Carbon Dioxide Flow Research Articles

A Review of Supercritical Carbon Dioxide Heat Transfer and Flow Properties in Pipes

Supercritical carbon dioxide (s‐CO2) has the characteristics of highly efficient and has been used in the engineering field. This article reviews the research progress on the heat transfer and flow properies in s‐CO2 tubes. To obtain the most accurate heat transfer and friction factor correlations, new correlations derived from experimental data are proposed, and the accuracy of the published correlations is assessed in conjunction with the experimental data. The results show how important variables such as mass flow, inlet temperature, and tube size relate to the properties of pressure drop and heat transfer in pipes that use s‐CO2 as the work material. The D‐M‐2011 heat transfer correlation had the highest accuracy, with 62.57% of the data having a relative deviation of less than ±20%, and the Wang‐2014 friction factor correlation had the highest accuracy, with 72.91% of the data having a relative deviation of less than ±20%. Considering the dimensionless number correction and segmented function correction to improve the correlation, 82.41% of the data in the new heat transfer correlation have a relative deviation less than ±20% and 83.53% of the data in the new friction factor correlation have a relative deviation less than ±20%.

Two-phase choked flow of trans critical carbon dioxide at the micro scale

An experimental study about two-phase carbon dioxide (CO2) choking flow inside parallel microchannels with hydraulic diameters of 66.6 μm is conducted. Trans critical CO2 with a reduced pressure ranging from 0.9 to 1.1 (i.e., from 6.5 to 8 MPa) is introduced at the inlet and is exhausted downstream at a reduced outlet pressure ranging from 0.135 to 1.016 (i.e., from 1 to 7.5 MPa). Mass flow rates as a function of pressure drop are obtained, and choking conditions are determined. Subsequently, the vapor and liquid velocities are inferred using the thermodynamic properties of the flow and several void fraction models. The speed of sound of the vapor, the liquid, and the mixture are calculated based on the homogenous flow model, slug flow model, and stratified flow model. All void fraction models that are examined predict the vapor Mach number at the onset of choking somewhere below unity. The stratified flow model provides a more accurate prediction of the experimentally obtained flow choking, indicating that the liquid achieves its effective sonic velocity well before the vapor and is therefore conjectured to control flow choking. Temperature drop across the microdevice is discussed, and measured two-phase flow Joule–Thomson coefficients (JT) are compared to calculated values with the mean average error of 1.27 K/MPa.

Amoxicillin Removal by Microwave Irradiated Almond Shell-Based Activated Carbon: Optimization Study

Abstract The wastewater contamination containing amoxicillin (AMOX) antibiotic into the environment is harmful to aquatic creatures and humans. Therefore, this study developed almond shell-based activated carbon (ASAC) through microwave irradiation method under a continuous flow of carbon dioxide (CO2) gas. The resulted ASAC was used to adsorb AMOX in an aqueous solution. The optimization of the conditions for ASAC production was done by using response surface methodology (RSM), which identified 481 W and 4.64 min as the optimal conditions for radiation power and time, respectively. This resulted in 95.06% of AMOX removal and 39.64% of ASAC yield. An analysis of variance (ANOVA) indicated that radiation power significantly affects both AMOX removal and ASAC’s yield responses as compared to the radiation time. In equilibrium study, the adsorption uptakes were improved from 0.87 to 36.88 mg/g when the initial concentration of AMOX inclined (1 – 50 mg/L), whilst the percentage removal declined (86.80 – 73.76%). Isotherm study divulged that this adsorption process obeyed Langmuir model with a maximum monolayer adsorption capacity (Qm) of 63.29 mg/g.

Mathematical modelling of essential oil supercritical carbon dioxide extraction from chamomile flowers

AbstractThis study investigates the supercritical extraction process of essential oil from chamomile flowers. Essential oils of chamomile are used extensively for medicinal purposes. Many different chamomile products have been developed, the most popular of which is herbal tea. In this study, a mathematical model is formulated that describes the governing mass transfer phenomena in a solid–fluid environment under supercritical conditions using carbon dioxide. The concept of quasi‐one‐dimensional flow is applied to reduce the number of spatial dimensions. The flow of carbon dioxide is assumed to be uniform across any cross‐section, although the area available for the fluid phase can vary along the extractor. The physical properties of the solvent are estimated based on the Peng–Robinson equation of state. Model parameters, including the partition factor, internal diffusion coefficient, and decaying factor, were determined through maximum likelihood estimation based on experimental data assuming normally distributed errors. The model parameters were combined to obtain a set of correlations. The generalized process model is capable of reproducing the dataset with satisfactory accuracy.

Optimization of resource recovery technologies in the disassembly of waste lithium batteries: A study on selective lithium extraction

This study focuses on optimizing resource recovery technology in the dismantling process of retired lithium batteries to mitigate environmental pollution. Addressing the challenge of significant precious metal losses in traditional hydrometallurgical recycling methods, this study employs a reductive roasting-carbonation leaching process to selectively extract lithium from cathode materials using a reducing agent. The study examines the effects of parameters such as roasting temperature, time, and reducing agent dosage on lithium leaching efficiency, and explores additional factors including carbonation leaching time, carbon dioxide flow rate, liquid-to-solid ratio, and leaching temperature in conjunction with multi-stage countercurrent leaching technology. Characterization of the roasting products and leaching process is performed using X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The results demonstrate that, under conditions of a 700 °C roasting temperature, a 3-h roasting time, and a 15 % reducing agent dosage, the lithium leaching rate can achieve approximately 90 %. Following multi-stage countercurrent leaching, the lithium leaching rate exceeds 97 %, satisfying the purity requirements for battery-grade lithium carbonate. The innovation of this study is evident in its optimization of the recycling process, effectively separating and recovering cathode materials while reducing environmental pollution. This approach supports environmentally friendly waste treatment and contributes to the sustainable development of the battery industry.

Numercial modeling for enhanced heat transfer efficiency of spiral coils with supercritical fluid flow under different operating conditions

This research investigates the thermohydraulic performance and exergy destruction associated with the flow of supercritical carbon dioxide (sCO2) within spirally coiled mini tubes. The study examines the impact of different cross-sectional geometries. The primary objective of the study is to examine the impact of critical parameters, including shape, hydraulic diameter, inlet temperature, mass flux, and operating pressure, on important variables such as friction factor, heat transfer coefficient, and exergy efficiency. The computational simulation employs the RNG k−ε model. The Coupled algorithm was utilized for the determination of velocity and pressure fields, utilizing second-order discretization for domain partitioning and first-order discretization for other terms. The carbon dioxide (CO2) was conceptualized as a compressible gas with complex thermophysical attributes that are contingent upon variations in temperature and pressure. The thermophysical properties of carbon dioxide are evaluated within a defined range of operating conditions (298. 15 K < T < 455 K and 8 MPa < p < 10 MPa). The observed trends in HTC (heat transfer coefficient) demonstrate a correlation with specific heat, showing a peak at lower temperatures under increased operating pressures. Elevated operational pressure results in a reduction of the maximum HTC. The augmentation of mass flux results in an increase in heat transfer coefficient, thereby indicating an improvement in system efficiency. An augmentation in hydraulic diameter yields diminished heat transfer coefficients, mitigated pressure loss, and heightened exergy destruction.

Multiscale simulation of water/oil displacement with dissolved CO[formula omitted]: Implications for geological carbon storage and CO[formula omitted]-enhanced oil recovery

This study combines molecular and pore-scale simulations to enhance our understanding of water, carbon dioxide (CO2), and oil flow in a porous system for high-efficiency geological carbon storage and enhanced oil recovery. We use molecular dynamics simulations to study the variation of interfacial tension (IFT), viscosity, and contact angle across varying system CO2 concentrations. The study reveals that the IFT simulation accuracy in the three-component mixture system relates positively to the volume-to-interfacial area ratio, and IFT decreases with CO2 concentration. Oil–CO2 mixture viscosity decreases and shows an intersection with water viscosity as CO2 concentration increases. The contact angle on the hydrophobic surface of kaolinite first increases and then decreases with CO2 concentration, while the hydrophilic surface contact angle is not sensitive to the CO2 concentration. Visualizing CO2 density distribution reveals its accumulation at fluid–fluid and fluid–solid interfaces and the combined effect results in the highest CO2 density at contact-line regions. Meanwhile, the elevated CO2 density at fluid–fluid interfaces reduces IFT, contributing to the initial contact angle increase, while the CO2 density increase at fluids–solid surface explains the subsequent contact angle decrease. These findings are then upscaled into a core-scale system using lattice Boltzmann simulations. The results are summarized into a phase diagram, which reveals the non-monotonic variations of the initial–residual (I–R) curves across different CO2 concentrations, and the residual saturation overall decreases with CO2 concentration for high initial saturations. These findings underscore the critical roles of system CO2 concentration and rock components, particularly kaolinite clay minerals, in subsurface multiphase seepage confronted in geological carbon storage and CO2-enhanced oil recovery, highlighting the importance of digital rock physical chemistry.

Experimental investigation of non-uniform heating effect on flow and heat transfer of supercritical carbon dioxide:An application to solar parabolic trough collector

In order to reduce the carbon dioxide emission, the supercritical carbon dioxide (sCO2) Brayton cycle is a good choice to convert solar energy into power using solar parabolic trough collectors (PTCs). Because the earth rotation induced non-uniform flux distribution threatens the safe operation of absorber tubes, we investigate the flow and heat transfer of sCO2 in a horizontal tube under non-uniform heating, with the mass fluxes, average heat fluxes and pressures in the ranges of (397–1244) kg/m2s, (99–413) kW/m2, and (7.5–15.7) MPa, respectively. On the contrary to the classical treatment of supercritical fluid (SCF), SCF is treated in a multiphase framework. It is found that, compared with the sCO2 heat transfer in horizontal tubes under uniform heating, the non-uniform heating not only enhances heat transfer, but also increases friction factors. Besides, the non-uniform heating weakens the stratification effect, but the difference of heat transfer between the top and bottom generatrixes cannot be completed eliminated. It is observed that the larger vapor-like-layer thicknesses on tube walls may switch the sCO2 heat transfer from normal heat transfer (NHT) to heat transfer deterioration (HTD). Three heat transfer mechanisms are commented by using the dimensionless numbers regarding the pseudo-boiling in supercritical pressures.

Research on Carbon Dioxide Computational Fluid Dynamics Simulation of Urban Green Spaces under Different Vegetation Spatial Layout Morphologies

Urban green spaces (UGSs) are considered an important natural approach for improving urban climatic conditions, promoting sustainable urban development, and advancing the global “Carbon Peak and Carbon Neutrality” targets. Previous studies have found that different vegetation spatial morphologies significantly impact the capacity to obstruct and absorb CO2, but it is not yet well understood which morphology can retain and absorb more CO2. This study takes Nantong Central Park as an example and conducts a CFD (Computational Fluid Dynamics) carbon flow simulation for CO2 under different vegetation spatial morphologies to identify their CO2 retention and absorption effects. First, the carbon sink benefits of elements such as “vegetation, soil, and wetlands” within the park were calculated, and the elements with the highest carbon sink benefits were identified. Then, the park was divided into carbon welcoming zones, carbon flow zones, and carbon shadow zones for carbon flow simulation with the highest carbon sink benefits. The results show that in the carbon welcome area, the one-block long fan-shaped plant community with a spatial density of 40 m thickness can best meet the requirements of absorption and induction of a small amount of carbon dioxide, with the smallest air vortex and uniform distribution of carbon dioxide in the surrounding area. In the carbon flow area, combined with the visual effect, the planting pattern of 6 m spacing herringbone combined with natural structure was adopted, which has a good carbon dioxide blocking and absorption capacity. In the carbon-shaded area, a herringbone planting pattern with a total width of 40 m and a base angle of 60° was chosen, which had the strongest hindrance and absorption capacity. Urban park environment optimization can use Fluent simulation to analyze the flow of carbon dioxide between different elements affected by wind dynamics at the same time. Based on the results, the form, layout, and spatial distance are adjusted and optimized. This study can better guide the spatial layout of vegetation and contribute to the realization of the goal of “carbon peak and carbon neutrality”.

Numerical and Experimental Study of Thermohydraulic Processes in Slot Channels with Smooth-Streamlined Ribs and Staggered Arrays of Drop-Shaped Pins during Air and Carbon Dioxide Flow

Numerical and Experimental Study of Thermohydraulic Processes in Slot Channels with Smooth-Streamlined Ribs and Staggered Arrays of Drop-Shaped Pins during Air and Carbon Dioxide Flow

Modeling polydispersed droplets in non-equilibrium condensing CO2 flows through turbine cascades using moment-based methods for efficient energy utilization

The efficiency of a power cycle is significantly influenced by the condensation process and the size distribution of the droplets, as these factors directly affect heat transfer rates and overall energy conversion efficiency. Accurate numerical modeling of thermodynamic non-equilibrium condensation is crucial for predicting droplet nucleation and growth in carbon dioxide flows. This study applies moment-based polydispersed droplet models, such as the quadrature method of moments, to account for the droplet size spectrum. Additionally, discrete methods based on a predefined shape of the polydispersed droplet size spectrum are utilized and evaluated to reduce numerical complexity. Our results demonstrate that polydispersed models provide higher accuracy compared to monodispersed models when simulating steam and supercritical carbon dioxide flows in converging–diverging nozzles. In turbine cascades, the choice of model significantly influences the predicted mean droplet size and efficiency. Isentropic efficiency evaluations reveal higher values for carbon dioxide compared to steam, with efficiencies of 94.6–95.8% versus 91.8–92.9% for wet cases and 96.5–97.2% versus 95.8–96.5% for dry cases. Notably, spontaneous droplet nucleation slightly affects the efficiency of the blade cascade in carbon dioxide flows, whereas steam flows experience efficiency reductions between 3.58% and 4.01%. This work advances the understanding of droplet condensation processes in turbine cascades, highlighting the superior performance of polydispersed models and providing quantitative insights into their impact on efficiency.

Ethanol removal by vacuum-assisted gas stripping: Influence of operating conditions

One way to overcome the inhibitory effects caused by ethanol on yeast cell growth is the use of extractive fermentation, whereby ethanol is removed from the fermentation broth as it is produced. The present work investigates ethanol removal from solution by vacuum-assisted gas stripping, which is a promising method for enhancing performance, compared to conventional gas stripping. Evaluation was made of the effects of carbon dioxide flow rate (ϕCO2), temperature (T), and pressure (P) on ethanol removal performance. Bench-scale assays were performed using a 2-L bubble column containing 10 % v/v ethanol solution, with monitoring of the gas and liquid phases by FT-MIR spectroscopy. The ethanol entrainment factor (FE) increased with ϕCO2 and temperature, but decreased at higher pressure. Only ϕCO2 had significant and positive effects on the concentration factor (FC) and selectivity (αE/W), within the operating ranges of the variables studied. An ethanol removal model was obtained that provided an accurate description of the process behavior, with good agreement between the experimental and simulated data. In addition, the energy requirement for ethanol removal by vacuum-assisted gas stripping in the bioreactor was lower than for the conventional stripping process.

Molecular dynamics simulation of carbon dioxide flow in kaolinite pores

In order to estimate the effective storage capacity of carbon dioxide in geological storage, it makes great significance to understand the seepage mechanism of flowing carbon dioxide fluid and its influence on the occurrence state in micropore. In this paper, the molecular simulation method was used to obtain the optimal configuration of kaolinite micropore and carbon dioxide molecules. The molecular dynamics method was used to simulate the flow characteristics of carbon dioxide fluid in kaolinite pores in differential depth of burial under constant pressure drop. The results show that the adsorption capacity of carbon dioxide fluid on the wall of kaolinite decreases with the increase of burial depth, the fluid density in the center of the micropore increases with the increase of burial depth, the diffusion capacity of the fluid changes significantly when the burial depth is greater than 2 km; when a constant differential pressure is applied, the flow of carbon dioxide fluid in the pore conforms to the classical poiseulle flow, the diffusion ability of the fluid increases with the increase of burial depth, nearly doubling, and the slip length also increases with the increase of burial depth; the flow behavior significantly reduces the total amount of carbon dioxide in kaolinite micropore, where the density of the first adsorption layer near the wall decreases by at least 20%, and its effect on fluid is greater than that caused by the increase of burial depth. Therefore, when estimating the effective storage capacity of carbon dioxide in geological storage, the influence of pressure drop and burial depth on the total reduction of geological sequestration should be considered at the same time. The purpose is to provide more detailed theoretical basis for carbon dioxide geological sequestration.

Investigation of the transferability of calibration between alternative fluids for liquid and dense phase carbon dioxide flow measurement

Carbon Capture Utilisation and Storage (CCUS) technology is pivotal for achieving global emissions reduction goals. The rise in CCUS facilities, with a near doubling of global capture capacity, indicates industry momentum. Robust flow measurement across the CCUS transport and storage networks are essential for commercial contracts, financial incentives, and regulatory compliance since these are underpinned by accurate quantification of the CO2 quantity transferred across the CCUS chain. However, a critical gap exists in verification and quality assurance of flow meters as currently there are no traceable calibration facilities that operates with liquid and/or dense phase CO2. However, globally there are many accredited traceable water and oil calibration facilities in operation, which can meet the required flow rates and meter sizes. An experimental study was then conducted at TÜV SÜD National Engineering Laboratory, UK, and at the Institute for Energy Technologies, NO, to explore the transferability of calibration between water, oil, and CO2 using five flow meter technologies with the aim of providing a preliminary assessment of whether meters calibrated in alternative fluids can accurately measure liquid and supercritical CO2. The results suggest that this approach could work for Coriolis meters. The results also suggest caution in relying solely on using Equations of State to calculate density values and a recommendation is presented to currently employing direct density measurements until a more comprehensive understanding is achieved on Equations of State performance for CO2-rich mixtures. To the best of the author's knowledge this is the first time that such experimental investigation is conducted, and the results shared publicly.

Effect detection of using a modified Redlich-Kwong-Aungier equation of state on the calculation of carbon dioxide flow in a centrifugal compressor

Supercritical CO2 (S-CO2) cycles have found applications in power generation and can achieve high efficiency in a wide range of temperatures and pressures. The Redlich-Kwong-Aungier real gas equation of state is used to describe the thermodynamic properties of the CO2 working fluid. The main problem in its application lies in modeling the phase transition between different states and the region near the critical point of the working fluid. The object of the study is the working process in a centrifugal compressor located in the compression loop with the CO2 working fluid. The proposed mathematical model of the modified Redlich-Kwong-Aungier equation of state allows for a first-order phase transition from the liquid to the supercritical region even near the critical point. A scaling factor was added to the modified equation of state, significantly reducing the error in pressure determination in a wide range of temperatures compared to the original equation of state. The proposed mathematical model can be applied in the pure liquid region, limited to the temperature range from 220 K to 300 K. The mathematical model was used to solve the 3D gasdynamic problem, specifically to determine the thermodynamic and kinematic properties of the flow in a centrifugal compressor in a wide range of operating modes. A comparison of the calculation results with experimental data from the Sandia National Laboratories (USA) report was conducted. A satisfactory agreement of the results at the design point of the compressor characteristic was obtained (less than 5 % discrepancy). Due to the simplicity of the equation of state and the small number (seven) of empirical coefficients, the obtained mathematical model can be used for practical CFD tasks without significant computational time costs.

Numerical study on heat transfer deterioration of supercritical CO2 in lattice structure array channel

This study numerically explores the fluid flow and heat transfer features of supercritical carbon dioxide (CO2) in lattice structure array channel. The mitigation mechanism of the miniature cylindrical lattice structure array on heat transfer deterioration (HTD) of supercritical CO2 in vertically upward heated channel is studied. This paper evaluates the effect of several key influential parameters (length, diameter, pitch and number) of cylindrical lattice structure array on fluid flow field involving vortex structures, heat transfer coefficient, buoyancy effect and accelerated effect. The results indicate that the lattice structure can effectively suppress the HTD by generating the vortex structure which promoting the turbulent mixing effect and enhancing the turbulent kinetic energy (TKE) of the fluid. Compared with the smooth channel, the peak wall temperature of the lattice structure channel is reduced by about 50 °C, with a corresponding increase in the heat transfer coefficient of about 140 %. The average heat transfer coefficient of the channel is increased by more than 1/3. Furthermore, by increasing lattice length can reduce flow layer stratification and by increasing lattice diameter can creating a composite vortex, which enhance flow mixing strength. The larger the lattice pitch, the worse the overall suppression effect. A denser lattice arrangement produces more temperature valleys, thereby increasing the heat transfer coefficient. The conclusions in this study could provide the main theory support for security and stability of supercritical CO2 heat exchangers in power system.

Analysis of Reported Adverse Events Related to Hemospray: An FDA MAUDE Database Study.

Topical hemostatic powder is a mineral powder that forms an adherent barrier and coagulates active bleeding in the gastrointestinal (GI) tract. Hemospray is the first hemostatic powder approved by the Food and Drug Administration (FDA) in the United States. Hemospray has been increasingly used to manage GI bleeding. However, data on the adverse events of hemostatic powders are lacking. Therefore, we aim to report and analyze adverse events associated with Hemospray using the FDA's "Manufacturer and User Facility Device Experience" database. We analyzed the postmarketing surveillance data from the FDA's Manufacturer and User Facility Device Experience database for Hemospray, initially known as TC-325, from June 2018 through April 2022. Results of the search were classified into device-related technical issues, patient-related adverse events and health care staff-related adverse events. Five hundred two medical device reporting claims were identified from June 2018 through April 2022. Seven duplicate claims were identified, and some claims included more than one event type. Therefore, there were 558 device-related problems, 28 patient-related adverse events, and 2 adverse events in health care staff members. The most common device-related problems were activation failure or failure to fire (n = 385, 70.0%) and obstruction of carbon dioxide flow (n = 121, 21.7). The most common patient-related adverse events included tissue injury or bleeding (n = 21) and perforation (n = 5). Although Hemospray is a valuable tool in the armamentarium for endoscopists in managing GI bleeding, endoscopists must be mindful of deice-related problems and potential patient-related adverse events.

Numerical study of CO2 trans-critical process inside micromodel based porous structures under supercritical pressures

Understanding the flow, heat transfer, and trans-critical process of carbon dioxide in porous media is crucial for various applications, including CO2 sequestration, soil remediation and oil and gas recovery, due to its unique physical properties in the critical region. In this study, a porous media model on a microfluidic chip structure was simulated to emphasize the heat transfer and trans-critical process of CO2 under supercritical pressure in porous media. The study aims to observe the behaviors of CO2 during its transition from subcritical to supercritical temperature under supercritical pressure. The main objective is to observe the temperature distribution and pressure change of CO2 in a porous media model under the influence of bottom heating. At the same time, we observe the changes in the position of the critical temperature point of CO2 in porous media and analyze its heat exchange process in porous media. After the flow reaches a steady state, the temperature span near the grains is 1.6 K, and the pressure drop per unit length is 1480.3 Pa/mm. As the flow time progresses, the critical temperature line migrates from outlet region to inlet region, the range of sCO2 narrows from 81.7 % to 84.7 % in the porous media region. Finally, the influence of different working conditions on the trans-critical region is studied. It is hoped that this study will contribute to the understanding of the trans-critical process of CO2 in porous media.

The Diagnostic Evaluation of the SINEH Cardiopulmonary Triage Scale and the Emergency Severity Index in the Emergency Department: A Comparative Study.

The diagnostic evaluation of the emergency severity index (ESI) in the triage of patients with cardiopulmonary complaints has a high sensitivity but a low specificity in the emergency department (ED). Therefore, triage scales with more accurate diagnostic evaluation are required. As a result, accuracy of the SINEH triage scale (SinTS) and the ESI was compared to compare mistriage of critically ill patients with cardiopulmonary complaints. This descriptive, analytical and cross-sectional study was conducted between December 2022 and April 2023. In this study, two nurses independently examined each patient using two triage scales. The admission unit and length of hospital stay were also recorded. The outcome was classified as high-risk admission (cardiac care unit and intensive care unit) and low-risk admission (internal unit or discharge from the ED). Undertriage and overtiage were defined as high-risk admission with triage level 3 and 4 and low-risk admission with triage level 1 or 2, respectively. A panel of experts evaluated content validity of SinTS and kappa designating agreement on relevance reported. The inter-rater reliability of two scales was also reported. Finally, the study included 145 patients. The average age of the patients studied was 61.35 years. SinTS has a total mistriage of 29.63%, with 4.13% being undertriage and 25.5% being overtriage. In ESI, the total mistriage is 66.8%, with 1.3% being undertriage and 65.5% being overtriage. The undertriage of the two scales did not differ significantly by admission unit (p=0.26), but the overtriage of the two methods did (p=0.001). The sensitivity, specificity, and accuracy of SinTS were 86.3%, 63.37%, and 72.27%, respectively, while those of ESI were 95.4%, 5.94%, and 32.79%, respectively. SINEH triage scale has achieved the optimal accuracy in recognizing the acuity of the patients with chest pain and dyspnea by using SpO2, pressure of end-tidal carbon dioxide, troponin I, and peak expiratory flow. When triaging patients with chest pain and dyspnea, SinTS may exhibit a higher level of accuracy compared to ESI. More research is needed to improve accuracy of triage scales in patient with cardiopulmonary complaints.

Effects of cross-sectional shape on flow and heat transfer of the laminar flow of supercritical carbon dioxide inside horizontal microchannels

Supercritical carbon dioxide (sCO2) flow at the micro scale provides an excellent heat transfer solutions for a range of microelectronics cooling applications. The cross-sectional shape of the microchannel (in combination with the abruptly changing thermophysical properties of sCO2) affects the heat transfer and flow characteristics, but these effects are not well understood at constant wall temperatures as most of the previous studies were performed at constant surface heat fluxes. Current study numerically investigated, using CFD, the effects of different cross-sectional shapes, such as circle, equilateral triangle, semi-circle, and square, in zero gravity (space) and in terrestrial conditions, at constant wall temperatures.In all cases, the hydraulic diameter of the microchannel was 100 μm, the total length was 27 mm, and the heated length was 25 mm. A total of 216 cases were analyzed to predict the effects of surface temperature ranging from 310 to 330 K, pressures ranging from 8 to 10 MPa, and Reynolds numbers from 100 to 500 on the heat transfer and flow. It was revealed that the microchannel with triangular cross-section has the highest heat transfer rate, highest mass flow rate, and lowest pressure drop both in zero gravity and in terrestrial conditions. The total surface heat transfer rate for the triangular microchannel was about 49% higher than the circular microchannel at a pressure of 8 MPa, around 53% higher at 9 MPa, and about 55% higher at 10 MPa. However, the average surface heat transfer coefficient displayed a complex behavior, and it depends on the combination of surface temperature, Reynolds number, and operating pressure. The surface heat transfer rate and pressure drop were increased for all shapes at terrestrial conditions, emphasizing that the effects of buoyancy cannot be neglected. Overall, this study revealed a complex behavior of the flow of sCO2 inside microchannels of different cross-sectional shapes, and the triangular cross-section performed better than other shapes.