Solid Wall Research Articles

Research on Application of Composite Facades for Civilian Reconstruction of Industrial Heritage in Cold Regions Based on Thermal Buffering Effect

Previous studies on the civil transformation of industrial heritage have been conducted mainly from the perspective of architectural history, culture and aesthetics, but rarely focus on energy-saving and the comfort of the new users. Most industrial heritage facades are of high conservation value, but efforts to preserve the authenticity of the facade can lead to the application of limited energy-saving technologies, ultimately resulting in poor indoor thermal environments. Therefore, it is valuable to research how to solve the contradiction between protecting the authenticity of the preserved facades of industrial heritage and improving the indoor environmental performance. This paper proposes two composite facade application strategies based on thermal buffer effects, takes two composite facades renovation methods of Shenyang Dongmao No. 2 Warehouse as an example, utilizes the natural environmental resources to enhance the spatial quality of industrial heritage. With the help of DesignBuilder software modelling simulation analysis, in-depth comparative analysis of the two types of composite facades on the indoor thermal environment of the industrial heritage of the impact and scope. Key findings show that the application of two different composite facade retrofitting techniques not only protects the skin texture of the wall, but also effectively increases the indoor temperature and reduces the indoor energy consumption of the industrial heritage. The composite facade of the external solid wall and the internal glass is more stable in raising the indoor temperature, more effective in reducing the building energy consumption, and more suitable for the civilian transformation of industrial heritage in cold areas. The research findings provide reference for studies on the civil transformation of industrial heritage, and serve as technical references for architects.

Physical modeling of conjugate heat transfer for multiregion and multiphase systems with the Volume-of-Fluid method

AbstractThe Volume-of-Fluid (VOF) method is commonly used for numerical simulations of phase change phenomena, such as nucleate boiling or droplet evaporation. A key issue with the standard VOF method is the averaging of the liquid and vapor properties in interface cells, which causes non-physical conjugate heat transfer with a solid wall. Therefore, we aim at a physical model for conjugate heat transfer between a solid and a multiphase fluid. The first measure for higher quality simulations is the splitting of the single temperature field in the fluid region into separate liquid and vapor temperature fields. The second measure is the development of a new, more physical temperature boundary condition for conjugate heat transfer between a solid region and a multiphase fluid, based on experimental results, theoretical models and theoretical considerations. In interface cells, the vapor phase is excluded from the conjugate heat transfer because only heat transfer to the liquid phase occurs resp. dominates. Additionally, the conjugate heat transfer between solid and liquid in the interface cells is performed with virtual subcells, depending on the respective volume fraction of the liquid phase. This new approach (we name it distinctive approach) is successfully validated for energy conservation, and stability issues are discussed for the first time. Significant differences to simulations with averaged properties are observed due to the (now) physically correct modeling of conjugate heat transfer. In our boiling cases, the more accurate numerical simulations lead to considerably larger bubble growth rates. Higher quality simulations are also expected for nearly all applications, where there is a three-phase contact line, be it vapor bubbles in nucleate boiling or droplets impacting on a heated surface.

Internal flow stability analysis of vertical mixed-flow pump device based on EGT and FFT

With the purpose of researching the internal flow stability of the vertical mixed-flow pump device (VMFPD), the entire flow field was solved through the very large-eddy simulation (VLES) k- ω model and the internal flow characteristics of the pump device were quantitatively analyzed with the use of the energy gradient theory (EGT) along with the physical parameters of the flow field. The research elucidates the variety rule of the pressure along the VMFPD and the energy gradient function K as well as the time-frequency features of the pressure pulsation (PP) in the impeller and guide vane. The results demonstrate that the solid wall restriction of the guide vane and the impeller rotation cause a significant shift in the velocity and direction of the water flow. This causes a significant pressure difference between the water bodies, which makes it easier to create an unstable flow. The suction surface of the impeller blade possesses the great concentration of the area with energy gradient function K > 107, which is the critical area influencing the internal flow stability of the pump device.

MRI Evaluation and Characterization of Ovarian Lesions Based on Ovarian-Adnexal Reporting and Data System MRI.

Background Managing ovarian lesions requires differentiating between benign and malignant cases. The development of a multiparametric MRI approach combining anatomical and functional criteria has led to the creation of the Ovarian-Adnexal Reporting and Data System (O-RADS) MRI scoring system, which enhances diagnostic accuracy. Objectives To study ovarian lesions and their characteristics, along with their risk stratification based on MRI O-RADS. Methods A prospective study used the O-RADS MRI criteria to categorize ovarian lesions. Clinical findings and MRI results were compared with histopathological outcomes to assess diagnostic accuracy. Results We identifiedabdominal pain as the most prevalent clinical finding among our cases (64, 91.43%), followed by a lump in the abdomen (33, 47.5%), dysmenorrhea (33, 47.5%), bleeding per vaginal (15, 21.43%), and weight loss (11, 15.71%). A total of 80 ovarian lesions were examined and characterized on the basis of the O-RADSMRI risk stratification system.Among the 80 ovarian lesions, 54 were histopathologically confirmed ovarian lesions (39 (72.22%) were benign, and 15 (27.77%) were malignant). The most common benign lesions were ovarian serous cystadenoma (28.20%) and ovarian mucinous cystadenoma (20.51%), while the most common malignant lesions were serous carcinoma (33.33%) and mucinous carcinoma (20%). Using the O-RADS MRI scoring system, we categorized six lesions (7.5%) as O-RADS 1 (all benign), 34 lesions (42.50%) as O-RADS 2 (32 benign and 2 malignant), 24 lesions (30%) as O-RADS 3 (23 benign and 1 malignant), seven lesions (8.75%) as O-RADS 4 (four benign and three malignant), and nine lesions (11.25%) as O-RADS 5 (all malignant). Our findings revealed significant differences in the size of lesions, the presence of thick septa, high T2-weighted signal intensity within solid tissue, and patterns of solid component enhancement and wall irregularity between malignant and benign lesions. The MRI cut-off score of ≥4 for malignancy demonstrated a sensitivity of 94.59%, a specificity of 97.5%, an accuracy of 97.62%, a positive predictive value of 94.5%, and a negative predictive value of 97.5%. The positive likelihood ratio was 32.7, while the negative likelihood ratio was 0.025. These results affirm the high diagnostic accuracy of the O-RADS MRI scoring system in distinguishing benign from malignant ovarian lesions. Conclusion The O-RADS MRI score is a highly accurate tool for differentiating between benign and malignant ovarian lesions. Its application can significantly enhance the management and treatment outcomes for patients with adnexal masses. The study confirms the scoring system's high sensitivity, specificity, and overall diagnostic accuracy.

A formulation for fluid–structure interaction problems with immersed flexible solids: Application to splitters subjected to flow past cylinders with different cross-sections

In the finite element method framework, a fluid–structure formulation is developed by coupling an Eulerian fixed-mesh fluid approach with a Lagrangian deforming-mesh description for a flexible solid. The coupled formulation is solved using a staggered scheme during time. For the fluid solution stage, the solid walls are considered as a time-variable internal boundary. The velocity and pressure fields are obtained by solving the weak form of the fluid dynamic equations in which the solid velocity is imposed on the internal boundary via a penalization term. For the solid solution stage, the displacement field is obtained by solving the discrete solid dynamic equations which consider traction forces computed by integrating pressures and viscous stresses on the nodes belonging to the solid walls. This novel technique is firstly applied to analyze a flexible splitter under the shedding of a flow past square cylinder due to this problem is considered as a benchmark in the literature. The present solutions agree with those computed using body-fitted techniques, thus validating the proposal. Secondly, flexible splitter motions under the shedding of flow past cylinders with different cross-sections and splitter lengths are comprehensively studied. Overall, the computed results confirmed that the hydrodynamic coefficients on the cylinders were reduced because of the presence of the splitter.

Thermal and hydraulic characteristics of a single reverse nanofluid jet in a double-wall cooling configuration

AbstractThis work investigates the thermo-hydraulic characteristics of a novel reverse jet impingement cooling 3-D module for high-power systems, entailing a single jet impinging upon a concave hemispherical surface within a double-wall cooling configuration. Water-based nanofluids, with Al2O3 and multi-wall carbon nanotubes (MWCNT), were subject to a comprehensive examination at a range of Reynolds numbers from 10,000 to 40,000. The computational framework utilized the volume of fluid (VOF) model for precise phase interface tracking, along with the $$k-\omega$$ k - ω SST turbulence model. The results demonstrated that nanofluids have remarkable heat transfer enhancement, compared to water. The maximum Nusselt number augmentation reached 61.76% and 77.47% for 2.0% Al2O3 and 0.04% MWCNT nanofluids, respectively. The thermal performance improved when escalating nanoparticle concentration and Reynolds numbers, reaching a cooling module’s thermal resistance of only 0.0266 K W−1. However, mild increments in pressure drop of up to 7.80 and 3.04% were noticed at the lowest Reynolds number for the two nanofluids, respectively. MWCNT nanofluids exhibited superior thermal enhancement over their Al2O3 counterparts despite their lower concentrations. The greatest combined thermo-hydraulic performance was attained with a 0.04% MWCNT nanofluid at a Reynolds number of 20,000, where the energy performance was boosted by 77%, compared to water. The study identified significant conjugate heat transfer effects, demonstrating how temperature gradients within the solid walls directly influenced heat transfer coefficients and thermal resistances within the fluid phase. These findings provide a deeper understanding of thermal management strategies for high-power systems. Graphic abstract

Blood transport without solid walls

In this paper, a blood microfluidic transport system without solid pipe wall is introduced, and the transport process of the microfluidic transport system is simulated by using the transient simulation of unidirectional flow of blood non-Newtonian fluid, two-phase flow of blood-magneto-fluid. The microfluidic transport system is verified to reach a flow rate of 40 ml/min by comparing the parameter flow rate, drag reduction factor (DR), velocity, and drop pressure with those of a conventional microfluidic system, and it also proves that the magneto-fluidic liquid pipe wall not only improves the transport efficiency of the blood, but also can better control the speed and flow rate size. At the same time, it reduces the loss of the blood in the process of delivery and guarantees the quality of the transported blood.

Thermodynamic analysis and equilibration response time prediction of recuperator in the SCO2 Brayton cycle

The recuperator of supercritical carbon dioxide (SCO2) Brayton cycle significantly affects the system's flexible control due to its thermal inertia. In this study, the structural parameters and operating parameters of recuperator are considered to quantitatively analyze the law of their influence on equilibration response time. Chebyshev spectrum method has been innovatively applied to the one-dimensional dynamic response model of recuperator. The dynamic response time of recuperator under the condition of temperature variation on the hot side is analyzed. The results show that reducing the thermal inertia of solid wall (by increasing the specific surface area of recuperator) can effectively decrease the equilibrium time. Additionally, the rate of inlet temperature variation should not be too large to reduce the thermal inertia of fluid. The zigzag channel demonstrates better dynamic response characteristic than straight channel. A novel dimensionless formula, based on structure and operating parameters, is proposed to quantitatively characterize and predict the equilibrium time for both straight and zigzag channel, the error is within ±20 %. Moreover, a high-precision neural network is trained to predict the equilibrium time directly. The results provide significant theoretical and application support for alleviating the thermal inertia of PCHE and improving the flexibility of SCO2 system.

Hygrothermal assessment of three bio-based insulation systems for internal retrofitting solid masonry walls

The present project investigated the hygrothermal performance and risk of mould growth in solid masonry walls retrofitted internally with three diffusion-open bio-based insulation materials (two loose-fill cellulose and one hemp fibre), installed in test containers with controlled indoor climate. Focus was on bio-based insulation materials, as these are upcoming due to necessary CO2 reductions and because the hygroscopic properties of bio-based materials are different from traditional insulation materials like mineral wool therefore, some manufacturers claim a vapour barrier is unnecessary, even in relatively cold climates. The project was a large experimental study in two reefer containers with reconfigured facades, in which solid masonry walls with embedded wooden elements were constructed. The study focused on the conditions in the masonry/insulation interface and in the embedded wooden elements. The effect of hydrophobization and different indoor moisture loads were also investigated. Moreover, the bio-based insulation systems were compared with a wall insulated with the traditional mineral wool and vapour barrier system. Relative humidity and temperature were measured at several locations in the test walls for 1 year and 9 months. Measurements show that exposed masonry walls retrofitted internally with diffusion-open bio-based insulation materials resulted in unacceptably high moisture levels (>80% RH over longer periods). Lower moisture levels were observed when the internal insulation was combined with hydrophobization against wind-driven rain, but unacceptably high moisture levels still occurred (60%–70% in summer and 95%–100% in winter in the interface). Hydrophobization reduced the moisture levels in the interface and embedded wooden elements only in walls facing southwest, which is the direction with the most wind-driven rain. Mould growth tests showed no growth in the interface in walls insulated with cellulose insulation (mycometer surface value <25). Meanwhile growth was found in all four walls insulated with hemp fibre matts (mycometer surface value >400).

Topographic variation and fluid flow characteristics in rough contact interface

Understanding flow characteristics of fluid near rough contact is important for the design of fluid-based lubrication and basic of tribology physics. In this study, the spreading and seepage processes of anhydrous ethanol in the interface between glass and rough PDMS are observed by a homemade optical in-situ tester. Digital image processing technology and numerical simulation software are adapted to identify and extract the topological properties of interface and thin fluid flow characteristics. Particular attention is paid to the dynamic evolution of the contact interface morphology under different stresses, the distribution of microchannels in the interface, the spreading characteristics of the fluid in contact interface, as well as the mechanical driving mechanism. Original surface morphology and the contact stress have a significant impact on the interface topography and the distribution of interfacial microchannels, which shows that the feature lengths of the microchannels, the spreading area and the spreading rate of the fluid are inversely proportional to the load. And the flow path of the fluid in the interface is mainly divided into three stages: along the wall of the island, generating liquid bridges, and moving from the tip side to the root side in the wedge-shaped channel. The main mechanical mechanism of liquid flow in the interface is the equilibrium between the capillary force that drives the liquid spreading and viscous resistance of solid wall to liquid. In addition, the phenomenon of “trapped air” occurs during the flow process due to the irregular characteristics of the microchannel. This study lays a certain theoretical foundation for the research of microscopic flow behavior of the liquid in the rough contact interface, the friction and lubrication of the mechanical system, and the sealing mechanism.

Stress Responses in Horses Housed in Different Stable Designs during Summer in a Tropical Savanna Climate.

Single-confinement housing can pose welfare risks to domestic horses. This study investigated horses' stress responses when confined to single stalls in different stable designs in a tropical savanna region to address a gap in the literature. In total, 23 horses were assigned to a stable with a central corridor and solid external walls (A) (N = 8), a stable with one side corridor and solid external walls (B) (N = 6), or a stable with a central corridor and no solid external walls (C) (N = 9). Air velocity, relative humidity, air temperature, and noxious gases were measured inside the stables, and the heart rate and HRV of the horses were also determined. The relative humidity was lower in stable C than in stable A (p < 0.05), while the air temperature was higher in stable C than in stable B (p < 0.05) during the day. The airflow and ammonia levels were higher in stable C than in stables B and A (p < 0.01-0.0001). Overall, horses' HRV in stable A was lower than in those in stables B and C (p < 0.05-0.01). Horses in stable A tended to experience more stress than those in other stables.

Solid and Homogeneous Thermal Wall of Cored Lightweight Concrete Blocks Solidarized in situ

Abstract: The exterior walls of buildings play a major role in the road for a near-zero energy building. Nowadays, in Portugal, the ETICS system is the most used technology to ensure the thermal insulation of exterior walls of buildings. However, the ETICS system has low resistance to impacts and requires a self-supporting sheet of wall, among other disadvantages. Here, the concept of new technology for exterior walls of residential and commercial buildings is presented. It consists of a hybrid technology for the easy and quick execution of a single sheet wall, which may provide high thermal efficiency for buildings. This hybrid technology relates to parallelepipedshaped cored lightweight concrete blocks comprising two parallel sides separated by one or more solid connectors in which the connectors allow the filling of the block core with lightweight concrete. No bed or head joints are used to connect the blocks because the wall made of cored blocks gets solid and homogeneous when filled with lightweight concrete. When the block thickness is 30 cm and the thermal conductivity of the lightweight concrete is lower than 0.09 W/m.ºC, in Portugal, this type of exterior wall does not require the application of extra thermal insulation materials.

Seismic behavior of a hollow precast concrete shear wall with insulation under high axial compression ratios

A hollow precast concrete shear wall (HPCSW) with multiple vertical hollow cores that is advanced in lightweight and thermal insulation is studied in this paper. Novel tapered grouted sleeves (TGSs) are developed to connect the adjacent shear walls, which can avoid grouting defects through visible grouting processes. Seven full-size specimens with an aspect ratio of 3.3, including three solid precast shear walls, three hollow precast shear walls, and a cast-in-place (CIP) shear wall, were subjected to cyclic loading tests, which considered different and high axial compression ratios (ACRs) of 0.3, 0.45, and 0.6. The results show that the solid precast shear wall with the TGS connection displays comparable failure mode and seismic behavior with the CIP one. In contrast, the HPCSW suffers hollow core crushing under high ACRs, leading to a significant reduction in deformation and energy dissipation capacity. Finally, numerical models of HPCSW specimens with different layouts of the hollow cores were established using ABAQUS to evidence the test results and optimize the structure. The results show that the configuration of the outer hollow cores influences the seismic behavior of the HPCSW vastly. It is recommended that the concrete is partially filled into the outer hollow cores to obtain good insulation and seismic capacity simultaneously, with the filling height greater than the predicted crushing height.

Parameter sensitivity of a wood chips flow model

AbstractA computational fluid dynamics (CFD) study of the parameter sensitivity of a wood chips model was performed on an industrial impregnation vessel, which is the first step in a continuous cooking system. The solid and liquid phases were both treated as continua and it was found that the continuum model for the solid wood chips phase could capture the previously observed oscillating formation of arches in the contracting part of the vessel, which will occur at different levels of volume fraction depending on the material constants. The parameters that were examined are the solid pressure, permeability, viscosity, and wall friction. It was found that all the parameters strongly affect the distribution of the wood chips in the vessel as well as the oscillation effects, hence also the flow field which is important to accurately predict in order to ensure optimal performance of the impregnation vessel. Thus, correct material data for these types of simulations are crucial to the outcome and should be chosen for the appropriate situation and bio‐material.

Influence of an inclined thick partition on free convection heat transfer performance under surface radiation in a hollow block

In the present work, a computational analysis of the combined energy transfer by free convection, radiation, and heat conduction in 2D hollow block with an inclined partition was carried out. The inclined partition was made of a heat-conducting material and had a finite thickness. The closed space inside the brick was filled with air (Pr = 0.71) and the airflow is laminar. The external surfaces of the vertical borders are considered to be isothermal, and the remaining horizontal surfaces are supposed to be adiabatic. The finite difference technique is employed to work out numerically the differential equations. The in-house computational code was verified in detail using various problems. The major characteristics that determine the considered phenomena are surface emissivity of internal walls, Ra number, and material of solid walls and partition. As a result of the research, the distributions of streamlines and isotherms combined with the average Nusselt numbers were obtained. Depending on the material of the partition, the flow structure in the cavity changes significantly, which reflects the distribution of streamlines, namely, for the materials with low thermal conductivity the convective cell in the upper part of the cavity is elongated, while in the lower part it is shifted to the lower and left borders. The isotherms reflect the more intensive heating in the left part of the area. With an increase in the thermal conductivity coefficient, the streamlines reflecting the nature of the flow are restructured. It was shown that the presence of an inclined partition significantly reduces the intensity of convective heat transfer.

Regression analysis of MHD conjugate natural convection of ferrofluid filled within a porous annular enclosure with inner heat generating solid cylinder using response surface methodology

Utilizing response surface methodology, this work gives a thorough numerical evaluation of ferrofluid’s conjugate magnetohydrodynamic (MHD) natural convective flow within a porous annular chamber. The system is made up of an inner solid cylinder that generates heat and is subjected to an external magnetic field, which causes Joule heating effects. To explain the conservation equations for momentum and energy, the research uses a finite element method and systematically changes important parameters. By adjusting these factors, we may study how changes affect thermal performance, flow patterns, and the Nusselt number. The findings show a complex interplay between magnetohydrodynamics, Joule heating, and the effects of porous media, offering important clues for improving thermal management and energy efficiency in state-of-the-art MHD systems. Incorporating a response surface methodology (RSM) is a significant innovation in this work. Results reveal that the increment in the thermal conductivity of the solid wall upsurges the fluid velocity and the rate of convective heat transfer. There is a significant difference in the value of the local Nusselt number as the values of the thermal conductivity of the solid wall increase. Adding nanoparticles to the dusty fluid makes the flow stronger, but also improves heat transmission significantly.

Kármán Street-Boundary Layer Interactions In Turbulent Flow

Understanding the intricate interplay between turbulent boundary layers and wake structures caused by obstacles in the flow is key to assessing the local shear stress fields as well as the drag. These types of flows can be relevant to natural phenomena including sediment and nutrient transport. While existing literature predominantly explores the flow downstream of cylinders mounted perpendicular to bounding surfaces or downstream of cylinders positioned outside the boundary layer region, this work experimentally studies the turbulent boundary layer passing over a cylindrical obstacle positioned near and parallel to the surface of an underlying solid wall. Planar particle image velocimetry (PIV) was performed in an open recirculating water channel for three test cases at a friction Reynolds number Reτ = 1320. Key parameters investigated include the cylinder diameter relative to the boundary layer thickness (D/δ = 0.09 and 0.01) and the gap between the cylinder and the wall (G/δ = 0.09), where the range of D/δ used is smaller than most examples found in the literature. Instantaneous and averaged velocity and vorticity fields are examined based on the PIV measurements. The results in Fig. 1 show how von Kármán vortex streets and turbulent boundary layer structures interact to form unique flow features. The larger cylinder generates a clear separation downstream of its axis as well as a wake that remains coherent over a distance δ downstream. The smaller cylinder with D/δ = 0.01 generates a much narrower and weaker wake, but still shows a clear influence on time-averaged velocity profile. Future experiments will evaluate flow conditions further downstream as well as additional values of G/δ for the same D/δ values.

Unsteady electroosmotic flow of Carreau–Newtonian fluids through a cylindrical tube

The present study aims to investigate the fully developed electroosmotic flow of Carreau–Newtonian fluids within a circular tube, considering two different boundary conditions of zeta potential. The unsteady behavior of Carreau–Newtonian fluids, is attributed to the pulsatile pressure-driven flow. Studying two distinct formulations, slip and no-slip zeta potentials, illustrates the relative movement of fluid particles and the charged surface. The proposed study’s framework is divided into two regions: a central region containing a non-Newtonian Carreau fluid exhibiting both shear-thinning and thickening behavior, and a peripheral region containing a Newtonian fluid with the effect of an electrical double layer at the solid wall of the cylindrical tube. The Poisson–Boltzmann equation under the assumption of Debye–Hückel approximation governs the potential distribution due to the electric double layer, facilitating the examination of electroosmotic flow through tube. Obtaining analytical solutions for the momentum equations in both regions becomes challenging due to the inclusion of pulsatile pressure-driven flow and a non-Newtonian Carreau fluid. Asymptotic series expansions are employed, utilizing small parameters such as the Weissenberg number (We≪1) and a pulsatile Reynolds number (α≪1), to derive velocity expressions for both regions. Wall shear stress fluctuations, as indicated by time-averaged wall shear stress and oscillatory shear index are assessed to gauge the temporal variation of wall shear stress from the dominant blood flow direction. By utilizing potential and hydrodynamic variables, an asymptotic formulation for the streaming potential is developed to ascertain the asymptotic expression of electrokinetic energy conversion efficiency and scrutinize the impacts of pertinent physical parameters on it. The proposed study prominently shows that the Debye–Hückel parameter, Weissenberg number, pulsatile Reynolds number, and time-dependent pressure gradient significantly influence the fluid velocity, flow rate, and flow resistance. The notable determination of the present study is that the velocity amplitude and electrokinetic energy conversion efficiency are enlarged in the slip-dependent case relative to the no-slip zeta potential. It is noteworthy that as inertial forces become more prominent compared to viscous forces, both time-average wall shear stress and oscillatory shear index experience a slight decrease, although the reduction in oscillatory shear index is minimal owing to the absence of obstruction within the tube wall. The NDSolve numerical scheme in Mathematica software is employed to calculate numerical solutions for the governing equations, which are subsequently verified against results obtained through asymptotic analysis. The findings of this study are expected to deepen our understanding of unsteady electroosmotic flows of Carreau fluid and contribute to the design and development of advanced microfluidic devices with enhanced performance for various applications.

A Heterogeneous Viscosity Flow Model for Liquid Transport through Nanopores Considering Pore Size and Wettability.

The confinement effect in micro- and nanopores gives rise to distinct flow characteristics in fluids. Clarifying the fluid migration pattern in confined space is crucial for understanding and explaining the abnormal flow phenomena in unconventional reservoirs. In this study, flow characteristics of water and oil in alumina nanochannels were investigated with diameters ranging from 21 nm to 120 nm, and a heterogeneous viscosity flow model considering boundary fluid was proposed. Compared with the prediction of the HP equation, both types of fluids exhibit significant flow suppression in nanochannels. As the channel size decreases, the deviation degree increases. The fluid viscosity of the boundary region displays an upward trend as the channel size decreases and the influence of the interaction between the liquid and solid walls intensifies. The thickness of the boundary region gradually decreases with increasing pressure and eventually reaches a stable value, which is primarily determined by the strength of the interaction between the liquid and solid surfaces. Both the pore size and wettability are essential factors that affect the fluid flow. When the space scale is extremely small, the impact of wettability becomes more pronounced. Finally, the application of the heterogeneous flow model for permeability evaluation has yielded favorable fitting results. The model is of great significance for studying the fluid flow behavior in unconventional reservoirs.

Conjugate heat transfer analysis of developing region of square ducts for isothermal and isoflux boundary conditions

Purpose This paper aims to present a comprehensive analysis of conjugate heat transfer phenomena occurring within the developing region of square ducts under both isothermal and isoflux boundary conditions. The study involves a rigorous numerical investigation, using advanced computational methods to simulate the complex heat exchange interactions between solid structures and surrounding fluid flows. The results of this analysis provide valuable insights into the heat transfer characteristics of such systems and contribute to a deeper understanding of fluid–thermal interactions in duct flows. Design/methodology/approach The manuscript outlines a detailed numerical methodology, combining computational fluid dynamics and finite element analysis, to accurately model the conjugate heat transfer process. This approach ensures both the thermal behaviour of the solid walls and the fluid flow dynamics are well captured. Findings The results presented in the manuscript reveal significant variations in heat transfer characteristics for isothermal and isoflux boundary conditions. These findings have implications for optimizing heat exchangers and enhancing thermal performance in various engineering applications. Practical implications The insights gained from this study have the potential to influence the design and optimization of heat exchange systems, contributing to advancements in energy efficiency and engineering practices. Originality/value The research introduces a novel approach to study conjugate heat transfer in square ducts, particularly focusing on the developing region. This unique perspective offers fresh insights into heat transfer mechanisms that were previously not thoroughly explored.