CO2 In Region Research Articles

CO2 capture and storage by metal and non-metal decorated silicon carbide nanotubes: a DFT study

This study addressed the nano-mechanism of CO2 capture by Al-doped, B-doped and N-doped single-walled silicon carbide nanotubes (SWSiCNTs) using the prominent density functional theory. The results showed absolute interactions between CO2 and B- and N- impurity atoms of the SWSiCNT surface with the highest adsorption energy of −1.85 eV and −1.83 eV respectively. Analysis of the binding energy of CO2 to Al-doped SWSiCNT revealed that chemisorption between them is stronger than B-doped and N-doped SWSiCNTs. Results from optical adsorption spectra revealed that both B-and N-doped systems adsorb CO2 in the visible region of the electromagnetic spectrum while B-doped SiCNT shows the highest adsorption. This study recommends B- and N-doped SiCNTs as candidates for CO2 capture and storage with higher efficiency by B-doped SiCNT, while the performance of the Al-doped system was underscored.

Experiment and numerical investigation on flow characteristics and near-field structure of dense phase CO2 pipeline leakage

Accidental leakage of high-pressure CO2 is not only a safety hazard, but also may have a great negative impact on the operating efficiency of some circulating systems. To analyze the accident hazards and improve the ability to predict the transient release flow behavior of high-pressure CO2, a set of small pipeline leakage test equipment was built. The changes of near-field pressure, temperature, and jet structure under different upstream pressure (6–12 MPa), temperature (280–300 K) and orifice diameter (5 mm, 10 mm, 20 mm, 40 mm) were analyzed. Secondly, as a supplement to the experiment, the near-field CO2 gas phase distribution and critical mass flow were studied by numerical model. The results show that the near field pressure peak is negatively correlated with the initial upstream pressure, but positively correlated with the release diameter. In addition, the increase of upstream initial pressure and release diameter will lead to the increase of radial development range of near-field jet cloud. Based on the numerical results, an empirical correlation of critical mass flow based on upstream initial conditions and RHP is established. The error between the experimental data and the predicted value within the range of the correlation is within ± 18%. The research data and results can help to enhance the understanding of the rapid release characteristics of high-pressure CO2 in the near field region and provide a basis for the study of CO2 diffusion in the far field region and the leakage risk assessment.

Impact of interphase component transfer on CO2 distribution and pH during CO2 injection in the subsurface

Single phase CO2 injection and CO2 water alternating gas (WAG) injection processes are simulated using reactive transport modelling to understand the inter-phase component transfer between CO2, brine and oil, and to address geochemical (aqueous) reactions induced by CO2 in the near wellbore region. In this research, calculations are performed using a numerical one-dimensional cartesian model with homogenous properties. We investigate how fast the pH changes as CO2 is injected into the system and how the presence of oil affects the velocity of the pH front. We measure the velocity of the front at which oil becomes completely desaturated with respect to CO2 – referred to as the “CO2 desaturation front” and compare it with the classical Buckley-Leverett saturation front displacement during WAG injection. We also study the impact of the WAG cycles on the CO2 desaturation front velocity and the pH change. The study showed that the presence of hydrocarbons in the model buffers and delays the pH drop. By the end of each water cycle all the CO2 was removed from the contacted oil phase within the first few meters from the well. The CO2 desaturation front travels at approximately one twentieth of the phase saturation front velocity during the first three WAG cycles, but it then stopped for later cycles, which gives an indication of the extent of the desaturation of oil. During the WAG injection, different pH fronts developed due to the impact of each cycle on the fluid composition and component transfer. The pH reduction during the last WAG cycles was greater near the injection well as most of the lighter hydrocarbon components were displaced out of the residual “oil”, meaning the CO2 content of this residual phase was higher than for initial cycles. This would result in a greater risk of calcite dissolution around the injection well if there were calcite present in the rock formation.

Assessment of soil CO2 and NO fluxes in a semi-arid region using machine learning approaches

Agricultural lands are sources and sinks of greenhouse gases (GHGs). The identification of the main drivers affecting GHGs is crucial for planning sustainable agronomic practices and mitigating global warming potential. The main aim of this research was to evaluate the impact of environmental drivers (soil temperature and water-filled pore space, WFPS) and crop residue rates on CO2, NO, and NOx fluxes under conventional tillage (CT) and no-tillage (NT) systems. The accuracy of Random Forest Regression (RFR), Multiple Adaptive Regression Splines (MARS), and General Linear Models (GLM) in predicting CO2, NO, and NOx fluxes were also assessed.In both CT and NT systems, CO2, NO, and NOx fluxes decreased with increasing WFPS. Increasing temperature resulted in higher CO2 emissions and lower NO and NOx emissions. Higher residue rates resulted in significant increases in CO2 emission, whereas the NO and NOx emissions increased by decreasing the ratio of residue. For CO2 prediction, the RFR provided the largest R2 with the observed data. For NO–N and NOx-N prediction, RFR was the most efficient algorithm, but NO–N can be predicted with better accuracy. The output of this research highlights the importance of agronomic practices for climate mitigation, along with the possibility of using RFR to predict GHGs fluxes.

Numerical and Chemical Kinetic Analyses on the Formation of CO and CO2 for C1–C4 Hydrocarbon Alkanes in a Hot Co-Flow under MILD Combustion

In this present study, computational fluid dynamics and chemical kinetic analysis are conducted to explore the formation of CO and CO2 for a fuel jet comprising C1–C4 hydrocarbon alkanes in a hot co-flow burner under a moderate or intense low-oxygen dilution (MILD) combustion environment. The fuel jet comprises three cases of fuel mixture (case 1: CH4 + H2, case 2: C3H8 + H2, and case 3: C4H10 + H2) having constant mixture density and operating under a fixed jet Reynolds number. The combustion and emission characteristics are analyzed in terms of radial profiles of temperature and mass fraction of OH, CH2O, HCO, CO, CO2, and C2H2 in the MILD combustion region. The formations of CO and CO2 are examined with the help of reacting flow analysis using the computational fluid dynamics (CFD) tool. The formation of CO is reported as maximum for case 3 and minimum for case 1. However, the reverse trend is observed in the case of CO2 formation. The reacting flow analysis from the CFD work suggests that the reaction C2H2 + O = CH2 + CO strongly influences CO formation in all three fuel mixtures cases. In the current study, acetylene is found to be the primary species that affects the CO formation in the adopted fuel mixtures and is mainly responsible for the increased CO concentration in case 3. Likewise, the formation of CO2 is majorly influenced by the reaction CO + OH = CO2 + H. The reacting flow analysis is assisted with the help of a zero-dimensional perfectly stirred reactor (PSR) model to elucidate the underlying chemistry and explore the significant reaction pathways influencing the formation of CO and CO2. The ethylene route in the reaction pathway substantially plays a vital role in the CO formation in all three fuel mixtures.

Carbon Dioxide Emissions and Economic Growth Nexus in Nigeria: The Role of Financial Development

This study examines the effect of carbon dioxide emissions on economic growth, including investigating whether the CO2-economic growth relationship is dependent on financial development in Nigeria between 1980 and 2020. Due to dwindling economic growth, Nigeria experienced two recessions in one decade. Besides poor growth rates, Nigeria remains a leading emitter of CO2 in the Sub-Saharan region. The motivation for this study derived from the rising level of carbon dioxide emissions in Nigeria which might affect economic growth by dwindling agricultural activities (low output) in some regions, pose health challenges and create a shortage of inputs to agro-allied industries. Hence, this paper attempted to see if there was a causal relationship between carbon dioxide emissions, financial development, and economic growth in Nigeria. The relationship between the variables was examined using the Autoregressive Distributed Lag estimation technique (ARDL) estimation method. The framework for this study has its basis in the endogenous growth theory and utilizes the growth and pollution stock model which showed that sustainable economic growth is influenced by a large stock of pollution (CO2 emission). The results of the boundaries test for cointegration showed a long-term relationship between CO2 emissions, economic expansion, financial development, and energy use. According to empirical data, CO2 emissions have little long-term impact on economic growth. However, there is evidence that the interaction of CO2 emissions and financial development promotes economic growth over the long term, suggesting that CO2 emissions only have an economic influence when there is financial development.

Nonthermal plasma: An emerging innovative technology for the efficient removal of cooking fumes

Cooking fumes (CFs) pose a considerable threat to the atmospheric environment and health, thus requiring appropriate mitigation measures. In this study, a nonthermal plasma (NTP) method based on a glass-bead-packed-bed dielectric barrier discharge (DBD) reactor was used to remove CFs. The results revealed that the introduction of glass beads into the DBD reactor considerably enhanced the electrical field, resulting in the marked improvement of the removal of CFs. At a discharge power of 7.4 W, the removal efficiencies of CFs, nonmethane hydrocarbons, and particulate matter with an aerodynamic diameter of ≤ 10 µm (PM10) reached 89.5%, 98%, and 79%, respectively. Moreover, a high COx yield of 25.3% and an energy yield of COx of 41.19 g·kWh−1 were achieved due to the oxidation of carbon-containing compounds. The use of air as the carrier gas resulted in the more efficient removal of CFs compared with the use of nitrogen because of the oxidation effect of active oxygen-containing species derived from the dissociation of oxygen molecules. The performance of the glass-bead-packed-bed DBD reactor was positively correlated with discharge power. Furthermore, on the basis of the identification of byproducts, a reaction pathway underlying the NTP removal of CFs was proposed. The main carbon-containing compounds identified in CFs were esters, hydrocarbons, aldehydes, ketones, and S/Cl-containing compounds, which underwent destruction through a series of dissociation and oxidation reactions, forming CO2 and H2O in the plasma region. This study provides evidence for the use of NTP as an innovative technology for the highly efficient removal of CFs.

Driving Factors on Greenhouse Gas Emissions in Permafrost Region of Daxing'an Mountains, Northeast China

AbstractPermafrost regions are an important source of greenhouse gases. However, the effects of different permafrost wetland types on greenhouse gas emissions and the driving factors are still unclear in the permafrost region. Here, we selected three typical permafrost wetlands from the Daxing'an Mountains to investigate the effects of permafrost wetland types on greenhouse gas emissions. The cumulative N2O, CO2, and CH4 emissions were 84–122, 657,942–1,446,121, and 173–16,924 kg km−2, respectively. The linear mixed effects model indicated that N2O emissions were significantly affected by the NO3−‐N content, whereas CO2 emissions were mainly driven by soil temperature, water table level, and NO3−‐N content. CH4 emissions were affected by soil temperature and water table level. Permafrost wetland types significantly affected the average and cumulative N2O, CO2, and CH4 emissions. The cumulative N2O emissions were highest in the Larix gmelinii ‐ Carex appendiculata (LC) wetland and lowest in the Betula fruticosa Pall. (B) wetland, driven by NO3−‐N content. The cumulative CO2 emissions were highest in the B wetland and lowest in the L. gmelinii ‐ Ledum palustre var. dilatatum (LL) wetland. The cumulative CH4 emissions from B wetland were significantly higher than those from LL and LC wetlands. The differences in cumulative CO2 and CH4 emissions were driven by the water table level. Our findings indicate that NO3−‐N content affect the spatial‐temporal variation of N2O emissions, whereas water table level influence the spatial‐temporal variation of CO2 and CH4 emissions in the permafrost region of the Daxing'an Mountains.

Variations in Seawater pCO2 Associated With Vertical Mixing During Tropical Cyclone Season in the Northwestern Subtropical Pacific Ocean

This study examines interannual variations in the seawater CO2 partial pressure (pCO2) for months (August–October) with frequent tropical cyclone (TC) events in the northwestern subtropical Pacific Ocean (22°N–28°N, 135°E–145°E) between 2007 and 2017. The temperature-normalized pCO2 averaged over August–October showed a year-to-year variation ranging from 346 to 359 μatm over the 11 study years, which appeared to be related to the variation in vertical mixing that likely results from the TC activity in these months. Sea surface temperature and wind data consistently supported the association between mixing and TC intensity. Nonetheless, the pCO2 reduction caused by negative sea-surface temperature anomalies found over the TC season (July–October) shifted the study area from a CO2 source to a CO2 sink over these months. In the south (17°N–22°N) of the study area, mixing-driven variations in pCO2 were smaller during the same months, which appeared to be caused by the relatively deeper mixed layer depth and the more homogenous profile of CO2 in this tropical region. These results suggest that more extensive pCO2 measurements are required to fully resolve the effect of TCs on the carbonate system from the regional- to the basin-scale in the western Pacific Ocean, where TC intensity is expected to increase in the future.

Analysis of the temporal variability of CO2, CH4 and CO concentrations at Lamto, West Africa

The 10-year observations of the atmospheric molar fractions of CO2, CH4 and CO in West Africa were analyzed using a high precision measurement of the Lamto (LTO) station (6°31 N and 5°02 W) in Côte d’Ivoire. At daily scale, high concentrations appear at night with significant peaks around 7 a.m. local time and minimum concentrations in the afternoon for CO2 and CH4. The CO concentrations show two peaks around 8 h and 20 h corresponding to the maximum in road traffic of a northern motorway located 14 km from the station. The long-term increase rates of CH4 (∼7 ppb year−1) and CO2 (∼2.24 ppm year−1) at Lamto are very close to global trends. The variations of the concentrations of the three gases show strong seasonality with a peak in January for all gases and minima in September for CO2 and CH4, and in June for CO. The CO variation suggests a significant impact of fires on the CO, CO2 and CH4 anomalies in the Lamto region during the dry season (December to February). CO and CH4 show strong correlations (at synoptic-scale and monthly based) in January (r = 0.84), February (r = 0.90), April (r = 0.74), November (r = 0.79) and December (r = 0.72) reflecting similar sources of emission for both gases. The trajectories of polluted air masses at LTO, also indicate continental sources of emission associated with Harmattan winds.

Highly Sensitive Gas Sensing Material for Environmentally Toxic Gases Based on Janus NbSeTe Monolayer.

Recently, a new family of the Janus NbSeTe monolayer has exciting development prospects for two-dimensional (2D) asymmetric layered materials that demonstrate outstanding properties for high-performance nanoelectronics and optoelectronics applications. Motivated by the fascinating properties of the Janus monolayer, we have studied the gas sensing properties of the Janus NbSeTe monolayer for CO, CO, NO, NO, HS, and SO gas molecules using first-principles calculations that will have eminent application in the field of personal security, protection of the environment, and various other industries. We have calculated the adsorption energies and sensing height from the Janus NbSeTe monolayer surface to the gas molecules to detect the binding strength for these considered toxic gases. In addition, considerable charge transfer between Janus monolayer and gas molecules were calculated to confirm the detection of toxic gases. Due to the presence of asymmetric structures of the Janus NbSeTe monolayer, the projected density of states, charge transfer, binding strength, and transport properties displayed distinct behavior when these toxic gases absorbed at Se- and Te-sites of the Janus monolayer. Based on the ultra-low recovery time in the order of for NO and NO and for CO, CO, HS, and SO gas molecules in the visible region at room temperature suggest that the Janus monolayer as a better candidate for reusable sensors for gas sensing materials. From the transport properties, it can be observed that there is a significant variation of characteristics and sensitivity of the Janus NbSeTe monolayer before and after adsorbing gas molecules demonstrates the feasibility of NbSeTe material that makes it an ideal material for a high-sensitivity gas sensor.

Research on Laser Absorption Spectrum Detection Technology for CO2 and NH3 Regional Emission

High-sensitivity emission monitoring of CO2 and NH3 in farmland region is very important for analyzing environment and climate change. The on-line detection technology was studied based on open-path tunable diode laser absorption spectroscopy technology (OP-TDLAS). The detection spectrum of open path was extracted to realize accurate concentration inversion by designing the multi-line fitting algorithm. The system detection stability was evaluated by Allan variance that the detection limit of NH3 and CO2 were about 0.048 L/L and 4.31 L/L respectively. The detection experiment was carried out in farmland of north Anhui to prove that both of the fertilization and straw returning to the field were the emission source of CO2 and NH3 from soil. The growth effect of the former was slower but higher than that of fertilization. This stable spectrum detection method can obtain large-scale concentration results and clear emission rules, which provide technical support for the environment-friendly agriculture

The Thermodynamic Properties of CO2 up to 200 MPa Including the Critical Region, Calculated by a New Combined Equation of State with Few Parameters

Heat capacities Cv, Cp, and sound velocity W of carbon dioxide are calculated on the basis of a new thermal combined equation of state (EoS) with a low number of regulated constants. This equation includes a new regular EoS with 11 coefficients, a scaling EoS with six coefficients, and a regular transition function containing two adjustable parameters. Calculating results for thermodynamic properties of CO2 in the regular behavior range of up to 200 MPa correspond to the accuracy level of modern practical equations of state with large numbers of determined constants. This makes it possible to calculate the properties of CO2 in the critical region, taking into account the achievements of scaling theory. To determine the constants of the calculated equations, only p,ρ,T-data for CO2 were used. The experimental and tabular data on Cv, Cp, S, H, and W were not involved except isochoric heat capacity Cv in the ideal gas state. These data were used to compare the calculated results with the experimental and tabulated values. The universal critical exponents were taken in accordance with the three-dimensional Ising model. The average errors in describing the thermal properties of CO2 do not exceed errors: rms error is 0.93 % in pressure and max deviation in Cv is 10 %. Divergences in the critical region relate to application of the scaling equation of state, in contrast to the regular equations. The comparison was made with calculated Cv, Cp using the current crossover EoSs for CO2.

La tecnología en la aeronáutica en pro de las energias renovables y de la Bio-Sustentabilidad

Basic sciences, technology and human sciences in aeronautics are integrated in favor of renewable energies for sustainable development.Thus, the objective of this project is to create a rainwater and condensed water storage system with automated irrigation, powered by solar energy that provides crop moisture and contributes to the reduction of CO2 in the semi-desert region of Querétaro. The methodology used is action research, which consists of observing and detecting a real problem to immediately analyze and assess the possibilities of intervention. In this case it was the waste of natural resources in the university (water and solar energy). An action strategy was designed afterwards which consisted in: 1. Integration of a team of specialist teachers and students. 2. General planning of the project. 3. Theoretical and field research. 4. Systems design: hydraulic, structures, automated irrigation with solar energy. 5.Application of device tests and the study of the process of crop growing and composting. Our contribution in this project is above all social and ecological and not to science; university social responsibility is encouraged emphasizing the importance that the application of technology offer alternatives for the care and use of natural resources and greater use of renewable energy. As an added value, the project contributes to applied research with an interdisciplinary approach of professors and students of different aeronautical careers in favor of sustainable development. It is clarified that during this initial stage there is still no scientific contribution made as we plan ,in a subsequent stage, to test and show levels of radiation and humidity in the region.

Diffuser performance of centrifugal compressor in supercritical CO2 power systems

The paper focuses on understanding the performance of a vaned diffuser in a supercritical CO2 compressor using real gas assumptions. The rapidly changing properties of CO2 in the non-ideal thermodynamic region can have a significant impact on the performance of the diffuser. To account for this, the relationship between the flow properties (i.e. fundamental derivative) and the local geometry (i.e. cross-sectional area of the nozzle) has been discussed theoretically. To examine it analytically, the study has considered the influence of real gas properties on the performance of a vaned diffuser using computational fluid dynamics (CFD) modelling. The selected compressor stage geometry is similar to the compressor impeller tested in the Sandia sCO2 compression loop facility. The effect of changes in the number of blades and the corresponding changes in the cross throat area on the flow properties such as density and speed of sound were investigated and discussed. The results illustrate that a diffuser with a higher number of blades (smaller throat area) compared to a diffuser with a wider throat area has a higher probability of creating flow instability in the passage stage.

Impact of sub-grid scale models on resolving mixing and thermal shear layers in large eddy simulation of JHC flames

Predictive performance of sub-grid scale (SGS) models is investigated in Large Eddy Simulation (LES) of a methane/hydrogen jet-in-hot coflow (JHC) flame using a conceptual analysis proposed for the mean values of major combustion products. It is shown that mean values of major combustion products consist of valuable information on several characteristics of JHC flames such as flame thickness, flame volume and reaction intensity. In particular, sudden change of CO2 and H2O mass fractions from coflow contents to higher values, predicted by static SGS models, demonstrated a thin flame constricted around the center line. However, uniform ascending manner of CO2 and H2O contents in the coflow region predicted by dynamic SGS models revealed their ability on capturing characteristics of a distributed volumetric flame. For the temperature fluctuations in shear layers, the dynamic Smagorinsky model is also shown to provide better predictions than the constant-coefficient Smagorinsky model, the latter exhibiting significant over-predictions. It is also observed that the dynamic kinetic energy SGS model with its unique assumption of non-equilibrium turbulence is the best fitted SGS model for the JHC flames as it provides improved accuracy on developing mixing and thermal shear layers by solving an extra transport equation for turbulent kinetic energy.

Gas-Dynamic Model of the Expansion of a Pulse Jet of Supercritical Carbon Dioxide: The Strategy of the Experiment

An experimental strategy for determining the coil–globule transition parameters of a polymer chain in supercritical carbon dioxide has been developed on the basis of a gas-dynamic model of the expansion of a pulse jet of a van der Waals gas [1]. Taking into account the behavior of CO2 in the near-critical region and isentropic conditions of the jet expansion process, starting conditions that arise in the nozzle and correspond to the proposed model are determined. The design of the experiment (geometrical and size parameters of the key components of the equipment, pulse valve duration, etc.) is developed. Possible options for carrying out the experiment and processing the experimental data are discussed. Calculation procedures for the case corresponding to the experimental conditions described in [2, 3] are given as an example.

Tree growth rate regulate the influence of elevated CO2 on soil biochemical responses under tropical condition

Tree growth rate can complicate our understandings of plant belowground responses to elevated CO2 (eCO2) in tropical ecosystems. We studied the effects of eCO2 on plant growth parameters, and rhizospheric soil properties including soil organic carbon (SOC), glomalin related soil protein (GRSP), microbial biomass C (Cmic), CO2 efflux (Cefflux), and microbial extracellular enzyme activities under two tropical tree saplings of fast-growing Tectona grandis (Teak) and slow-growing Butea monosperma (Butea). We exposed these saplings to eCO2 (∼550 ppm) and ambient CO2 (aCO2; ∼395 ppm) in the Indo-Gangetic plain region, and further (after 10 and 46 months) measured the changes in their rhizospheric soil properties. With respect to aCO2 treatment, eCO2 significantly increased plant height, stem and shoot weight, and total plant biomass of Teak. However, these plant traits did not considerably differed between eCO2 and aCO2 treatments of Butea. The eCO2 induced greater extent of increase in rhizospheric soil properties including SOC fractions (particulate OC, non-particulate OC and total OC), GRSP fractions (easily extractable- GRSP, difficulty extractable- GRSP and total- GRSP), Cmic, Cefflux and extracellular enzyme activities (phosphatase, dehydrogenase, β-glucosidase and fluorescein diacetate) were observed under Teak compared with Butea. Compared with aCO2 treatment, eCO2 slightly reduced soil available N and P under the Teak, but no changes were apparent between eCO2 and aCO2 treatments of the Butea. The greater extent of responses from soil variables observed after longer period (46 months) of CO2 exposure. The multivariate analysis confirmed that eCO2 treatment with Teak is more responsive compared with other treatments of Teak and Butea. This contrasting rhizospheric soil feedback to eCO2 between two tropical trees, suggesting fast-growing species will be more responsive to future climate. Such species will have a competitive advantage over coexisting less responsive species (e.g. Butea) under future eCO2 climate.

Nitrogen-Doped Graphene Quantum Dots Enhance the Activity of Bi2 O3 Nanosheets for Electrochemical Reduction of CO2 in a Wide Negative Potential Region.

Large numbers of catalysts have been developed for the electrochemical reduction of CO2 to value-added liquid fuels. However, it remains a challenge to maintain a high current efficiency in a wide negative potential range for achieving a high production rate of the target products. Herein, we report a 2D/0D composite catalyst composed of bismuth oxide nanosheets and nitrogen-doped graphene quantum dots (Bi2 O3 -NGQDs) for highly efficient electrochemical reduction of CO2 to formate. Bi2 O3 -NGQDs demonstrates a nearly 100 % formate Faraday efficiency (FE) at a moderate overpotential of 0.7 V with a good stability. Strikingly, Bi2 O3 -NGQDs exhibit a high activity (average formate FE of 95.6 %) from -0.9 V to -1.2 V vs. RHE. Additionally, DFT calculations reveal that the origin of enhanced activity in this wide negative potential range can be attributed to the increased adsorption energy of CO2 (ads) and OCHO* intermediate after combination with NGQDs.

Simulation Research of Heat Transfer Characteristics of Carbon Dioxide in Microchannel Evaporator

Abstract In this paper, the simulation model of two-dimensional (2D) distribution parameter of a CO2 microchannel evaporator was developed using the finite element method. The simulation model of the CO2 microchannel evaporator was written using matlab both considering the dry and wet conditions on air side, and different heat transfer characteristics of CO2 in two-phase region and overheated region. The experimental and simulation results in terms of CO2 temperature, wall temperature, inlet and outlet air temperatures, and convective heat transfer coefficient were compared. The simulation results have the same tendency with the experimental correlation results. The convective heat transfer efficient increases with the growth of CO2 inlet dryness, mass flow rate and air speed, while decreases along with the increase of evaporation pressure in two-phase region. The dry-out point appears earlier with larger CO2 inlet dryness, and higher air temperature, humidity and speed; however, it appears later with the increasing evaporation pressure and mass flow rate. The convective heat transfer coefficient at the dry-out point decreases dramatically due to the deteriorated heat transfer at this position, which indicates the necessity to prevent or retard the appearance of dry-out point.