The Effect of Real Gas Approximations on S-CO2 Compressor Design

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Jekyoung Lee ◽  
Seong Kuk Cho ◽  
Jeong Ik Lee
Keyword(s):  
Critical Point ◽  
High Efficiency ◽  
Technology Development ◽  
Static Condition ◽  
Component Technology ◽  
Brayton Cycle ◽  
Real Gas ◽  
Compressor Design ◽  
The Future ◽  
The Impact

From the efforts of many researchers and engineers related to the S-CO2 Brayton cycle technology development, the S-CO2 Brayton cycle is now considered as one of the key power technologies for the future. Since the S-CO2 Brayton cycle has advantages in economics due to high efficiency and compactness of the system, various industries have been trying to develop baseline technology on the design and analysis of the S-CO2 Brayton cycle components. According to the previous researches on the S-CO2 Brayton cycle component technology, the treatment of a thermodynamic property near the critical point of CO2 is one of the main concerns since conventional design and analysis methodologies cannot be used for the near critical point region. Among many thermodynamic properties, the stagnation to static condition conversion process is important since the flow in a compressor is at high flow velocity. In this paper, the impact of various stagnation to static conversion methods on the S-CO2 compressor design near the critical point will be evaluated. From the evaluation, the limitation of a certain stagnation to static conversion method will be discussed to provide a guideline for the future S-CO2 compressor designers.

Sensitivity Study of S-CO2 Compressor Design for Different Real Gas Approximations

2016 ◽  
Author(s):  
Jekyoung Lee ◽  
Seong Kuk Cho ◽  
Jae Eun Cha ◽  
Jeong Ik Lee
Keyword(s):  
Thermodynamic Property ◽  
Critical Point ◽  
Technology Development ◽  
Static Condition ◽  
Sensitivity Study ◽  
Ideal Gas ◽  
Brayton Cycle ◽  
Real Gas ◽  
Compressor Design ◽  
Turbomachinery Design

With the efforts of many researchers and engineers on the Supercritical CO2 (S-CO2) Brayton cycle technology development, the S-CO2 Brayton cycle is now considered as one of the key power technologies for the future. Since S-CO2 Brayton cycle has advantages in economics due to high efficiency and compactness of system, various industries have been trying to develop technologies on the design and analysis of S-CO2 Brayton cycle components. Among various technical issues on the S-CO2 Brayton cycle technology development, treatment of thermodynamic property near the critical point of S-CO2 is very important since the property shows non-linear variation which causes large error on design and analysis results for ideal gas based methodologies. Due to the special behavior of thermodynamic property of CO2 near the critical point, KAIST research team has been trying to develop a S-CO2 compressor design and analysis tool to reflect real gas effect accurately for better design and performance prediction results. The main motivation for developing an in-house code is to establish turbomachinery design methodology based on general equations to improve accuracy of design and analysis results for various working fluids including S-CO2. One of the key improvements of KAIST_TMD which is an in-house tool for S-CO2 turbomachinery design and analysis is the conversion process between stagnation condition and static condition. Since fluid is moving with high flow velocity in a compressor, the conversion process between stagnation and static condition is important and it can have an impact on the design and analysis results significantly. A common process for the conversion is based on the specific heat ratio which is typically a constant from ideal gas assumption. However, specific heat ratio cannot be assumed as a constant for the case of S-CO2 compressor design and analysis because it varies dramatically near the critical point. Thus, in this paper, sensitivity study results on the state condition conversion between stagnation and static conditions with different approaches will be presented and further analysis on impact of the selected approaches on the final impeller design results will be discussed.

Supercritical CO2 Brayton Cycle Power Generation Development Program and Initial Test Results

2009 ◽  
Author(s):  
Steven A. Wright ◽  
Paul S. Pickard ◽  
Robert Fuller ◽  
Ross F. Radel ◽  
Milton E. Vernon
Keyword(s):  
Critical Point ◽  
Supercritical Co2 ◽  
High Efficiency ◽  
Power Conversion ◽  
Development Program ◽  
Brayton Cycle ◽  
Heat Sources ◽  
Split Flow ◽  
Thrust Load ◽  
Density Of Water

The DOE Office of Nuclear Energy and Sandia National Labs are investigating supercritical CO2 Brayton cycles as a potentially more efficient and compact power conversion system for advanced nuclear reactors, and other heat sources including solar, geothermal, and fossil or bio fuel systems. The focus of this work is on the supercritical CO2 Brayton cycle which has the potential for both high efficiency, in temperature range (400–750 C), and for reduced capital costs due to very compact turbomachinery. The cycle achieves high efficiency due to the non-ideal behavior of supercritical CO2, and it achieves extremely high power density because the fluid in the turbomachinery is very dense, 10%–60% the density of water. Sandia and its contractor Barber Nichols Inc. have fabricated and are operating a supercritical CO2 (S-CO2) compression test-loop to investigate the key technology issues associated with this cycle. The compression loop is part of a multi-year phased development program to develop a megawatt (MW) heater-class closed S-CO2 Brayton cycle to demonstrate the applicability of this cycle to heat sources above 400 C. Other portions of the program include modifications to the compression loop to operate it as a simple heated Brayton loop by adding a small turbine and a heater, but with no recuperator. The early testing of this simple Brayton cycle is under way. A more ambitious effort is currently constructing a recompression cycle Brayton loop (1) which is some times called a split-flow Brayton cycle. This cycle is used to increase the efficiency of the system by providing large amounts of recuperation using printed circuit heat exchangers. The re-compression (or split-flow) Brayton cycle is designed to operate at 1000 F (538 C) and produce up to 250 kWe with a 1.47″ OD radial compressor and a 2.68″ OD radial turbine. The current compression loop uses a main compressor that is identical to the main compressors in all the Brayton cycles that are being developed at Sandia. The key issues for the supercritical Brayton cycle include the fundamental issues of compressor fluid performance and system control near the critical point. Near the critical point very non ideal fluid behavior is observed which means that standard tools for analyzing compressor performance cannot be used. Thus one of the goals of the program is to develop data that can be used to validate the tools and models that are used to design the turbomachinery. Other supporting technology issues that are essential to achieving efficiency and cost objectives include bearing type, thrust load and thrust load balancing, bearing cooling, sealing technologies, and rotor windage losses. The current tests are providing the first measurements and information on these important supercritical CO2 power conversion system questions. Some of this data is presented in this report. In the testing to date, the turbomachinery has reached maximum speeds of 65,000 rpm, peak flow rates of over 9 lb/s and pressure ratios of just over 1.65. Compressor inlet fluid densities have been varied from 14% to 70% the density of water. Although the data from these tests are only the first results to be analyzed, they indicate that the basic design and performance predictions are sound. The loops have operated the turbo-compressor on the liquid and vapor side of the saturation curve, very near the critical point, above the critical point and even on the saturation dome. We have also operated the compressor near the choked flow regime and even in surge. At the current operating speeds and pressures, the observed performance map data agrees extremely well with the model predictions. These results have positive implications for the ultimate success of the S-CO2 cycle. In general the main compressor shows no adverse behavior while operating over a wide range of normal operating conditions. It operates reliably and with performance values that are very near the predicted results. Future efforts will focus on operating the Brayton cycle loop at sufficiently high temperatures that electrical power can be produced near the end of 2009. The compression-loop hardware is now the test bed for confirming the remaining parameters to support the next stage of development — which is the 1 MW heater-class split-flow or re-compressor Brayton cycle.

Cooling of Electronic Chips Using Microchannel and Micro-Pin Fin Heat Exchangers

2008 ◽  
Author(s):  
Ravi Prasher ◽  
Je-Young Chang
Keyword(s):  
Integrated Circuit ◽  
Heat Exchangers ◽  
High Efficiency ◽  
Technology Development ◽  
Electronic Systems ◽  
Liquid Cooling ◽  
Future Technology ◽  
Pin Fin ◽  
Microchannel Cooling ◽  
The Impact

The research community is experiencing a revolution in microscale and nanoscale heat transfer, with a focus on developing fundamental experiments and theoretical techniques. More recently, these advancements have begun to influence the design of electronic systems. A futuristic electronic cooling solution might include high efficiency thermoelectric devices made from nanomaterials for the cooling of hotspots on a chip, nano/micro particle laden thermal interface materials and micro-pin fin/microchannel based heat exchanger. Liquid cooling using integrated microscale heat exchangers is a promising future technology to address issues associated with integrated circuit thermal management. In this paper recent advances made by us on technology development of microchannel/micro-pin-fin heat exchangers is presented. Particular attention is given to the impact of hotspots on the performance of microchannel cooling.

Off Design Performance Map Similarity Study of Radial Type Turbomachinery in Supercritical CO2 Brayton Cycle

2015 ◽  
Author(s):  
Seong Kuk Cho ◽  
Jekyoung Lee ◽  
Jeong Ik Lee
Keyword(s):  
Critical Point ◽  
Pressure Ratio ◽  
National Laboratory ◽  
Sandia National Laboratory ◽  
Power Conversion ◽  
Design Tool ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Performance Map ◽  
The Future

A supercritical carbon dioxide (S-CO2) Brayton cycle has received attention as one of the future power conversion systems because of its high thermal efficiency at relatively low turbine inlet temperature. However, the design process of the S-CO2 compressor is known to be difficult because the fluid properties vary significantly near the critical point. This paper discusses about the design methodology of a S-CO2 compressor on the basis of the existing design practice and performance map of Sandia National Laboratory, which is the only reported experimental data for the S-CO2 compressor. Five parameters are mainly used for verifying the turbomachinery similarity. When all of 5 parameters coincide with the prototype and the conceptually designed turbomachinery, similar performance can be assumed. As a result, the data of SNL are insufficient to design a single stage compressor which is able to compress from near critical point to 20MPa. The optimum cycle pressure ratio is reported to be around 2.6∼2.7 in the previous S-CO2 Brayton cycle research works. The minimum number of stages is required at least two to utilize the existing data in the compressor design. So this study focuses on two main purposes. The first is to check whether the SNL data can be extended for the larger scale S-CO2 system. Second, the performance map obtained from KAIST_TMD, which is from an in-house code developed by the Korea Advanced Institute of Science and Technology (KAIST) research team, was compared to the SNL data, so that KAIST_TMD can be used as a design tool for a larger scale S-CO2 power conversion system in the future.

Centrifugal Compressor Design for Near-Critical Point Applications

2018 ◽  
Vol 141 (3) ◽  
Author(s):  
Alireza Ameli ◽  
Ali Afzalifar ◽  
Teemu Turunen-Saaresti ◽  
Jari Backman
Keyword(s):  
Critical Point ◽  
Centrifugal Compressor ◽  
Compressibility Factor ◽  
Design Procedure ◽  
Operating Conditions ◽  
Brayton Cycle ◽  
Compressor Design ◽  
Lower Temperature ◽  
The Individual ◽  
Line Design

The supercritical CO2 (sCO2) Brayton cycle has been attracting much attention to produce the electricity power, chiefly due to its higher thermal efficiency with the relatively lower temperature at the turbine inlet compared to other common energy conversion cycles. Centrifugal compressor operating conditions in the supercritical Brayton cycle are commonly set in vicinity of the critical point, owing to smaller compressibility factor and eventually lower compressor work. This paper investigates and compares different centrifugal compressor design methodologies in close proximity to the critical point and suggests the most accurate design procedure based on the findings. An in-house mean-line design code, which is based on the individual enthalpy loss models, is compared to stage efficiency correlation design methods. Moreover, modifications are introduced to the skin friction loss calculation to establish an accurate one-dimensional design methodology. Moreover, compressor performance is compared to the experimental measurements.

Centrifugal Compressor Design for Near-Critical Point Applications

2018 ◽  
Author(s):  
Alireza Ameli ◽  
Ali Afzalifar ◽  
Teemu Turunen-Saaresti ◽  
Jari Backman
Keyword(s):  
Critical Point ◽  
Centrifugal Compressor ◽  
Compressibility Factor ◽  
Design Procedure ◽  
Operating Conditions ◽  
Brayton Cycle ◽  
Compressor Design ◽  
Lower Temperature ◽  
The Individual ◽  
Line Design

The supercritical CO2 (sCO2) Brayton cycle has been attracting much attention to produce the electricity power, chiefly due to its higher thermal efficiency with the relatively lower temperature at the turbine inlet compared to other common energy conversion cycles. Centrifugal compressor operating conditions in the supercritical Brayton cycle are commonly set in vicinity of the critical point, owing to smaller compressibility factor and eventually lower compressor work. This paper investigates and compares different centrifugal compressor design methodologies in close proximity to the critical point and suggests the most accurate design procedure based on the findings. An in-house mean-line design code, which is based on the individual enthalpy loss models, is compared to stage efficiency correlation design methods. Moreover, modifications are introduced to the skin friction loss calculation to establish an accurate 1-D design methodology. Moreover, compressor performances are compared to the experimental measurements.

Numerical Modelling and Experimental Validation of a Supercritical Co2-lubricated Hydrodynamic Journal Bearing

2021 ◽  
Author(s):  
Nathan Colgan ◽  
Ken Cragin ◽  
Jeffrey Breedlove ◽  
Gregory Nellis ◽  
Mark Anderson
Keyword(s):  
Critical Point ◽  
Critical Pressure ◽  
Journal Bearing ◽  
Constant Property ◽  
Real Gas ◽  
The Real ◽  
Hydrodynamic Bearing ◽  
Bearing Stiffness ◽  
Hydrodynamic Journal Bearing ◽  
The Impact

Abstract This paper describes the development of a simple numerical model of a hydrodynamic journal bearing operating under laminar conditions. The model incorporates the real gas properties of sCO2 and therefore can be used to qualitatively investigate the impact of operation near the critical point. The model predictions are compared to a model assuming constant fluid properties in order to assess the effects of the large gradients in properties that occur near the critical point. The modeling results show that bearing drag should not rise significantly throughout the subcritical regime, but rises by approximately 50% at the critical pressure. Similarly, bearing stiffness increases by about 50% at the critical pressure. However, the behavior predicted by the real gas model closely matches those obtained from the constant-property model for all conditions that are more than 3 kPa away from the critical pressure. To demonstrate operation near the critical pressure, a test assembly consisting of a turbomachine driven by a motor and supported on tilt-pad hydrodynamic gas journal bearing was operated in a high-pressure CO2 environment at 35°C with pressures up to 1050 psig. The bearing operated smoothly and did not exhibit signs of instability such as whirl. Coast down measurements were conducted to estimate the bearing drag at various pressures up to 800 psig. These results indicate that hydrodynamic bearing operation using sCO2 is possible without significant reduction in bearing performance; however, further testing should be carried out in order to validate the model results concerning bearing stiffness.

Unique Silicon Passive Component Technology for Medical implants combining highly flexible integration with outstanding performances.

2016 ◽  
Vol 2016 (1) ◽  
pp. 000151-000153
Author(s):  
Catherine Bunel ◽  
Franck Murray
Keyword(s):  
Technology Development ◽  
Electrical Power ◽  
Life Time ◽  
System Size ◽  
Component Technology ◽  
Passive Component ◽  
Implantable Medical Devices ◽  
Battery Lifetime ◽  
Low Leakage ◽  
The Impact

Abstract Many implantable medical devices such as pacemakers, cochlear implants and neurostimulation devices have been developed and tremendously improved in electrical power consumption, battery lifetime, functionality, system delivery, and wireless communication but there is still a lot of room for improvement and these devices are still facing challenges with size shrinkage and reliability. Many efforts have been engaged to miniaturize and to facilitate the implantation of the device in order to reduce the impact of the surgery. IPDiA's technology is strongly contributing to this progress by providing passive components such as capacitor arrays or RC networks, with a high contribution to miniaturization, a very low profile, extremely low leakage and outstanding reliability. In this paper, the enablers such as design flexibility, co-integration, low leakage, extended life time will be presented and illustrated by several examples of solutions. Firstly, the recent progress in the capacitor technology development will be presented, secondly the impact of the component technology on the overall system size and performances through advanced packaging solutions will be highlighted together with other key differentiators and finally some of the applications where this technology is essential will be presented.

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