Average Convective Heat Transfer Research Articles

Drying characteristics of bamboo bundles and the heat transfer model

To optimize the drying process of bamboo bundles, this study investigates the heat and mass transfer behavior during the drying process by using temperature sensors to measure the temperature field at different positions and track the overall moisture content over time. Additionally, a heat transfer model is used to simulate and predict the drying process. The analysis of the experimental results indicates that the diameter of the bamboo bundles has a greater impact on the drying rate than the drying temperature. At the same temperature, the drying time significantly decreases as the temperature increases. Under drying conditions at 80 °C, the average drying rate constant is 0.072 for bamboo bundles with a diameter of 40 mm, whereas it is only 0.015 for bundles with a diameter of 100 mm. Using Newton’s law of cooling, the convective heat transfer coefficient calculation method was derived. The average convective heat transfer coefficients at 40, 60, and 80 °C were calculated to be 6.16 W/(m2 K), 7.14 W/(m2 K), and 7.22 W/(m2 K), respectively. A mathematical model was established for the temperature at the center of the bamboo bundles, the temperature of the drying medium, the diameter of the bamboo bundles, and the drying time. This model effectively simulates the temperature variation inside the bamboo bundles, and the temperature simulation data fits well with the measured values, with a standard error of less than 2.8 °C and a prediction error of less than 6.1%. This coupled model and method provide a theoretical basis for predicting and controlling the bamboo bundle drying process, reducing energy and time consumption in actual production.

Numerical investigation of natural convection from a horizontal heat sink with an array of rectangular fins

This research focuses on the numerical analysis of a rectangular fin array with a horizontal heat sink to examine its performance in natural convection heat transfer. The study uses air as the primary working medium. Steady-state 3D modeling is carried out using the finite volume method (FVM), allowing velocity and temperature distributions to be evaluated by solving equations relating to mass conservation, fluid dynamics, turbulence, and heat transfer. This research details temperature and velocity variations as well as fluid trajectories. It also explores how the intensification of heat flow, varying from 361 W/m2 to 2527 W/m2, influences the cooling efficiency of the fins. It is observed that the increase in heat flux reduces the formation of vortices and intensifies natural convection by rising the temperature gradient between the radiator and the surrounding. The temperature increases at all parts of the heat sink fin array as heat flux increases. Besides, it is noticed that the maximum temperature is generated at the mid-region of the base plate heat sink and gradually dissipates to the surroundings through the bodies of the fins. Moreover, the study indicates that the average convection heat transfer coefficient (hav) and the average Nusselt number (Nus) increase by 86 % and 84 %, respectively, when the heat flux is increased from 361 W/m2 to 2527 W/m2. These observations are corroborated by a comparison with existing experimental data, showing an agreement of less than 9 %. The digital model is validated by comparing pre-existing data on radiators with horizontal rectangular louvers, revealing minimal deviations of less than 2 %.

Performance analysis and optimization of the Gyroid-type triply periodic minimal surface heat sink incorporated with fin structures

The Triply Periodic Minimal Surface (TPMS) structures demonstrate substantial value and development potential in applications and research concerning heat sinks and heat exchangers. To further enhance the convective heat transfer performance of TPMS, this study proposes a novel method of incorporating fin structures into TPMS. This method is applicable to various types of TPMS, and the new structure constructed using this method is termed “TPMS with Fin Structures (TFS).” Subsequently, a TFS-Gyroid heat sink based on the Gyroid-type TPMS was constructed. This study presents a calculation method for the fin height in TFS-Gyroid (HTFS-Gyroid). Numerical simulation methods were employed to investigate the influence and mechanism of HTFS-Gyroid on the convective heat transfer performance and flow resistance of the TFS-Gyroid heat sink model, with air as the working fluid and under constant wall temperature (100 °C) conditions. The results indicate that within the flow range of 24–120 L/min, as HTFS-Gyroid increases from 0 to 1.6 mm, the average surface convective heat transfer coefficient (h̅) of the TFS-Gyroid heat sink model increases by 27.4 %-34.6 %, and the inlet–outlet pressure drop (ΔP) increases by 42.5–632.8 Pa. As HTFS-Gyroid increases, the PEC of the TFS-Gyroid heat sink model gradually decreases, whereas j/f gradually increases. The primary mechanisms by which the fin structures enhance the convective heat transfer performance of the TFS-Gyroid heat sink are: 1) increased heat exchange area, 2) the fin structures induce a large number of longitudinal vortices and secondary flows within the flow channels, and 3) the formation of “Fins Occupying the Perforated Structure (FOPS)” within the flow channels.

Experimental study on convection heat transfer properties in rough-walled fractures of granite: The effect of fracture roughness

The fracture-dominated convection heat transfer behavior is commonly involved in the development, utilization and storage of thermal energy in fractured rock engineering. An experimental system assembled by a peristaltic pump drive, a liquid preheater and an electric blast drying oven is developed to quantify the effect of fracture roughness on the convection heat transfer characteristics. The overall heat transfer coefficient (OHTC) and the amount of heat transfer quantity from six fracture samples with different inlet temperatures and flow rates are calculated by the data acquisition at five observation points. In general, the average convective heat transfer efficiency between water and rock decreases gradually with time, and then enters a stage of thermal equilibrium while the temperatures at the five observation points become constant. The increasing flow rate can lead to the gradual increase of the OHTC and the slowdown of its growth rate. The OHTC is negatively correlated with the inlet temperature. With the increase of fracture surface roughness, the dominant flow effect is significantly enhanced, which leads to the weakening of heat transfer characteristics and the gradual reduction of OHTC. Finally, the heat transfer quantity decreases with the increase of roughness, and exists an inflection point with the flow rate.

Enhancing heat transfer in rectangular solar air heater channels: a numerical exploration of multiple Boomerang-shaped roughness elements with variable gaps

ABSTRACT In the current study, numerical investigations are carried out to enhance the convective heat transfer rate in a solar air heater embedded with multiple boomerang-shaped roughness. The boomerang roughness is attached to the absorber plate which is supplied with uniform heat flux. The boomerang roughness geometry is defined by the ratios of height to hydraulic diameter (e/Dh) at 0.09, pitch space to height (P/e) of 10.5 to 18, and the gap between the multiple boomerang arm (g) at 8.5 to 13.1 mm. These parameters are examined for turbulent flow conditions having Reynolds number (Re) ranging from 4000 to 22,000. Heat transfer and friction characteristics in the present work are defined and examined by nondimensional parameters Nusselt number (Nu) and friction factor (fr), respectively. The study compared Nusselt number and friction factor readings to measurements of a smooth channel under similar flow conditions. It compared friction and the Nusselt number coefficient to a smooth rectangular channel and a rough, purposely rough channel. The aim was to determine better heat transfer and reduced friction. The study found that the average Nusselt number (Nu/Nus) and convective heat movement were 3.39 times higher at g = 8.5 mm (θ = 90º) compared to g = 10.9 mm (θ = 80º) and 13.1 mm (θ = 70º) at p = 71. mm and Re = 22,000. The lowest Nu/Nus was 1.75 times for g = 13.1 mm and p = 71.3 mm at Re = 4000. Thinner boundary layers increased the average Nusselt number and convective heat transfer coefficients in systems with smaller gaps. The design model has a maximum THPP = 1.93 at a pitch space between roughness (p = 71.3 and P/e = 15.5, where e = 4.6 mm), gap (g = 8.5), and Re = 22,000.

Analysis and optimization of the heat transfer behavior in the melt-spinning process of Nd-Fe-B ribbons

Heat transfer plays a significant role on the quality of Nd-Fe-B ribbons in the melt-spinning (MS) process. In this paper, the heat transfer behavior in the MS process of Nd-Fe-B ribbons was investigated by experiment and simulation. A full flow channel heat transfer model with high accuracy is established using the “fluid-thermal” coupling method. The temperature distribution of the cooling roller and fluid field in steady-state is obtained. The simulated and experimental results of the outlet temperature are compared and the relative error is within 5%. The microstructures of the free surface and roller-sticking surface of Nd-Fe-B melt-spun ribbons are characterized by FE-SEM, and the refined grains are formed on the roller-sticking surface of Nd-Fe-B ribbons due to rapid solidification caused by the heat transfer from the roller. Moreover, a multi-nozzle structure is proposed for the MS process. The temperature distribution on the surface of the cooling roller in the axial direction is more uniform compared with the original single-nozzle structure, and the average convective heat transfer coefficient is increased by about 1.27 times after the modification of multi-nozzle structure, with a productivity of three times. Finally, the experimental design method of Latin hypercube sampling response surface design is used to obtain the response surface relationships of rotational speed, inlet flow rate, and water inlet temperature on the surface temperature of the cooling roller, respectively. NSGA-II multi-objective genetic algorithm (MOGA) is adopted for multi-objective optimization of process parameters. The optimized combination of process parameters is obtained with a relative error of about 0.41%. The research results are helpful to understand the heat transfer behaviors in the MS process of Nd-Fe-B ribbons, improve the utilization rate of the cooling roller and enhance the production efficiency in the actual application.

Multi-tiered configurations improved flow boiling performance: Comparation investigation of leaf vein inspired two-tiered and three-tiered open microchannels

Microchannel heat sinks with expanding flow area along with the flow direction are able to suppress flow instability and reduce pressure drop during two-phase flow boiling by offering broadening volume for bubble elongation and growth that suppress the slug blockage and flow reversal. In this regard, microchannels with expanding area perpendicular to flow direction are supposed to obtain the comparable results, as the bubbles migrate to the downstream and top of microchannels simultaneously. However, the relevant study about multi-tiered microchannel heat sinks was limited and the corresponding flow boiling characteristics remained elusive. In this work, leaf vein inspired two-tiered open microchannel (LTWOMC) and three-tiered one (LTHOMC) were proposed and comparative flow boiling experiments were carried out. The outcomes indicated that LTWOMC obtained earlier ONB, which was 6.4 °C lower than LTHOMC at G = 220 kg/m2·s, the average local convective heat transfer coefficient (hcon) and average two-phase one (htp) of LTWOMC were maximumly enhanced up to 36.3% and 148.7% at G = 150 kg/m2·s, respectively. The pressure drop (ΔP) of LTWOMC was generally larger than LTHOMC at all mass fluxes, which led to the cooling coefficient of performances (COPs) of LTHOMC superior compared to LTWOMC under all working conditions. Moreover, LTHOMC exhibited better flow stability than LTWOMC with lower amplitudes and standard deviations of both wall temperature and pressure drop. In general, the three-tiered hierarchical configuration is more suitable than two-tiered one for flow boiling heat transfer.

Convective heat transfer with condensation in crossflow of a circular cylinder: Experiments and simulations

Forced convection heat transfer has been widely studied but not with the inclusion of condensation phenomenon particularly in crossflow of a cylinder. In this study, the convective heat transfer with moisture condensation of the air that is relevant for food thawing applications with the airflow around a circular cylinder was investigated. Experiments were carried out that represents food air-thawing conditions such as the Re number within a subcritical range, and the relative humidity of air being varied. Heat flux was measured at different angles around the cylinder to characterize the local heat transfer. A three-dimensional CFD modeling was subsequently carried out with the appropriate choice of turbulence model, and the condensation with the presence of non-condensable gasses. The simulation results were well correlated with the experimental data. The heat transfer rate on the leeward side is enhanced with the development of the detached vortex at higher Re number; hence, changing it within a certain range is an effective method to improve the uniformity of convective condensation heat transfer. An increase in the relative humidity was found to enhance the average convective condensation heat transfer. An empirical correlation that predicts the overall heat transfer was developed adopting Nu, Re, and Pr numbers.

Effect of an Exhaust Heat Exchanger with Inserts on the Performance of Thermoelectric Generators

A thermoelectric generator is used as a waste heat recovery system for generating electric power. The thermoelectric generator system consists of an exhaust heat exchanger, a thermoelectric module, and a water heat exchanger. The aim of the current work is to explore different types of inserts used in the test section of the exhaust heat exchanger and power generation of thermoelectric generators at different operating conditions. An experimental setup has been developed for conducting experimental investigation on thermoelectric generators to find the effect of the exhaust heat exchanger (EHE) with inserts on the performance of thermoelectric generators. The cone (G-type test section) and cone-cylinder (H-type test section) type inserts were introduced to enhance the performance of the thermoelectric generator. Compared with an insert-free (empty, F-type) thermoelectric generator with cone and cone-cylinder type inserts in terms of the output power, the average heat transfer rate and convection heat transfer coefficient of F-type, G-type, and H-type test sections of the EHE are 358, 468, and 459 W and 76, 100, and 97 W/m2K, respectively. It shows that the G-type test section of EHE exchanges more heat from engine exhaust to the hot surface of the thermoelectric module through the wall of the EHE. The G-type test section created more temperature difference; obviously, it generated more power output. It was observed that the G-type and H-type test sections of exhaust heat exchangers improved average maximum output power by 29.49% and 26.11% than that by the F-type test section of heat exchanger, respectively. The F-type, G-type, and H-type test sections of exhaust heat exchangers showed a maximum average efficiency of 0.80, 0.78, and 0.70%, respectively.

An investigation over the influence of a radiant thermal mat's dimensions on its local and average convective and radiative heat transfer characteristics

An investigation over the influence of a radiant thermal mat's dimensions on its local and average convective and radiative heat transfer characteristics

Preparation and application of rice husk-based SiO2/water nanofluids in heat transfer enhancement under pulsation

Rice husk was used as raw-material to produce nano-SiO2 by the heat treatment method, and the structural characteristics of rice husk SiO2 (R-SiO2) was compared with the commercial SiO2 (C-SiO2) by various characterization methods. SiO2/water nanofluids were prepared by a two-step dispersion method using various sources SiO2 (R-SiO2 and C-SiO2) and applied in the convective heat transfer of corrugated tube channels in a self-built experimental platform. The experimental results showed that the specific surface area of the rice husk-based silica was high, reaching 335 m2/g. For the same nanofluids concentration, the thermal conductivity enhancement rate of R-SiO2/water nanofluid was higher than that of C-SiO2/water and the enhancement rate of 0.5% R-SiO2/water at 25 and 40 °C reached 14.01% and 12.16%, respectively. The convective heat transfer coefficient of R-SiO2/water was slightly better than that of commercial C-SiO2/water, which indicated that R-SiO2 has great potential to be a substitute of C-SiO2 for application in heat exchangers. The convective heat transfer characteristics of R-SiO2/water nanofluids in corrugated tube at different Re and volume concentrations were compared. It was found Nu augmented as Re increased. And a higher nanofluids concentration might result in a drastic increment in convective heat transfer coefficient. When a pulsating wave was imposed, the larger pulsation amplitude resulted in a higher heat transfer enhancement rate. And the enhancement rate at lower Re was better. Under the conditions of Re = 385, f = 0.67 and A = A15, the maximum average convective heat transfer enhancement rate reached 143%.

Methodology for determining convective heat transfer coefficients on the tubesheet surface of shell-and-tube heat exchangers under single-phase flow

Designing shell-and-tube heat exchangers requires reliable methods to calculate the convective heat transfer coefficient (CHTC) on the tubesheet, due to its impact on thermal stress. To address this, we established numerical models for both the tube and shell sides of the tubesheet. Using computational fluid dynamics (CFD), we systematically investigated the distribution of convective heat transfer on the tubesheet surface and its variations with structural and process parameters. The results showed that when fluid flowed into the tubesheet, the average convective heat transfer coefficient on the tube side of the tubesheet surface was 26% higher than when it flowed out. Additionally, the average convective heat transfer coefficient in the perforated region of the tubesheet was 1.39 to 2.57 times greater than in its periphery. Furthermore, the local CHTC on the shell side of the tubesheet surface gradually decreased along the downstream direction from the inlet of the shell-side fluid. Through simulations conducted across various structural and process parameters, we derived empirical formulas to rapidly calculate the average CHTC on the tubesheet surface. These formulas incorporated a tubesheet porosity factor for the tube side and introduced a new method for calculating the equivalent tubesheet diameter on the shell side. Random testing verified that our proposed formula reliably predicted the numerical simulation results.

Experimental investigation on heat transfer of nitrogen flowing in a circular tube

Average and local convective heat transfer coefficients of nitrogen are measured experimentally in an electrically heated circular tube for a range of Reynolds number from 1.08 × 104 to 3.60 × 104, and wall-to-bulk temperature ratio from 1.01 to 1.77. The exit Mach number is up to 0.17, and the heat flux is up to 46 kW·m−2. The molybdenum test section has a 62 diameters heated section with an inside diameter of 5 mm and a 30 diameters entrance section to ensure the fully-developed flow. Uncertainty of Nusselt number is less than 1.6 % in this study. The results indicate that the average heat transfer correlations evaluated by both the bulk and the modified film Reynolds numbers agree well with the experimental data. The local heat transfer results based on bulk properties are compared with previous empirical correlations. New prediction correlations are recommended which are significantly affected by the property variation and heated length. The comparison between the proposed correlations and experimental points shows that 88 % of experimental data fall into an error of 10 %, and almost all data are within an error of 20 %.

Flow and heat transfer in rotating smooth and ribbed multi-channel double-wall structure with multiple-jet impingement cooling

In this study, the heat transfer of multiple-jet impingement in rotating smooth and ribbed multichannel double-wall cooling structure with film extraction are investigated. The dimensionless jet-to-target spacing is 1, and the dimensionless jet-to-jet spacing is 3.55. In ribbed channel, the rib height is 1 mm and rib spacing is 8 mm. The experimental jet Reynolds number ranges from 2000 to 8000, and the maximum jet rotation number is 0.22. The test section contains five impingement channels. The local average convective heat transfer coefficient is measured by the “copper plate method”. The SST k-ω model is used to study the effect of rotation on the flow in channels. The results show that the heat transfer gap between high and low radius is more evident with an increase of the Roj. This is because the rotation effect increases and decreases the mass flow rate at high and low radius, respectively. Moreover, rotation can strengthen the impingement effect of the trailing side (TS) while weakening the effect of the leading side (LS) when the Roj is less than 0.06, Which causes differences in the heat transfer between the LS and TS of the impingement channel. Furthermore, affected by the ribs, the average heat transfer of ribbed target surface is improved. The area of high heat transfer region generated by impingement decreases, and an inverted butterfly-shaped high heat transfer region is generated near the film hole. Finally, the rib weakens the effect of rotation on the flow of target surface to some extent.

An isothermal constant surface area horizontal helical coil under natural convection and radiative heat loss: A CFD study

This paper presents a numerical analysis of a horizontally oriented constant surface area isothermal helical coil under natural convection heat transfer and surface radiation. Numerical computationsare carried out in the laminar regime of Rayleigh number (104 ≤ Ra ≤ 108), surface emissivity (0 ≤ ε ≤ 1), and geometrical parameters of the helical-coil, like diameter of the coil (8 ≤ D/d ≤ 24), pitch (3 ≤ p/d ≤ 7.5), and coil height (40 ≤ H/d ≤ 60) to study the heat transfer characteristics. This study is used for effectively designing the helical coils, which are typically manufactured at an extremely high temperature. The numerical computation has been validated by comparing the average Nusselt number (Nu) with the previous experimental results. Temperature-dependent fluid properties are incorporated to achieve precise results over a wide range of temperatures. The effect of the geometrical parameters on the heat transfer characteristics has been depicted graphically in terms of average Nu, relative convection and radiation heat transfer rate, and the temperature profile. It is found that the relative contribution of radiative heat transfer is 87.8% at an emissivity of 0.9 and Ra of 10(Ali, 19944), whereas, for an emissivity of 0.1 and Ra of 10(Moawed, 20058), the relative contribution of radiation heat transfer is only 6.4%. Lastly, a correlation has been developed for the average Nu based on all the pertinent parameters which can be beneficial to the engineers in the industry and also academic researchers. The developed correlation has been used to predict the cooling curve of the helical coil in certain situations.

Study on dynamical characteristics of cooling fluid in engine piston

The cooling of engine piston is very important, and the fluid vibration characteristics of its internal cooling oil is the key to affect the heat transfer efficiency. In order to effectively ensure that the piston temperature will not be overloaded and avoid the reduction of sealing performance, a two-phase flow model in the piston cooling chamber is established in the paper. The flow field and heat transfer characteristics of the cooling oil are simulated by finite element method using FLUENT. In terms of model selection, VOF multiphase flow calculation and SST k-ω model are selected as turbulence model. The setting of boundary conditions combines the piston stroke characteristics of the hydraulic cylinder, so as to obtain accurate inlet parameters, and obtain the oil liquid phase proportion distribution, oil velocity field and the change law of convective heat transfer coefficient under different piston positions. The results show that the instantaneous ratio of cooling oil is closely related to the speed, and increasing the oil speed is an important means to improve the heat transfer performance. The multiphase flow model has high reliability, and there is no obvious difference between the average convective heat transfer coefficient obtained by the near-wall model method and the wall function method.

A novel convective heat transfer enhancement method based on precise control of Gyroid-type TPMS lattice structure

Innovative single-phase flow heat transfer enhancement technologies can improve heat dissipation efficiency and reduce the weight and volume of heat dissipation equipment. Triply Periodic Minimal Surfaces (TPMS) hold promise as a outstanding single-phase heat transfer enhancement structure. To further improve the convective heat transfer performance of TPMS, this study independently presents a novel lattice structure control method specifically designed for Gyroid-type TPMS, along with the corresponding mathematical equation. By adjusting the parameter “α” in the equation, the Gyroid lattice geometry can be controlled. This study named “α” as the “Lattice deformation control parameter of Gyroid”. Numerical simulations indicate that increasing α from 0 to 0.25 within the Reynolds number range of 282–2579 can lead to a 19.9–28.9% increase in the average convective heat transfer coefficient (h¯) of the Gyroid, a 0.3%-4.5% increase in the Nusselt number (Nu), and a 13.0%-20.3% decrease in the average friction factor (f¯). The research results suggest that optimizing α is a promising new technology for enhancing convective heat transfer of Gyroid-type TPMS, as it not only improves its heat transfer performance but also reduces its flow resistance. The main reason for the convective heat transfer enhancement of Gyroid-type TPMS with increasing α is the increase in the heat transfer area, while the reduction of flow resistance is mainly due to the formation of the “flow-guiding structure” inside the Gyroid.

Comparison of cooling performance of nanofluid flows in mini/micro-channel stacked double-layer heat sink and single-layer micro-channel heat sink

Mini/micro-channel heat sinks are the advanced cooling method to fulfill the cooling demand of electronic equipment integrated with high-power circuit packages. Many designs are provided to enhance the thermal performance of micro-channel. In the present experimental study, the mini/micro-channel stacked double-layer heat sink is designed and tested for the first time. The mini/micro-channel stacked double-layer heat sink is composed of a single-layer micro-channel heat sink stacked with a mini-channel heat sink. The pure water and alumina-water nanofluid are considered as the coolant. A comparison is conducted between the heat dissipation performance of mini/micro-channel stacked double-layer heat sink and single-layer micro-channel heat sink. The results showed that as compared with the case of single-layer micro-channel heat sink, the pressure drop can be reduced considerably by using the mini/micro-channel stacked double-layer heat sink. For the flow rate ratio less than 2.0, the average convection heat transfer coefficient of the mini/micro-channel stacked double-layer heat sink is higher than that of the single-layer micro-channel heat sink. Finally, the FOM ratios are greater than unity for all cases. This indicates that the use of mini/micro-channel stacked double-layer heat sinks has more advantages in engineering applications than the single-layer micro-channel heat sinks.

Experimental investigation on the impact of fin structure factors on the finned-Trombe wall thermal performance

By increasing surface area, fins can enhance the heat transfer and improve the Trombe wall thermal performance. However, there is still a lack of detailed experimental research on the impact of fin structure factors on the thermal performance of finned-Trombe wall (F-TW). This experiment establishes a platform under laboratory conditions to investigate the impact of fin height and spacing on the F-TW thermal performance. Electric heating is used to simulate the solar radiation. The results indicate that in areas with relatively low solar radiation intensity, the F-TW is more cost-effective for improving F-TW thermal performance. The F-TW thermal parameters including air temperature rise, mass flow rate, thermal efficiency and overall natural convective heat transfer coefficient are enlarged as the fin height increases and fin spacing decreases, while the heat loss coefficient of glass cover is opposite. The fin spacing has a more significant influence on the F-TW thermal performance and natural convective heat transfer in the channel than the fin height does. The maximum thermal efficiency of 63.75% is obtained at heat flux of 860W/m2, relative fin height of 0.75 and relative fin spacing of 0.06. Finally, for the engineering design and performance assessment of F-TW, the experimental correlation is provided to calculate the average natural convective heat transfer Nusselt number in the channel.

Heat transfer characteristics of nanofluid under the action of magnetic field based on molecular dynamics and flow states

Theoretical analysis, numerical simulations, and experimental studies are used to comprehensively investigate the changes in the heat transfer characteristics of Fe3O4–water magnetic nanofluid under different types of magnetic fields and the heat transfer mechanism, providing new ideas for its practical application. By combining the fundamental conservation theorem and the Boussinesq approximation, dimensionless control equations have been established. The analysis of the variation pattern of the calculated values of the source terms under different boundary conditions, as well as the order of magnitude analysis, concludes that: the enhanced trend of Brownian motion and thermophoretic motion is the main reason for the enhanced heat transfer capability of the magnetic nanofluid; where the thermophoretic motion contributes slightly more to the heat transfer; the increase in Joule heat is the reason for the further enhancement of the heat transfer capability by the magnetic field. Volume fraction, temperature, and magnetic field strength are positively correlated with the average convective heat transfer coefficient. The reason for magnetic fields to enhance heat transfer is revealed by the deflection of the magnetic nanofluid by the magnetic body flow under local magnetic fields to form localized reflux. The alternating magnetic field further enhances the ability of magnetic fields to enhance heat transfer in magnetic nanofluids. Overall, the effect of the applied magnetic field on the motion of the magnetic nanoparticles causes the disruption of the thermal boundary layer, which is responsible for the enhanced heat transfer capacity of magnetic nanofluids.