Heat Transfer In Channel Research Articles

A local synergy angle of velocity, temperature and pressure fields for enhancement of comprehensive heat transfer performance

The field synergy principles for convective heat transfer and flow resistance are integrated in this study. A local three-field synergy angle of velocity, temperature and pressure fields is proposed to evaluate the local comprehensive performance of heat transfer and pumping power consumption. The angle is based on the polar angle of a plot with dot products of velocity and enthalpy/total pressure gradients, respectively, as coordinates. The polar angle is then shifted by the observation that the enhancement of heat transfer rate at the cost of pumping power decreases from the second quadrant to the forth quadrant. The application of the synergy angle is demonstrated by examples of flow and heat transfer in channels with different fin structures. Inspired by the distribution of the synergy angle, Airfoil-Rect fin and Rhom-Rect fin structures are designed, which can improve the heat transfer rate with constraints of pumping power consumption. The present study provides a possible approach for heat transfer enhancement.

Experimental and numerical investigation on a hybrid high-temperature downhole thermal management system integrating liquid cooling and phase change material

The downhole electronics must operate in an extremely thermal environment for several hours. Previous researches have proved that passive thermal management systems (PTMSs) are able to protect downhole electronics over extended durations. However, conventional PTMSs commonly suffer from a significant thermal resistance between the electronics and phase change materials (PCM), which restricting the efficient heat transfer to the PCM and consequently reducing the effective operating time. In this study, a hybrid thermal management system (HTMS) integrating liquid cooling and phase change thermal energy storage technique was proposed to enhance the internal heat transfer performance of downhole electronics and extend the operation duration. An active heat transfer channel was established between the electronics and PCM through liquid cooling system, and thus the generated heat was efficiently transferred and stored in PCM. The thermal performance of the proposed HTMS was investigated both experimentally and numerically. The accuracy of the numerical model was validated through experimental results, with a deviation lower than 6 %. The experimental results show that the temperature difference between the heat source and the heat storage module (HSM) was reduced by up to 51.9 °C, and the workable time was increased by up to 166 mins compared to the system without liquid cooling. The proposed HTMS exhibits superior heat transfer performance, which contributes to achieving a longer effective operation duration and holds extensive and profound application prospects in the field of thermal management for downhole electronic devices.

The comprehensive analysis of magnetohydrodynamic Casson fluid flow with rectangular porous medium through expanding/contracting channel

PurposeThis study examines fluid flow within a rectangular porous medium bounded by walls capable of expansion or contraction. It focuses on a non-Newtonian fluid with Casson characteristics, incompressibility, and electrical conductivity, demonstrating temperature-dependent impacts on viscosity.Design/methodology/approachThe flow is two-dimensional, unsteady, and laminar, influenced by a small electromagnetic force and electrical conductivity. The Hybrid Analytical and Numerical Method (HAN method) resolves the constitutive differential equations.FindingsThe fluid’s velocity is influenced by the Casson parameter, viscosity variation parameter, and resistive force, while the fluid’s temperature is affected by the radiation parameter, Prandtl number, and power-law index. Increasing the Casson parameter from 0.1 to 50 results in a 4.699% increase in maximum fluid velocity and a 0.123% increase in average velocity. Viscosity variation from 0 to 15 decreases average velocity by 1.42%. Wall expansion (a from −4 to 4) increases maximum velocity by 19.07% and average velocity by 1.09%. The average fluid temperature increases by 100.92% with wall expansion and decreases by 51.47% with a Prandtl number change from 0 to 7.Originality/valueUnderstanding fluid dynamics in various environments is crucial for engineering and natural systems. This research emphasizes the critical role of wall movements in fluid dynamics and offers valuable insights for designing systems requiring fluid flow and heat transfer. The study presents new findings on heat transfer and fluid flow in a rectangular channel with two parallel, porous walls capable of expansion and contraction, which have not been previously reported.

Improvement of heat transfer in microchannels using nanofluids by numerical contribution on a sinusoidal shaped dissipator

This research conducts an extensive numerical investigation into the enhancement of heat transfer in wavy-walled channels using aluminum oxide-water nanofluids. The study examines the impact of key parameters, including geometric aspects (wave spacing ratio: 0-1), operational conditions (Reynolds number: 5,000-20,000), and varying nanofluid concentrations (1-6% by volume). The results indicate that zero wave spacing combined with a nanofluid concentration of 4% provides the most favorable thermal performance, resulting in a heat transfer enhancement of up to 2.5 times when compared to conventional smooth channels. While the wavy channel geometries significantly improve heat transfer, they also impose additional pressure drops, revealing a critical trade-off between enhanced thermal performance and the increased pumping power required. The study highlights the balance necessary between maximizing heat transfer and maintaining operational efficiency, particularly in systems where space is limited. These findings contribute valuable insights to the design of heat exchange systems that demand both high thermal efficiency and compact dimensions, such as those used in electronics cooling or energy-efficient HVAC systems. Additionally, the study explores the influence of the Reynolds number on both thermal and hydrodynamic behavior within the wavy channels, providing a thorough performance evaluation across different operational ranges. The conclusions drawn from this investigation offer practical guidance for optimizing heat exchanger designs, taking into account both thermal resistance and overall system performance under varying conditions.

Heat transfer performance optimization of turbine blade internal cooling channel with pin-fins and recessed-extruded endwalls

This paper involves implementing and optimizing a novel recessed-extruded endwall design for a rectangular cooling channel equipped with pin-fins. The study encompasses an in-depth exploration of the flow dynamics, pondering the generation and sustenance of vortices within the channel, using Reynolds-averaged Navier-Stokes analysis. The study delves into the evaluation of heat transfer characteristics, considering crucial parameters such as Nusselt number, friction factor, and overall heat transfer performance. These attributes are contrasted with the corresponding values observed in cases featuring flat endwalls, concerning Reynolds numbers spanning from 7400 to 36,000. A parametric study of the channel with recessed-extruded endwalls is conducted, aiming to comprehend the influence of geometric factors on channel heat transfer. A single-objective optimization process focusing on enhancing heat transfer effectiveness, quantified through the heat transfer efficiency index (HTEI), is conducted with three design variables. The results indicate that the new endwall configuration significantly enlarges the high heat transfer areas near the pin-fins compared to the flat endwall across all Reynolds numbers. This novel endwall design substantially elevates the heat transfer levels adjacent to the pin-fins, showcasing an impressive 62.4% increase in HTEI at Re = 21,500 compared to the flat endwall, with a protrusion height of 2.5% of the channel height. Furthermore, by increasing the height, the recessed-extruded endwall configuration can achieve a remarkable 91.1% increase in HTEI compared to the flat endwall. This achievement is reached with a protrusion height equivalent to 5% of the channel height at Re = 7400. Through design optimization using the radial basis neural network (RBNN) surrogate model and particle swarm optimization (PSO) technique, the HTEI of the recessed-extruded endwall design shows enhancements of 91.7% and 18.0% compared with the flat endwall and reference designs, respectively, at a Reynolds number of 21,500. The present work demonstrates the potential for enhancing the heat transfer of pin-fins channels by improving endwall design.

Vascular bundle-structured polymeric composites with fire-safe, self-detecting and heat warning capabilities for power batteries thermal management

The trend of miniaturization and integration poses challenges to the thermal management of electronic devices, requiring high thermal conductivity and potential fire safety, etc. In this study, inspired by plant vascular structure, we developed a polymer composite with a vertical vascular bundle structure via a sacrificial template method and subsequent assembly of transition metal carbides/nitrides (MXene) nanosheets and phytic acid (PA) coordinated cobalt ions (Co2+) complex. The embedded MXene and PA@Co exhibit multilayer multiscale structural features, forming heat transfer channels and protective cells within the composite. The resultant composites possess high out-of-plane thermal conductivity (∼1.54 W‧m−1‧k−1) and excellent flame retardancy, including self-extinguishing, and significantly reduced heat and smoke release. Interestingly, the MXene vascular bundle structure imparts heat early warning capabilities and intelligent damage self-detection, suggesting an effective means of preventing early-stage fires and real-time monitoring of composite structural and functional integrity. Such biomimetic strategies enable new insights into the designing of multifunctional, intelligent polymer composites.

Impact of graphene oxide lateral sizes on the mechanical and thermal properties of carbon fiber composites

AbstractThe impact of carbon fiber (CF) composites sizing with graphene oxide (GO) to form brick‐and‐mortar structures on their mechanical properties and thermal conductivity has not been closely examined. This study systematically investigates the effect of GO sheet size on the interfacial properties and thermal conductivity of CF composites. Three sizes of GO—small (0.11 μm), medium (0.33 μm), and large (0.97 μm)—were used to modify CF surfaces via layer‐by‐layer self‐assembly, forming the brick‐and‐mortar structures. The mechanical properties were assessed through flexural tests, interlaminar shear strength (ILSS) tests and tensile tests, while thermal conductivity was measured using a thermal constant analyzer. The results revealed that medium‐sized GO (GO‐M) significantly enhanced the interfacial strength and toughness of the composites. This improvement is attributed to the orderly arrangement of GO‐M on the CF surface, which enhances stress transfer between the fiber and the matrix. In contrast, small‐sized GO (GO‐S) tended to scatter, resulting in less effective reinforcement, while large‐sized GO (GO‐L) exhibited stacking and agglomeration, limiting its reinforcement effectiveness. However, GO‐L provided the highest thermal conductivity due to the formation of continuous heat conduction pathways. These findings suggest that GO‐M offers a balanced improvement in mechanical properties, whereas GO‐L is more suitable for applications requiring high thermal conductivity. This work underscores the importance of selecting the appropriate GO sheet size to optimize the interfacial properties and thermal conductivity of CF composites, which is crucial for enhancing their performance in high‐end engineering applications, such as aerospace, automotive, and marine industries.Highlights Modification of CF composites by GO‐M sheets significantly improved toughness and strength. GO‐L sheets formed an effective heat transfer channel with the highest thermal conductivity. The study emphasized the critical role of selecting the appropriate GO sheet size to optimize the mechanical and thermal properties of CF composites.

Modeling Heat and Mass Transfer in a Wet Terracotta Tube Channel for Evaporative Cooling Application: Influence of Geometrical Parameters

This study investigates the influence of design parameters on the performance of a terracotta tube-type evaporative cooling system. A mathematical model was developed based on double film theory and energy and mass conservation equations of the humid air and the wet tube wall in a one-dimensional geometry by applying correlations for heat and mass transfer coefficients and air psychometric properties. A system of non-linear differential equations was established and analytically integrated to obtain the relationship between the operating and the geometrical parameters of the system. Various geometrical parameters were simulated to assess their effects on outlet air temperature, cooling capacity, and wet-bulb effectiveness. The results indicate that increasing the tube equivalent diameter results in higher outlet temperatures and cooling capacity but decreases wet-bulb effectiveness. Conversely, an increased flatness ratio significantly enhances cooling performance and wet-bulb effectiveness due to a larger surface area for heat exchange. Additionally, longer tubes correlate with lower outlet temperatures and higher cooling capacity, indicating improved cooling performance. These findings emphasize the importance of selecting appropriate tube dimensions to optimize cooling efficiency in evaporative cooling systems. By balancing hydraulic diameter, flatness ratio, and tube length, engineers can design compact and effective cooling solutions suitable for various applications, ultimately contributing to energy-efficient and sustainable cooling technologies. The modeling approach developed in this study can also be applied to address challenges in geothermal energy extraction, drying of porous solids, food processing and storage, building thermal insulation, nuclear reactor cooling, and seawater desalination.

Numerical Simulation and Neural Network Model for Hydromagnetic Nanofluid Convection in a Porous Wavy Channel with Thermal Non-Equilibrium Model

Abstract The present study aims to analyze the nonfluid MHD convective heat transfer in a porous wavy channel with a local thermal non-equilibrium (LTNE) model. Such a model finds applications related to enhancement in thermal performance, increasing the heat transfer coefficient in the compact design of heat exchangers for the aerospace and automotive industries and elevation in the efficiency of the solar collector. A sinusoidal porous wavy LTNE channel containing nanofluid and subjected to the induced and applied magnetic fields is considered. A uniform magnetic field is applied orthogonal to the channel and the induced magnetic field effects are considered due to the large magnetic Reynolds number. The momentum, continuity, energy, and nanoparticle volume fraction equations constitute the coupled nonlinear system of differential equations and are solved using the Galerkin finite element method. The reliability of the technique is assessed by comparing the proposed procedure with the results from earlier sources. A detailed analysis is presented to determine the effects of different physical parameters arising in the system on temperature, nanoparticle concentration, and velocity profiles. As an illustration, the findings exhibit that increasing the modified diffusivity ratio increases the values of the nanoparticle volume fraction whereas, reducing the modified diffusivity ratio enhances the temperature distribution. A higher value of thermal Rayleigh number presents a significant involvement of buoyancy forces, potentially resulting in the development of convective currents. A higher Nield number indicates more effective heat transport from the solid surface to the nanofluid. Consequently, there is a minimal thermal difference between the solid surface and the bulk nanofluid. Effective heat transmission enhances the nanofluid ability to absorb heat and generates a more consistent dispersion of temperature inside the fluid. The performance of the designed algorithms of the artificial neural network, namely, the Levenberg – Marquardt algorithm, in the problem under consideration is evaluated and the methodology is found reasonably precise with the matching of order around 6 to 7 decimal places of accuracy.

Achieving high-thermal-conductivity brazed joint between carbon-based composites and Mo-Cu alloys by increasing the heat transfer area

Carbon-fiber-reinforced carbon matrix (Cf/C)-Mo30Cu brazed joints play an important role in the cooling systems of thermonuclear reactors. However, the limited contact area of heterogeneous interfaces severely limits the heat transfer efficiency. To overcome this drawback, we prepare three-dimensional porous interfaces by pre-oxidizing the Cf/C composite. Results show that circular gaps are formed between the carbon fibers and the pyrolyzed carbon after pre-oxidization at 600 °C in air. Fster braze penetration in the Cf/C composite is achieved, and the heat-transfer area across the interface is dramatically increased. The room-temperature thermal conductivity of the joints reaches a maximum value of 146 W·m−1·K−1 at a pre-oxidation time of 2 min; this value is 30 % higher than that obtained without treatment. The enhancement in thermal conductivity is mainly attributed to the increased contact area at the interface between the brazing seam and the Cf/C matrix, which provides more channels for heat transfer. This method of significantly improving the thermal conductivity is an important guide for the thermal management of thermonuclear reactors.

Convective heat transfer in porous channel with multi-layer fractures under Local thermal non-equilibrium condition

Based on Brinkman-extended-Darcy model and Local thermal non-equilibrium (LTNE) model, analytical solutions of velocity and temperature fields, pressure drop and Nusselt number of porous channels containing different number of fracture layers are obtained. The characteristics of fluid flow and heat transfer in multi-layer parallel fractured channels are further studied. Results show that for a single-layer or multi-layer fractured channel, the pressure drop changes sensitively at small hollow ratio and increases as the number of fracture layers increases with decreasing increase degree, but the pressure drop tends to be consistent regardless of the number of fracture layers when Darcy number is high. For small ratio of effective thermal conductivity, LTE model is valid regardless of Biot number, and the heat transfer intensity in multi-layer fractured channels is always higher than that in single-layer fractured channel at any hollow ratio, but the heat transfer intensity is still low. For large ratio of effective thermal conductivity, increasing Biot number or fracture layer number makes the Nusselt number increase under very small hollow ratio for both single and multiple fracture cases, and when both the ratio of effective thermal conductivity and Biot number are high, there is an intersection point occurs at hollow ratio near 0.1, which makes same heat transfer effect under different fracture numbers.

Research on improving heat transfer performance by using wavy ribs with different cross sections

Based on the change of the cross section in blade internal cooling channel rib caused by the service wear, starting from the widely used rectangular cross section, the most likely isosceles trapezoid and rectangular-semicircular cross section are considered, and the extreme design of the cross section (isosceles triangle) and the tentative exploration (spindle) are carried out. In this paper, the numerical calculation of SST k-ω turbulence model and the experimental research method of TSP measurement are used to thoroughly investigate the impact mechanisms of five different wavy rib cross-sections on the flow and heat transfer in turbine blade ribbed channels. The results show that different rib cross-sections alter the flow and heat transfer in channel by modifying flow allocation in height and width directions. The inclined sidewalls of the wavy ribs accumulate most of cooling air near the rib, which is the ultimate cause of the significant cooling effect. Under small rib radius and small rib angle, the heat transfer advantages of isosceles triangle and isosceles trapezoid cross-section wavy ribs are more obvious, which are increased by 14.88 % and 20.66 % respectively, but their friction factor is also 1.2 ∼ 2.0 times that of rectangular cross-section. The heat transfer of the large rib height on the isosceles triangular and isosceles trapezoidal cross-section wavy ribs is increased by 73.29 % and 185.31 %. Changes in Reynolds number have minimal impact on the friction factor, but significantly impact the overall heat transfer.

High performance flexible phase change hydrogel applied to thermal management of new cigarette device

To address the thermal management challenges of new heat-not-burn (HNB) cigarette devices, this study aims to enhance overall energy conversion efficiency while maintaining unchanged battery capacity. The goal is to minimize heat dissipation and reduce the temperature of the device's housing that contacts the user. In this research, CaCl2·6H2O (CCH) was selected as the phase change material (PCM), and a polyacrylamide (PAM) phase change hydrogel encapsulating CCH was prepared via in-situ polymerization. Additionally, konjac glucomannan (KGM) was incorporated into the three-dimensional network structure of PAM through hydrogen bonding to promote the formation of a porous gel structure. CNTs-CuO composites, featuring in-situ generated CuO nanoparticles on carbon nanotubes (CNTs), were synthesized using a microwave hydrothermal method and employed to enhance the thermal conductivity of the phase change hydrogel.This study demonstrates that the three-dimensional porous network structure of the hydrogel not only provides effective encapsulation protection for CCH and maintains high latent heat (144.9 J/g), but also imparts excellent flexibility and stability to the composites. The incorporation of CNTs-CuO composites introduces efficient heat transfer channels, significantly increasing the thermal conductivity of the hydrogels by approximately 37 % (0.687 W·m−1·K−1). Moreover, the hydrogel composites exhibit exceptional temperature regulation properties.The innovative design and preparation of these hydrated salt-based flexible hydrogel composites offer a novel approach in the fields of thermal management and energy storage. This material demonstrates practical applications not only in HNB devices but also in various thermal management systems, such as wearable electronics, battery thermal management, and electronic device cooling. Furthermore, its application in energy storage systems, including thermal energy storage units and smart textiles, underscores its broad applicability and significance.

Numerical study on flow-boiling heat transfer in square channels partially centrally filled with gradient porous media

Boiling heat transfer is widely used in industry and daily life and can be enhanced by porous media structure. Previously HPM have been shown to significantly improve heat transfer performance, but how the porosity gradient affects boiling heat transfer remains unknown. In this paper, the subcooled flow boiling in vertical square channels partially filled with gradient porous media was numerically investigated by using a newly developed solver named GPMPhaseChangeFoam embedded in the open-source platform OpenFOAM. The results indicate that in positive GPM inserted channels, when z ≤ 0.16 m Nuz increases with increasing Hp*, and when z ≥ 0.16 m Nuz increases with increasing Hp* from 0.2 to 0.8 but deceases with Hp* rises from 0.8 to 1.0, and the effect of Hp* on Nuz is more pronounced in the entrance region over the exit region. In negative GPM inserted channels, Nuz increases with increasing Hp* throughout the channel length in positive GPM inserted channels, and the effect of Hp* on Nuz is less pronounced in the entrance region than the exit region. Flow resistance increases with Hp*, but changes little with Δε, and Nufd increases with Hp* in both positive and negative GPM inserted channels. However, Nufd decreases with an increase in ∆ε from 0 to 0.3 in positive GPM inserted channels, from -0.3 to 0 in negative GPM inserted channels, and ∆ε = -0.3 at Hp* = 1.0 is 13.4 % higher than that of ∆ε = 0.3. Furthermore, the negative GPM inserted channel behaves higher flow boiling heat transfer performance than the HPM and positive GPM.

Experimental and numerical study on the flow and heat transfer of ring-ribbed tank in deep-sea manned submersible

The ring-ribbed tank is the key equipment of cooling system of deep-sea manned submersible. The heat transfer characteristics of the outer wall and the heat transfer and flow characteristics of the inner flow channel of the ring-ribbed tank for different inlet and outlet temperatures and flow rates were studied through a water tank test. The results indicate that Nusselt number for the inner flow channel correlates with Reynolds and Prandtl numbers, while for the outer wall, it correlates with Grashof and Prandtl numbers with an overall error within 5%. A numerical study using the Realizable k-ε turbulence model and Boussinesq approximation of the flow-solid conjugate heat transfer is conducted, which can accurately determine the heat exchange capacity and the import and export differential pressure with an average relative error of 1.98% for hot water temperature and 7.73% for shell wall temperature. Additional simulations for determining the heat transfer capacity and flow resistance characteristics of the ring-ribbed tank in open water results demonstrate that the differential pressure and its coefficient are basically consistent with model test results. The cooling system can achieve a heat transfer rate of up to 17 kW with an external seawater flow velocity of approximately 2 knots.

Effects of turning vane on flow control and heat transfer in ribbed two-pass channel with varied rib patterns

Faced with the escalating cooling requirements of turbine blades, two-pass channels with ribs on the internal surfaces have been extensively employed to enhance internal wall heat transfer. Considering the potential to mitigate flow separation and pressure losses generated by channel curvature, in this study, a computational fluid dynamics approach based on the realizable k-ε turbulence model is employed to explore the effects of turning vane introduction on the flow and heat transfer characteristics of two-pass channels with varying rib configurations. The rib configurations are identified as NN, NP, PP and PN. “N” denotes the ribs rotated 45° clockwise relative to the flow direction, while “P” denotes the ribs rotated 45° counterclockwise. The results indicate that the introduction of turning vanes improves the flow uniformity in the downstream channel of the two-pass channel with N-patterned upstream ribs, enhancing inter-rib heat transfer in the downstream channel. It also strengthens the heat transfer performance at the bend region of the two-pass channel with P-patterned upstream ribs. Furthermore, the introduction of turning vanes results in a decrease in friction loss factor for two-pass channels with various rib arrangements at varying levels of Reynolds numbers. The reduction is more pronounced in the two-pass channel featuring N-patterned upstream ribs, with a maximum decrease of 18.6 %. In contrast, the decrease is only 5.2 % in the PP-patterned rib channel. Additionally, the thermal performance factor of NP-patterned and NN-patterned rib channels increases by 8.5 % and 8.7 % respectively after the insertion of turning vanes. However, the enhancement is limited in the PP-patterned and PN-patterned rib channels.

Entrance effect of curved endwall on heat transfer and flow structure in a confluent channel with pin fins

In advanced turbine blade internal cooling channels, the majority of the remaining coolant converges into the trailing edge and constitutes a confluent flow before the slot entrance. The entrance effects of curved endwalls (convex, concave) for confluent internal cooling channel are numerically investigated in this paper. The overall heat transfer performances and flow structures are compared in the slot channel with pin fin cooling at the five momentum ratios (M = 0.1–2.1). Among all the cases studied, the higher momentum inflow not only enhance heat transfer but also reduce pressure loss in the slot channel with concave endwalls. In particular, the substantial comprehensive heat transfer factor (η) increase reaches 29.4% higher than the flat endwalls at the given relative curvature height ratio of 1.83. For the models with convex endwalls, the jet-like flow improves the η at the most by 12.1% compared to the flat endwalls. As the curvature height ratio increases, the effects of curved endwalls diminish eventually. In addition, the momentum ratio determines the formation and specified impact of the above flow characteristics in the confluent flow. The curved endwalls exhibit more increase in the η at lower M.

Large eddy simulation of turbulent transport and thermal enhancement in a steam-cooled ribbed channel

Pulsating flow, as an active heat transfer enhancement technique, is expected to further improve thermal performance. To demonstrate the potential value of pulsating flow in blade cooling, a numerical investigation is conducted on the flow and heat transfer in a steam-cooled ribbed channel under steady and pulsating inflow at Re = 12000. LES, based on OpenFOAM-8, is employed and precursor simulation method is used to generate fully developed turbulent inflow. Three operating conditions, steady inflow (StF = 0), low frequency pulsation (StF = 0.02) and medium frequency pulsation (StF = 0.08), are studied. The features under steady inflow condition (StF = 0) are firstly discussed, indicating that, due to the entry effect, the ribbed channel can be divided into two regions with different vortex motion behaviors. The ejections induced by vortex evolution enhance turbulent and energy transport between the sidewall and mainstream. Two cases of pulsating inflow are then carried out, finding that stronger ejections appear and low heat transfer area is significantly improved. Corresponding to low frequency pulsation (StF = 0.02) and medium frequency pulsation (StF = 0.08), the Nusselt number has an increase of 3.511 % and 14.242 %, respectively, and friction factor has a rise of 3.934 % and 8.253 %, compared with steady inflow. The thermal performance factor is increased by 11.262 % at StF = 0.08, indicating better cooling performance than the rise of 2.188 % at StF = 0.02. It is suggested that pulsating flow with medium frequency pulsation has positive performance in a steam-cooled ribbed channel.

Effect of electric field on bubble dynamics in channel flow boiling using lattice Boltzmann method

The application of an electric field in flow boiling has been proven to effectively enhance heat transfer and reduce pressure drop instability. This study aims to elucidate the mechanism of the impact of electric fields on flow boiling bubble dynamics through the pseudo-potential lattice Boltzmann method (LBM). The interplay between the externally imposed electric field incoming velocity in different gravity conditions examined. These factors can regulate flow boiling heat transfer in horizontal channel. The results demonstrate a competitive relationship between electric field and gravity and between incoming velocity and gravity. Therefore, under higher gravity condition, an electric field is less effective to enhance flow boiling heat transfer than in low gravity condition and vice versa. Additionally, there exists a synergistic relationship between incoming velocity and the electric field that mitigates their competition. Moreover, when considering multipoint nucleation processes, applying an electric field can attenuates bubble–bubble interactions and inhibit large bubble formation so as to accelerates bubble condensation in supercooled flows and enhance boiling heat transfer. This work provides comprehensive physical insights into the mechanism of electric field to enhance the heat transfer in flow boiling, which is instructive for the development of electrohydrodynamic technique in flow boiling enhancement.

Heat Transfer in A Non-Uniform Channel Under the Action of Peristalsis

Heat Transfer in A Non-Uniform Channel Under the Action of Peristalsis