Siloxanes as Working Fluids for Mini-ORC Systems Based on High-Speed Turbogenerator Technology

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Antti Uusitalo ◽  
Teemu Turunen-Saaresti ◽  
Juha Honkatukia ◽  
Piero Colonna ◽  
Jaakko Larjola
Keyword(s):  
Molecular Weight ◽  
Power Output ◽  
High Speed ◽  
Thermodynamic Cycle ◽  
Turbine Rotor ◽  
Working Fluid ◽  
Specific Enthalpy ◽  
Working Fluids ◽  
Simulated Performance ◽  
Component Design

This paper presents a study aimed at evaluating the use of siloxanes as the working fluid of a small-capacity (≈10kWe) ORC turbogenerator based on the “high-speed technology” concept, combining the turbine, the pump, and the electrical generator on one shaft, whereby the whole assembly is hermetically sealed, and the bearings are lubricated by the working fluid. The effects of adopting different siloxane working fluids on the thermodynamic cycle configuration, power output, and on the turbine and component design are studied by means of simulations. Toluene is included into the analysis as a reference fluid in order to make comparisons between siloxanes and a suitable low molecular weight hydrocarbon. The most influential working fluid parameters are the critical temperature and pressure, molecular complexity and weight, and, related to them, the condensation pressure, density and specific enthalpy over the expansion, which affect the optimal design of the turbine. The fluid thermal stability is also extremely relevant in the considered applications. Exhaust gas heat recovery from a 120 kW diesel engine is considered in this study. The highest power output, 13.1 kW, is achieved with toluene as the working fluid, while, among siloxanes, D4 provides the best simulated performance, namely 10.9 kW. The high molecular weight of siloxanes is beneficial in low power capacity applications, because it leads to larger turbines with larger blade heights at the turbine rotor outlet, and lower rotational speed if compares, for instance, to toluene.

Performance Optimization and Economic Analysis of Geothermal Power Generation by Subcritical and Supercritical Organic Rankine Cycles

2016 ◽  
Author(s):  
Changwei Liu ◽  
Tieyu Gao ◽  
Jiangnan Zhu ◽  
Jiamin Xu
Keyword(s):  
Economic Analysis ◽  
Power Output ◽  
Performance Optimization ◽  
Supercritical Condition ◽  
Working Fluid ◽  
Outlet Temperature ◽  
Working Fluids ◽  
Turbine Inlet ◽  
Net Power Output ◽  
Subcritical Condition

In a sustainability context, using renewable energy sources to hedge against increasing consumption of fossil fuels and reduce greenhouse gas emissions becomes increasingly important. The geothermal resource has a great application prospect due to its rich reserves and convenient utilization, and Organic Rankine Cycle (ORC) is a effective method to convert the low-grade geothermal to electricity. To improve the performance of geothermal ORC system, working fluid selection, system parameter optimization and the cycle design are the main approaches. Zeotropic mixtures may show superiority as ORC working fluids due to the temperature glides during the phase transitions, which leads to better temperature matches between the working fluid and the heat source/sink. Moreover, owing to the changing temperature during the transition from liquid to vapor in the vapor generator, supercritical ORC provides a great potential in geothermal utilization and irreversibility reduction. This paper displays an investigation on the performance optimization and economic analysis of various working fluids under subcritical and supercritical conditions. To avoid the silica oversaturation, the geothermal water reinjection temperature should not be less than 70 °C. Turbine inlet temperature, condenser outlet temperature as well as turbine inlet pressure (for supercritical ORC) are optimized to maximize the net power output. Moreover, economic analysis is conducted by taking heat exchanger area per unit power output (APR) and the specific investment cost (SIC) as indicators under the optimal net power output condition. The results shows that working fluid with a medium critical temperature yields greater net power output in supercritical ORC and mixture produces larger net power output compared with its pure components in subcritical ORC. Compared with isobutane (R600a) under subcritical condition, isobutane/isopentane (R600a/R601a) and isobutane/pentane (R600a/R601) under subcritical condition, R134a and R1234ze(E) under supercritical condition yield 3.9%, 3.8%, 8.5% and 8.8% more net power outputs, respectively. In addition, R600a/R601a and R600a/R601 under subcritical condition own higher APR and SIC while R134a and R1234ze(E) under supercritical condition possess lower APR and SIC.

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.

Stirling Power Unit: Impact of a Controlled Displacer Piston on Efficiency and Power Output

2015 ◽  
Author(s):  
Anna Winkelmann ◽  
Eric J. Barth
Keyword(s):  
Dynamic Model ◽  
Power Unit ◽  
Power Output ◽  
Dynamic Models ◽  
Thermodynamic Cycle ◽  
Working Fluid ◽  
Electric Generator ◽  
Power Extraction ◽  
Extraction Unit ◽  
Pressure Dynamics

This paper presents the design and dynamic model of a novel “controlled Stirling power unit” with an independently controlled displacer piston. Breaking the coupling traditionally seen in Stirling devices between the power piston and the displacer piston, realized either kinematically or dynamically, allows an additional control degree of freedom that can be used to shape the thermodynamic cycle independent of the load. The device presented combines such a controlled Stirling engine (called a pressurizer) with a power extraction unit. The dynamic models of three different power extraction units are presented. The dynamic model builds on a previous experimentally validated first-principles model of a Stirling pressurizer. The model is a lumped parameter compressible fluid power dynamic model that captures the pressure dynamics of the high pressure helium working fluid as it is affected in time by volume, mass and heat flux changes. The dynamic model of a pressurizer combined with a linear electric generator is used to study different displacer motion profiles with regard to the shape of the thermodynamic cycle, and the effect on the power output and efficiency of the device.

Organic Working Fluids for a Combined Power and Cooling Cycle

2005 ◽  
Vol 127 (2) ◽  
pp. 125-130 ◽  
Author(s):  
Sanjay Vijayaraghavan ◽  
D. Y. Goswami
Keyword(s):  
Power Plants ◽  
Thermodynamic Cycle ◽  
Working Fluid ◽  
Water Mixture ◽  
Heat Sources ◽  
Absorption Refrigeration ◽  
Ammonia Water ◽  
Working Fluids ◽  
Fluid Mixtures ◽  
Advantages And Disadvantages

A new thermodynamic cycle has been developed for the simultaneous production of power and cooling from low-temperature heat sources. The proposed cycle combines the Rankine and absorption refrigeration cycles, providing power and cooling as useful outputs. Initial studies were performed with an ammonia-water mixture as the working fluid in the cycle. This work extends the application of the cycle to working fluids consisting of organic fluid mixtures. Organic working fluids have been used successfully in geothermal power plants, as working fluids in Rankine cycles. An advantage of using organic working fluids is that the industry has experience with building turbines for these fluids. A commercially available optimization program has been used to maximize the thermodynamic performance of the cycle. The advantages and disadvantages of using organic fluid mixtures as opposed to an ammonia-water mixture are discussed. It is found that thermodynamic efficiencies achievable with organic fluid mixtures, under optimum conditions, are lower than those obtained with ammonia-water mixtures. Further, the refrigeration temperatures achievable using organic fluid mixtures are higher than those using ammonia-water mixtures.

Generalized Parameters for Selection of Turbines and Working Fluids for OTEC Power Systems

1980 ◽  
Vol 102 (1) ◽  
pp. 215-222 ◽  
Author(s):  
D. D. Rosard
Keyword(s):  
Power Systems ◽  
Power Output ◽  
Design Parameters ◽  
Working Fluid ◽  
Working Fluids ◽  
Economy Of Scale ◽  
Scaling Parameters ◽  
Design Characteristics ◽  
Generalized Parameters ◽  
Ocean Thermal Energy

The choice of working fluid has a significant impact on the size and design characteristics of turbines for closed cycle OTEC (Ocean Thermal Energy Conversion) power systems. This paper examines turbine sizes and speeds for various candidate working fluids. The turbine performance and design limits are strongly influenced by blade stress criteria which have been ignored by previous investigators. Illustrative design parameters are given for a turbine using ammonia and scaling parameters are listed to compare the power outputs of turbines using other fluids. The design of a turbine for open-cycle OTEC power systems is largely dictated by the very high specific volume of the exhaust steam at a pressure of about 0.14 psia. In order to minimize the cost of turbines and generators through economy of scale, it is desirable to maximize the power output of a single turbine, and this leads to very large diameters and blade lengths. This paper explores the considerations which influence the choice of turbine size, blade length, speed, power output and efficiency.

Organic Working Fluids for a Combined Power and Cooling Cycle

2003 ◽  
Author(s):  
Sanjay Vijayaraghavan ◽  
D. Y. Goswami
Keyword(s):  
Power Plants ◽  
Thermodynamic Cycle ◽  
Working Fluid ◽  
Water Mixture ◽  
Heat Sources ◽  
Absorption Refrigeration ◽  
Ammonia Water ◽  
Working Fluids ◽  
Fluid Mixtures ◽  
Advantages And Disadvantages

A new thermodynamic cycle has been developed for the simultaneous production of power and cooling from low temperature heat sources. The proposed cycle combines the Rankine and absorption refrigeration cycles, providing power and cooling as useful outputs. Initial studies were performed with an ammonia-water mixture as the working fluid in the cycle. This work extends the application of the cycle to working fluids consisting of organic fluid mixtures. Organic working fluids have been used successfully in geothermal power plants, as working fluids in Rankine cycles. An advantage of using organic working fluids is that the industry has experience with building turbines for these fluids. A commercially available optimization program has been used to maximize the thermodynamic performance of the cycle. The advantages and disadvantages of using organic fluid mixtures as opposed to an ammonia-water mixture are discussed. It is found that thermodynamic efficiencies achievable with organic fluid mixtures, under optimum conditions, are lower than those obtained with ammonia-water mixtures. Further, the refrigeration temperatures achievable using organic fluid mixtures are higher than those using ammonia-water mixtures.

scholarly journals Influence of metal working fluid on chip formation and mechanical loads in orthogonal cutting

2021 ◽  
Author(s):  
Berend Denkena ◽  
Alexander Krödel ◽  
Lars Ellersiek
Keyword(s):  
Chip Formation ◽  
High Speed ◽  
Orthogonal Cutting ◽  
Machining Process ◽  
Working Fluid ◽  
Rake Face ◽  
Metal Working ◽  
Mechanical Loads ◽  
Working Fluids ◽  
Process Forces

AbstractMetal working fluids are used in machining processes of many hard-to-cut materials to increase tool life and productivity. Thereby, the metal working fluids act on the thermal and on the mechanical loads of the tool. The changing mechanical loads can mostly be attributed to the changing friction between rake face and chip and changes in the chip formation, e.g., the contact length between rake face and chip. However, analyzing those effects is challenging, since a detailed look at the chip formation process is prevented by the metal working fluid. In this paper, a novel planing test rig is presented, which enables high-speed recordings of the machining process and process force measurements while using metal working fluids. Experiments reveal that process forces are reduced with increasing pressure of the metal working fluid. However, the average friction coefficient only changes slightly, which indicates that the reduced process forces are mainly the result of reduced contact lengths between rake face and chip.

Organic Rankine Cycle Optimization With Explicit Designs of Evaporator and Radial Inflow Turbine

2020 ◽  
Vol 142 (7) ◽  
Author(s):  
Hasan Eren Bekiloğlu ◽  
Hasan Bedir ◽  
Günay Anlaş
Keyword(s):  
Power Output ◽  
Pressure Ratio ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Working Fluids ◽  
Source Temperature ◽  
Order Preference ◽  
Radial Inflow Turbine ◽  
Net Power Output

Abstract Although there are studies on optimizing organic Rankine cycles (ORCs) through individual components, in this study, for the first time, both evaporator and turbine designs are included in a multiobjective optimization. Twenty-eight working fluids are used to find optimum cycle parameters for three source temperatures (90, 120, and 150 °C). A mean-line radial inflow turbine model is used. Nondominated Sorting Genetic Algorithm II is utilized to minimize total evaporator area per net power output and maximize performance factor simultaneously. The technique for Order Preference by Similarity to Ideal Situation (TOPSIS) procedure is followed to obtain ideal solutions. A group of working fluids with highest net power output is determined for each heat source temperature. Optimized geometric parameters of the evaporator vary in a narrow range independent of the working fluid and the source temperature, but evaporator PPTD and degree of superheating depend on the working fluid. The specific speed, the pressure ratio through the turbine, and the nozzle inlet-to-outlet radius ratio do not change significantly with cycle conditions.

Centrifugal Compressor Working Fluids for Refrigeration Cycle

2009 ◽  
Author(s):  
Pekka Ro¨ytta¨ ◽  
Juha Honkatukia ◽  
Teemu Turunen-Saaresti
Keyword(s):  
High Speed ◽  
High Efficiency ◽  
Working Fluid ◽  
Accurate Estimation ◽  
Cooling Power ◽  
Condensation Temperature ◽  
Refrigeration Cycle ◽  
Light Weight ◽  
Centrifugal Compressors ◽  
Working Fluids

A centrifugal high-speed compressor is an effective light weight option to power a refrigeration cycle for air conditioning purposes. Perhaps the most important decision in design is the working fluid selection. Modern high-speed technology makes it possible for the refrigeration compressor to be completely oil free, which considerably broadens the scale of possible working fluids. Furthermore, many traditional fluids have become banned and the industry standard R134a might face the same faith in some European countries because of its relatively high global warming potential. In this study eleven different fluids were studied and compared and R22 was used as a reference. It was found that there are many potential fluids for centrifugal compressors that provide better efficiencies than the most common fluids in use today. The purpose of this study is to initially screen a larger set of candidate fluids for more accurate estimation later on. The fluids are evaluated by the efficiency of the cycle, but also mechanical feasibility and dimensions are considered as light weight of the machinery was an important criterion in design process. The comparison was made with constant evaporation and condensation temperature and fixed cooling power for all the fluids. In selection of the working fluid the safety factors often play a dominant role which was also shortly considered. In our study we found out that for a residential HVAC size cooling cycle there are environmentally friendly fluids with high efficiency leading to feasible mechanical designs with centrifugal compressors.

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.

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