scholarly journals Entropy, Entransy and Exergy Analysis of a Dual-Loop Organic Rankine Cycle (DORC) Using Mixture Working Fluids for Engine Waste Heat Recovery

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1301 ◽  
Author(s):  
Shuang Wang ◽  
Wei Zhang ◽  
Yong-Qiang Feng ◽  
Xin Wang ◽  
Qian Wang ◽  
...  
Keyword(s):  
Entropy Generation ◽  
Exergy Analysis ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Working Fluid ◽  
Working Fluids ◽  
Entransy Loss

The exergy, entropy, and entransy analysis for a dual-loop organic Rankine cycle (DORC) using a mixture of working fluids have been investigated in this study. A high-temperature (HT) loop was used to recover waste heat from internal combustion engine in 350 °C, and a low-temperature loop (LT) was used to absorb residual heat of engine exhaust gas and HT loop working fluids. Hexane/toluene, cyclopentane/toluene, and R123/toluene were selected as working fluid mixtures for HT loop, while R245fa/pentane was chosen for LT loop. Results indicated that the variation of entropy generation rate, entransy loss, entransy efficiency, and exergy loss are insensitive to the working fluids. The entransy loss rate and system net power output present the same variation trends, whereas a reverse trend for entropy generation rate and entransy efficiency, while the exergy analysis proved to be only utilized under fixed stream conditions. The results also showed that hexane/toluene is the preferred mixture fluid for DORC.

Theoretical and experimental investigation of an organic Rankine cycle for a waste heat recovery system

2009 ◽  
Vol 223 (5) ◽  
pp. 523-533 ◽  
Author(s):  
W Gu ◽  
Y Weng ◽  
Y Wang ◽  
B Zheng
Keyword(s):  
Heat Source ◽  
Entropy Generation ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Entropy Generation Rate ◽  
Working Fluid ◽  
Total Entropy ◽  
Waste Heat Recovery System ◽  
Cycle Efficiency

This article describes and evaluates an organic Rankine cycle (ORC) for a waste heat recovery system by both theoretical and experimental studies. Theoretical analysis of several working fluids shows that cycle efficiency is very sensitive to evaporating pressure, but insensitive to expander inlet temperature. Second law analysis was carried out using R600a as a working fluid and a flow of hot air as a heat source, which is not isothermal, along the evaporator. The result discloses that the evaporator's internal and external entropy generation is the main source of total entropy generation. The effect of the heat source temperature, evaporating pressure, and evaporator size on the entropy generation rate is also presented. The obtained useful power is directly linked to the total entropy generation rate according to the Gouy—Stodola theorem. The ORC testing system was established and operated using R600a as a working fluid and hot water as a heat source. The maximum cycle efficiency of the testing system is 5.2 per cent, and the testing result also proves that cycle efficiency is insensitive to heat source temperature, but sensitive to evaporating pressure. The entropy result also shows that internal and external entropy of the evaporator is the main source of total entropy generation.

Second Law Analysis of Evaporator for Organic Rankine Cycle System

2008 ◽  
Author(s):  
Wei Gu ◽  
Yiwu Weng
Keyword(s):  
Entropy Generation ◽  
Temperature Difference ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Second Law ◽  
Fluid Temperature ◽  
Working Fluids ◽  
Second Law Analysis

The evaporator is a key component for Organic Rankine Cycle (ORC) system. Second law analysis of the evaporator was carried out in this work. Three processes were included and studied: pre-heating, boiling and super-heating. Firstly, ε–NTU method was applied to study the heat transfer area of evaporator. Then, internal entropy generation for three processes of evaporator was studied by entropy generation number. Thirdly, entropy generation distribution (ds/dA) was predicted by analyzing the temperature difference between the two sides of single stage counter-flow evaporator, for both pure and mixed working fluids. The results show that increase of waste heat fluid temperature increases internal irreversibility, and higher evaporator pressure decreases this irreversibility. The results also show that temperature difference at the end part of boiling process is larger for pure working fluids; and for mixed fluids, because of its’ increasing boiling temperature, this irreversibility decreases remarkably. In conclusion, second law analysis shows that the evaporating pressure plays a key role in evaporator design for ORC system; and both evaporator and working fluid should be well designed to minimize the second law loss.

scholarly journals A Simple Method of Finding New Dry and Isentropic Working Fluids for Organic Rankine Cycle

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 480 ◽  
Author(s):  
Gábor Györke ◽  
Axel Groniewsky ◽  
Attila Imre
Keyword(s):  
Low Temperature ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Electricity Production ◽  
Working Fluid ◽  
Heat Sources ◽  
Simple Method ◽  
Working Fluids ◽  
Temperature Heat

One of the most crucial challenges of sustainable development is the use of low-temperature heat sources (60–200 °C), such as thermal solar, geothermal, biomass, or waste heat, for electricity production. Since conventional water-based thermodynamic cycles are not suitable in this temperature range or at least operate with very low efficiency, other working fluids need to be applied. Organic Rankine Cycle (ORC) uses organic working fluids, which results in higher thermal efficiency for low-temperature heat sources. Traditionally, new working fluids are found using a trial-and-error procedure through experience among chemically similar materials. This approach, however, carries a high risk of excluding the ideal working fluid. Therefore, a new method and a simple rule of thumb—based on a correlation related to molar isochoric specific heat capacity of saturated vapor states—were developed. With the application of this thumb rule, novel isentropic and dry working fluids can be found applicable for given low-temperature heat sources. Additionally, the importance of molar quantities—usually ignored by energy engineers—was demonstrated.

scholarly journals Thermo-Economic Performance of an Organic Rankine Cycle System Recovering Waste Heat Onboard an Offshore Service Vessel

2020 ◽  
Vol 8 (5) ◽  
pp. 351 ◽  
Author(s):  
ChunWee Ng ◽  
Ivan C. K. Tam ◽  
Dawei Wu
Keyword(s):  
Entropy Generation ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Simple Cycle ◽  
Entropy Generation Rate ◽  
Fuel Saving ◽  
Maritime Industry ◽  
Design Data ◽  
Cycle System

Recent regulatory developments in the global maritime industry have signalled an increased emphasis on the improvement of energy efficiency onboard ships. Among the various efficiency enhancement options, recovering waste heat using the organic Rankine cycle (ORC) has been studied and identified as a promising one in many earlier studies. In this paper, a marine application of ORC for waste heat recovery will be discussed by performing the first law thermodynamic analysis based on the operating profile and machinery design data of an offshore service vessel (OSV) and defining four standard cycle configurations that include simple, recuperated, dual heat source, and with intermediate heating. The use of five hydrocarbon working fluids that are suitable for shipboard usage comprising cyclopentane, n-heptane, n-octane, methanol and ethanol are examined. The economic analysis found that annual fuel saving between 5% and 9% is possible and estimated a specific installation cost of $5000–8000 USD/kW. Among the various options, the methanol ORC in a simple cycle configuration is found to have the shortest payback time relatively balancing between annual fuel saving and total module cost. Finally, the simple cycle ORC running on methanol is further examined using the second law entropy generation analysis and it is found that the heat exchangers in the system accounted for nearly 95% of the overall entropy generation rate and further work is recommended to reduce this in the future.

scholarly journals Experimental Study and Optimization of the Organic Rankine Cycle with Pure NovecTM649 and Zeotropic Mixture NovecTM649/HFE7000 as Working Fluid

2019 ◽  
Vol 9 (9) ◽  
pp. 1865 ◽  
Author(s):  
Quentin Blondel ◽  
Nicolas Tauveron ◽  
Nadia Caney ◽  
Nicolas Voeltzel
Keyword(s):  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Mass Composition ◽  
Low Grade ◽  
Working Fluids ◽  
Replacement Fluid ◽  
Pure Fluid ◽  
Zeotropic Mixture

The Organic Rankine Cycle (ORC) is widely used in industry to recover low-grade heat. Recently, some research on the ORC has focused on micro power production with new low global warming potential (GWP) replacement working fluids. However, few experimental tests have investigated the real performance level of this system in comparison with the ORC using classical fluids. This study concerns the experimental analysis and comparison of a compact (0.25 m3) Organic Rankine Cycle installation using as working fluids the NovecTM649 pure fluid and a zeotropic mixture composed of 80% NovecTM649 and 20% HFE7000 (mass composition) for low-grade waste heat conversion to produce low power. The purpose of this experimental test bench is to study replacement fluids and characterize them as possible replacement fluid candidates for an existing ORC system. The ORC performance with the pure fluid, which is the media specifically designed for this conversion system, shows good results as a replacement fluid in comparison with the ORC literature. The use of the mixture leads to a 10% increase in the global performance of the installation. Concerning the expansion component, an axial micro-turbine, its performance is only slightly affected by the use of the mixture. These results show that zeotropic mixtures can be used as an adjustment parameter for a given ORC installation and thus allow for the best use of the heat source available to produce electricity.

scholarly journals Organic Rankine Cycle Optimization Performance Analysis Based on Super-Heater Pressure: Comparison of Working Fluids

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2548
Author(s):  
Ana Fernández-Guillamón ◽  
Ángel Molina-García ◽  
Francisco Vera-García ◽  
José A. Almendros-Ibáñez
Keyword(s):  
Waste Heat ◽  
Saturation Pressure ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Low Grade ◽  
Ambient Conditions ◽  
Working Fluids ◽  
Super Heater ◽  
Condensing Pressure

The organic Rankine cycle (ORC) is widely accepted to produce electricity from low-grade thermal heat sources. In fact, it is a developed technology for waste-heat to electricity conversions. In this paper, an ORC made up of super-heater, turbine, regenerator, condenser, pump, economizer and evaporator is considered. An optimization model to obtain the maximum performance of such ORC, depending on the super-heater pressure, is proposed and assessed, in order to find possible new working fluids that are less pollutant with similar behavior to those traditionally used. The different super-heater pressures under analysis lie in between the condenser pressure and 80% of the critical pressure of each working fluid, taking 100 values uniformly distributed. The system and optimization algorithm have been simulated in Matlab with the CoolProp library. Results show that the twelve working fluids can be categorized into four main groups, depending on the saturation pressure at ambient conditions (condenser pressure), observing that the fluids belonging to Group 1, which corresponds with the lower condensing pressure (around 100 kPa), provide the highest thermal efficiency, with values around η=23−25%. Moreover, it is also seen that R123 can be a good candidate to substitute R141B and R11; R114 can replace R236EA and R245FA; and both R1234ZE and R1234YF have similar behavior to R134A.

Second Law Analysis and Optimization of Organic Rankine Cycle

2006 ◽  
Author(s):  
C. Somayaji ◽  
P. J. Mago ◽  
L. M. Chamra
Keyword(s):  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Second Law ◽  
Low Grade ◽  
Heat Sources ◽  
Working Fluids ◽  
Second Law Analysis

This paper presents a second law analysis and optimization for the use of Organic Rankine Cycle “ORC” to convert waste energy to power from low grade heat sources. The working fluids used in this study are organic substances which have a low boiling point and a low latent heat for using low grade waste heat sources. The organic working fluids under investigation are R134a and R113 and their results are compared with those of ammonia and water under similar operating conditions. A combined first and second law analysis is performed by varying some system operating parameters at various reference temperatures. Some of the results show that the efficiency of ORC is typically below 20% depending on the temperatures and matched working fluid. In addition, it has been found that organic working fluids are more suited for heat recovery than water for low temperature applications, which justifies the use of organic working fluids at the lower waste source temperatures.

scholarly journals Energy and exergy analysis of a combined refrigeration and waste heat driven organic Rankine cycle system

2017 ◽  
Vol 21 (6 Part A) ◽  
pp. 2621-2631 ◽  
Author(s):  
Ertugrul Cihan ◽  
Barıs Kavasogullari
Keyword(s):  
Exergy Analysis ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Power Cycle ◽  
Cycle System ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis ◽  
Organic Fluids

Energy and exergy analysis of a combined refrigeration and waste heat driven organic Rankine cycle system were studied theoretically in this paper. In order to complete refrigeration process, the obtained kinetic energy was supplied to the compressor of the refrigeration cycle. Turbine, in power cycle, was driven by organic working fluid that exits boiler with high temperature and pressure. Theoretical performances of proposed system were evaluated employing five different organic fluids which are R123, R600, R245fa, R141b, and R600a. Moreover, the change of thermal and exergy efficiencies were examined by changing the boiling, condensing, and evaporating temperatures. As a result of energy and exergy analysis of the proposed system, most appropriate organic working fluid was determined as R141b.

Working Fluid Selection for an Organic Rankine Cycle for Waste Heat Recovery under Different Heat Source Temperatures

2013 ◽  
Vol 732-733 ◽  
pp. 213-217 ◽  
Author(s):  
Shuang Yang ◽  
Bing Zhang ◽  
Jin Liang Xu ◽  
Wei Zhang ◽  
Chao Xian Wang
Keyword(s):  
Heat Source ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Working Fluids ◽  
Working Fluid Selection ◽  
Cycle Efficiency ◽  
Optimum Working

Optimum working conditions of 11 working fluids under different heat source temperatures in an organic Rankine cycle were systematically investigated. Cycle efficiency of each fluid was compared at their optimal operating conditions were then analyzed. R141b appears to be the best choice when the heat source temperature is around 200oC. Heptane is suggested the suitable working fluids for the ORC system when the heat source is 300oC.

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