H2O Mixtures Research Articles

Simulation Study on Diffusion and Local Structure of CH4, CO2, SO2, and H2O Mixtures into Double-Layers Graphene.

Graphene has been widely studied as an ideal material for the adsorption and separation. In this work, we used molecular dynamics simulations to investigate the evolution of diffusion and local structure of CH4, CO2, SO2, and H2O mixtures into double-layers graphene under seven different interlayer spacings and four different CO2 concentrations. The results showed that the adsorption of CH4 and CO2 molecules on the graphene surface weakened with increased interlayer spacing. The diffusion capacities of CH4 and CO2 in the mixed system were significantly improved by increasing the interlayer spacing. In interlayer spacings ranging from 5 to 10 nm, the diffusion capacities of each component varied significantly in the order CH4 > CO2 ≫ H2O > SO2. Compared with CH4 and CO2, the local structures of SO2 and H2O were more affected by the interlayer spacing. Larger interlayer spacings or higher CO2 concentrations were advantageous for the formation of stronger hydrogen bond structures between H2O molecules. When the CO2 concentrations were between 10% and 20% and the interlayer spacing of graphene was 8 nm, the graphene structure exhibited the best adsorption and separation effects on CH4 and other components.

A simple explicit thermodynamic closure for multi-fluid simulations including complex vapor–liquid equilibria: Application to NH3[sbnd]H2O mixtures

This paper presents a new thermodynamic closure formulation appropriate for the simulation of subcritical multiphase flows, where two liquid/vapor components need to be considered, in addition of an arbitrary number of perfect gas non-condensable components. Assuming each component to follow the Noble-Abel Stiffened Gas (NASG) equation of state allows to derive a fully explicit formulation for the mixture pressure. A matching phase transition solver is then proposed to compute efficiently and accurately the thermochemical equilibrium of the said mixture. The model capabilities are then illustrated through a two-dimensional simulation of a liquid ammonia tank leak into 80%-saturated humid air, where water is found to significantly condensate when interacting with the ammonia jet.

Electrothermal Conversion of Methane to Methanol at RoomTemperature with Phosphotungstic Acid.

Traditional methods for the aerobic oxidation of methane to methanol frequently require the use of noble metal catalysts or flammable H2-O2 mixtures. While electrochemical methods enhance safety and may avoid the use of noble metals, these processes suffer from low yields due to limited current density and/or low selectivity. Here, we design an electrothermal process to conduct aerobic oxidation of methane to methanol at room temperature using phosphotungstic acid (PTA) as a redox mediator. When electrochemically reduced, PTA activates methane with O2 to produce methanol selectively. The optimum productivity reaches 29.45 [[EQUATION]] with approximately 20.3% overall electron yield. Under continuous operation, we achieved 19.90 [[EQUATION]] catalytic activity, over 74.3% methanol selectivity, and 10 hours durability. This approach leverages reduced PTA to initiate thermal catalysis in solution phase, addressing slow methane oxidation kinetics and preventing overoxidations on electrode surfaces. The current density towards methanol production increased over 40 times compared with direct electrochemical processes. The in-situ generated hydroxyl radical, from the reaction of reduced PTA and oxygen, plays an important role in the methane conversion. This study demonstrates reduced polyoxotungstate as a viable platform to integrate thermo- and electrochemical methane oxidation at ambient conditions.

Thermodynamic study of pyridoxine in different solvents and temperatures: DFT study

The equivalent conductivities (Λ) of B6 vitamin (pyridoxine) in HշՕ and MeOH were measured at different temperatures between 293 to 313 K, as well as in mixtures of H₂O and MeOH at percentages of 10, 20, 30, 40, and, 50% MeOH at 310 K. All the practical results were mathematically processed using the Lee Wheaton equation, which is applied to the derived conductivity of electrolytes with a similar composition (1:1). This equation calculates various conductivity components, including the equivalent conductance at infinite dilution (Λₒ), the ionic conductivity, the distance between ions (R), and also the constant of ionic aggregation (Ka) at best-fit values of (ϬΛ). The values of these parameters differed from one solvent to another depending on the molecular interactions in the solution and the physical properties of the solvents, such as viscosity and dielectric constant. Finally, thermodynamic quantities for the ion association reaction (ΔG°, ΔH°, and ΔS°) were also studied. Density functional theory (DFT) calculations (B3LYP/6-31G (d,p)) were employed to analyze vitamin B6 in the gas phase and diverse solvents. Three different continuum methods, namely AM1, PM3, and HF, were utilized, followed by DFT. The final method was utilized to explore the effects on its characteristics. KEY WORDS: Electrical conductivity, Lee-Wheaton equation, Theoretical chemistry, DFT. Bull. Chem. Soc. Ethiop. 2025, 39(1), 165-176. DOI: https://dx.doi.org/10.4314/bcse.v39i1.14

Restricted Intramolecular Rotation: A Dual Fluorescence Response to Hg2+ Quenching and Ag+ Enhancement in Live Rhizoctonia Solani Cells.

A novel imidazo[1,2-a]pyridine derivative probe (R) was designed, synthesized, and characterized via various characterization techniques, such as ESI-MS, 1H NMR, 13C NMR, and Dept-135 NMR. The data obtained from single-crystal XRD reveal that probe R has a coplanar configuration and is part of the monoclinic crystal system, designated the P2(1)/n space group. The fluorescence of (R) is further enhanced by silver (I) ions. On the other hand, Hg2+ significantly quenches the fluorescence of probe R. The presence of other common metal ions does not influence the fluorescence of probe R in the CH3CN: H2O (1:1) mixture, as they neither increase nor quench it. From the fluorescence enhancement data, the low detection limit (LOD) for Ag + ions was determined to be 1.24 × 10- 8 M, whereas the quenching caused by Hg2+ resulted in an LOD of 5.69 × 10- 9 M. The complex of probe R with Ag+/Hg2+ exhibited a 1:1 stoichiometry, as confirmed by mass spectrometry and a Job plot. Single-crystal XRD analysis of R and its complex with Hg2+ revealed a loss of coplanarity, which confirmed their nonfluorescent behavior. We present a promising application of probe R in visualizing living Rhizoctonia oryzae cells exposed to silver (I) and mercury (II) ions.

Fumed-Si-Pr-Ald-Barb as a Fluorescent Chemosensor for the Hg2+ Detection and Cr2O72- Ions: A Combined Experimental and Computational Perspective.

The surface of fumed silica nanoparticles was modified by pyridine carbaldehyde and barbituric acid to provide fumed-Si-Pr-Ald-Barb. The structure was identified and investigated through diverse techniques, such as FT-IR, EDX, Mapping, BET, XRD, SEM, and TGA. This nanocomposite was used to detect different cations and anions in a mixture of H2O:EtOH. The results showed that fumed-Si-Pr-Ald-Barb can selectively detect Hg2+ and Cr2O72- ions. The detection limits were calculated at about 5.4 × 10-3 M for Hg2+ and 3.3 × 10-3 M for Cr2O72- ions. A computational method (DFT) was applied to determine the active sites on the Pr-Ald-Barb for electrophilic and nucleophilic attacks. The HOMO-LUMO molecular orbital was calculated by B3LYP/6-311G(d,p)/LANL2DZ theoretical methods. The energy gap for the Pr-Ald-Barb and Pr-Ald-Barb+ion complexes was predicted by the EHOMO and ELUMO values. The DFT calculation confirms the suggested experimental mechanism for interacting the Pr-Ald-Barb with ions.

Effect of percentage of methanol on micellization position of mixed surfactant interaction in the absence and presence of dye

The interaction behavior of mixed surfactant-dye systems, i.e., anionic surfactant sodium dodecyl sulfate (SDS), cationic surfactant cetyl pyridinium chloride (CPC), and dye methyl orange (MO) was investigated through the allocation of micelles using conductivity measurements. Conductivity as a function of surfactant concentration was monitored to calculate the critical micelle concentration (CMC). The conductivity increased sharply as the surfactant content increased, according to the results. Moreover, the conductivity rises with temperature, whereas it falls with increased methanol (CH3OH). CH3OH-H2O mixed solvent media containing 0 %, 10 %, 20 %, and 30 % of CH3OH at 298.15, 308.15, and 318.15 K to work out the basic micelle fixation, gives significant understanding to the arrangement of the mixed surfactants. The CMC and degree of micellar dissociation (α) of SDS with CPC increase in the CH3OH and H2O mixture. The CMC and α values are increased by increasing the temperature. Various thermodynamic parameters, i.e. Standard free energy of micellization (ΔGmo), Standard enthalpy of micellization (ΔHmo), and Standard entropy of micellization (ΔSmo) were computed in SDS-CPC without MO. ΔGmo values for SDS-CPC in the presence of MO results in micellization more probable with MO.

Fast and Simple Extraction for LCMSMS Analysis of Oxytetracycline Residue in Pork

Pork is very popular as an animal-base protein source of peoples in the Lao PDR. The pig growth promotion, treatment and prevention of diseases frequently relies on the use of antibiotics. In terms of food safety, the analysis of antibiotic residue in pork would be therefore important. Oxytetracycline (OTC) is one of antibiotics used in the pig husbandry. In this study, a fast and simple extraction and analysis method for determining OTC residue in pork was developed. Briefly, 1.0 g of homogenized pork sample in a 50mL-centrifµge tube was extracted with 10 mL of CH3OH: H2O mixture (9:1 ratio) assisted with vortex for 10 min, treated with QuEChERS salt and subjected to centrifugation at 5000 rpm. The methanolic extract (1.5 mL) was then cleaned up with 2mL-dSPE tube (containing MgSO4, PSA, and C18), filtered through syringe filter 0.45 micron and analyzed with ESI-LCMS/MS optimized and operated in MRM positive mode. Calibration was prepared with OTC standard solutions (5-100 ng/g). The analytical method was validated with triplicated recovery tests at a spiked level of 50 ng/g. The results unveiled that the method gave very good recovery of 88.7±3.24%. The limits of detection (LOD) and quantification (LOQ) were achieved with 0.36 ± 0.02 and 1.19 ±0.04 ng/g. In consequence, the developed method would be suitable for OTC determination in pork samples.

Transport numbers of ion-exchange membranes in ternary mixtures of KCl, H2O and ethanol relevant for electrodialysis and desalination processes

Understanding the transport phenomena in electrolyte mixtures involved in electrochemical processes is of utmost importance for the modelling and improvement of battery technology, fuel cells, ion-exchange membrane processes, and much more. In this work, we derive relations and present methods for the analysis of electric potential measurements of concentration cells and ion-exchange membrane permselectivity with ternary mixtures of KCl, H2O and ethanol (EtOH). Measurements of electric potentials across the Selemion CMVN (cation-exchange) and AMVN (anion-exchange) membranes in this ternary mixture suggest that the presence of EtOH affects the membrane permselectivity, but that the transference of EtOH is zero; i.e., ta=0. Instead, the decrease in membrane permselectivity can be explained by a varying water transference coefficient, tw. In the absence of EtOH we find tw≈4 in both membranes, and that the decrease in tw is proportional to the average thermodynamic activity of EtOH in mixtures adjacent to the membranes. The membranes were also found to be charge selective, as quantified by the ionic transport numbers; i.e., tK+=1 for the Selemion CMVN and tK+=0 for the Selemion AMVN. The presented method can readily be extended and leveraged to determine transference coefficients in other electrochemical systems.

Bismuth Film Electrodes: Characterization and Analytical Application

Bismuth film electrodes (BiFE) were first introduced more than two decades ago and have been regarded as a posible alternative to toxic traditional mercury electrodes, both for electro-synthesis and electro-analytical endeavors. However, despite all the associated benefits, there hasn’t been a proper characterization reported for this electrodes and their use is still limited.The present work shows the results of a physicochemical characterization of Bismuth film electrodes, as well as the application of BiFE for the detection and quantification of heavy metals (such as cadmium), which for years have been considered to be important pollutants and are toxic for humans and the environment at large; there for putting at risk the health of all organisms that come into contact with them. The analysis is carried out in a EtOH:H2O mixture at pH 5, simulating the matrix of a traditional mexican alcoholic beverage, Mezcal.The characterization includes: the calculation of the geometric area as well as the electro-active area of the electrode, the composition of the deposited film and it’s texture, and the electrical properties of the modified electrode.The analysis is carried out using Anodic Stripping Square Wave Voltammetry (ASSWV), this allows us to make use of the electrode’s ability to form strong interactions with the analyte, in a similar manner to that of mercury drop electrodes; along with the high sensitivity of this technique.

A MEPS-UHPLC-MS/MS analytical platform to detect isoprostanoids and specialized pro-resolving mediators in the urinary extracellular vesicles of mountain ultramarathon runners

Oxylipins are powerful signalling compounds derived from polyunsaturated fatty acids (PUFAs) and involved in regulating the immune system response. A mass spectrometry-based method was developed and validated for the targeted profiling of 52 oxylipins (e.g., isoprostanoids, prostaglandins, epoxy- and hydroxy-fatty acids, specialized pro-resolving mediators) and 4 PUFAs in small urinary extracellular vesicles (uEVs). Ultrasound-assisted extraction using a 50:50 v/v MeOH:H2O mixture ensured optimal analytical performances. Limits of detection ranged between 10 and 400 pg/mL for oxylipins and 0.10–3 ng/mL for PUFAs. Satisfactory recoveries (85–116 %) and good intra- and inter-day precisions (RSD ≤15 %) were obtained for all the analytes. The reliability of the procedure was tested in a real case scenario by monitoring ultramarathon runners during the world Tor des Géants® (TDG) race. Both F2- and E2-isoprostanes were detected in small uEVs of the ultramarathon runners, suggesting the onset of an oxidant insult. 5-F2t-IsoP exhibited significant pre- to post-race variations, thus potentially representing a non-invasive marker of in-vivo lipid peroxidation. The presence of specialized pro-resolving mediators suggests the activation of pro-resolution signalling cascade resolving inflammation. These outcomes may help manage post-exercise recovery and improve training.

Comparison of the Impact of NaIO4-Accelerated, Cu2+/H2O2-Accelerated, and Novel Ion-Accelerated Methods of Poly(l-DOPA) Coating on Collagen-Sealed Vascular Prostheses: Strengths and Weaknesses.

Sensitive biomaterials subjected to surface modification require delicate methods to preserve their structures and key properties. These include collagen-sealed polyester vascular prostheses. For their functionalization, coating with polycatecholamines (PCAs) can be used. PCAs change some important biological properties of biomaterials, e.g., hydrophilicity, bioactivity, antibacterial activity, and drug binding. The coating process can be stimulated by oxidants, organic solvents, or process conditions. However, these factors may change the properties of the PCA layer and the matrix itself. In this work, collagen-sealed vascular grafts were functionalized with a poly(l-DOPA) (PLD) layer using novel seawater-inspired ion combination as an accelerator, compared to the sodium periodate, Cu2+/H2O2 mixture, and accelerator-free reference methods. Then, poly(l-DOPA) was used as the interface for antibiotic binding. The coated prostheses were characterized (SEM, FIB-SEM, FTIR, UV/vis), and their important functional parameters (mechanical, antioxidant, hemolytic, and prothrombotic properties, bioactivity, stability in human blood and simulated body fluid (SBF), antibiotic binding, release, and antibacterial activity) were compared. It was found that although sodium periodate increased the strength and drug-binding capacity of the prosthesis, it also increased the blood hemolysis risk. Cu2+/H2O2 destabilized the mechanical properties of the coating and the graft. The seawater-inspired ion-accelerated method was efficient, stable, and matrix- and human blood-friendly, and it stimulated hydroxyapatite formation on the prosthesis surface. The results lead to the conclusion that selection of the PCA formation accelerator should be based on a careful analysis of the biological properties of medical devices. They also suggest that the ion-accelerated method of PLD coating on medical devices may be highly effective and safer than the oxidant-accelerated coating method.

An activity coefficient model for mixed-solvent electrolyte mixtures based on Gibbs–Duhem’s equation: A case study of mixtures of water, KCl and ethanol

Thermodynamic properties of mixtures with several fluid components and electrolytes are challenging to model. Models are needed to develop and improve a wide range of electrochemical systems such as fuel cells, lithium-ion batteries, and processes with ion-exchange membranes. In the literature, activity coefficients are extracted using fundamentally different experimental methods that rely on electrochemical cells, vapour pressure measurements, solubility measurements, etc. The reference states of the activity coefficients obtained from these methods are likely to differ. This makes it difficult to combine or compare activity coefficient models from different sources. In this work, we present a method using Gibbs–Duhem’s equation for the development of activity coefficient models of mixtures that are based on experimental data from different methods. We use the ternary mixture of KCl, H2O and ethanol as example. First, empirical expressions are developed for the logarithm of the activity coefficients of KCl and ethanol. The expression for the activity coefficient of H2O is next derived using Gibbs–Duhem’s equation. The resulting three activity coefficient models are fitted to available experimentally data from several sources, generating linear and relatively low-complexity activity coefficient models. The empirical activity coefficient models are next compared to the electrolyte cubic plus association (e-CPA) equation of state. The models give saturation pressures in ternary mixtures that have average absolute relative deviations for water/ethanol of 8.3/3.4% for the empirical model and 11.8/3.3% for e-CPA. Experimental data reduction procedures for concentration cells, formation cells, and vapour pressure measurements are discussed, and the freedom to choose the reference state and the consequences are highlighted.

Modifications of astrophysical ices induced by cosmic rays

Aims. Astrophysical ices on dust grain mantles in the interstellar medium (ISM) and dense circumstellar envelopes (CSEs) are continuously exposed to galactic cosmic rays (GCRs). In a laboratory setting, we studied the physical and chemical modifications of ice layers induced by energetic heavy ions as GCR analogues. The ice layers used have a molecular composition similar to that of icy grain mantles. Methods. Mixtures of H2O:CO:CH3OH molecules (percentages 73:24:3, 68:30:3, and 58:38:3) were condensed on a substrate at 15 K and irradiated with 40 MeV 58Ni11+ ion beams. Irradiation-induced modifications were followed using the mid-infrared absorption spectroscopy technique. Results. We observed the evolution of infrared bands of CO2, HCO, HCOOH, CH4, H2CO,H2O2, and more complex synthesised molecules. From the molecular column densities, cross-sections and sputtering yields were determined and compared to published results of water and carbon monoxide. Analysis of the chemical modifications reveals that the precursors are easily destroyed when they are in a molecular mixture, while others are desorbed. Conclusions. The main radiolitic modifications induced by GCR irradiations are molecular decomposition and sputtering. Extrapolation to astrophysical radiation conditions shows a strong dependence on the intensity of the GCR distributions at low energies, which allows the analysis of the ice evolution at timescales comparable to those of the ISM and CSE.

A molecular simulation study on pore-scale behaviour of nitrogen-based fracking fluids for potential geo-energy applications

Molecular simulations are efficient tools in differentiating individual effects of fluid-fluid interactions and pore-fluid interactions on thermophysical properties of confined fluids; e.g. the molecular packing, adsorption mechanics and availability of accessible pore volume for confined fluids and therefore, indicate the rock fracturing phenomena as a function of geological conditions, fracking fluids nature, its composition and rock mineralogy. Presently, we have deployed the classical GCMC molecular simulations to quantify the adsorption of pure nitrogen and N2–H2O mixture (50%–50% and 30%–70%) inside porous silica rocks. While we found that adsorption and molecular packing of pure nitrogen inside silica slit pores are only a function of pore height, which quantifies the pore-fluid interactions; however, for N2–H2O mixture adsorption and molecular packing of N2 inside silica slit pores has been additionally affected by the water content in the equilibrium bulk mixture that as well describes fluid-fluid interactions inside pores. It is interestingly noted that water in N2–H2O mixture results in water-assisted nitrogen adsorption inside hydrophilic silica slit pores, which has been further proven through the radial distribution function data calculations inside each slit pore. Also, the hydrophilic nature of silica increases water adsorption and hence reduces N2 adsorption inside the smallest pore of H = 20 Å. Such a reduction in N2 adsorption density below its bulk density without layering effect, inside 20 Å pore, further initiates the possibility of negative excess adsorption density.

A synergistic approach for lignin biofuel production: Integrating non-catalytic solvolysis with catalytic product upgrading

Enzymatic hydrolysis lignin (EHL) is a large-scale industrial waste generated from the bio-ethanol production process. Its complex and heterogeneous nature as well as its low solubility in common solvents, has posed a persistent barrier to its effective utilization. Here, EHL was converted into biofuel through a two-step process, involving non-catalytic solvolysis followed by catalytic product upgrading. The non-catalytic solvolysis step achieved complete EHL liquefaction in a mixture of isopropanol and H2O without char formation. In this step, H2O disrupts the hydrogen bonds in EHL and isopropanol break π-π stacking interactions between the aromatic rings in EHL·H2O also enhances EHL depolymerization, while isopropanol, as a hydrogen donor solvent, provides hydrogen that stabilizes active intermediates. In the catalytic product upgrading step, the liquid product of the first step was transformed into biofuels rich in cycloalkanes, arenes and alkylphenols, with a total carbon yield of 45.6 %. Isopropanol-H2O reforming reactions provided hydrogen for the upgrading process, avoiding the introduction of H2. This work demonstrates an effective approach for converting EHL into biofuels.

Mathematical modeling of unsteady process of cold storage within a container filled with nanomaterial incorporating Galerkin method

This research focuses on simulating the freezing involving a mixture of H2O and alumina nano-powders. It sheds light on the complex relationship between the characteristics of nano-powders and freezing dynamics, offering valuable insights applicable to various fields, including cryopreservation and thermal energy storage. By utilizing the Galerkin approach and incorporating an adaptive grid, the research introduces an elliptic container with a cold surface and strategically placed rectangular fins. The investigation examines how the characteristics of nano-powders, particularly their size (dp) and concentration (ϕ), influence different scenarios. Notably, changes in powder size have a significant effect on freezing time, initially decreasing by approximately 20.22 % before increasing by 19.1 %. Moreover, the sensitivity of powder size decreases with lower powder concentrations. For example, at ϕ = 0.02, an augment in dp primarily reduces the time by about 11.72 %, followed by an increase of 10.98 %. The most substantial improvement occurs when ϕ is optimized, resulting in a remarkable 41.27 % reduction in freezing time.

A Schiff base functioning as a highly selective colorimetric sensor for Cu2+ ion

In this study, we employed a Schiff base ligand (L = 6,6′-((1E,1′E)-(cyclohexane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(2,4-di-tert-butylphenol)) to serve as a chemosensor exclusively for detecting Cu2+ ions over other metal ions and anions in a THF:H2O mixture (7:3, v/v). L exhibits an absorption band at 330 nm, which undergoes a bathochromic shift to 377 nm upon interaction with solely Cu2+ ions, suggesting a restricted internal charge transfer process of L. Analysis via ESI-MS and Job’s plot confirmed a 1:1 stoichiometric ratio between L and Cu2+. L demonstrated the capability to detect Cu2+ ions at a concentration as low as 0.46 μM. Furthermore, we investigated the effectiveness of L in developing molecular logic gates and its applications in analyzing Cu2+ in water samples.

Corrosion damages of nickel-based alloy G3 in 600 °C H2O[sbnd]CO2[sbnd]H2S[sbnd]H2 steam

Corrosion damage mechanisms of nickel-based alloy G3 at 600 °C with a mixture of H2O, CO2, H2S and H2 were explored using ultra-high-temperature and high-pressure corrosion experiments, slow strain rate tensile tests and a series of microscopic characterization methods. Results unveil that G3 alloy exhibited a low corrosion rate on average. The corrosion product film consists of two layers – an inner layer of Cr2O3 and an outer layer of a mixture of Ni3S2 and Cr2O3. The material experienced plasticity losses of 49.5 % and 24.3 % after corrosion and aging, respectively. Precipitation of M23C6 at grain boundary occurred after corrosion and aging, resulting in chromium depletion and intergranular corrosion within weak grain boundary regions, which reduced plasticity of G3 alloy.

Combined radiation and convection in developing flow in a parallel plate channel with real gas behavior: Contrast between gas cooling and heating

Laminar thermally developing gas flow in a two-dimensional parallel plate channel with real gas radiation has been investigated numerically. Real gas spectral radiation effects are accounted for by using the Spectral Line Weighted-sum-of-gray-gases model. Gas mixtures of H2O and CO2, either alone in mixture with N2 or as a mixture of H2O and CO2 are considered. The phenomena are investigated for a range of differences between wall and inlet gas temperature, mole fraction of the radiating species, and total pressure. Predictions for the cases of gas heating and gas cooling are contrasted with results presented by the classical no-radiation case, commonly known as the Graetz solution. The impact of gas radiation on the local mean temperature, convective and radiative wall heat fluxes, and the convective, radiative, and total local Nusselt numbers are studied.The predictions reveal that the inclusion of participating gas radiation results in a much more rapid change in temperature of the gas in the channel than for the convection-only case, for both the gas heating and gas cooling cases. Further, unique differences in the heat transfer behavior for gas cooling (wall temperature below the inlet gas temperature) and gas heating (wall temperature above the inlet gas temperature) scenarios are shown. However, significant differences between the cases of heating and cooling exist. In the classical Graetz solution, for constant thermophysical properties and using appropriately nondimensionalized heat transfer parameters (e.g., Nusselt number, inverse Graetz number) the predictions for fluid heating and cooling are identical. However, the results of this study including the influence of gas radiation demonstrate that the heat transfer behavior depends heavily on whether the gas is heated or cooled. An apparent thermally fully developed condition may exist for the case of gas cooling, whereas the variation in local Nusselt number with dimensionless axial location exhibits a local minimum for the case of gas heating. Further, the case of gas heating results in a more rapid streamwise change in mean temperature in the channel than for the cooling case. The thermal physics of the developing flow for combined convective-radiative transfer with real gas effects are explored for a range of wall and gas inlet temperatures, radiating species mole fractions, and total pressures.