Experimental and Numerical Study of Supercritical Carbon Dioxide Flow Through Valves

2016 ◽  
Vol 2 (3) ◽  
Author(s):  
Haomin Yuan ◽  
Mark Anderson
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Validation Data ◽  
Choked Flow ◽  
Numerical Predictions ◽  
Valve Model ◽  
Supercritical Carbon

The supercritical carbon dioxide (sCO2) Brayton cycle shows advantages such as high efficiency, compactness, and low capital cost. These benefits make it a competitive candidate for future-generation power-conversion cycles. In order to study this cycle, valve characteristics under sCO2 flow conditions must be studied. However, the traditional models for valves may not be accurate due to the real gas property of sCO2. In this study, this problem was studied both experimentally and numerically. A small valve was tested in the authors’ experiment facility first to provide validation data. For this valve, numerical predictions of mass flow rate agree with experimental data. Then, simulations were scaled up to valves in a real power-cycle design. The traditional gas-service valve model fails to predict mass flow rate at low-pressure ratios. A modification was proposed to improve the current gas-service valve model by changing the choked-flow check.

Numerical Simulation of the Performance of an Axial Compressor Operating With Supercritical Carbon Dioxide

2018 ◽  
Author(s):  
Jinlan Gou ◽  
Wei Wang ◽  
Can Ma ◽  
Yong Li ◽  
Yuansheng Lin ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Numerical Simulation ◽  
Supercritical Carbon Dioxide ◽  
Critical Point ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Axial Compressor ◽  
Brayton Cycle ◽  
Supercritical Carbon

Using supercritical carbon dioxide (SCO2) as the working fluid of a closed Brayton cycle gas turbine is widely recognized nowadays, because of its compact layout and high efficiency for modest turbine inlet temperature. It is an attractive option for geothermal, nuclear and solar energy conversion. Compressor is one of the key components for the supercritical carbon dioxide Brayton cycle. With established or developing small power supercritical carbon dioxide test loop, centrifugal compressor with small mass flow rate is mainly investigated and manufactured in the literature; however, nuclear energy conversion contains more power, and axial compressor is preferred to provide SCO2 compression with larger mass flow rate which is less studied in the literature. The performance of the axial supercritical carbon dioxide compressor is investigated in the current work. An axial supercritical carbon dioxide compressor with mass flow rate of 1000kg/s is designed. The thermodynamic region of the carbon dioxide is slightly above the vapor-liquid critical point with inlet total temperature 310K and total pressure 9MPa. Numerical simulation is then conducted to assess this axial compressor with look-up table adopted to handle the nonlinear variation property of supercritical carbon dioxide near the critical point. The results show that the performance of the design point of the designed axial compressor matches the primary target. Small corner separation occurs near the hub, and the flow motion of the tip leakage fluid is similar with the well-studied air compressor. Violent property variation near the critical point creates troubles for convergence near the stall condition, and the stall mechanism predictions are more difficult for the axial supercritical carbon dioxide compressor.

scholarly journals Determination of concentration equilibrium of the substance being measured in a supercritical solvent with a dynamic research method

2020 ◽  
Vol 64 (10) ◽  
pp. 68-73
Author(s):  
Lenar Yu. Yarullin ◽  
◽  
Farizan R. Gabitov ◽  
Lyudmila Y. Sabirova ◽  
Polina V. Antonova ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Composition Analysis ◽  
Universal Method ◽  
Saturation State ◽  
Supercritical Carbon

At present, there is no universal method for studying the solubility of substances in supercritical fluid media. The expediency of combining certain methods of solution saturation and composition analysis is determined by the object of study, the range of concentrations. In the case of low solubility of solids in the solvent, a flow-through system or dynamic solubility measurement method is usually used to obtain the required amount of precision weighing material. The dynamic method for measuring the solubility of substances in supercritical carbon dioxide is not without its drawbacks, which primarily include the need to strictly control the mass flow rate of supercritical carbon dioxide in the cell with the substance being measured. With an increase in the consumption of supercritical dioxide from zero (static method) to a certain value, the concentration of the measured substance in supercritical carbon dioxide within the acceptable level of uncertainty for measuring the solubility of 4-6% can be considered unchanged. The plateau of the concentration of the measured substance in supercritical carbon dioxide from the flow rate obtained in the diagram corresponds to the saturation state of the solvent, which is carbon dioxide and the solute, which corresponds to the concept of solubility. However, with a further increase in the consumption of carbon dioxide, the concentration begins to decrease and it can no longer be considered equilibrium. This is due to the fact that at significantly high flow rates of carbon dioxide, which is a solvent, coming into contact with the substance being dissolved, it does not have time to saturate it and, accordingly, weakly dissolves it. This concentration does not correspond to the concept of solubility. Thus, the determination of the range of mass flow rate at which the conditional state of saturation of the solvent and the solute is reached is the most important stage in studies to measure the solubility of substances in supercritical fluids. Based on the results of experimental data measuring the solubility of tannin in supercritical carbon dioxide, the dependences of the concentration of tannin in supercritical carbon dioxide on the mass flow rate are presented. It follows from the results that, in the flow rate range of 0-0.6 g/min, the tannin concentration in supercritical carbon dioxide is practically independent of the solvent flow rate, which is evidence of the equilibrium of this concentration and its compliance with the concept of solubility.

scholarly journals Extraction of essential oils from lime (Citrus latifolia Tanaka) by hydrodistillation and supercritical carbon dioxide

2005 ◽  
Vol 48 (1) ◽  
pp. 155-160 ◽  
Author(s):  
Ana Cristina Atti-Santos ◽  
Marcelo Rossato ◽  
Luciana Atti Serafini ◽  
Eduardo Cassel ◽  
Patrick Moyna
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Essential Oils ◽  
Flow Rate ◽  
Plant Material ◽  
Supercritical Extraction ◽  
Extraction Time ◽  
Citrus Latifolia ◽  
Co2 Flow ◽  
Supercritical Carbon

In this work lime essential oils were extracted by hydrodistillation and supercritical carbon dioxide. In the case of hydrodistillation, the parameters evaluated were extraction time and characteristics of the plant material. In supercritical extraction, the parameters evaluated were temperature, pressure, CO2 flow, extraction time and material characteristics. Considering citral content, the best results for hydrodistillation were obtained with a distillation time of 3 hours using whole peels. The best results for supercritical extraction were found using 60ºC, 90 bar, at a CO2 flow rate of 1 mL/ min for 30 minutes using milled peels. The best yields of lime oil were obtained by hydrodistillation (5.45% w/w) and supercritical extraction (7.93% w/w) for milled peels.

Numerical Performance and Flow Field Study of Centrifugal Compressor With Supercritical Carbon-Dioxide (SCO2)

2019 ◽  
Author(s):  
Hemant Kumar ◽  
Chetan S. Mistry
Keyword(s):  
Carbon Dioxide ◽  
Thermodynamic Properties ◽  
Critical Point ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Compressor Inlet

Abstract The Supercritical carbon-dioxide Brayton cycle main attraction is due to the Supercritical characteristic of the working fluid, carbon-dioxide (SCO2). Some of the advantages of using SCO2 are relatively low turbine inlet temperature, the compression work will be low, and the system will be compact due to the variation of thermodynamic properties (like density, and specific heat ratio) of SCO2 near the critical point. SCO2 behave more like liquid when its state is near the critical point (Total Pressure = 7.39 MPa, Total Temperature = 305 K), operating compressor inlet near critical point can minimize compression work. For present study the centrifugal compressor was designed to operate at 75,000 rpm with pressure ratio (P.R) = 1.8 and mass flow rate = 3.53 kg/s as available from Sandai report. Meanline design for centrifugal compressor with SCO2 properties was done. The blade geometry was developed using commercial CAD Ansys Bladegen. The flow domain was meshed using Ansys TurboGrid. ANSYS CFX was used as a solver for present numerical study. The thermodynamic properties of SCO2 were imported from the ANSYS flow material library using SCO2.RPG [NIST thermal physics properties of fluid system]. In order to ensure the change in flow physics the mesh independence study was also conducted. The present paper discuss about the performance and flow field study targeting different mass flow rates as exit boundary condition. The comparison of overall performance (Pressure Ratio, the Blade loading, Stage efficiency and Density variation) was done with three different mass flow rates. The designed and simulated centrifugal compressor meets the designed pressure rise requirement. The variation of mass flow rate on performance of centrifugal compressor was tend to be similar to conventional centrifugal compressor. The paper discusses about the effect of variation in density, specific heat ratio and pressure of SCO2 with different mass flow outlet condition. The performance map of numerical study were validated with experiment results and found in good agreement with experimental results. The change in flow properties within the rotor flow passage are found to be interesting and very informative for future such centrifugal compressor design for special application of SCO2 Brayton cycle. 80% mass flow rate has given better results in terms of aerodynamic performance. Abrupt change in thermodynamic properties was observed near impeller inlet region. Strong density variations are observed at compressor inlet.

Fast Heating Induced Thermoacoustic Waves in Supercritical Fluids: Experimental and Numerical Studies

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Nusair Hasan ◽  
Bakhtier Farouk
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Supercritical Fluid ◽  
Thermal Energy ◽  
Acoustic Waves ◽  
Electrical Heating ◽  
Temperature Perturbation ◽  
Energy Propagation ◽  
Numerical Predictions ◽  
Supercritical Carbon

Thermoacoustic waves in near-critical supercritical carbon dioxide are investigated experimentally on acoustic time scales using a fast electrical heating system along with high speed pressure measurements. Supercritical carbon dioxide (near the critical or the pseudocritical states) in an enclosure is subjected to fast boundary heating with a thin nickel foil and an R-C circuit. The combination of very high thermal compressibilities and vanishingly small thermal diffusivities of the near-critical fluid affect the thermal energy propagation, leading to the formation of acoustic waves as carriers of thermal energy (the so called piston effect). The experimental results show that under the same temperature perturbation at the boundary, the strength of the acoustic field is enhanced as the initial state of the supercritical fluid approaches criticality. The heating rate, at which the boundary temperature is raised, is a key factor in the generation of these acoustic waves. The effect of different rates of boundary heating on the acoustic wave formation mechanism near the critical point is studied. The thermoacoustic wave generation and propagation in near-critical supercritical fluid is also investigated numerically and compared with the experimental measurements. The numerical predictions show a good agreement with the experimental data.

Transient Response of a Cross Flow Heat Exchanger Subjected to Temperature and Flow Perturbations

2015 ◽  
Author(s):  
Karthik Silaipillayarputhur ◽  
Stephen A. Idem
Keyword(s):  
Heat Exchanger ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Transient Performance ◽  
Numerical Predictions ◽  
Minimum Capacity ◽  
Flow Heat

The transient performance of a multi-pass cross flow heat exchanger subjected to temperature and mass flow rate perturbations, where the heat exchanger flow circuiting is neither parallel flow nor counter flow, is considered in this work. A detailed numerical study was performed for representative single-pass, two-pass, and three-pass heat exchangers. Numerical predictions were obtained for cases where the minimum capacity rate fluid was subjected to a step change in inlet temperature in absence of mass flow rate perturbations. Likewise, numerical predictions were obtained for the heat exchangers operating initially at steady state, where a step mass flow rate change of the minimum capacity rate fluid was imposed in the absence of any fluid temperature perturbations. The transient performance of this particular heat exchanger configuration subjected to these temperature and flow disturbances has not been discussed previously in the available literature. In the present study the energy balance equations for the hot and cold fluids and the heat exchanger wall were solved using an implicit central finite difference method. A parametric study was conducted by varying the dimensionless quantities that govern the transient response of the heat exchanger over a typical range of values. Because of the storage of energy in the heat exchanger wall, and finite propagation times associated with the inlet perturbations, the outlet temperatures of both fluids do not respond instantaneously. The results are compared with previously published transient performance predictions of multi-pass counter flow and parallel flow heat exchangers.

scholarly journals Aerodynamic Optimization Design of a 150 kW High Performance Supercritical Carbon Dioxide Centrifugal Compressor without a High Speed Requirement

2020 ◽  
Vol 10 (6) ◽  
pp. 2093 ◽  
Author(s):  
Dongbo Shi ◽  
Yonghui Xie
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
High Speed ◽  
Design Method ◽  
Pressure Ratio ◽  
Aerodynamic Optimization ◽  
Design Software ◽  
Supercritical Carbon

Supercritical carbon dioxide (S-CO2) Brayton cycle technology has the advantages of excellent energy density and heat transfer. The compressor is the most critical and complex component of the cycle. Especially, in order to make the system more reliable and economical, the design method of a high efficiency compressor without a high speed requirement is particularly important. In this paper, thermodynamic design software of a S-CO2 centrifugal compressor is developed. It is used to design the 150 kW grade S-CO2 compressor at the speed of 40,000 rpm. The performance of the initial design is carried out by a 3-D aerodynamic analysis. The aerodynamic optimization includes three aspects: numerical calculation, design software and the flow part geometry parameters. The aerodynamic performance and the off-design performance of the optimal design are obtained. The results show that the total static efficiency of the compressor is 79.54%. The total pressure ratio is up to 1.9. The performance is excellent, and it can operate normally within the mass flow rate range of 5.97 kg/s to 11.05 kg/s. This research provides an intelligent and efficient design method for S-CO2 centrifugal compressors with a low flow rate and low speed, but high pressure ratio.

Determination of Supercritical Carbon Dioxide Extraction Parameters for Quercus infectoria Galls and the Effects on Extraction Yield and Antioxidant Activity

2014 ◽  
Vol 67 (2) ◽  
Author(s):  
Liza Md Salleh ◽  
Hasmida Mohd Nasir ◽  
Harisun Yaakob ◽  
Mohd Azizi Che Yunus
Keyword(s):  
Carbon Dioxide ◽  
Antioxidant Activity ◽  
Supercritical Carbon Dioxide ◽  
Medicinal Plant ◽  
Flow Rate ◽  
Total Phenolic ◽  
Extraction Parameters ◽  
Quercus Infectoria ◽  
Supercritical Carbon

Currently, finding alternative ways of extracting medicinal plant gain more interest from the researchers.  Quercus infectoria, a medicinal plant, is rich with bioactive compound being extracted using supercritical carbon dioxide (SC-CO2) extraction which helps to maintain the quality of the product as well as green environment. CO2 is widely used as solvent due to moderate critical conditions, nontoxic and easily removed from the products. This work was performed to determine the optimum extraction parameters of SC-CO2 extraction and their effects on the total phenolic content and antioxidant activity of Q.infectoria extract. Hence, two different parameters have been investigated which were extraction time and CO2 flow rate (2, 3, 4 ml/min) while pressure (P) and temperature (T) were fixed at highest density (P = 30 MPa, T = 40oC). The results obtained from this study show that the solvent flow rate of 2 ml/min gives the highest percentage of yield (0.3652%) and the complete extraction of the sample was achieved at 80 minutes. Better quality of the extract was shown at 2 ml/min as resulted in high amount of phenolic compound in the extract presented as gallic acid equivalent (GAE) (2.04×102 mg GAE/g sample). The extracts were screened for possible antioxidant activity by 2,2-diphenyl-1-picryl hydrazyl (DPPH) free radical scavenging assays. In this study, the best result obtained for antioxidant activity was at flow rate of 3 ml/min with inhibition percentage of 96.97%.

Numerical Simulation of Supercritical Carbon Dioxide Critical Flow in the Nozzle Tube

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Zhou Yuan ◽  
Wang Yangle ◽  
Chen Jingtan ◽  
Xia Zhaoyang ◽  
Wang Junfeng
Keyword(s):  
Experimental Data ◽  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Gas Phase ◽  
Mass Flow ◽  
Critical Mass ◽  
Critical Flow ◽  
Supercritical Phase ◽  
Simulation Results ◽  
Supercritical Carbon

The supercritical carbon dioxide (S-CO2) Brayton gas turbine cycle has been studied as an efficient and cost-effective option for advanced power systems. One major safety issue for any power cycle is a pipe break and the associated discharge of the working fluid and subsequent decrease in system pressure. In this paper, an S-CO2 critical flow in the nozzle tube is analyzed numerically with fluent 15.0. The Redlich–Kwong real gas equation is selected to calculate carbon dioxide density and the standard k-epsilon turbulence model is selected. Experimental data are used as a benchmark to examine the capability of the current approach. Compared with experimental data, the simulation results overestimate the critical mass flux; the error range is between 15% and 25%. The simulation results show that as L/D increases, critical mass flow decreases. As stagnation temperature increases, critical mass flow decreases. The complex thermal hydraulic behavior in the nozzle tubes is analyzed. Three flow patterns in the nozzle tube during transient critical flow are obtained and discussed. From inlet to outlet of the tube, CO2 may undergo the following phases in turn: (1) supercritical phase; (2) supercritical phase—gas phase; (3) supercritical phase—gas phase—liquid phase. The simulation results are also helpful for further experimental and theoretical research.

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