathering heat tracing, direct and indirect heating, and oil recovery was presented. The objective is to improve the system efficiency. The results show that R601a has the highest cycle performance ... [Show full abstract] and auxiliary cold sources do increase the power output. Replacing oil boilers with geothermal water as the heat source of gathering heat tracing (GHT) can save about 8163 tons of oil a year. About 34,600 tons of oil can be recovered each year. Moreover, the system can also provide heating for sixty 5000-square-meter residential buildings and domestic hot water for over 8000 people.

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Organic Rankine Cycles

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Recommended publications

Multi-objective optimization of low-temperature waste-heat ORC power generation systems

The discussion of composition shift in organic Rankine cycle using zeotropic mixtures

Technoeconomic analysis of internal combustion engine-organic Rankine cycle cogeneration systems in...

A novel geothermal system combined power generation, gathering heat tracing, heating/domestic hot wa...