scholarly journals Working-Fluid Replacement in Supersonic Organic Rankine Cycle Turbines

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Martin T. White ◽  
Christos N. Markides ◽  
Abdulnaser I. Sayma
Keyword(s):  
Organic Rankine Cycle ◽  
Thermodynamic Cycle ◽  
Rankine Cycle ◽  
Fluid Replacement ◽  
Working Fluid ◽  
Polytropic Index ◽  
Working Fluids ◽  
Economy Of Scale ◽  
Power Outputs ◽  
Turbine Design

In this paper, the effect of working-fluid replacement within an organic Rankine cycle (ORC) turbine is investigated by evaluating the performance of two supersonic stators operating with different working fluids. After designing the two stators, intended for operation with R245fa and Toluene with stator exit absolute Mach numbers of 1.4 and 1.7, respectively, the performance of each stator is evaluated using ANSYS cfx. Based on the principle that the design of a given stator is dependent on the amount of flow turning, it is hypothesized that a stator's design point can be scaled to alternative working fluids by conserving the Prandtl–Meyer function and the polytropic index within the nozzle. A scaling method is developed and further computational fluid dynamics (CFD) simulations for the scaled operating points verify that the Mach number distributions within the stator, and the nondimensional velocity triangles at the stator exit, remain unchanged. This confirms that the method developed can predict stator performance following a change in the working fluid. Finally, a study investigating the effect of working-fluid replacement on the thermodynamic cycle is completed. The results show that the same turbine could be used in different systems with power outputs varying between 17 and 112 kW, suggesting the potential of matching the same turbine to multiple heat sources by tailoring the working fluid selected. This further implies that the same turbine design could be deployed in different applications, thus leading to economy-of-scale improvements.

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.

Aerodynamic Considerations in the Thermodynamic Analysis of Organic Rankine Cycles

2014 ◽  
Author(s):  
Maria E. Mondejar ◽  
Marcus Thern ◽  
Magnus Genrup
Keyword(s):  
Thermodynamic Analysis ◽  
Equations Of State ◽  
Organic Rankine Cycle ◽  
Thermodynamic Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Working Fluids ◽  
Turbine Efficiency ◽  
Cycle Simulation ◽  
Organic Rankine Cycles

Due to the increasing interest of producing power from renewable and non-conventional resources, organic Rankine cycles are finding their place in today’s thermal energy mix. The main influencers on the efficiency of an organic Rankine cycle are the working fluid and the expander. Therefore most of the research done up to date turns around the selection of the best performance working media and the optimization of the expansion unit design. However, few studies consider the interaction of the working fluids in the turbine design, and how this fact can affect the overall thermodynamic cycle analysis. In this work we aim at including the aerodynamic behavior of the working fluids and their effect on the turbine efficiency in the thermodynamic analysis of an organic Rankine cycle. To that end, we proposed a method for the estimation of the characteristics of an axial in-flow turbine in an organic Rankine cycle simulation model. The code developed for the characterization of the turbine behavior under the working fluid properties evaluated the irreversibilities associated to the aerodynamic losses in the turbine. The organic Rankine cycle was analyzed by using IPSEpro process simulator. A set of candidate working fluids composed of selected organofluorines and organochlorines was chosen for the analysis. The thermophysical properties of the fluids were estimated with the equations of state implemented in Refprop. Results on the energy and exergy overall performances of the cycle were analyzed for a case study with standard source and sink temperatures. For each fluid the number of stages and geometry of the turbine were optimized. It was observed that some working fluids that could initially be considered as advantageous from a thermodynamic point of view, had an unfavorable impact on the turbine efficiency, thus increasing the irreversibilities of the cycle. We concluded that if the influence of the working fluid on the turbine performance is underestimated, the real performance of the organic Rankine cycle could show unexpected deviations from the theoretical results.

Model, simulation and experiments for a Buoyancy Organic Rankine Cycle

2020 ◽  
Vol 92 (1) ◽  
pp. 10906
Author(s):  
Jeroen Schoenmaker ◽  
Pâmella Gonçalves Martins ◽  
Guilherme Corsi Miranda da Silva ◽  
Julio Carlos Teixeira
Keyword(s):  
Model Simulation ◽  
Organic Rankine Cycle ◽  
Thermodynamic Cycle ◽  
Rankine Cycle ◽  
Test Body ◽  
Working Fluid ◽  
Proof Of Concept ◽  
Energy Scenario ◽  
New Type ◽  
Fluid Reservoir

Organic Rankine Cycle (ORC) systems are increasingly gaining relevance in the renewable and sustainable energy scenario. Recently our research group published a manuscript identifying a new type of thermodynamic cycle entitled Buoyancy Organic Rankine Cycle (BORC) [J. Schoenmaker, J.F.Q. Rey, K.R. Pirota, Renew. Energy 36, 999 (2011)]. In this work we present two main contributions. First, we propose a refined thermodynamic model for BORC systems accounting for the specific heat of the working fluid. Considering the refined model, the efficiencies for Pentane and Dichloromethane at temperatures up to 100 °C were estimated to be 17.2%. Second, we show a proof of concept BORC system using a 3 m tall, 0.062 m diameter polycarbonate tube as a column-fluid reservoir. We used water as a column fluid. The thermal stability and uniformity throughout the tube has been carefully simulated and verified experimentally. After the thermal parameters of the water column have been fully characterized, we developed a test body to allow an adequate assessment of the BORC-system's efficiency. We obtained 0.84% efficiency for 43.8 °C working temperature. This corresponds to 35% of the Carnot efficiency calculated for the same temperature difference. Limitations of the model and the apparatus are put into perspective, pointing directions for further developments of BORC systems.

Method for the Preliminary Fluid Dynamic Design of High-Temperature Mini-Organic Rankine Cycle Turbines

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Sebastian Bahamonde ◽  
Matteo Pini ◽  
Carlo De Servi ◽  
Antonio Rubino ◽  
Piero Colonna
Keyword(s):  
Power Plants ◽  
Design Space ◽  
Organic Rankine Cycle ◽  
Thermodynamic Cycle ◽  
Rankine Cycle ◽  
Inlet Temperature ◽  
Preliminary Design ◽  
Design Calculations ◽  
Radial Outflow ◽  
Turbine Design

Widespread adoption of renewable energy technologies will arguably benefit from the availability of economically viable distributed thermal power conversion systems. For this reason, considerable efforts have been dedicated in recent years to R&D over mini-organic Rankine cycle (ORC) power plants, thus with a power capacity approximately in the 3–50 kW range. The application of these systems for waste heat recovery from diesel engines of long-haul trucks stands out because of the possibility of achieving economy of production. Many technical challenges need to be solved, as the system must be sufficiently efficient, light, and compact. The design paradigm is therefore completely different from that of conventional stationary ORC power plants of much larger capacity. A high speed turbine is arguably the expander of choice, if high conversion efficiency is targeted, thus high maximum cycle temperature. Given the lack of knowledge on the design of these turbines, which depends on a large number of constraints, a novel optimal design method integrating the preliminary design of the thermodynamic cycle and that of the turbine has been developed. The method is applicable to radial inflow, axial and radial outflow turbines, and to superheated and supercritical cycle configurations. After a limited number of working fluids are selected, the feasible design space is explored by means of thermodynamic cycle design calculations integrated with a simplified turbine design procedure, whereby the isentropic expansion efficiency is prescribed. Starting from the resulting design space, optimal preliminary designs are obtained by combining cycle calculations with a 1D mean-line code, subject to constraints. The application of the procedure is illustrated for a test case: the design of turbines to be tested in a new experimental setup named organic rankine cycle hybrid integrated device (ORCHID) which is being constructed at the Delft University of Technology, Delft, The Netherlands. The first turbine selected for further design and construction employs siloxane MM (hexamethyldisiloxane, C6H18OSi2), supercritical cycle, and the radial inflow configuration. The main preliminary design specifications are power output equal to 11.6 kW, turbine inlet temperature equal to 300 °C, maximum cycle pressure equal to 19.9 bar, expansion ratio equal to 72, rotational speed equal to 90 krpm, inlet diameter equal to 75 mm, minimum blade height equal to 2 mm, degree of reaction equal to 0.44, and estimated total-to-static efficiency equal to 77.3%. Results of the design calculations are affected by considerable uncertainty related to the loss correlations employed for the preliminary turbine design, as they have not been validated yet for this highly unconventional supersonic and transonic mini turbine. Future work will be dedicated to the extension of the method to encompass the preliminary design of heat exchangers and the off-design operation of the system.

Performance Evaluation of a Small Scale High Efficiency Cogeneration System

2006 ◽  
Author(s):  
Mauro Reini
Keyword(s):  
High Efficiency ◽  
Pressure Ratio ◽  
Organic Rankine Cycle ◽  
Thermodynamic Cycle ◽  
Rankine Cycle ◽  
Combined Cycle ◽  
Working Fluid ◽  
Small Scale ◽  
Performance Parameters ◽  
Cogeneration System

In recent years, a big effort has been made to improve microturbines thermal efficiency, in order to approach 40%. Two main options may be considered: i) a wide usage of advanced materials for hot ends components, like impeller and recuperator; ii) implementing more complicated thermodynamic cycle, like combined cycle. In the frame of the second option, the paper deals with the hypothesis of bottoming a low pressure ratio, recuperated gas cycle, typically realized in actual microturbines, with an Organic Rankine Cycle (ORC). The object is to evaluate the expected nominal performance parameters of the integrated-combined cycle cogeneration system, taking account of different options for working fluid, vapor pressure and component’s performance parameters. Both options of recuperated and not recuperated bottom cycles are discussed, in relation with ORC working fluid nature and possible stack temperature for microturbine exhaust gases. Finally, some preliminary consideration about the arrangement of the combined cycle unit, and the effects of possible future progress of gas cycle microturbines are presented.

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 Experimental and Techno-Economic Analysis of Solar-Geothermal Organic Rankine Cycle Technology for Power Generation in Nepal

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Suresh Baral
Keyword(s):  
Power Generation ◽  
Heat Source ◽  
Power Output ◽  
Solar Collector ◽  
Hot Spring ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Maximum Temperature ◽  
Working Fluid ◽  
Working Fluids

The current research study focuses on the feasibility of stand-alone hybrid solar-geothermal organic Rankine cycle (ORC) technology for power generation from hot springs of Bhurung Tatopani, Myagdi, Nepal. For the study, the temperature of the hot spring was measured on the particular site of the heat source of the hot spring. The measured temperature could be used for operating the ORC system. Temperature of hot spring can also further be increased by adopting the solar collector for rising the temperature. This hybrid type of the system can have a high-temperature heat source which could power more energy from ORC technology. There are various types of organic working fluids available on the market, but R134a and R245fa are environmentally friendly and have low global warming potential candidates. The thermodynamic models have been developed for predicting the performance analysis of the system. The input parameter for the model is the temperature which was measured experimentally. The maximum temperature of the hot spring was found to be 69.7°C. Expander power output, thermal efficiency, heat of evaporation, solar collector area, and hybrid solar ORC system power output and efficiency are the outputs from the developed model. From the simulation, it was found that 1 kg/s of working fluid could produce 17.5 kW and 22.5 kW power output for R134a and R245fa, respectively, when the geothermal source temperature was around 70°C. Later when the hot spring was heated with a solar collector, the power output produced were 25 kW and 30 kW for R134a and R245fa, respectively, when the heat source was 99°C. The study also further determines the cost of electricity generation for the system with working fluids R134a and R245fa to be $0.17/kWh and $0.14/kWh, respectively. The levelised cost of the electricity (LCOE) was $0.38/kWh in order to be highly feasible investment. The payback period for such hybrid system was found to have 7.5 years and 10.5 years for R245fa and R134a, respectively.

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.

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.

Performance Analysis of Near-Critical and Subcritical Organic Rankine Cycle

2013 ◽  
Vol 448-453 ◽  
pp. 3270-3276
Author(s):  
Yu Ping Wang ◽  
Yi Wu Weng ◽  
Ping Yang ◽  
Lei Tang
Keyword(s):  
Performance Analysis ◽  
Thermophysical Properties ◽  
Thermodynamic Model ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Vapor Generation ◽  
Working Fluids ◽  
The Difference ◽  
Better Than

In this paper, three typical working fluids were selected for the near-critical ORC and subcritical ORC. The difference of performance between the near-critical ORC and subcritical ORC was analyzed by establishing the thermodynamic model. The reason for difference was analyzed in terms of the thermophysical properties. The results indicate that the performance of the near-critical ORC is better than the subcritical ORC. The net absorbed heat, net power and efficiency of the near-critical ORC vary slowly with the vapor generation temperature, which means that the near-critical ORC has good off-design performance. The dry working fluid R236fa is best adapted for the near-critical ORC among the three working fluids. The singular performance of the near-critical ORC depends on the properties of latent heat and type of working fluid in near-critical region.

Sign in / Sign up

Export Citation Format

Share Document