A Comparative Study of Scroll Expander Performance Using CO2 and Zeotropic Mixtures As Working Fluids

2019 ◽  
Author(s):  
Arun Kumar Narasimhan ◽  
Diego Guillen Perez ◽  
D. Yogi Goswami
Keyword(s):  
Comparative Study ◽  
Organic Rankine Cycle ◽  
Volume Ratio ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Cycle Performance ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Working Fluids ◽  
Scroll Expander

Abstract Scroll expanders are generally used for low temperature power generation applications due to their inherently small built-in volume ratio. The working fluid and operating conditions play an important role in the expander performance as well as its physical size and volume ratio. Hence, a comparative study of scroll expander performance was carried out between two different working fluids, R433C and supercritical (s-CO2). The s-CO2 Brayton cycle achieved a maximum cycle efficiency of 13.6% at an expander supply pressure of 11 MPa. Two separate scroll geometries were modeled for supercritical Organic Rankine Cycle (SORC) using R433C and s-CO2 Brayton cycle for the operating conditions that provided the maximum cycle performance. The s-CO2 scroll geometry achieved a maximum expander efficiency of 80% with a volume ratio of 2.5 and a diameter of 19 cm. The high inlet temperatures required a much higher volume ratio of 6.2 and scroll diameter of 30 cm for the R433C based SORC leading to greater leakages and lower expander efficiency of 62%. The comparative study shows that s-CO2 is better suited for scroll expander than R433C at such high expander supply temperatures.

Integration of Organic Rankine Cycle and Scroll Expander Models for Effective Design and Performance Using Organic Working Fluids

2017 ◽  
Author(s):  
Arun Kumar Narasimhan ◽  
Chatura Wickramaratne ◽  
Rajeev Kamal ◽  
Punit Singh ◽  
D. Y. Goswami
Keyword(s):  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Performance Comparison ◽  
Operating Conditions ◽  
Cycle Performance ◽  
Working Fluids ◽  
Scroll Expander ◽  
And Performance ◽  
Low Global Warming Potential ◽  
Effective Design

This paper presents the organic Rankine cycle performance comparison of several working fluids with low global warming potential and low ozone depletion potential at several heat source temperatures. At an evaporating temperature of 80°C, maximum first law efficiency of 5.8% was achieved with ammonia, while at 145°C and 180°C, diethyl ether provides the maximum cycle efficiencies of 11.4% and 13% respectively. For the best operating conditions of the ORC model, a suitable two-stage scroll geometry was modeled and its performance was evaluated. Stage I and stage II scroll geometries with volume ratios of 5.3 each were modeled for the supply conditions of 180°C and 2.6 MPa. The geometries provided a combined shaft work of 8.7 kW at combined expander efficiency of 89% accounting for the losses due to the leakage in the expander.

scholarly journals Development of a Pattern Recognition Methodology with Thermography and Implementation in an Experimental Study of a Boiler for a WHRS-ORC

2019 ◽  
Author(s):  
Concepción Paz ◽  
Eduardo Suarez ◽  
Miguel Concheiro ◽  
Antonio Diaz
Keyword(s):  
Pattern Recognition ◽  
Wall Temperature ◽  
Waste Heat ◽  
Combustion Engine ◽  
Organic Rankine Cycle ◽  
Exhaust System ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Cycle Performance ◽  
Working Fluid

Waste heat dissipated in the exhaust system in a combustion engine represents a major source of energy to be recovered and converted into useful work. A waste heat recovery system (WHRS) based on an Organic Rankine Cycle (ORC) is a promising approach, and has gained interest in the last few years in an automotive industry interested in reducing fuel consumption and exhaust emissions. Understanding the thermodynamic response of the boiler employed in an ORC plays an important role in steam cycle performance prediction and control system design. The aim of this study is therefore to present a methodology to study these devices by means of pattern recognition with infrared thermography. In addition, the experimental test bench and its operating conditions are described. The methodology proposed identifies the wall coordinates, traces paths, and tracks wall temperature along them in a way that can be exported for subsequent post-processing and analysis. As for the results, through the wall temperature paths on both sides (exhaust gas and working fluid) it was possible to quantitatively estimate the temperature evolution along the boiler and, in particular, the beginning and end of evaporation.

Scaling a radial flow turbine from air to multiple compressible fluids and performance evaluation using computational fluid dynamics

2020 ◽  
pp. 095765092092207
Author(s):  
K Vijayaraj ◽  
Punit Singh
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Mach Number ◽  
Radial Flow ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Compressible Fluids ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Working Fluids

Many new turbine designs may take large timelines to prove their worth. For getting duty condition at optimum efficiency, one can always scale speed, diameter, if a very efficient benchmark is available. This paper examines the similarity-based scaling strategy to develop radial inflow turbines for different compressible fluids from a well-established NASA radial flow turbine designed and experimentally tested with air as the working fluid. The NASA 1730 air turbine experimental data have been used as the benchmark here and adopted multiple fluids to understand scaling. The considered fluids are supercritical carbon dioxide for the Brayton cycle, helium for the cryogenic liquefaction cycle, and R143a for the organic Rankine cycle. The uniqueness here is to have three types of cycles, viz. closed-loop Brayton cycle, organic Rankine cycle, and cryogenic helium liquefaction cycle, which employ different working fluids, adapting the same NASA turbine geometry. This paper has described the scaling methodology and presented the simulated turbine performance of SCO2, helium, and R143a using computational fluid dynamics. The dimensionless curves for these fluids are plotted on the corresponding experimental characteristics of the NASA turbine. Out of the three fluids, SCO2 showed the perfect Mach number matching for the flow and torque coefficient curves. The Mach number deviations in the case of helium were small, and the variations were slightly higher for R143a. The efficiencies were the highest for R143a, followed by SCO2 and helium. Thus, the scaling was found to be effective in all cases. Thus, the standard turbomachinery space developed for air as fluid can be used effectively for the development of turboexpanders for various cycles with different working fluids without redesigning the entire shape using similarity-based scaling. The benchmark NASA 1730 turbine has proven this in three special cases. This paper is not against designing new machines but is only trying to say that when such good benchmark machines like NASA 1730 turbine is available; designers must use the power of similitude to adapt it to match new fluids and new conditions.

scholarly journals Development of a Pattern Recognition Methodology with Thermography and Implementation in an Experimental Study of a Boiler for a WHRS-ORC

Sensors ◽  
2019 ◽  
Vol 19 (7) ◽  
pp. 1680
Author(s):  
Concepción Paz ◽  
Eduardo Suárez ◽  
Miguel Concheiro ◽  
Antonio Diaz
Keyword(s):  
Pattern Recognition ◽  
Wall Temperature ◽  
Waste Heat ◽  
Combustion Engine ◽  
Organic Rankine Cycle ◽  
Exhaust System ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Cycle Performance ◽  
Working Fluid

Waste heat dissipated in the exhaust system in a combustion engine represents a major source of energy to be recovered and converted into useful work. A waste heat recovery system (WHRS) based on an Organic Rankine Cycle (ORC) is a promising approach, and it gained interest in the last few years in an automotive industry interested in reducing fuel consumption and exhaust emissions. Understanding the thermodynamic response of the boiler employed in an ORC plays an important role in steam cycle performance prediction and control system design. The aim of this study is, therefore, to present a methodology to study these devices by means of pattern recognition with infrared thermography. In addition, the experimental test bench and its operating conditions are described. The methodology proposed identifies the wall coordinates, traces the paths, and tracks the wall temperature along them in a way that can be exported for subsequent post-processing and analysis. As for the results, through the wall temperature paths on both sides (exhaust gas and working fluid), it was possible to quantitatively estimate the temperature evolution along the boiler and, in particular, the beginning and end of evaporation.

Working Fluid Selection for Organic Rankine Cycles from a Molecular Structural Point of View

2013 ◽  
Vol 805-806 ◽  
pp. 649-653
Author(s):  
Bing Zhang ◽  
Shuang Yang ◽  
Jin Liang Xu ◽  
Guang Lin Liu
Keyword(s):  
Critical Temperature ◽  
Heat Source ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Point Of View ◽  
Operating Conditions ◽  
Working Fluid ◽  
Working Fluids ◽  
Organic Fluids ◽  
Cycle Efficiency

The optimum working conditions of 11 working fluids under different heat source temperatures for an organic Rankine cycle (ORC) were located in our previous work. In the current work, the system irreversibility of each candidate were calculated and compared at their optimal operating conditions. Obvious variation trends of both the cycle efficiency and irreversibility were found for different types of organic fluids. It is suggested, when selecting working fluid for our ORC system, the critical temperature should be as close as possible to the heat source temperature to achieve high cycle efficiency but avoid large irreversibility. The relationships between the structure of the molecules and the critical temperature of the working fluids are investigated qualitatively and potentially meaningful for the rational selection of proper organic fluids for certain ORCs.

scholarly journals Numerical Study of Multistage Transcritical Organic Rankine Cycle Axial Turbines

2014 ◽  
Vol 136 (8) ◽  
Author(s):  
L. Sciacovelli ◽  
P. Cinnella
Keyword(s):  
Numerical Study ◽  
Pressure Ratio ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Dense Gas ◽  
Working Fluids ◽  
Inlet Conditions ◽  
The Impact

Transonic flows through axial, multistage, transcritical organic rankine cycle (ORC) turbines are investigated by using a numerical solver including advanced multiparameter equations of state and a high-order discretization scheme. The working fluids in use are the refrigerants R134a and R245fa, classified as dense gases due to their complex molecules and relatively high molecular weight. Both inviscid and viscous numerical simulations are carried out to quantify the impact of dense gas effects and viscous effects on turbine performance. Both supercritical and subcritical inlet conditions are studied for the considered working fluids. In the former case, flow across the turbine is transcritical, since turbine output pressure is subcritical. Numerical results show that, due to dense gas effects characterizing the flow at supercritical inlet conditions, supercritical ORC turbines enable, for a given pressure ratio, a higher isentropic efficiency than subcritical turbines using the same working fluid. Moreover, for the selected operating conditions, R134a provides a better performance than R245fa.

Effect of the Working Fluid on Performance of the ORC and Combined Brayton/ORC Cycle

2017 ◽  
Author(s):  
Alireza Javanshir ◽  
Nenad Sarunac
Keyword(s):  
Thermal Efficiency ◽  
Organic Rankine Cycle ◽  
Combined Cycle ◽  
Operating Conditions ◽  
Cycle Performance ◽  
Working Fluid ◽  
Working Fluids ◽  
Power Cycles ◽  
Topping Cycle ◽  
Selection Of

This study focuses on the power cycles such as organic Rankine cycle (ORC) and combined regenerative Brayton/ORC. The selection of working fluids and power cycles is traditionally conducted by trial and error method and performing a large number of parametric calculations over a range of operating conditions. A methodology for selection of optimal working fluid based on the cycle operating conditions and thermophysical properties of the working fluids was developed in this study. Thermodynamic performance (thermal efficiency and net power output) of a simple subcritical and supercritical ORC was analyzed over a range of operating conditions for a number of working fluids to determine the effect of operating parameters on cycle performance and select the best working fluid. New expressions for thermal efficiency of a simple ORC are proposed. In case of a regenerative Brayton/ORC, the results show that CO2 is the best working fluid for the topping cycle. Depending on the exhaust temperature of the topping cycle, Isobutane, R11 and Ethanol are the preferred working fluids for the bottoming (ORC) cycle, resulting in highest efficiency of the combined cycle. Finally, a performance map is presented as guidance for selection of the best working fluid for specific cycle operating conditions.

Investigating the Effect of Changing the Working Fluid on the Three-Dimensional Flow Within Organic Rankine Cycle Turbines

2016 ◽  
Author(s):  
M. White ◽  
A. I. Sayma
Keyword(s):  
Low Cost ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
High Volume ◽  
Detailed Comparison ◽  
Operating Conditions ◽  
Working Fluid ◽  
Working Fluids ◽  
Turbine Design ◽  
Similitude Theory

For small and micro scale (< 50 kWe) organic Rankine cycle (ORC) systems to be commercially viable, systems are required that can operate efficiently over a range of operating conditions. This will lead to the high volume, low cost production that is critical to improve the current economy of scale, and reduce system costs. This requirement will inevitably mean utilising the same system within a range of different applications and may also require the same turbine to operate in different systems where the working fluid may change. Under these circumstances it is therefore important to develop suitable models that can determine the off design performance of these turbines. This will help to understand how the performance of existing ORC turbines responds to such changes. This topic is also of interest when considering retrofitting existing systems with more modern working fluids, which meet current environmental regulations. Recent work by the authors has developed a turbine design model and produced a candidate radial turbine design. Furthermore a modified similitude theory has been developed and validated, which can be used to predict turbine performance following a change in working fluid. This paper extends this analysis to a wider array of working fluids, and in addition to comparing the important performance parameters such as mass flow rate and turbine efficiency, a detailed comparison of the resulting flow field, blade loading distributions and velocity triangles is also presented. Predictions made using the modified similitude theory are compared to steady and unsteady 3D RANS CFD simulations completed using the commercial solver ANSYS CFX. Real fluid properties are accounted for by generating property tables using REFPROP. By comparing these important flow features the validity of the modified similitude model can be examined to a much greater extent.

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.

Preliminary Design Optimization of an Organic Rankine Cycle Radial Turbine Rotor

2017 ◽  
Author(s):  
Edna Raimunda da Silva ◽  
Konstantinos G. Kyprianidis ◽  
Michael Säterskog ◽  
Ramiro G. Ramirez Camacho ◽  
Angie L. Espinosa Sarmiento
Keyword(s):  
Design Optimization ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Design Approach ◽  
Optimization Process ◽  
Working Fluid ◽  
Preliminary Design ◽  
Working Fluids ◽  
Radial Turbine

The present study describes the application of a preliminary design approach for the optimization of an organic Rankine cycle radial turbine. Losses in the nozzle the rotor have initially been modelled using a mean-line design approach. The work focuses on a typical small-scale application of 50 kW, and two working fluids, R245fa (1,1,1,3,3,-pentafluoropropane) and R236fa (1,1,1,3,3,3-hexafluoropropane) are considered for validation purposes. Real gas formulations have been used based on the NIST REFPROP database. The validation is based on a design from the literature, and the results demonstrate close agreement the reference geometry and thermodynamic parameters. The total-to-total efficiencies of the reference turbine designs were 72% and 79%. Following the validation exercise, an optimization process was performed using a controlled random search algorithm with the turbine efficiency set as the figure of merit. The optimization focuses on the R245fa working fluid since it is more suitable for the operating conditions of the proposed cycle, enables an overpressure in the condenser and allows higher system efficiency levels. The R236fa working fluid was also used for comparison with the literature, and the reason is the positive slope of the saturation curve, somehow is possible to work with lower temperatures. Key preliminary design variables such as flow coefficient, loading coefficient, and length parameter have been considered. While several optimized preliminary designs are available in the literature with efficiency levels of up to 90%, the preliminary design choices made will only hold true for machines operating with ideal gases, i.e. typical exhaust gases from an air-breathing combustion engine. For machines operating with real gases, such as organic working fluids, the design choices need to be rethought and a preliminary design optimization process needs to be introduced. The efficiency achieved in the final radial turbine design operating with R245fa following the optimization process was 82.4%. A three-dimensional analysis of the flow through the blade section using computational fluid dynamics was carried out on the final optimized design to confirm the preliminary design and further analyze its characteristics.

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