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.

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 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.

Optimization of Cycle and Expander Design of an Organic Rankine Cycle Unit Using Multi-Component Working Fluids

2016 ◽  
Author(s):  
Andrea Meroni ◽  
Jesper Graa Andreasen ◽  
Leonardo Pierobon ◽  
Fredrik Haglind
Keyword(s):  
Low Temperature ◽  
Power Systems ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Fluid Temperature ◽  
Heat Sources ◽  
Working Fluids ◽  
Turbine Performance ◽  
Temperature Heat

Organic Rankine cycle (ORC) power systems represent attractive solutions for power conversion from low temperature heat sources, and the use of these power systems is gaining increasing attention in the marine industry. This paper proposes the combined optimal design of cycle and expander for an organic Rankine cycle unit utilizing waste heat from low temperature heat sources. The study addresses a case where the minimum temperature of the heat source is constrained and a case where no constraint is imposed. The former case is the waste heat recovery from jacket cooling water of a marine diesel engine onboard a large ship, and the latter is representative of a low-temperature geothermal, solar or waste heat recovery application. Multi-component working fluids are investigated, as they allow improving the match between the temperature profiles in the heat exchangers and, consequently, reducing the irreversibility in the ORC system. This work considers mixtures of R245fa/pentane and propane/isobutane. The use of multi-component working fluids typically results in increased heat transfer areas and different expander designs compared to pure fluids. In order to properly account for turbine performance and design constraints in the cycle calculation, the thermodynamic cycle and the turbine are optimized simultaneously in the molar composition range of each mixture. Such novel optimization approach enables one to identify to which extent the cycle or the turbine behaviour influences the selection of the optimal solution. It also enables one to find the composition for which an optimal compromise between cycle and turbine performance is achieved. The optimal ORC unit employs pure R245fa and provides approximately 200 kW when the minimum hot fluid temperature is constrained. Conversely, the mixture R245fa/pentane (0.5/0.5) is selected and provides approximately 444 kW when the hot fluid temperature is not constrained to a lower value. In both cases, a compact and efficient turbine can be manufactured.

scholarly journals Investigation of an Innovative Cascade Cycle Combining a Trilateral Cycle and an Organic Rankine Cycle (TLC-ORC) for Industry or Transport Application

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 3032 ◽  
Author(s):  
Xiaoli Yu ◽  
Zhi Li ◽  
Yiji Lu ◽  
Rui Huang ◽  
Anthony Roskilly
Keyword(s):  
High Temperature ◽  
System Performance ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Exergy Efficiency ◽  
Working Fluid ◽  
Second Law ◽  
Exergy Destruction ◽  
Second Law Analysis ◽  
Net Power Output

An innovative cascade cycle combining a trilateral cycle and an organic Rankine cycle (TLC-ORC) system is proposed in this paper. The proposed TLC-ORC system aims at obtaining better performance of temperature matching between working fluid and heat source, leading to better overall system performance than that of the conventional dual-loop ORC system. The proposed cascade cycle adopts TLC to replace the High-Temperature (HT) cycle of the conventional dual-loop ORC system. The comprehensive comparisons between the conventional dual-loop ORC and the proposed TLC-ORC system have been conducted using the first and second law analysis. Effects of evaporating temperature for HT and Low-Temperature (LT) cycle, as well as different HT and LT working fluids, are systematically investigated. The comparisons of exergy destruction and exergy efficiency of each component in the two systems have been studied. Results illustrate that the maximum net power output, thermal efficiency, and exergy efficiency of a conventional dual-loop ORC are 8.8 kW, 18.7%, and 50.0%, respectively, obtained by the system using cyclohexane as HT working fluid at THT,evap = 470 K and TLT,evap = 343 K. While for the TLC-ORC, the corresponding values are 11.8 kW, 25.0%, and 65.6%, obtained by the system using toluene as a HT working fluid at THT,evap = 470 K and TLT,evap = 343 K, which are 34.1%, 33.7%, and 31.2% higher than that of a conventional dual-loop ORC.

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 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.

scholarly journals Techno-Economic Analysis of Hybrid Binary Cycles with Geothermal Energy and Biogas Waste Heat Recovery

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1969 ◽  
Author(s):  
Davide Toselli ◽  
Florian Heberle ◽  
Dieter Brüggemann
Keyword(s):  
Electric Power ◽  
Waste Heat ◽  
Thermal Power ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Secondary Source ◽  
Fluid Temperature ◽  
Levelized Cost Of Electricity ◽  
Hybrid Configuration

In Germany, enhancing renewable power generation represents a leading step to comply with the requirements of the Energiewende agenda. The geothermal reservoir in Oberhaching is assumed as a case study, with a gross electric power equal to 4.3 MWel. The intent of this work is to design a hybrid binary geothermal power plant and to integrate it into the German energy market. Biogas waste thermal power equal to 1350 kWth is assumed as a secondary source. Two different layouts are defined for the hybrid solution: increasing the geothermal fluid temperature before entering the organic Rankine cycle (ORC) unit and superheating the working fluid after the evaporator. Stationary and quasi-stationary simulations have been performed with Aspen Plus V8.8. Results demonstrate how hybridization allows a maximum electric power increase of about 240 kWel. Off-design conditions are investigated regarding both the switch-off of exhaust gases and the annual ambient temperature fluctuations. In spite of the additional secondary source, the selected case studies cannot comply with the Minute reserve requirements (MRL). Moreover, economic results for both power-only and combined heat and power (CHP) configuration are provided. In the power-only configuration, the new-build hybrid system provides 15.42 €ct/kWh as levelized cost of electricity (LCOE), slightly lower than 16.4 €ct/kWh, as calculated in the geothermal-only solution. A CHP hybrid configuration shows a +19.22% increase in net cash flow at the end of the investment on the CHP geothermal solution.

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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