Sinusoidal Channels Research Articles

Intergrowth MFI Zeolite with Inverse Al Zoning and Predominant Sinusoidal Channels for Highly Selective Production of Styrene.

ZSM-5 zeolites with accessible micropore architecture and tunable acid-base sites are important shape-selective catalysts. However, the presence of exposed straight channels and the external acid-base sites of conventional ZSM-5 has a negative impact on shape selectivity. Herein, we report on the direct synthesis of an intergrowth ZSM-5 zeolite mimicking the mortise-tenon joints. It can be revealed by various methods that the mortise-tenon ZSM-5 shows an inverse Al gradient from the surface to the core of the zeolite. More importantly, the sinusoidal channels predominantly opened to their external surfaces are constructed. The shape-selective capability of the ZSM-5 zeolite has been fully exploited due to the intrinsic inert external surface and unique sinusoidal channel features, thereby resulting in high styrene selectivity (>90%) and good catalytic stability (>100 h) in the toluene side-chain alkylation reaction. In addition, in situ DRIFTS confirms that this intergrowth ZSM-5 contributes to the formation of more active intermediates of HCOO* and H3CO*, which is another reason responsible for the superior performance.

Numerical Simulation and Neural Network Model for Hydromagnetic Nanofluid Convection in a Porous Wavy Channel with Thermal Non-Equilibrium Model

Abstract The present study aims to analyze the nonfluid MHD convective heat transfer in a porous wavy channel with a local thermal non-equilibrium (LTNE) model. Such a model finds applications related to enhancement in thermal performance, increasing the heat transfer coefficient in the compact design of heat exchangers for the aerospace and automotive industries and elevation in the efficiency of the solar collector. A sinusoidal porous wavy LTNE channel containing nanofluid and subjected to the induced and applied magnetic fields is considered. A uniform magnetic field is applied orthogonal to the channel and the induced magnetic field effects are considered due to the large magnetic Reynolds number. The momentum, continuity, energy, and nanoparticle volume fraction equations constitute the coupled nonlinear system of differential equations and are solved using the Galerkin finite element method. The reliability of the technique is assessed by comparing the proposed procedure with the results from earlier sources. A detailed analysis is presented to determine the effects of different physical parameters arising in the system on temperature, nanoparticle concentration, and velocity profiles. As an illustration, the findings exhibit that increasing the modified diffusivity ratio increases the values of the nanoparticle volume fraction whereas, reducing the modified diffusivity ratio enhances the temperature distribution. A higher value of thermal Rayleigh number presents a significant involvement of buoyancy forces, potentially resulting in the development of convective currents. A higher Nield number indicates more effective heat transport from the solid surface to the nanofluid. Consequently, there is a minimal thermal difference between the solid surface and the bulk nanofluid. Effective heat transmission enhances the nanofluid ability to absorb heat and generates a more consistent dispersion of temperature inside the fluid. The performance of the designed algorithms of the artificial neural network, namely, the Levenberg – Marquardt algorithm, in the problem under consideration is evaluated and the methodology is found reasonably precise with the matching of order around 6 to 7 decimal places of accuracy.

On the effect of wave amplitude and corrugation profile of certain types of corrugated channels on thermal performance and entropy generation

This study aims to examine experimentally and numerically the thermal-hydraulic performance and entropy generation of wavy channels: sinusoidal and triangular, and compare them with respect to the straight channel. Various wavy amplitudes and corrugation profiles are considered in a sinusoidal wavy channel and a triangular wavy channel and assessed with the straight channel. Experimental test rig is built and the experiments are carried out on laminar air flow and used to verify the simulation results. The main findings show that the HT rate, fluid flow, and entropy generation are affected by the corrugation profile and wave amplitude of the wavy channel. The maximum Nusselt number of 11.17 occurred in a sinusoidal wavy channel with a wave amplitude equal to 1.75, and high friction factor also happens in this model. It was found that the sinusoidal and triangular wavy channels with A = 0.75 and a flow rate range of 1–1.75 have the highest overall thermal performance factor. Also, the total entropy generation of the straight channel was lower than all corrugated channel models. In conclusion, it has been found that the best compromise between enhanced HT and the accompanying increase in both pressure drop and entropy generation is occurred in case of A = 0.75 at flow rate ranged from 1 to 1.67 LPM.

Ternary nanofluid cooling of an elastic plate by using double sinusoidal wavy channels under different magnetic fields

Ternary nanofluid cooling of an elastic plate by using double sinusoidal wavy channels under different magnetic fields

Ni-Based Molecular Sieves Nanomaterials for Dry Methane Reforming: Role of Porous Structure and Active Sites Distribution on Hydrogen Production.

Global warming, driven by greenhouse gases like CH4 and CO2, necessitates efficient catalytic conversion to syngas. Herein, Ni containing different molecular sieve nanomaterials are investigated for dry reforming of methane (DRM). The reduced catalysts are characterized by surface area porosity, X-ray diffraction, Raman infrared spectroscopy, CO2 temperature-programmed desorption techniques, and transmission electron microscopy. The active sites over each molecular sieve remain stable under oxidizing gas CO2 during DRM. The reduced 5Ni/CBV10A catalyst, characterized by the lowest silica-alumina ratio, smallest surface area and pore volume, and narrow 8-ring connecting channels, generated the maximum number of active sites on its outer surface. In contrast, the reduced-5Ni/CBV3024E catalyst, with the highest silica-alumina ratio, more than double the surface area and pore volume, 12-ring sinusoidal porous channels, and smallest Ni crystallite, produced the highest H2 output (44%) after 300 min of operation at 700 °C, with a CH4:CO2 = 1:1, P = 1 atom, gas hour space velocity (GHSV) = 42 L gcat-1 h-1. This performance was achieved despite having 25% fewer initial active sites, suggesting that a larger fraction of these sites is stabilized within the pore channels, leading to sustained catalytic activity. Using central composite design and response surface methodology, we successfully optimized the process conditions for the 5Ni/CBV3024E catalyst. The optimized conditions yielded a desirable H2 to CO ratio of 1.00, with a H2 yield of 91.92% and a CO yield of 89.16%, indicating high efficiency in gas production. The experimental results closely aligned with the predicted values, demonstrating the effectiveness of the optimization approach.

Direct methane utilization through benzene dehydroalkylation catalyzed by Co2+ sites in ZSM-5 intersections

Cobalt cations exchanged in ZSM-5 are active for the direct dehydromethylation of benzene with CH4. While toluene is the primary product, an alternate reaction pathway leads also to the formation of biphenyl and phenyltoluene. This not only diminishes the selectivity but also contributes to the deactivation of the catalyst. Temperature-programmed surface reactions show that benzene adsorbs strongly on the exchanged Co2+ cations, essentially blocking the sites for alkylation below 400 °C. At temperatures exceeding 400 °C, the partial desorption of benzene enables its reaction with CH4, leading to the formation of toluene. The formation of biphenyl is kinetically hindered, and its onset is only observed at temperatures above 450 °C. When CH4 is allowed to chemisorb on Co2+ sites prior to exposure to benzene, the formation of toluene is detected at temperatures below 400 °C. By infrared spectroscopy of benzene adsorption and UV–Vis spectroscopic characterization, we identified the existence of intersections in ZSM-5 where three H+ are in proximity. The ion exchange of a zeolite lattice Al3+ pair in such positions leads to the formation of a Co2+ site near a free Brønsted acid site. We observed a correlation between the concentration of this type of Co2+ sites and the catalytic activity of Co-ZSM-5 in benzene alkylation with CH4. This is further supported by the catalytic tests of Co-ZSM-5 materials with specifically a larger proportion of Co sites in sinusoidal channels, as a result of acidic conditions during ion exchange. Based on this, we propose that toluene formation takes place via heterolytic dissociation of CH4 on a Co2+ site at intersections followed by reaction with benzene strongly interacting with an adjacent BAS.

Boron doped Mo/HMCM-22 catalyst for improving coke resistance in methane dehydroaromatization

Mo/HMCM-22 is one of the candidate catalysts for methane dehydroaromatization (MDA) reaction. However, serious coke deposition would deactivate the catalyst, resulting in a rapid decrease of aromatics yield. Here, we adjusted the acidity of MCM-22 zeolite by doping boron into the framework. Boron species replace some of framework aluminum and prompt aluminum to locate in sinusoidal channel. It optimizes the ratio of strong/weak Brønsted acid, as well as enhances the interaction between molybdenum and HMCM-22 to facilitate the dispersion of molybdenum species. After 10 h of MDA reaction, the yield of aromatics over Mo/H[B]MCM-22 (SBR 30) is 3.5 times higher than that of Mo/H[B]MCM-22 (SBR 5). It decreases by only 4.8 % in comparison to the initial yield. Meanwhile, Mo/H[B]MCM-22 (SBR 30) shows significantly better resistance to coke deposition. Therefore, the established structure–activity relationships provide valuable insights for future research on the modification of zeolite acidity in methane dehydroaromatization reaction.

ZSM-5 monolithic microreactors with hierarchical porosity: Maximizing selective production of para-xylene

ZSM-5 monoliths with Si/Al ∼40 were achieved by steam assisted conversion of micro-/macroporous silica-alumina monoliths synthesized by an optimized combination of spinodal decomposition and sol-gel process. ZSM-5 monoliths exhibit a homogeneous and interconnected network of macropores of ∼30 μm diameter, with a macropore volume of ∼1 mL g−1 and a micropore volume of 0.16 mL g−1, as waited for pure ZSM-5. The skeleton of ZSM-5 monoliths featured a 3D aggregation of spherical particles of 6 μm in diameter. The latter were composed by a stacking of thin plate-like shaped crystallites. The catalytic properties of the ZSM-5 monoliths were assessed through their use as catalytic microreactor in the continuous flow alkylation of toluene with methanol. An outstanding for para-xylene selectivity of 81 % was achieved possibly ascribable due to the maximization of pore openings of sinusoidal channels as a result of the plate-like morphology of the ZSM-5 crystallites.

Elasto-inertial particle focusing in sinusoidal microfluidic channels.

Dean flow existing in sinusoidal channels could enhance the throughput and efficiency for elasto-inertial particle focusing. However, the fundamental mechanisms of elasto-inertial focusing in sinusoidal channels are still unclear. This work employs four microfluidic devices with symmetric and asymmetric sinusoidal channels to explore the elasto-inertial focusing mechanisms over a wide range of flow rates. The effects of rheological property, flow rate, sinusoidal channel curvature, particle size, and asymmetric geometry on particle focusing performance are investigated. It is intriguing to find that the Dean flow makes a substantial contribution to the particle elasto-inertial focusing. The results illustrate that a better particle focusing performance and a faster focusing process are obtained in the sinusoidal channel with a small curvature radius due to stronger Dean flow. In addition, the particle focusing performance is also related to particle diameter and rheological properties, the larger particles show a better focusing performance than smaller particles, and the smaller flow rate is required for particles to achieve stable focusing at the outlet in the higher concentration of polyvinylpyrrolidone solutions. Our work offers an increased knowledge of the mechanisms of elasto-inertial focusing in sinusoidal channels. Ultimately, these results provide supportive guidelines into the design and development of sinusoidal elasto-inertial microfluidic devices for high-performance focusing.

Numerical investigation on thermal-hydraulic performance of cryogenic LNG in sinusoidal channel with airfoil fins under marine dynamic load

For floating liquefied natural gas (FLNG), printed circuit heat exchanger (PCHE) is an optimal choice owing to its compactness and large temperature difference heat transfer in a short time. In this study, a novel sinusoidal channel configuration was established which is with airfoil fins, and its thermal-hydraulic performance was numerically studied. Meanwhile, the effects of marine dynamic load and inlet mass flow rate (IMFR) on the novel configuration were studied. The cold fluid was supercritical liquefied natural gas (S-LNG) at 113.15 K and 32 MPa, while the hot fluid was ethylene glycol at 293.15 K and 0.1 MPa. The pressures are given as relative pressures. The results show that the novel configuration has better comprehensive performance. The local turbulent kinetic energy of the novel configuration is improved by about 19.78%. The temperature and velocity uniformity are improved. Marine dynamic load deteriorates the comprehensive performance of the novel configuration.

Effect of slip boundary conditions on unsteady pulsatile nanofluid flow through a sinusoidal channel: an analytical study

A novel analysis of the pulsatile nano-blood flow through a sinusoidal wavy channel, emphasizing the significance of diverse influences in the modelling, is investigated in this paper. This study examines the collective effects of slip boundary conditions, magnetic field, porosity, channel waviness, nanoparticle concentration, and heat source on nano-blood flow in a two-dimensional wavy channel. In contrast to prior research that assumed a constant pulsatile pressure gradient during channel waviness, this innovative study introduces a variable pressure gradient that significantly influences several associated parameters. The mathematical model characterising nano-blood flow in a horizontally wavy channel is solved using the perturbation technique. Analytical solutions for fundamental variables such as stream function, velocity, wall shear stress, pressure gradient, and temperature are visually depicted across different physical parameter values. The findings obtained for various parameter values in the given problem demonstrate a significant influence of the amplitude ratio parameter of channel waviness, Hartmann number of the magnetic field, permeability parameter of the porous medium, Knudsen number due to the slip boundary, volume fraction of nanoparticles, radiation parameter, Prandtl number, and heat source parameters on the flow dynamics. The simulations provide valuable insights into the decrease in velocity with increasing magnetic field and its increase with increasing permeability and slip parameters. Additionally, the temperature increases with increasing nanoparticle volume fraction and radiation parameter, while it decreases with increasing Prandtl number.

Numerical analysis of the effect of wave amplitude on thermohydraulic performance in a heat exchanger with sinusoidal wavy channels

With the increasing application of heat exchangers, the research has become increasingly comprehensive. Previous studies mainly focused on comparing the amplitudes to investigate the performance of heat exchangers, while the study of variable amplitude channel structures was limited. This study investigated the thermal-hydraulic performance of seven different sinusoidal channels with inclination angles of 20° and 30°, and their combinations. Using the CFD solver, simulations were conducted to assess the heat transfer capabilities of sinusoidal channels under various Reynolds numbers and different amplitude conditions, compared to straight channels and single amplitude sinusoidal channels. The results indicated that within one period, both the pressure drop and temperature difference exhibited a ripple trend of gradually decreasing amplitude. When evaluating the comprehensive performance of the channels, three trends emerged across the seven models, with the performance of the cold fluid and the hot fluid within the same group showing opposite trends. This suggested that more variations could enhance the overall performance of the hot fluid while reducing the performance of the cold fluid. For structures with the same amplitude, in terms of amplitude variation frequency, models with six periods per group exhibited higher overall heat transfer performance than those with three periods per group, with an average increase of 36.37%. For the arrangement of amplitudes (taking the hot fluid inlet as an example), configurations with a smaller amplitude at the inlet outperformed those with a larger amplitude, indicating that in combined amplitude models, a structure with a larger group and a smaller amplitude at the inlet (taking the hot fluid as an example) should be designed.

Effects of silanol defects and Ti site location within Ti-MWW on alkene epoxidation with aqueous hydrogen peroxide

Catalytic reaction kinetics and thermodynamics within zeolites respond to the physical properties of the framework through noncovalent interactions with solvents. Here, we demonstrate that rates of alkene epoxidations depend sensitively upon the topological location of Ti atoms and the density of silanol ((SiOH)x) defects in hydrothermally synthesized Ti-MWW catalysts. Turnover rates for 1-hexene epoxidation do not change systematically with (SiOH)x density unlike previous reports for other zeolite framework. Site-averaged turnover rates on Ti-MWW catalysts with the greatest portion of Ti sites located in sinusoidal channels exceed those on materials with most Ti in supercages by a factor of 40-fold. These differences appear to reflect free energy contributions and compensation between activation enthalpies and entropies, induced by the structural organization of solvent molecules that responds differently to the topological locations of active sites and the presence of defects.

Modulation of Al Distribution in High-Silica ZSM-5 Zeolites for Enhancing Catalytic Performance.

The spatial distribution of framework Al (AlF) has been one of the important factors that affect the catalytic properties of zeolites in diverse chemical reactions; however, the synthesis of high-silica zeolites with special AlF distribution remains a challenge. In this study, we successfully synthesized high-silica ZSM-5 zeolites with a unique AlF distribution by employing pentaerythritol (PET) as an additive in the presence of a few tetrapropylammonium hydroxide (TPAOH). The results demonstrated that the introduction of PET led to a higher proportion of Al atoms located at the sinusoidal and/or straight channels. It was observed that the addition of PET prevented the interaction between TPA+ and tetrahedral [AlO4]- during the crystallization process, resulting in enhanced availability of TPA species in the form of ion-paired TPA+. This effect leads to AlF atoms dominantly distributed away from the intersection and located in narrow channels, where acidic sites more effectively inhibit hydrogen transfer and coke formation. In the reaction of dimethyl ether (DME) to olefins, the catalyst with a unique Al distribution exhibited a significant prolonged catalytic lifetime, surpassing traditional TPA-ZSM-5 by more than 2-fold and maintaining DME conversion above 90% for a maximum of 148 h. The results of multiple pulse experiments also showed that these PET-assisted ZSM-5 zeolites significantly enhanced the selectivity of propene and butene. This approach provides an effective strategy to regulate AlF distribution in high-silica ZSM-5 catalysts with the assistance of neutral alcohol. It holds great potential for application in the synthesis of other high-silica zeolites, thereby enriching the diversity of zeolite catalysis.

Corrugation characteristics effect of channel on heat transfer and pressure Drop: Experimental study

Four sinusoidal wavy channels were examined experimentally under turbulent flow conditions of air to clarify the potentials of such configuration in terms of heat transfer and hydrodynamic performance. The subjected heat flux on these wavy walls (sinusoidal wavy plates) were (500, 750, and 1000) W /m2. The ratio of corrugation wavelength (λ) to corrugation amplitude (a) had a range of (5.7–12.6), and the four wavy channels are scrutinized at zero angles (0°) of phase shift. According to the applied range of Reynolds number which is (1.932 × 103–3.286 × 103) and duct entrance dimension, the supplied inlet velocities were (0.3––0.67) m/s. The collected outcomes of the tested wavy sections showed a gained in heat transfer coefficient of (11–39 %) compared to the conventional duct, this increase is originally came out due to the occurred gained of the enhancement factors which is (1.1–1.4). regarding the pressure drop, the acquired decay of the wavy channels is (17–45 %) compared to the conventional channels. Also the results showed the corrugation angle 54.5° is the best in terms of thermal performance factor TPF at Re ≈ 3300 with appreciable high pressure drop, while the corrugation angle of 32.5° has a poor TPF at Re ≈ 1950.

Direct numerical simulation of channel flow with real surface roughness using a ghost cell immersed boundary method

This paper investigates the impact of real surface roughness on channel flow using direct numerical simulation assisted by a ghost cell immersed boundary method (DNS-GCIBM). The principles and implementations of DNS-GCIBM are first introduced. Two test cases, including the two-dimensional flow around a cylinder and the three-dimensional flow in a sinusoidal roughness channel are employed to demonstrate the practicability and accuracy of the proposed approach, especially in numerical studies on the rough wall-bounded flow. Using DNS-GCIBM, channel flows under conditions of Ma = 0.3 and Reτ≈300, with both the real-world and regular roughness surfaces are studied. The results are statistically analyzed using the triple decomposition technique. The outer layer similarity in the streamwise mean velocity and Reynolds stress profiles indicate that the impact of roughness on the boundary layer primarily localizes within roughness sub-layer. In the streamwise mean velocity profile, both regular and real-world roughness surfaces induce obvious increase to the roughness function ΔU+ as roughness height Ra increases, while discrepancy of ΔU+ between the two types of roughness can be found. Furthermore, turbulence statistics are sensitive to the variations of Ra. As Ra increases, it becomes challenging to organize coherent structures near the wall, resulting in the reduction of streamwise Reynolds stress intensity. In addition, although the skin friction coefficient and ΔU+ are almost the same, the real-world roughness and the corresponding equivalent regular roughness manifest different flow structures near the wall. The real-world roughness contributes greater spatial inhomogeneity but lower turbulence intensity.

Tailoring the product distribution of CO2 hydrogenation via engineering of Al location in zeolite

Even though tremendous progress has been made on modified Fischer-Tropsch synthesis (FTS) multifunctional catalyst that composed of Fe-based component and acidic zeolite H-ZSM-5 for CO2 hydrogenation into value-added chemicals, the structure-function relationship between the acidic zeolite H-ZSM-5 and product distribution is still under debate. Herein, a series of H-ZSM-5 zeolites with different Al locations and acidic properties are fabricated by varying the synthesis raw agents and conditions. After combining with the carbon-encapsulated Fe-based catalyst for alkenes synthesis from CO2 hydrogenation, aromatics are directionally produced from the ellipsoidal H-ZSM-5 with Al species mainly located at the intersection of straight and sinusoidal channels, while the main products shift to iso-paraffins for the H-ZSM-5 with pillared nanosheet morphology owing to its Brønsted acid site-rich property. The Al location in H-ZSM-5 and the corresponding acidic property are systematically investigated, and the theoretical simulations illustrate that the Al species at the intersection channels could lower the energy barrier of key aromatization step. The Al richly located at straight/sinusoidal would boost the isomerization reaction. Our work not only clarifies the structure-function relationship of acidic zeolite H-ZSM-5 in valuable chemicals synthesis from CO2 hydrogenation but also provides a novel protocol for controlled synthesis.

Regulating framework aluminum location towards boosted light olefins generation in ex-situ catalytic pyrolysis of low-density polyethylene

Amidst the global focus on recycling and treatment of waste plastics for resource sustainability, it remains an enormous challenge to convert waste plastics into light olefin. Herein, the impact of framework Al (AlF) location in ZSM-5 catalyst, controlled by regulating Al sources, on the ex-situ catalytic pyrolysis of low-density polyethylene (LDPE) has been investigated. Based on multi-techniques, such as 27Al MAS NMR, ICP-AES, Co-UV–vis-DRS, XRD, SEM, N2 adsorption-desorption, NH3-TPD, Py-IR and FTIR. It is found that the AlF located at the channel intersections show more Al pairs, and this location offers ample space for secondary reactions, which include Diels-Alder reaction, cyclization reaction and dehydrogenation reaction, resulting in the low yield of light olefins (10.6 wt%) and the generation of light alkanes and aromatics from light olefins. In contrast, AlF located in the straight and sinusoidal channels exists mainly in the form of single Al. The substantial steric hindrance for this location facilitates the cracking reaction, mainly referring to the cracking reactions of LDPE that produce light olefins and generate enhanced yield of light olefins (52.8 wt%). These results provide new perspectives towarding boosted light olefins generation in ex-situ catalytic pyrolysis of LDPE.

Numerical study on the effect of a parallel to the flow barrier on the flow and heat transfer characteristics of a symmetric sinusoidal channels

Numerical study on the effect of a parallel to the flow barrier on the flow and heat transfer characteristics of a symmetric sinusoidal channels

Numerical study and machine learning on local flow and heat transfer characteristics of supercritical carbon dioxide mixtures in a sinusoidal wavy channel PCHE

The ambient temperature has a great influence on the practical application of the supercritical carbon dioxide(S-CO2) Brayton cycle. The introduction of mixtures is an effective way to change the critical characteristics of the working fluid, which allows the system to better match the ambient temperature. The mixtures not only affect the overall performance of the power system, but also affect the flow and heat transfer processes in various heat exchange equipment. In this investigation, the physical model of a sinusoidal wavy channel printed circuit heat exchangers (PCHE) is built, and numerical simulations are conducted firstly on the flow and heat transfer characteristics of three S-CO2 mixtures (CO2-He, CO2-Ke and CO2-Xe). Effects of the mole fraction and type of the additive gasses on the thermal-hydraulic performance are discussed, as well as the variations of the local heat transfer coefficients and pressure drop along the flow direction. It's found that transfer coefficient and pressure drop of CO2-He increase with the increase of the additive gas mole fraction n, with maximum heat increases of 396 % and 1147 % against pure S-CO2, respectively. With the increase of n, heat transfer coefficient and pressure drop of CO2-Kr and CO2-Xe decrease. Maximum decreases of 71 % and 38 % can be seen for the heat transfer coefficient and pressure drop against pure CO2 for CO2-Kr, and 80 % and 64 % against pure CO2 for CO2-Xe, respectively. CO2-Xe yields the best thermal-hydraulic performance of the PCHE among the three mixtures. Secondly, machine learning is adopted to predict the local flow and heat transfer characteristics of S-CO2 mixtures in response to the significant variation of S-CO2 mixtures along the flow direction within the PCHE. Four machine learning models including Support vector machine (SVR), Artificial neural network (ANN), Random forest (RF) and Extreme Boosting Tree (XGBoost) are used and the corresponding prediction performance are analysed. It is found that machine learning is efficient and accurate in the prediction. Among the four machine learning models, XGBoost has a strong fitting ability to the local Nu and f, with an R2 of 0.9992 and 0.9718 on the test set, respectively. The prediction results of the XGBoost model can reflect the variations of local Nusselt number and friction factor along the flow direction well. However, ANN has stronger generalization ability in the prediction under new working conditions. The use of machine learning can greatly help the design and optimization of PCHEs with S-CO2 mixtures as working fluids.