Heat Transfer Rate Research Articles

Selected Physical and Mechanical Properties of Alpaca Fibers Differing in Color

ABSTRACT Demand for alpaca fiber is subject to an increase, which is due to its beneficial properties. The study aimed to determine the differences in physical and mechanical properties, as well as heat insulation properties of alpaca fibers differing in color. The research material consisted of Huacaya alpaca fiber samples of white (W), light fawn (LF), medium fawn (MF), dark fawn (DF), and black (BLK) colors. The following properties were examined: diameter, comfort factor (CF), breaking force, elongation at break, tenacity and heat transfer rate. The finest fibers were found in W and DF fleece, while the coarsest ones in MF. CF was the highest in DF fibers. Breaking force LF varied between 6.4 (DF) and 11.7 cN (BLK), while elongation at break was 43.6 (LF) to 54.7% (BLK). No significant differences were found in case of tenacity. The best insulation properties were found for DF fibers. Correlations were confirmed between diameter and mechanical properties, and they differed slightly depending on colors.

Improving phase change heat transfer in an enclosure partially filled by uniform and anisotropic metal foam layers

Anisotropic metal foams exhibit exceptional potential for improving the efficiency of latent heat thermal energy storage (LHTES) units by enhancing heat transfer and thermal energy storage rates. This study explores the largely uncharted area of thermal behavior of anisotropic metal foams in varied configurations and enclosure designs. The research focuses on an LHTES unit with a specific channel configuration, constructed using copper and containing three layers of copper metal foam, one of which is anisotropic and infused with paraffin wax. The finite element method was utilized to manage the complexities emerging from phase change, and the anisotropic angle varied from 0 to 90° in three different placements of the AMFL: top, middle, or bottom of the enclosure. The ideal design was achieved with an AMFL in the middle with a 0°angle, resulting in a 3.7 % reduction in melting time and approximately a 2.3 % reduction in solidification time. However, AMFL designs at the middle placement with a 75° anisotropic angle were less effective, hampering the melting and solidification processes, thus potentially extending charging and discharging times. The study concludes that the placement and angle of the AMFL layer are vital for the heat transfer capabilities of phase change materials. AMFL at the middle with a 0° angle optimally leverages temperature gradients, enhancing heat transfer compared to other investigated cases. An AMFL in the middle with a 0° angle exhibits approximately 7.1 % and 6.3 % improvements for melting fractions of 0.9 and 0.95, respectively, underscoring its potential for efficient thermal energy storage.

Exploration of Heat Transfer Rate and Chemically Reactive Bio-convection Flow of Micropolar Nanofluid with Gyrotactic Microorganisms

Exploration of Heat Transfer Rate and Chemically Reactive Bio-convection Flow of Micropolar Nanofluid with Gyrotactic Microorganisms

Optimizing of a metal foam-assisted solar air heater performance: a thermo-hydraulic analysis of porous insert placement.

A numerical assessment of the heat transfer efficacy of a solar air heater (SAH) was carried out. The SAH is supplied with a porous metal foam layer to improve thermal mixing. Both the local thermal non-equilibrium (LTNE) and Darcy-extended Forchheimer (DEF) models were employed to forecast fluid and thermal transport within the partly filled SAH channel. The analysis was performed for various values of dimensionless foam layer lengths ( ), pore densities ( ), and Reynolds numbers ( ) at a fixed value of layer thickness ( ). Based on the position of the porous layer, three distinct arrangements, marked as Case 1, Case 2, and Case 3, were explored. Regarding the parameters examined, the findings indicate a definite improvement in the average Nusselt number ( ), but unfortunately, the friction factor also increases unfavorably. By reducing the length of the porous layer, a reasonable reduction in heat transfer rate and a significant decrease in pressure drop were noticed. The results showed about 26.64%, 48.73%, and 70.74% reductions in pressure drop by reducing the dimensionless foam length from 1 to 0.25, 0.5, and 0.75 respectively for at . On the other side, there are only about 11.05%, 23.11%, and 40.78% reductions in . The exhaustive analysis of the thermal performance of SAH was conducted using the thermal performance factor (TPF), which considers the trade-off between the SAH channel's potential for improved heat transmission and its cost for pressure loss. The TPF may reach a maximum of 2.82 compared to the empty channel when the metal foam layer is inserted with , for , and .

Bridging theory and practice: CFD simulation and interactive VR for conduction heat transfer learning

AbstractSoftware simulation programs and virtual reality (VR) have become powerful tools for several educational purposes, and recently, they were used in a wide range of applications. In cases of inaccessibility to labs, workshops, or industries, as happened before in the coronavirus disease 2019 pandemic, these tools could be effectively integrated with practical lab experiments. In this study, a computational fluid dynamics (CFD) simulation and a VR module were utilized to simulate heat transfer by conduction through various experimental cases. The CFD simulation results were obtained using ANSYS/FLUENT software. Meantime, the experimental data were obtained by carrying out three experiments of heat conduction with different heat transfer rates through simple, composite, and different cross‐sectional area bars. At last, the experimental procedure and devices used were virtually constructed using SolidWorks software as three‐dimensional models, which were then extruded into VR and augmented reality models. It was found that the simulation results closely align with the experimental ones, and the temperature profile in both cases has the same behavior with small differences, which indicates the validity of the developed module to be used as a simulation of the actual experiments. In addition to improving knowledge of heat transfer principles, this combination of simulation and VR technology advances many Sustainable Development Goals (SDGs), including advancing quality education (SDG 4) and innovation in higher education (SDG 9). Additionally, this method assists in achieving the course learning objectives by mimicking real‐world lab experiments, guaranteeing that students graduate from the course with the required information and abilities.

Numerical analysis of non-linear radiative Casson fluids containing CNTs having length and radius over permeable moving plate

Abstract Casson fluids containing carbon nanotubes of various lengths and radii on a moving permeable plate reduce friction and improve equipment efficiency. They improve plate flow dynamics to improve heat transfer, particularly in electronic cooling and heat exchangers. The core objective of this study is to investigate the heat transmission mechanism and identify the prerequisites for achieving high cooling speeds within a two-dimensional, stable, axisymmetric boundary layer. This study considers a sodium alginate-based nanofluid containing single/multi-wall carbon nanotubes (SWCNTs/MWCNTs) and Casson nanofluid flow on a permeable moving plate with varying length, radius, and nonlinear thermal radiation effects. The plate has the capacity to move either parallel to or perpendicular to the free stream. The governing partial differential equations for the boundary layer, which are interconnected, are transformed into standard differential equations. These equations are then numerically solved using the Runge–Kutta fourth-order scheme incorporated in the shooting method. This research analyses and graphically displays the effects of factors including mass suction, nanoparticle volume fraction, Casson parameter, thermal radiation, and temperature ratio. Additionally, a comparison is made between the present result and the previous finding, which presented in a tabular format. The coefficient of skin friction decreases in correlation with an increase in Casson fluid parameters and Prandtl number. Heat transfer rate decreases with a variation in viscosity parameter, while it is increasing with an increase in Prandtl number. In addition, this study demonstrates that heat transfer rate for MWCNT is significantly higher than that of SWCNT nanoparticles. Thermal radiation and temperature ratio reduce the heat transfer rate, whereas nanoparticle volume fraction and Casson parameter enhance it over a shrinking surface.

Compact heat pipe heat exchanger for waste heat recovery within a low-temperature range

Heat pipe heat exchangers (HPHX) are attracting attention for being capable of effective heat exchange through phase change. Much waste heat is generated at low-temperature sources, but there has been a lack of research on this. Most previous studies focus on large HPHXs over 1 m in length. In the present study, a compact HPHX (185 × 70 × 140 mm3) with nine heat pipes was fabricated, and the potential for waste heat recovery (WHR) was investigated at low heat sources. Also, the thermal performance of the HPHX was compared with and without the fin of the heat pipe. Experiments were conducted by changing the hot-side gas temperatures (50, 75, 100, and 125 °C) and mass flow rates (0.03, 0.04, and 0.05 kg/s). The heat transfer rate and pressure loss had a linear relationship with the hot-side temperature and mass flow rate. Despite a low temperature 50 °C, more than 100 W of heat can be recovered using a compact HPHX. At least 1.8 times improved thermal performance was obtained in HPHX in which finned heat pipes were installed. These results are expected to serve as indicators for various applications that generate low-temperature waste heat, such as clothes dryers and kitchen hoods.

Fractional Analysis of Magnetohydrodynamics Maxwell Flow Over an Inclined Plate with the Effect of Thermal Radiation

This current study provides a comprehensive examination of a novel method for studying the dynamics of a fractionalized Maxwell flow near an inclined plate, considering non-uniform mass transfer through a permeable media. Through the use of partial differential equations, incorporating heat and mass movement effects, the study employs a combination of generalized Fick’s and Fourier’s law with the Caputo operator. Transforming the fractionalized model into dimensionless form using appropriate dimensionless values, semi-analytical solutions for the non-dimensional transmitted fractional model are obtained via the Laplace transformation method. Through graphical analysis, the precise contributions of key parameters such as heat generation, radiation, and chemical reactions are elucidated, including their impacts on the calculated heat generation parameter (Qo), radiation parameter (Nr), and others. The study’s significance lies in its implications for the design of efficient heat exchangers, fluid flow systems, and cooling components in complex engineering systems, including nuclear reactors and power generation plants. Furthermore, the fractional derivative approach offers a more accurate representation of the viscoelastic behavior of materials like polymers, crucial for optimizing fabrication processes such as extrusion and molding. The insights gained from this study extend to the realm of miniaturized fluidic devices, including bio-analysis tools, lab-on-a-chip technology, and microfluidic drug delivery systems, where improved performance and control need a grasp of Maxwell fluid dynamics. The physical outcome of this research lays the groundwork for future investigations that will maximize heat transfer efficiency in real-world systems and give insightful information on the behavior of complicated fluids. We compute and display the skin friction, mass and heat transfer rate in tabular form.

Effects of rotational speed on transient cooling performance of nozzle spray with liquid nitrogen in a rotor-stator cavity

This paper presents the results of an experimental investigation into the cooling performance of a rotor-stator cavity with liquid nitrogen spraying. The experiments were conducted under varying rotational Reynolds numbers ranging from 1.70 × 106 to 5.12 × 106. The effects of rotational speed on temperature drop rate are studied and compared in detail, as well as the heat transfer coefficient distribution. Sufficient data, such as heat flux, injection rate, and injection pressure, were collected to provide a basis for further study in explaining the spray and evaporation over the cavity. It was found that the cooling performance of the rotating disc is strongly affected by the rotational speed. The short-term period exhibits a peak cooling rate of 14°C/s, in contrast to the sustained cooling rate during the spray process at rotational speeds of 500r/min, which amounts to 0.9°C/s. The occurrence of cavitation and evaporation within the nozzle results in a reduction of flow coefficient and fluctuation of the injection differential pressure. The transient cooling performance is well-explained by the temperature changes and cooling-down time under different rotational speeds. The analysis of the heat transfer coefficient is further enhanced through an evaluation of the convective and conductive heat transfer rates using a one-dimensional theoretical approach. The average temperature of the disc is expected to decrease by 100°C within a time frame no longer than 120 s. Additionally, after a duration of 120 s, the average heat transfer rate on the cold side is anticipated to surpass 8000 W/(m·K).

Analytical and numerical investigation for viscoelastic fluid with heat transfer analysis during rollover-web coating phenomena

Abstract The current study theoretically and computationally analyses the viscoelastic Sisko fluids during the non-isothermal rollover web phenomenon. The mathematical modeling produces a system of partial differential equations, which we further simplify into ordinary differential equations through appropriate transformations. We have formulated the problem based on the lubrication approximation theory. The solution has been obtained with the perturbation method, and the outcomes are found in mathematical, tabular, and graphical forms that highlight the influence of pertinent parameters on velocity profiles, pressure gradients, flow rates per unit width, Nusselt number, pressure profile, temperature distributions, and other significant engineering quantities. Further, A comparative analysis between analytic and numerical solutions, utilizing the middefer method in the Maple environment, demonstrates reasonable agreement. Also, we observe that the fluid parameter significantly influences both velocity and temperature profiles. Moreover, the determination of a separation point 2.5000, accompanied by the observation of a maximum coating thickness of 0.6960. The enhancement in fluid heat transfer rate is approximately 5% compared to non-Newtonian fluid parameter values, with potential for further improvement by increasing the non-Newtonian parameter values. This comprehensive investigation offers valuable insights for practical implementation and future scholarly endeavors, with zero-order findings showcasing enhanced precision.

Thompson and Troian slip effect on ternary nanofluid flow over a stretching surface influenced by induced magnetic field and surface catalyzed reaction

This research scrutinizes the impact of the Thompson and Troian slip effect on a two-dimensional flow of ternary nanoliquid induced by an extending sheet near a stagnation point. Nanoparticles Iron oxide (Fe2O3), Nickle Zinc ferrite (NiZnFe2O4), and Magnesium zinc iron oxide (MnZnFe2O4) are dispersed in Ethylene glycol (C2H6O2) to establish ternary nanofluid. The induced magnetic field influences the flow, and the analysis of heat and mass transfers takes into account the Cattaneo–Christov (C–C) heat flux with homogenous–heterogeneous (H–H) reactions, respectively. To expedite the reaction, a surface-catalyzed process is introduced to efficiently control both (H–H) reactions within a reduced time frame. Utilizing the Tiwari and Das framework, the fluid flow characteristics are elucidated. Appropriate transformations are applied to derive ordinary differential equations (ODEs), which are then numerically deciphered via the bvp4c scheme. Graphs are portrayed to highlight the consequence of non-dimension quantities on the flow and temperature profiles. The surface drag coefficient and heat flux rate are also assessed and summarized. Outcomes revealed that for large estimates of the velocity slip parameter, the surface drag coefficient is enhanced while the heat flux rate is reduced. It is also interesting to note that because of the high estimations of ferromagnetic nanoparticles, the rate of heat transfer is elevated significantly. The validation of the proposed model is also included.

Peristaltic transport of diethylene glycol-based magnesium aluminate nanofluid under the effects of viscous dissipation and Hall current

ABSTRACT The fundamental importance of peristaltic phenomena in numerous biological systems, including dialysis, heart-lung machines, urine transportation, invertebrate locomotion, and the passage of gallbladder bile into the intestines, persuaded scientists to investigate the different aspects of it over the past few years. In addition, peristaltic pumping is an important consideration in industrial processes including, roller pumps used for the transport of sanitary materials, finger pumps, cell separation, and endoscopes. Keeping such inspirational applications in mind, the present investigation is dedicated to exploring the peristaltic transport of a Cross-magneto nanofluid through a curved geometry in the presence of heat transfer. The inspection of the heat transfer is conducted by utilizing variable viscosity and ohmic heating aspects. This study also retains the characteristics of viscous dissipation, heat generation/absorption, and thermal conductivity of nanofluids. Modeling of the 2D, incompressible Cross nanofluid with peristaltic movement is carried out using a curvilinear coordinate system. The basic equations of the problem are mPodeled in the light of physical laws and then simplified by adopting the lubrication theory. The solutions of the resulting nonlinear system are computed numerically. The outcomes of the related flow parameters on the nanofluid’s temperature, pressure gradient, velocity distribution, heat transfer, streamlines pattern, and stresses at the wall are discussed through graphs. The graphical results depict that the rates of heat transfer are augmented by increasing the curvature parameter, Hartmann number, and nanoparticles’ volume fraction while decreasing the Hall parameter and temperature-dependent viscosity parameter. Moreover, the nanofluid’s temperature increases by improving the values of the heat generation parameter, whereas it decreases for the Hall parameter. Furthermore, a reduction in the axial velocity occurs near the center of the channel, when Hartmann number attains higher values.

Consequences of Thermal Diffusion and Chemical Reaction on Mixed Convection MHD Casson Fluid through Porous Media with Inclined Plates

In this present article, we analyzed the effects of Thermal diffusion and chemical reaction on nonlinear mixed convection MHD flow of viscous, incompressible and electrically conducting fluid past an inclined porous channel under the influence of thermal radiation and chemical reaction. The transformed conservation equations are solved analytically subject to physically appropriate boundary conditions by using two term perturbation technique. The numerical values of fluid velocity, fluid temperature and species concentration are displayed graphically whereas those of skin friction coefficient, rate of heat transfer and rate of mass transfer at the plate are presented in tabular form for various values of pertinent flow parameters. It is observed that the velocity is decreased with increasing magnetic field parameter. The resultant velocity and concentration has enhances with increasing thermal diffusion parameters. The study is relevant to chemical materials processing applications.

Local entropy generation optimization and thermodynamic irreversibility analysis of oval-shaped coaxial ground heat exchangers: A detailed numerical investigation

Optimizing the heat transfer and thermodynamic efficiency of Ground Heat Exchangers (GHE) is crucial for maximizing the energy efficiency of Ground-coupled Heat Pump (GCHP) systems utilized in building heating and cooling applications. This study pioneers an effective approach of both the first and second laws of thermodynamics of the newly oval-shaped coaxial GHEs (oval-CGHEs), assessing heat transfer, thermohydraulic performance, and local entropy generation rate to explore the optimum design and operational conditions for heat exchange maximization and entropy generation minimization. Utilizing a three-dimensional numerical model validated by experimental results, this study examines the trade-offs between heat transfer improvements and entropy generation rate intensification of the oval-CGHEs in comparison to the typical circular-shaped CGHE (circle-CGHE) further than exploring the effect of key operational and design parameters and performing sensitivity analysis. The results reveal that oval-CGHEs exhibit higher irreversibility as a penalty for their superior heat transfer capabilities compared to traditional circular-shaped CGHEs (circle-CGHE), which can be mitigated by optimizing the position of the inner tube. Moreover, the study underscores the criticality of maintaining a balance between enhanced heat transfer and the associated rise in irreversibility, particularly concerning the factors of mass flow rates and installation depths.

Effect of connection methods on hygrothermal performance of prefabricated concrete building walls

With the ongoing surge in global energy demand and the escalating environmental concerns, attention has turned to building energy consumption in numerous countries. According to a 2019 report by the International Energy Agency (IEA), the global building industry is responsible for 36 % of energy consumption, ranking first among all industries. The 2022 China Building Energy Consumption and Carbon Emissions Research Report highlighted that in 2020, China's building energy consumption and carbon emissions represented 45.5 % and 50.9 % of the national total, respectively. Achieving carbon neutrality now hinges on decarbonizing buildings. Prefabricated buildings, as a prime example of industrialized construction, aid in reducing carbon emissions through standardized, factory-based production. However, unlike conventional construction, prefabricated concrete buildings (the dominant form of prefabricated buildings) employ metal connectors to join the prefabricated components. These metal connectors generate thermal bridges that can influence heat and moisture transfer through the walls. In this study, a coupled heat and moisture transfer model will be established to analyze the influence of different connection methods on the hygrothermal performance in prefabricated concrete building envelopes. Two typical connection methods for prefabricated buildings are mainly investigated: the grouted sleeve connection and the bolted connection. The findings indicate that different connection methods for prefabricated building connectors increase both the heat and moisture transfer rates in prefabricated concrete structures. Compared to the grouted sleeve connection method, the bolt connection method has a more significant impact on the thermal and moisture performance of the wall. In the tests on the T-shaped structure, the grouted sleeve connections increase heat transfer by 9%–10 %, while the bolt connections increase it by 52%–55 %. During summer, the bolt connections show a 7.42 % higher moisture transfer than the grouted sleeve connections, whereas, in winter, the bolt connections reduce moisture transfer by 12.4 % more than the grouted sleeve connections.

A Comparative study of flow and C[sbnd]C heat flux over a magnetic field under the influence of nanomaterial and carbon nanotubes

The aim of this study is to investigate convective heat transfer on a flat surface in the presence of magneto-hydro-dynamic (MHD) flow. The analysis considers the Darcy-Forchheimer porosity medium in the flow. The study focuses on analyzing the heat transfer rate, incorporating joule heating and convective-conductive heat flux effects. The influence of varying fluid properties on the flow behavior is examined. The governing flow equations are initially expressed as partial differential equations (PDEs) and then transformed into ordinary differential equations (ODEs) using appropriate similarity transformations. The numerical method RKF-45 is employed to solve these ODEs. The results highlight the impact of different parameters in the model. It is observed that a higher Darcy parameter leads to a decrease in fluid velocity. Additionally, the performance of carbon nanotubes is superior compared to MoS2 nanoparticles in this study.

Mixed Convection Flow of a Casson Fluid Past a Thin Needle

Mixed Convection Flow of a Casson Fluid Past a Thin Needle

Experimental investigation of the effects of graphene nano particle added water fluid on heat transfer in a smooth tube with double inserts

In this study, experimental studies were carried out to increase the performance of heat exchangers. The effects of two techniques (inserts and nanofluid) on thermohydraulic performance was investigated simultaneously. The twisted tape and the helically wire coil were originally created. The two separation ratios (0.1 and 0.05), the eight twisted tape pitch ratios (1.9/2.3/2.7/3 and 2.1/2.4/2.8/3.2), the four coil wire pitch ratios (0.8/1.2/1.5/1.6) and three weight fractions (0.5/0.75/1 %) for graphene-water nanofluids were used with the Reynolds number ranging from 5000 to 26,000. Experiments in which a coiled wire coil and twisted tape are used together have been found to increase both the heat transfer rate and the friction factor compared to experiments using distilled water in an empty tube. According to the results of all experiments, it was found that the highest heat transfer rate and friction factor were obtained with the model containing graphene-water fluid used at a weight fraction of 1 %. The highest performance evaluation criteria is found as 2.5 b y using the graphene-water mixture model with a wall separation ratio of 0.05, a twisted tape ratio of 2.1, a wire coil ratio of 0.8 and a 1 % weight fraction among all combinations.

Experimental Study of Thermal Contacts for the Enhancement of Interfacial Heat Transfer

Abstract The thermal management in high-performance electronic devices demands the enhanced rate of heat dissipation for controlling operational temperatures and achieving optimal functioning. There are many interfaces in the heat dissipation circuit where thermal interface materials are applied to enhance heat transfer rate. An experimental investigation is presented on metallic contacts to study the interfacial heat transfer with and without a thermal interface material. Thermal contact conductance is known to be an important parameter estimated for the analysis of interfacial heat transfer across the thermal contacts. Therefore, the thermal contact conductance has been evaluated to identify an effective thermal interface material suitable for the present range of contact pressure and heat flux conditions. Silicone grease is a widely used thermal interface material in electronic industry. Thus, commercially available Silicone grease is evaluated in different boundary line thicknesses for a range of contact pressure and mean interface temperatures. Further, a novel composite thermal paste has been prepared by mixing cupric oxide nanopowder and Silicone grease in three different mass concentrations. Eventually, the results for the new thermal paste showed improved thermal contact conductance and lower interfacial temperature drops as compared to Silicone grease for similar test conditions with few limitations.

Enhancement of thermal energy transfer behind a double consecutive expansion utilizing a variable magnetic field

This research focuses on utilizing non-uniform magnetic fields, induced by dipoles, to control and enhance thermal energy transfer in a two-dimensional cooling conduit including a double backward-facing step. The presence of electronic equipment along the straight channel path creates such arrangements, and cooling is often ineffective in the corners of the formed steps. The use of a non-constant magnetic field is a passive technique to improve the cooling rate in these sections without changing the internal geometry, thereby increasing the heat transfer rate. A commercial software based on the finite volume technique is employed to solve the governing equations of fluid flow and heat transfer. Multiple parameters are examined in this study, including the flow Reynolds number (12.5–50), dipole location and strength (0.1–5 A-m), and the number of dipoles (single or double). The results indicate that all of these parameters have a significant impact on the thermal energy transfer. The results of the study show that a single dipole increase the average heat transfer by about 22%, two magnetic fields by 40%, the strength of the magnetic source by 24% with respect to the non-magnetic field in the present study.