Single-phase Fluid Research Articles

Analysis of wave propagation in non-isothermal poroelastic solids saturated by two-phase fluids

SUMMARY This work presents a model to characterize the behaviour of waves propagating in non-isothermal poroelastic solids saturated by two-phase fluids. The dynamic differential equations include the poroelasticity and heat equations with the solid, fluid and thermal fields combined using coupling terms. A plane wave analysis shows that five waves can propagate, three compressional, one fast (P1) and two slow (P2, P3), a shear fast (S) and a thermal slow (T). P2, P3 and T are diffusive waves at low frequencies, while P1 and S behave as propagating waves. The T wave is coupled with the compressional waves and uncoupled with the S wave. The plane wave analysis applied to a real sandstone saturated with gas–water mixtures compares phase velocities and attenuation factors for two-phase and effective single-phase fluids, considering or neglecting the coupling terms. It is observed that P1 and P2 waves have higher velocities for coupled cases, while P3 and T waves exhibit the opposite behaviour. Furthermore the plane wave analysis is performed in the coupled case for oil–water and gas–water two-phase fluids, with compressional waves exhibiting higher velocities for gas–water than for oil–water mixtures. The propagation of waves in a 1-D thermo-poroelastic medium saturated by a gas–water mixture is presented and analysed using a finite element procedure. Considering temperature may become important in high-pressure high-temperature hydrocarbon and geothermal reservoirs.

Genesis of Pb–Zn Mineralization in the Pulang Cu Polymetallic Deposit in Yunnan Province, China: Insights from Analyses of Geology, Fluid Inclusions and C–H–O–S Isotopes

The Pulang super-large porphyry Cu polymetallic deposit, located in the Sanjiang area of Yunnan Province, is one of the largest Cu deposits in China. This deposit hosts Cu resources of ~5 × 106 t and other ore-forming elements, such as Mo, Au, Ag, Pb, Zn, Pt and Pd. Recently, obvious hydrothermal vein-type Pb–Zn mineralization, with a Pb + Zn resource of ~0.4 × 106 t, has been detected in the North Ore Section of the deposit. However, the genesis of these Pb–Zn ore bodies, especially their relationship to the major Cu ore bodies in the South Ore Section, remains controversial. We conducted geologic description, fluid inclusion petrography and microthermometry, and C, H, O and S isotope studies to uncover the genesis of Pb–Zn vein-type mineralization in North Pulang. As a result, three types of Pb–Zn veins were identified: a quartz–pyrrhotite–chalcopyrite–sphalerite–galena vein, a quartz–pyrrhotite–sphalerite–galena vein, and a calcite–quartz–pyrrhotite–galena vein. All fluid inclusions in the quartz from different veins are liquid-rich inclusions, with homogenization temperatures in the range of 184 °C–235 °C and salinities between 10.4 wt.% and 17.8 wt.% NaCl eq., indicating that the Pb–Zn ore-forming fluid was a single-phase fluid with a low temperature and low-to-medium salinity. Hydrothermal quartz in different stages displays δDwater values ranging from −46.9‰ to −120.0‰ (V-SMOW), and the calculated δ18Owater values range from 2.4‰ to 4.3‰ (V-SMOW), implying that the mineralization fluids likely originated from magma, with a minor involvement of meteoric water. The δ13CCal values (−2.3‰ to −7.9‰ V-PDB) of calcite indicate that C likely originated from a deep-seated source. The δ34S values of chalcopyrite, pyrite, pyrrhotite and sphalerite reveal that S was possibly derived from magmatic rocks. Based on the above data, it is suggested that the Pb–Zn mineralization in North Pulang was the result of the northward migration of ore-forming fluids that originated from South Pulang along the NE-trending structural fractures. A strong water–rock interaction occurred during the migration process. However, the involvement of meteoric water and accompanied cooling of fluids were most likely responsible for the precipitation of galena and sphalerite.

Fine Particle Migration in a Gas Hydrate Sand: Single- and Two-Phase Fluid Using a Device for Observation at the Pore Scale

The production of natural gas hydrates will change the cementation strength, porosity, and effective stress in the stratum, which may lead to engineering and geological disasters. Sand production is a phenomenon where sand particles are carried out of the reservoir along with fluids during gas extraction, posing challenges to safe and sustainable production. This study explored the mechanism of fine particle migration in multiphase flow by a microscopic visualization test device. The device can inject a gas–liquid–solid phase at the same time and allow real-time observation. Experimental tests on fine particle migration of single- and two-phase fluid flow were carried out considering different conditions, i.e., fine particle concentration, fine particle size, fluid flow rate, and gas–liquid ratio. The results show that in single-phase fluid flow, the original gas will gradually dissolve in the liquid phase, and finally stay in the test device as bubbles, which can change the pore structures, resulting in the accumulation of fine particles at the gas–liquid interface. In two-phase fluid flow with mixed gas–water fluids, there are two flow modes of gas–liquid flow: mixed flow and separated flow. The interfacial tension at the gas–liquid interface can effectively migrate fine particles when the gas–liquid flows alternately and the sand production rate further increases as the gas–liquid ratio increases. In addition, changes in the concentration of fine particles, particle size, fluid flow rate, and the gas–liquid ratio will affect the migration of fine particles, leading to differences in the final sand production.

HEAT TRANSFER IN A FORM-STABLE DIRECT-CONTACT LATENT THERMAL ENERGY STORAGE UNIT

This study investigated various aspects of thermal storage concept, including material characterization and analysis of form-stable, unencapsulated phase-change materials (PCM) that underwent solid-solid phase transition and was in direct contact with the working fluid. The study focused on temperature range between 100-140°C (212-284°F). Mathematical heat transfer models were developed to examine the operating characteristics of the thermal energy storage unit, identify key parameters influencing storage, and conducted parametric studies. Both single-phase and phase-change working fluids were considered in the models. Experiments were conducted using a packed bed of PCM pellets and a single-phase working fluid (tri-ethylene glycol) to evaluate and demonstrate the heat storage concept during charging and discharging. The experimental results aligned well with the heat transfer models, validating their accuracy. Parametric studies explored a wide range of parameters not feasible in laboratory experiments, shedding light on charging, discharging, and thermal storage characteristics. These models facilitated the development and implementation of optimization algorithms for packed bed latent heat storage units. The findings indicated that form-stable latent heat units utilizing commercially available polymers undergoing solid-solid phase transition can serve as long-term stable thermal storage candidates for use with several single-phase working fluids as well as two-phase steam.

Effect of flow direction on heat transfer and flow characteristics of supercritical carbon dioxide

This work is devoted to investigating the difference in flow and heat transfer characteristics between vertical upward flow and horizontal flow of supercritical carbon dioxide (<inline-formula><tex-math id="Z-20240119215215">\begin{document}$\rm sCO_2$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20231142_Z-20240119215215.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20231142_Z-20240119215215.png"/></alternatives></inline-formula>) based on the pseudo-boiling theory and the experimental parameters: mass flux <i>G</i> = 496–1100 kg/m<sup>2</sup>s, heat flux <i>q</i><sub>w</sub> = 54.4–300.2 kW/m<sup>2,</sup> and pressure <i>P</i> = 7.531–20.513 MPa. The differences in flow and heat transfer characteristics between horizontal upward tube and vertical upward tube are compared at different mass fluxes, heat fluxes and pressures fully. Finally, unlike the classical treatment of flow and heat transfer for supercritical fluid, single-phase fluid assumption is abandoned, instead, the pseudo-boiling theory is introduced to deal with the flow transfer and heat transfer of <inline-formula><tex-math id="Z-20240119215113">\begin{document}$\rm sCO_2 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20231142_Z-20240119215113.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20231142_Z-20240119215113.png"/></alternatives></inline-formula> in the two tubes. Supercritical fluid is regarded as a multiphase structure in this work, including a vapor-like layer near the wall and a liquid-like fluid in tube core. The results are indicated below. 1) In terms of heat transfer, the inner-wall temperature of the vertical upward tube and the bottom generatrix of horizontal tube are basically the same under normal heat transfer mode. When the heat transfer deterioration occurs in the vertical upward tube, larger supercritical boiling number (<i>SBO</i>) will cause the wall temperature peak of the vertical upward tube to be much higher than the wall temperature at top generatrix of the horizontal tube at the corresponding enthalpy. The <i>SBO</i> (<i>SBO</i> = 5.126×10<sup>–4</sup>) distinguishes between normal heat transfer deterioration and heat transfer deterioration in the vertical upward tube. In the horizontal tubes, <i>SBO</i> dominates the maximum wall temperature difference between the top generatrix and the bottom generatrix. Comparing with vertical upward tubes, higher <i>q</i><sub>w</sub>/<i>G</i> is required for the heat transfer deterioration of supercritical fluid in the horizontal tubes under the same pressure. 2) In terms of flow, the increase in slope of pressure drop in the vertical upward tube is due to the orifice contraction effect. The mechanism that dominates the variation of pressure drop in the horizontal tube is the flow stratification effect, and we show that Froude number <i>Fr</i><sub>ave</sub> can be the similarity criterion number to connect the temperature difference between the top and bottom generatrix of horizontal tube and the pressure drop. The analysis suggests that mechanisms governing horizontal flow and vertical flow of <inline-formula><tex-math id="Z-20240119215057">\begin{document}$\rm sCO_2 $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20231142_Z-20240119215057.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20231142_Z-20240119215057.png"/></alternatives></inline-formula> are different in heat transfer deterioration mode. For the vertical flow, the <i>SBO</i> plays a leading role, while for the horizontal flow, the <i>Fr</i> plays an indispensable role.

Electromagnetohydrodynamic (EMHD) flow through porous media—Multiscale approach

Electromagnetohydrodynamic (EMHD) flow in porous media is recently gaining substantial attention from researchers. EMHD involves analyzing the combined effects of electric and magnetic fields on the behavior of fluid flow through a medium. The effective permeability of porous materials is of great interest for many environmental and industrial applications. The present study focuses on the modeling of single-phase fluid flow in porous media under combined effects of electric and magnetic fields at the pore scale by employing a two-scale computational homogenization technique. The primary objective of this study is to establish a definition of “electromagnetopermeability” that accurately characterizes the effective permeability of a porous medium under the EMHD effects. Additionally, the study investigates the impact of wall zeta potential, Debye length, and the intensity of external magnetic and electric fields, represented by the Hartmann number and the non-dimensional parameter S, respectively, on the electromagnetopermeability tensor within an idealized three-dimensional periodic porous domain. It is observed that the EM-permeability is significantly affected by the existence of the flow-assisting and flow-opposing components of the Lorentz force term in the momentum equation. The implications of this research extend to several industries, including geology, medicine, chemistry, and energy conversion.

Numerical and experimental analysis of fluid flow and flow visualization at low Reynolds numbers in a dimple pattern plate heat exchanger

This research discusses single-phase fluid flow conditions at low Reynolds number (Re) in the heat exchanger with a dimple structure of the heat plate. Flow at 70 ≤ Re ≤ 469 was investigated with laboratory experiments and computational fluid dynamics. It was found that in such a channel, two flow regimes exist, i.e., dead and live regimes. The volumetric fraction of the deadly regime gets bigger with increasing Re. At Re ≥ 469, a fully developed turbulent flow was found in the channel. Numerical analysis was made with a laminar flow model and two turbulence models, Realizable k−ε with an enhanced wall treatment and k−ω SST. The Realizable k−ε turbulent model with an enhanced wall treatment predicts pressure drop and shape of the live and dead regime more consistent with the real conditions in the channel. At the lowest considered Re = 70, computational fluid dynamics solutions deviate from laboratory experiments by −10.3 %. As the Re increases, the difference increases and reaches −18.3 % at Re = 141. As Re continues to increase, the result decreases and stabilizes at −8.3 %.

Control of brine composition over reactive transport processes in calcium carbonate rock dissolution: Time-lapse imaging of evolving dissolution patterns

This study investigates the impact of brine composition—specifically calcium ions and NaCl-based salinity—on the development of dissolution features in Ketton, a porous calcium carbonate rock. Utilizing a laboratory XMT (X-ray microtomography) scanner, we captured time-lapse in situ images of Ketton samples throughout various dissolution experiments, conducting four distinct flow-through experiments with differing brine solutions at a flow rate of 0.26 ml min⁻1. The scans yielded a voxel size of 6 μm, enabling the assessment of the temporal evolution of porosity and pore structure through image analysis and permeability evaluations via single-phase fluid flow simulations employing direct numerical solutions and network modeling, as opposed to direct measurement.Time-lapse imaging technique has delineated the extent to which the concentrations of CaCl₂ and NaCl in the injecting solution control the structural evolution of dissolution patterns, subsequently triggering the development of characteristic dissolution pattern. The inflow solution with no Ca2+ ions and with the minimal salt content manifested maximum dissolution near the sample inlet, coupled with the formation of numerous dissolution channels, i.e., wormholes. Conversely, solutions with a trace amount of Ca2⁺ ions induced focused dissolution, resulting in the formation of sparsely located channels. Inflow solutions with high concentrations of both Ca2⁺ ions and salt facilitated uniformly dispersed dissolution, primarily within microporous domains, initiating particle detachment and displacement and leading to localized pore-clogging. The relative increase in permeability, in each experiment, was correlated with the developed dissolution pattern. It was discerned that varying ratios of salt and calcium concentrations in the injected solution systematically influenced image-based permeability simulations and porosity, allowing for the depiction of an empirical porosity-permeability relationship.

Supercritical heat transfer of CO2 in horizontal tube emphasizing pseudo-boiling and stratification effects

Here, we investigate supercritical heat transfer of CO2 in a 10.0 mm diameter horizontal tube, covering pressures, mass fluxes and heat fluxes in the ranges of (7.531∼20.513) MPa, (496.7∼1346.2) kg/m2s, and (97.4∼400.3) kW/m2, respectively. It is surprising to find the non-monotonic increase of wall temperatures along the flow direction. Besides, either positive or negative wall temperature differences, ΔT, exist between bottom tube and top tube. The three-regime-model is introduced to explore the mechanisms that trigger the above abnormal findings. The stratified-wavy flow involves a liquid-like (LL) core and a vapor-like (VL) layer on the tube wall. The wavy interface is formed by the two separated phases of LL and VL. The oscillation of wall temperatures is explained by the thermal conduction in the solid wall interacted with the stratified-wavy flow in the tube. Once wall temperatures increase, the local heat flux decreases to decrease the evaporation momentum force, reducing the VL layer thickness to ensure the heat transfer recovery. A regime map clarifies the positive and negative temperature difference runs, and the maximum wall temperature differences are well correlated based on the LL phase Reynolds number, ReLL,ave. In the two-phase-like (TPL) regime, the measured heat transfer coefficients significantly deviate from the predictions based on the single-phase fluid assumption. The strong deviation of hbot/htop from 1 indicates both important effects of pseudo-boiling and stratification in horizontal tubes, where hbot and htop are the heat transfer coefficients at the bottom generatrix and the top generatrix, respectively. Based on this work, the pseudo-boiling theory is recommended to deal with the supercritical heat transfer.

Modelling a CO2 meter for a petroleum multiphase mixture at subsea conditions

Measuring high levels of carbon dioxide (CO2) in Brazilian pre-salt production flows remains a considerable technological challenge. The complexity of the three-phase flow and the variable CO2 solubility within each phase poses difficulties in accurately measuring CO2 in this scenario. Moreover, existing CO2 measurement techniques designed for single-phase fluids prove insufficient under mixed-phase conditions. This study proposes a methodology for a simple CO2 meter capable of determining the CO2 content in an oil and gas production stream. The proposed meter operates by analyzing the pressure change during a heating assay of an imprisoned sample. A computational model was developed in the ASPEN HYSYS® process simulator with the Peng-Robinson Equation of State to calculate the mixture properties emulating the isochoric process in the meter under different CO2 levels and initial conditions. The modelling results indicate that the pressure-temperature (P-T) behavior exhibits linearity with a slope that increases with higher CO2 content, which is characteristic of many pre-salt production fields. The model successfully reproduced published experimental data for an isochoric process.

Experimental study on flow resistance characteristics of the uniform steam injection outflow control device.

Introduction: Multi-point steam injection technology is a new completion method for heavy oil horizontal wells to solve the uneven distribution of the intake profile in the horizontal section. It is equipped with the flow control device to achieve the effect of balanced steam injection. Methods: The steady-state experiment method was adopted; Considering the variable mass complex flow of the steam-liquid two-phase flow in the downhole flow device, the pressure loss of downhole tools through uniform steam injection with different steam-liquid compositions was tested, the influencing factors of the pressure drop were analyzed, and a more reliable pressure drop calculation method was established. Results: The overflow pressure drop can be adjusted by changing the aperture, steam dryness, and fluid flow of the downhole outflow control device (OCD). Discussion: By comparing the experimental and theoretical results, the calculation method of the overflow resistance of single-phase and steam-liquid two-phase fluids in OCD is given, and the error is within the usable range.

Investigating the Effect of Electroplated Coatings on Single-Phase Fluid Flow and Heat Transfer in Microchannel

Investigating the Effect of Electroplated Coatings on Single-Phase Fluid Flow and Heat Transfer in Microchannel

Microchannels Formed Using Metal Microdroplets.

The metal microdroplet deposition manufacturing technique has gained extensive attention due to its potential applications in microstructure fabrication. In order to fabricate components such as microchannel heat sinks and microchannel reactors, this paper investigates the interactions and influences between microdroplets and substrates, as well as between microdroplets themselves. The transient phenomena during the fusion of metal microdroplets in contact with the substrate and the formation of inclined columns, as well as the solid-liquid coupling and morphology formation processes during the collision between microdroplets, are analyzed. The influence of microdroplet spacing on the morphology of microchannels during their formation is specifically studied. A three-dimensional finite element numerical model for the deposition of metal microdroplets forming inclined pillars is established based on the volume of fluid (VOF) method. The model treats the protective gas around the microdroplet as an empty zone and the microdroplet as a single-phase fluid. Simulation analysis is conducted to investigate the forming patterns of unsupported microdroplets at different spacing and their impact on the fusion morphology of microchannel components. Building upon this, a series of validation experiments are conducted using a piezoelectric microdroplet generator to produce uniform aluminum alloy microdroplets with a diameter of approximately 600 μm. A method for fabricating metal microchannel structures is obtained, which is expected to be applied in fields such as scattering structures for high-power electronic devices and microreactors in microchemical fields.

MULTIPHASE SPH SIMULATION FOR INCHAMBER IMPACT PRESSURE ON VERTICAL BREAKWATER WITH WAVE ABSOPTION CHAMBER

A numerical model of a vertical breakwater integrated with wave absorption chamber has been tested against regular wave in a virtual wave flume. The open source Smoothed-Particles Hydrodynamics, or SPH, (Lagrangian type) software called DualPSHysics was deployed for the simulation. Both the multiphase (air-water) and single-phase (water only) fluid were considered and compared with an experimental result. Single-phase and multiphase capture the water column elevation in an open chamber within a ratio of 0.92 and 0.70, respectively, when compared to experiments. However, single-phase is not able to capture the fully closed chamber effect. It is found that inside the fully closed chamber, the multiphase SPH captures the maximum (compressed) water elevation well but overestimates the air compression by a factor of 1.5.

Simulation of Mixing of Single-Phase Fluids in T-Junctions

Simulation of Mixing of Single-Phase Fluids in T-Junctions

Numerical Prediction of the Streamwise Fluidelastic Instability

Abstract Recent experimental investigations have shown that tube arrays can become unstable in the streamwise direction. This is contrary to the long-held notion that fluidelastic instability is only a concern in the direction transverse to the flow. The possibility of the streamwise fluidelastic instability (SFEI) as a potential threat to the integrity of tube bundles was confirmed by the recent failures of newly installed replacement steam generators. A number of investigations were conducted to uncover the nature of this mechanism. A theoretical framework was developed by Hassan and Weaver (2016, “Modeling of Streamwise and Transverse Fluidelastic Instability in Tube Arrays,” ASME J. Pressure Vessel Technol., 138(5), p. 051304) to model streamwise fluidelastic instability in a bundle of flexible tubes. The model utilized a simple time lag expression for the flow channel area perturbation. The current work aims at developing a numerical model to precisely predict the flow perturbation characteristics in a tube bundle due to streamwise tube motion. Flow simulations were carried out for single phase fluid flow in a parallel triangle tube bundle array with 1.2, 1.5, and 1.7 pitch to diameter ratios. The numerical model was validated against numerical and experimental results available in the fluidelastic instability literature. Simulations were carried out for a range of reduced flow velocities. The model results showed that the upstream flow perturbation magnitude and phase are different from those obtained downstream of the moving tube. The obtained flow perturbation characteristics were implemented in the Hassan and Weaver (2016, “Modeling of Streamwise and Transverse Fluidelastic Instability in Tube Arrays,” ASME J. Pressure Vessel Technol., 138(5), p. 051304) model and the streamwise FEI threshold was predicted.

Petrophysical parameters inversion for heavy oil reservoir based on a laboratory-calibrated frequency-variant rock-physics model

Heavy oil has high density and viscosity, and exhibits viscoelasticity. Gassmann's theory is not suitable for materials saturated with viscoelastic fluids. Directly applying such model leads to unreliable results for seismic inversion of heavy oil reservoir. To describe the viscoelastic behavior of heavy oil, we modeled the elastic properties of heavy oil with varying viscosity and frequency using the Cole-Cole-Maxwell (CCM) model. Then, we used a CCoherent Potential Approximation (CPA) instead of the Gassmann equations to account for the fluid effect, by extending the single-phase fluid condition to two-phase fluid (heavy oil and water) condition, so that partial saturation of heavy oil can be considered. This rock physics model establishes the relationship between the elastic modulus of reservoir rock and viscosity, frequency and saturation. The viscosity of the heavy oil and the elastic moduli and porosity of typical reservoir rock samples were measured in laboratory, which were used for calibration of the rock physics model. The well-calibrated frequency-variant CPA model was applied to the prediction of the P- and S-wave velocities in the seismic frequency range (1–100 Hz) and the inversion of petrophysical parameters for a heavy oil reservoir. The pre-stack inversion results of elastic parameters are improved compared with those results using the CPA model in the sonic logging frequency (∼10 kHz), or conventional rock physics model such as the Xu-Payne model. In addition, the inversion of the porosity of the reservoir was conducted with the simulated annealing method, and the result fits reasonably well with the logging curve and depicts the location of the heavy oil reservoir on the time slice. The application of the laboratory-calibrated CPA model provides better results with the velocity dispersion correction, suggesting the important role of accurate frequency dependent rock physics models in the seismic prediction of heavy oil reservoirs.

Vortex generation due to multiple localized magnetic fields in the hybrid nanofluid flow – A numerical investigation

Vortices capture the attention of every scientist (as soon as they come into existence) while studying any flow problem because of their significance in comprehending fluid mixing and mass transport processes. A vortex is indeed a physical phenomenon that happens when a liquid or a gas flow in a circular motion. They are generated due to the velocity difference and may be seen in hurricanes, air moving across the plane wing, tornadoes, etc. The study of vortices is important for understanding various natural phenomena in different settings. This work explores the complex dynamics of the Lorentz force that drives the rotation of nanostructures and the emergence of intricate vortex patterns in a hybrid fluid with Fe3O4–Cu nanoparticles. The hybrid nanofluid is modeled as a single-phase fluid, and the partial differential equations (PDEs) that govern its behavior are solved numerically. This work also introduces a novel analysis that enables us to visualize the flow lines and isotherms around the magnetic strips in the flow domain. The Lorentz force confined to the strips causes the spinning of hybrid nanoparticles, resulting in complex vortex structures in the flow domain. The results indicate that the magnetic field lowers the Nusselt number by 34% while raising the skin friction by 9%. The Reynolds number amplifies the influence of the localized magnetic field on the flow dynamics. Lastly, the nano-scaled structures in the flow enhance the Nusselt number significantly while having a minor effect on the skin friction factor.

Investigation of turbulent heat transfer performance of aviation turbine fuel multi-wall carbon nanotube nanofluid

Nanofluid is a novel heat transfer fluid prepared by suspending high thermal conductivity nano-sized particles in conventional fluids (water, engine oil and ethylene glycol). Thermo-physical properties (Thermal conductivity, dynamic viscosity and specific heat) and turbulent heat transfer performanceof Aviation Turbine Fuel (ATF) based Multiwall Carbon Nanotube (MWCNT) nanofluid are investigated experimentally for particle volume concentrations of 0–1% and at mean fluid temperatures of 30οC and 50οC for a potential regenerative heat transfer application in semi-cryogenic liquid propellant rocket engine. The experimental results show that the heat transfer coefficient of the nanofluid increases with particle volume concentration, with a maximum enhancement at 1% particle volume concentration of approximately 23% and 50% observed at 30οC and 50οC respectively. Two different numerical modelling approaches (a single phase fluid model with enhanced thermo-physical properties and an Eulerian-Lagrangian model called the “discrete phase model”) are employed to simulate the experimental conditions. The predictions from both numerical modelling approaches are found to compare reasonably well with the experimental data. The enhanced heat transfer performance is expressed on an equal power penalty basis to clearely show the advantage of the nanofluid.

Research on the forward-modeling method of viscoelastic Chapman extension in partially saturated rocks

The propagation of seismic waves in fractured rocks is greatly influenced by the fracture system and fluid content. Seismic anisotropy varies with frequency and fluid saturation. Previous theories on frequency-dependent anisotropy (FDA) are mostly limited to the assumption of single-phase fluid, whereas almost all reservoirs are usually partially or fully saturated with one or more fluids. The inelasticity, heterogeneity, and anisotropy exhibited by real earth media seriously challenge the traditional theory of uniform fully elastic media. Therefore, based on the Chapman elastic theory, we consider the viscoelastic model, the relative mobility of saturated fluids, and the coupled effects of commonly independently considered squirt flow and patch effects on the frequency-dependent anisotropic seismic wave propagation in viscoelastic media. By calculating the frequency-dependent anisotropic elastic coefficients of two-phase immiscible fluid-saturated fractured rocks, a new viscoelastic Chapman extension model for FDA in partially saturated rocks, which includes the unified seismic wave propagation effects of squirt flow and patch effects, is constructed. The effect of relative permeability is significant, and compared to the case of complete saturation, the effective fluid mobility in partially saturated rocks may be lower, which may lead to nonmonotonic changes in elastic modulus and water saturation. Numerical experiments are conducted on our viscoelastic Chapman extension model to discuss the coupling effects of squirt flow and patch effects on the FDA of viscoelastic media in cracked rocks with partially saturated reservoirs, under the conditions of no fractures and the existence of fractures. The simulation results of the P-wave modulus, P-wave velocity, and anisotropy parameters confirm the validity of our method and model. We link the anisotropy of viscoelastic media with fluid flow parameters in fractures, which is conducive to improving the understanding of frequency-dependent seismic anisotropy in partially saturated rocks with fractures and the combination of seismology and reservoir engineering.