Heat Transfer Mechanism Research Articles

Heat transfer analysis in hydromagnetic two‐phase Williamson fluid through tilted channel: Applications of gold and silver nanoparticles in solar thermal energy

AbstractThe heat transfer analysis in Poiseuille hydromagnetic multiphase flow of Williamson fluid suspended by gold and silver nanoparticles is discussed through the inclined channel under the impact of no‐slip boundary conditions. The present conducted research is novel as no one has explored the heat transfer analysis in the fluid‐particle suspension model of electrically conducting Williamson fluid mixed with gold and silver nanoparticles through steeply inclined channel. The highly nonlinear complex partial differential equations are transformed into simplified form by using the appropriate dimensionless transformation then obtain the analytical solution by adopting the regular perturbation method. The perturbation solution is also compared with the numerical solution. The velocity and temperature profiles are significantly affected by Hartmann number. Approximately 19% (gold suspension) and 20% (silver suspension) increment is observed in fluid phase and particle velocities respectively. The multiphase flow of non‐Newtonian (Williamson) fluid provides greater heat transfer to the system with the suspension of gold (10%) and silver (13%) nanoparticles as compared to multiphase Newtonian fluid with these suspensions. The heat transfer rate of multiphase flows is greater than single‐phase flows. The current study will help to understand the flow and heat transfer mechanism of two‐phase flows with the suspension of gold and silver nanoparticles through inclined parallel plates under the impact of the constant magnetic field. Further, the current study can help to design modern solar cell devices to store more solar energy due to the low heating release of considered nanoparticles. The present research is original and has not been conducted before.

Numerical simulation of a non-Newtonian nanofluid on mixed convection in a rectangular enclosure with two rotating cylinders

Non-Newtonian fluid flows are a present advancement in industrial heat transfer and fluid mechanics, with numerous applications in engineering field as well as in real life such as food industry, petroleum refiners, biological processes, biomedical engineering, chemical engineering, etc. As a result, this numerical investigation explore the heat transfer and fluid flow behaviour of a mixed convective non-Newtonian power-law nanofluid ( Al 2 O 3 - H 2 O ) in a rectangular enclosure. The physical model is considered as a two-dimensional rectangular enclosure consisting two rotating hot cylinders ( T H )in the middle part of the cavity, where one moving clockwise and the other counter-clockwise directions. The left and right walls of the chamber are taken relatively low temperature ( T C ) while the remaining top and bottom walls are insulated. The important thermophysical property, viscosity, depends on the fluid shear rate, and the thermal conductivity depends on the fluid temperature. The related governing equations are solved by using the finite element method, and to describe the response surfaces the response surface methodology (RSM) is applied. The influence of the relevant non-dimensional parameters, Prandtl number ( Pr = 6.2 ), Reynolds number ( Re = 10 , 100, 200 and 400), power-law index (n = 0.6, 0.8, 1.0 and 1.4), Richardson number ( Ri = 1.0 , 2.0, 4.0 and 6.0), and nanoparticle volume fraction ( ϕ = 0.00 , 0.01, 0.02 and 0.04), are explained with physical interpretation by using streamlines, isotherm lines, velocity profile, temperature profile, and average Nusselt number ( Nu av ). To visualise the response surfaces, 2D and 3D contour plots are explained using the RSM. It is concluded that by adding nanoparticle into base fluid, the rate of heat transfer developed significantly. Same phenomena exhibits for larger magnitudes of Ri and Re . And, by increasing the value of n from 0.6 to 1.4, the Nu av would go down by 39.8 percent.

The Numerical Simulation Study on the Heat Transfer Mechanism in Heavy Oil Reservoirs During In-Situ Combustion

The escalating energy demand has prompted nations to prioritize the development of high-viscosity and challenging-to-extract heavy and extra-heavy oil reserves. Consequently, the technique of in-situ combustion in oil reservoirs by injecting air to ignite heavy oil resources, leveraging the generated heat to enhance recovery rates, is a particularly critical extraction method. However, simulation studies of in-situ combustion techniques are still primarily conducted at a macroscopic level. Therefore, conducting more detailed numerical simulation studies holds significant importance. This paper establishes a mathematical model for heat transfer within reservoirs during in-situ combustion, thoroughly investigating the effects of inlet temperature, injection pressure, injection duration, and porosity on the heat transfer processes inside the reservoir. The research demonstrates that the reservoir’s internal temperature gradually rises as the injection duration increases. Additionally, porosity (an increase from 0.1 to 0.3 enhances the heat propagation rate by 15%) and injection pressure (an increase from 5 MPa to 8 MPa boosts the heat propagation rate by 25%) significantly affect the heat transfer rate.

Thermal conductivity and heat transfer mechanism of epoxy composites constructing by carbon fiber felt with three‐dimensional layered structure

AbstractThe preparation of lightweight polymer‐based composites with high thermal conductivity is an urgent requirement for thermal management applications. In this work, carbon fiber felt (CFF) with three‐dimensional (3D) layered structure was firstly prepared based on papermaking method. Then, high in‐plane thermal conductivity (TC) Epoxy resin/graphitized carbon fiber felt (Epoxy/G‐CFF) composites were prepared by graphitized CFF with different layers under vacuum assistance. The effect of graphitization on the thermal property was investigated, and the practical heat transfer behavior was analyzed. The results show that the Epoxy/G‐CFF composites exhibit the highest in‐plane thermal conductivity of 1.88 W/mK at 8.5 wt% loading, which is 889.47% higher than that of pure Epoxy. It represents the achievement of enhancing the thermal performance of polymer‐based composites with low additions. More importantly, the composites still exhibit low density and strong thermal management capability. This suggests that Epoxy/G‐CFF composites have promising applications in the thermal management field.Highlights The carbon fiber felt (CFF) with three‐dimensional (3D) layered structure was firstly prepared based on papermaking method. The graphitization process significantly increases the grain size and shortens the layer spacing, contributing to the comprehensive properties of G‐CFF. The Epoxy/G‐CFF composites exhibit the highest in‐plane thermal conductivity of 1.88 W/mK at 8.5 wt% loading.

Heat transfer mechanism for Newtonian and non-Newtonian casson hybrid nanofluid subject to thermophoresis and Brownian motion over a movable wedge surface

Heat transfer mechanism for Newtonian and non-Newtonian casson hybrid nanofluid subject to thermophoresis and Brownian motion over a movable wedge surface

Analysis of an unsteady mucus flow through an isothermal channel with thermal conduction: An analytical solution

The human body regularly produces mucus, and its presence does not mean that something bad is going on. The boundary tissues of mammals, including the nose, throat and lungs, serve as a barrier against pollution and are produced by our respiratory system. Our work describes the flow comprehension of the components moulding the fluid elements of respiratory irresistible infections. A mathematical model is introduced to concentrate on the mucus fluid flow driven by natural convection through asymmetric channel. This study also summarized biological disorder of human lung build-up fluid. The nonlinear governing equations contain importance of heat transfer and fluid motion of mucus fluid. The analytic solutions of unsteady mucus flow through an isothermal channel with thermal conduction are accomplished adopting Laplace transform method. Significance of mucus fluid heat source thermal conductivity on momentum distribution and energy distribution is enumerated. The comparison of various dimensionless parameters is shown graphically with the help of MATLAB software. In order to provide some understanding on the behavior of mucus fluids and heat transfer mechanisms, extension of this study explores at how temperature influences mucus flow properties.

Особенности формирования синтетических изображений радиометрических величин в ИК области спектра

Physically correct synthetic images of 3D scenes in a given wavelength range are of great importance in solving some applied problems. Such data generation is based on a physical interactions modelling, including electromagnetic radiation propagation in a scene space. This paper presents the results of a ray tracing mechanism development in a 3D scene modeling software package. An algorithm for calculation radiative heat transfer that allows accounting a radiation from multiple bodies in the scene is proposed. In order to be executed on graphical processors it is implemented in form of shader programs. Each emitted ray, which simulates the propagation of an electromagnetic wave, undergoes no more than two interactions with bodies and makes an addition to an observed area radiation in a number of photons given wavelengths range and solid angle. To evaluate the algorithm a number of model scenes were proposed, on which comparative study was carried out in case of infrared region modeling. As results show, taking into account the mechanisms of radiative heat transfer allow for qualitative improvement of the resulting images and makes a significant contribution to the background signal.

Coating V2O5@NaV6O15 Nanofibers with PPy Toward Prominent Sensitivity, Thermal Dissipation, Electromagnetic Protection, Waterproofing, and Mechanical Properties

AbstractExcellent mechanical flexibility, thermal conductivity, and microwave absorption are essential properties for multifunctional materials applied in next‐generation wearable electronics. However, it remains a great challenge to improve the incompatibility among these properties. Herein, high‐quantity V2O5@NaV6O15@PPy core‐shell nanofibers (CSNFs) are synthesized via a simple dissolution‐recrystallization and in situ redox polymerization process. Owing to regular, periodic, and stable sensing signals, their membrane can serve as a strain sensor to accurately detect word pronunciation and body movement. Their TPU films possess high strength, excellent hydrophobicity, and large thermal conductivity (3.56 W m−1 K−1); 7 wt.% load. Besides, the CSNFs exhibit efficient wide‐band microwave absorption (8.56 GHz) and RCS reduction (24.41 dBm2) at a low load (7 wt.%), outperforming most other absorbers. The boosted performance can be ascribed to their 1D structure with multiple heterostructures and abundant defects, which generate conductive loss, diverse polarizations, multiple microwave scattering, and the cooperative heat transfer of electrons and phonons. Further analyses reveal their heat transfer and dielectric loss mechanisms based on the density of states, electric field distribution, and the phonon density of states. Overall, the V2O5@NaV6O15@PPy CSNFs are promising as multifunctional materials for applications in wearable strain sensing, thermal management, EM protection, and Radar stealth, particularly in extreme environments.

Simulation of heat and mass transfer of peanut pods in combined hot air–radio frequency

To study the drying mechanism of peanut pods with combined hot air–radio frequency, this article applied numerical simulation to study the heat and mass transfer of peanut pods and verified the validity of the simulation with the experiment. Results demonstrated that the heat and mass transfer model was capable of effectively simulating the peanut pod thin-layer drying process. The experimental and simulated dehydration rates of peanut pods were 5.87%/h and 5.89%/h, respectively; the experimental and simulated dehydration rates of peanut kernels were 5.40%/h and 5.39%/h, respectively; the experimental and simulated dehydration rates of peanut shells were 7.66%/h and 7.49%/h, respectively. The maximum discrepancy between the simulated and experimental values for the moisture content of peanut pods, peanut kernels, and peanut shells were 7.06%, 5.84%, and 8.14%, respectively. The maximum discrepancy between the simulated and experimental values of surface temperature and internal temperature was 3.6 °C and 5.16 °C, with the minimum difference being 1.3 °C and 0.25 °C, respectively. This article explored the heat and mass transfer mechanism of the peanut pod in combined hot air–radio frequency drying process. It provides technical and theoretical guidance for accurately predicting the different moisture content of peanut pods.

Computational Behavior of Trihybrid Casson Nanofluid Blood Flow Occurring Inside the Conical Gap Between the Rotating Disk and the Cone

The investigation of the flow patterns of a trihybrid nanofluid flow situated in the conical gap that is created among a revolving disc and a stationary cone computationally examined in this study. Three different types of nanoparticles, Al2O3, TiO2 and Ag are examined with blood as the base fluid according to flow properties and energy phenomenon. While discussing the heat transfer mechanism in trihybrid nanofluid flow crossing through the disc and cone, four different types of cases are explored likewise the disc and cone may be rotating at the same rate or at different rates, or one may be stationary about the other. The numerical scheme is planted to observe the fluid flow and heat transfer patterns. In the current article, we investigated rheological parameters, including rotating speed, cone angle, and concentration of nanoparticles, and the effect of heat transfer performance over velocity and temperature patterns. The results shed light on the complex interactions between the geometric and nanofluid characteristics, providing useful information for fluid dynamics and thermal management applications. This fluid model is also useful for the study of blood pressure, arthritis, brain therapy, and malignant tumors. The graphs are plotted using the MATLAB program BVP4C to ensure convergence. Several variables, such as a magnetic parameter, Prandtl's number, and Reynold's number, have an impact on temperature and velocity profiles. It is evident that the amalgamation of the fraction of three nanoparticles reduces the velocity and enhances the temperature of the nanofluid. The momentum boundary layer expands when the cone and disc rotate in the same direction.

Computational Behavior of Trihybrid Casson Nanofluid Blood Flow Occurring Inside the Conical Gap Between the Rotating Disk and the Cone

The investigation of the flow patterns of a trihybrid nanofluid flow situated in the conical gap that is created among a revolving disc and a stationary cone computationally examined in this study. Three different types of nanoparticles, Al2O3, TiO2 and Ag are examined with blood as the base fluid according to flow properties and energy phenomenon. While discussing the heat transfer mechanism in trihybrid nanofluid flow crossing through the disc and cone, four different types of cases are explored likewise the disc and cone may be rotating at the same rate or at different rates, or one may be stationary about the other. The numerical scheme is planted to observe the fluid flow and heat transfer patterns. In the current article, we investigated rheological parameters, including rotating speed, cone angle, and concentration of nanoparticles, and the effect of heat transfer performance over velocity and temperature patterns. The results shed light on the complex interactions between the geometric and nanofluid characteristics, providing useful information for fluid dynamics and thermal management applications. This fluid model is also useful for the study of blood pressure, arthritis, brain therapy, and malignant tumors. The graphs are plotted using the MATLAB program BVP4C to ensure convergence. Several variables, such as a magnetic parameter, Prandtl's number, and Reynold's number, have an impact on temperature and velocity profiles. It is evident that the amalgamation of the fraction of three nanoparticles reduces the velocity and enhances the temperature of the nanofluid. The momentum boundary layer expands when the cone and disc rotate in the same direction.

Numerical study of convective heat transfer between core and steam generator in severe accident with loss of heat removal to secondary side of VVER reactors

The article discusses the possibility of overheating and failure of heat exchanging tubes in VVER steam generators in the course of severe accidents. The importance of this phenomenon is due to the risk of bypassing the containment by radioactive substances. Natural convection of superheated steam in the hot leg of the main circulation loop is considered as the major mechanism for heat transfer from the core to steam generators. To model convective flows and steam temperature distribution in a system, three-dimensional CFD codes are used. The simulation results demonstrate that the intensity of convective heat transfer from reactor to hot collector of steam generator is insufficient for significant heating and catastrophic degradation of strength of the heat exchange tubes material.

Design, Characterization, and Evaluation of Textile Systems and Coatings for Sports Use: Applications in the Design of High-Thermal Comfort Wearables.

Exposure to high temperatures during indoor and outdoor activities increases the risk of heat-related illness such as cramps, rashes, and heatstroke (HS). Fatal cases of HS are ten times more common than serious cardiac episodes in sporting scenarios, with untreated cases leading to mortality rates as high as 80%. Enhancing thermal comfort can be achieved through heat loss in enclosed spaces and the human body, utilizing heat transfer mechanisms such as radiation, conduction, convection, and evaporation, which do not require initial energy input. Among these, two primary mechanisms are commonly employed in the textile industry to enhance passive cooling: radiation and conduction. The radiation approach encompasses two aspects: (1) reflecting solar spectrum (SS) wavelengths and (2) transmitting and emitting in the atmospheric window (AW). Conduction involves dissipating heat through materials with a high thermal conductivity. Our study focuses on the combined effect of these radiative and conductive approaches to increase thermal energy loss, an area that has not been extensively studied to date. Therefore, the main objective of this project is to develop, characterize, and evaluate a nanocomposite polymeric textile system using electrospinning, incorporating graphene oxide (GO) nanosheets and titanium dioxide nanoparticles (TiO2 NPs) within a recycled polyethylene terephthalate (r-PET) matrix to improve thermal comfort through the dissipation of thermal energy by radiation and conduction. The textile system with a 5:1 molar ratio between TiO2 NPs and GO demonstrates 89.26% reflectance in the SS and 98.40% transmittance/emittance in the AW, correlating to superior cooling performance, with temperatures 20.06 and 1.27 °C lower than skin temperatures outdoors and indoors, respectively. Additionally, the textile exhibits a high thermal conductivity index of 0.66 W/m K, contact angles greater than 120°, and cell viability exceeding 80%. These findings highlight the potential of the engineered textiles in developing high-performance sports cooling fabrics, providing significant advancements in thermal comfort and safety for athletes.

Effect of fracture parameters on the thermal recovery performance of enhanced geothermal system

ABSTRACT Enhanced geothermal system (EGS) is an effective method for extracting thermal energy from Hot Dry Rock (HDR) reservoirs. Fracture characterization determines the pathways for fluid flow and the mechanisms of heat transfer, both of which exert a substantial influence on the thermal recovery performance of EGS. This study develops a two-dimensional discrete fracture thermal-hydraulic (TH) coupled numerical model to investigate the influence laws of fracture characteristic parameters on the thermal recovery performance of EGS. The reliability of the numerical model is verified by comparison with the analytical method. Moreover, the Morris method is employed to evaluate the extent to which various system parameters affect the output temperature of EGS. The findings indicate that when the fracture opening expands from 0.5 mm to 3 mm, the output temperature decreases from 120.75°C to 94°C, while electrical output power increases; When the fracture permeability increases from 1 × 10−9 m2 to 4 × 10−9 m2, the output temperature drops by 30.7%, but the electrical output power increases by 0.98 MW. That is, with higher fracture opening and permeability, the fluid will flow inside the fracture with higher velocity, leading to a reduction in the output temperature of EGS and an increase in electrical output power; Injection temperature holds the greatest influence on the system, while the system’s output temperature demonstrates insensitivity to the variation of rock permeability.

Unraveling Temperature Distribution Within Crystalline Silicon PV Modules by Different Finite Element Method‐Based Thermal Modeling Approaches

AbstractIn this work, the steady‐state spatial temperature distribution in commercial high‐efficiency crystalline silicon PV modules is studied using different FEM‐based thermal models that encompass conductive, convective, and radiative heat transfer mechanisms. The results show that the lateral temperature distribution within the PV module depends on the module inclination angle and may be highly inhomogeneous, with a temperature difference of ≈5 °C between its warmest and coolest solar cells. Furthermore, It is demonstrated that wind plays a crucial role in determining the operating temperature of PV devices. Specifically, it is shown that forced convection has an even more significant positive effect at higher wind speeds and larger PV module dimensions since the transformation of laminar to turbulent wind contributes to additional cooling. Finally, the power losses associated with the lateral temperature variations across the PV module are analyzed. The results show that the effect of temperature inhomogeneity plays a negligible role in the performance of standard single‐junction silicon PV modules due to a very small temperature coefficient of the solar cell short‐circuit current.

Numerical analysis of the energy efficiency measures for improving the truck cabin thermal performance

This paper presents the numerical analysis of the thermal performance of a truck cabin. The results obtained for a standard truck cabin setup are compared to the configurations with energy saving measures implemented. As a very promising energy efficiency measure, the application of the infrared panels is considered. Based on the radiative heat transfer mechanism, the infrared panels influence directly all inner cabin surfaces. This includes also the truck cabin occupants, whose perception of the indoor comfort reaches neutral values much faster and at lower ambient air temperatures. As a result, there is much lower energy demand for the cabin heating, required for maintaining the desired indoor comfort. The preliminary numerical analysis indicates the energy saving potential of around 30% for this innovative cabin thermal concept, as compared to the original energy demand for the traditional cabin heating configuration.

A fluorescence approach for assessing the composition of evaporating droplets

Accurate measurement of chemical composition is vital for understanding heat and mass transfer mechanisms in two-phase flows like sprays. This Letter presents an optical method based on laser-induced fluorescence and fluorescence lifetime measurement. While solvatochromism—shifts in the emission and absorption spectra based on solvent type that alter fluorescence intensity—is well-documented for many fluorescent dyes, fluorescence lifetime offers distinct advantages for two-phase flow applications. Unlike intensity-based methods, lifetime measurements exhibit greater resilience to light attenuation and scattering at liquid/gas interfaces and allow for more flexible detection band selection. The technique leverages the fluorescence lifetime of eosin Y, which is sensitive to solvent polarity while remaining unaffected by temperature—a crucial feature for systems with fluctuating temperature and composition. We validate this method using acoustically levitated droplets, showing that eosin Y's fluorescence lifetime can reliably distinguish components in binary mixtures like ethanol/water and isopropanol/water. The high volatility of ethanol and isopropanol causes significant cooling during droplet vaporization, leading to water condensation from the surrounding air. This approach enables detailed analysis of complex evaporation and condensation dynamics.

Heat Transfer Mechanism Study of an Embedded Heat Pipe for New Energy Consumption System Enhancement

Aiming at the demand for new energy consumption and mobile portable heat storage, a gravity heat pipe with embedded structure was designed. In order to explore the two-phase heat transfer mechanism of the embedded heat pipe, CFD numerical simulation technology was used to study the internal two-phase flow state and heat transfer process of the embedded heat pipe under different working conditions. The evolution law of the internal working medium of the heat pipe under different working conditions was obtained. With the increase in heating power, it is easier to form large bubbles and large vapor slugs inside the heat pipe. When the heating power increases to a certain extent, the shape of the vapor slugs can no longer be maintained at the bottom of the adiabatic section, and the vapor slugs begin to break and merge, forming local annular flow. When the filling ratio (FR) is relatively low, the bubble is easy to break through the liquid level and rupture, unable to form a vapor slug. With the increase in FR, the possibility of projectile flow and annular flow in the heat pipe increases. Under the same heating power, the temperature uniformity of the heat pipe becomes stronger with the increase in heating time. The velocity distribution in the heat pipe is affected by the FR. The heating power has almost no effect on the distribution of the velocity field inside the heat pipe, but the maximum velocity is different. At an FR of 30%, there are two typical velocity extremes in the tube near positions of 120 mm and 160 mm, respectively, and the velocity in the tube is basically unchanged above a position of 200 mm. There are also multiple velocity extremes at an FR of 70%, with the maximum velocity occurring near 240 mm.

Mechanisms of Separation of the Elastic Step and the Thermal Step

AbstractThe elastic interaction causes a two‐step conversion from the low‐spin (LS) to the high‐spin state (HS) following a femtosecond laser pulse excitation. These steps occur on different timescales: a spin conversion (elastic step) in a short time due to pressure propagation and a late spin conversion (thermal step) resulting from heat diffusion. In this paper, we provide a brief review of models for spin crossover phenomena, emphasizing the role of the difference of degeneracy of the HS state and LS state and elastic interaction due to changes in local structures. We also review theoretical approaches to these effects. Additionally, to analyze the dynamical process of spin conversion after photo‐irradiation, it is necessary to consider mechanisms of heat transfer among spins. Recently, we proposed a two‐temperature model that incorporates both lattice and spin temperatures, which enables us to reproduce the two steps under an early uniformization of the lattice temperature, highlighting the importance of the timescales of these processes. Furthermore, we explore possible mechanisms to separate the two steps by examining the different timescales of processes of spin conversions by mechanical and entropic forces, and also by considering changes of local temperature due to spin conversion.

Study on the total pressure and total temperature distortion of axial flow compressor based on different rain ingestion forms

Aero-engines are required to maintain stable operation under adverse weather conditions, such as heavy rain ingestion. Excessive water ingestion can significantly impact the aerodynamic performance of compressor, potentially leading to performance degradation and even stall. Current investigations reveal that rain ingestion causes losses in both total pressure and total temperature, contributing to the overall deterioration of the performance of compressor. However, these theoretical findings lack robust experimental validation, and the precise relationship between total pressure and temperature losses, alongside the heat and mass transfer mechanisms within the two-phase flow field inside the compressor, remains to be fully established. In this study, a comprehensive experimental and numerical investigation is conducted on a 1.5-stage compressor to assess the effects of water ingestion on compressor performance and internal flow characteristics with varying droplet size distributions and liquid water content (LWC). The results demonstrate that key performance indicators, such as total pressure ratio, efficiency, and the compressor’s stable operating range, are influenced by LWC, droplet size, and the spatial distribution of water ingestion at the inlet. Water ingestion induces non-uniformities in both total pressure and total temperature, with the extent of these distortions governed by factors such as droplet size, concentration, and ingestion patterns across different stages of the compressor. Specifically, increasing water ingestion rates and a concentrated droplet distribution exacerbate total pressure distortions, while simultaneously mitigating total temperature distortions due to the saturation of water vapor. Furthermore, the location and extent of the distorted regions are also influenced by these parameters.