Enhanced Heat Transfer Characteristics Research Articles

Numerical Investigations of Superconducting Material Cooling Using Buoyancy-Driven Heat Transport in Cryogenic Nanofluids

This study explores the effect of nanoparticle addition on the overall heat-carrying capacity of base liquid nitrogen in natural convection. Moreover, the work also addresses the nanoparticle sedimentation problem that is prominent in natural convection and proposes subtle modifications in heat source location to avoid sedimentation. For this, a 6 mm superconducting material is immersed in a cooling tub filled with liquid nitrogen. The cooling capacity of cryogenic fluids without boiling is considerably low. Hence, the alumina, silicon oxide, and titania nanoparticles are suspended in the base liquid nitrogen. A computational model, which relies on phase-averaged Eulerian tracking of nanoparticle suspensions, is employed to accurately predict the enhancement in heat transfer characteristics. Furthermore, the study addresses the influence of nanoparticle sedimentation in natural convection and proposes modifications to the cooling domain and superconducting material locations to mitigate sedimentation issues. The findings reveal a remarkable 70% increase in the heat transfer coefficient for 0.5% alumina nanoparticles suspension in the base liquid nitrogen. These results demonstrate the potential for significantly improving heat transfer performance in superconducting systems while minimizing the adverse effects of nanoparticle sedimentation.

Research on enhanced heat transfer characteristics of the condenser section of a non-powered hood cowl-type heat pipe radiator for waste heat removal

Research on enhanced heat transfer characteristics of the condenser section of a non-powered hood cowl-type heat pipe radiator for waste heat removal

Enhancement of Heat Transfer Characteristics by Inserted Novel Turbulators in Circular Tube Heat Exchanger

Enhancement of Heat Transfer Characteristics by Inserted Novel Turbulators in Circular Tube Heat Exchanger

Heat Transfer Enhancement Characteristics of Multiconfiguration Blunt-Headed Cylinder by Flow-Induced Vibration

Heat Transfer Enhancement Characteristics of Multiconfiguration Blunt-Headed Cylinder by Flow-Induced Vibration

An Experimental Study on the Heat Transfer and Flow Characteristics of Aluminum Heating Elements Coated with Graphene

With the rapid development of clean heating, electric heating has received increasing attention. As a common electric heating device, heaters are also widely used in residential and industrial heating, as well as in other fields. In order to improve the reliability and heat transfer flow characteristics of the electric heating element of the heater, a new type of structural electric heating element was designed and developed based on the surface heat transfer enhancement and pit drag reduction characteristics of graphene. The heat transfer and flow characteristics of the electric heating element were analyzed through experiments, and the results showed that the average surface emissivity increases from 0.25 with the non-graphene-coated sample to 0.94 with the graphene-coated one, and the surface temperature of the electric heating element decreased from 289 °C to 237.5 °C. Through wind-tunnel experiments, it was found that the PEC value of the electric heating element with pits was 1.0693, and the Nusselt number increased by 6.22% compared with the smooth surface. Furthermore, after coating with graphene, the Nusselt number increased by 30.3% compared with the smooth surface.

Heat transfer enhancement and flow resistance reduction characteristics of non-uniform electrohydrodynamic conduction pumping in microchannels

In this study, the thermo-hydraulic performance of non-uniform electrohydrodynamic (EHD) conduction pumping in rectangular and straight microchannels was experimentally investigated. Electrodes are arranged in two ways: dimensions constant, spacing varies (Cases 1–3); both dimensions and spacing vary (Cases 4–6). The results show that EHD conduction pumping significantly enhances heat transfer performance, increasing the average Nusselt number (Nu) by 17.9 %-87 % compared to a smooth microchannel. As Re increases, the inertial force of the fluid dominates, diminishing EHD-induced vortices and limiting heat transfer enhancement. EHD conduction pumping enhances heat transfer by creating vortices that mimic solid pseudo-roughness microelements, increasing fluid disturbance and mixing near the wall. However, these vortices also impede the flow, resulting in a trade-off with increased pressure drop resistance. This paper innovatively adopts an arrangement of increasing electrode size (non-uniform), which effectively reduces the pressure drop resistance in the microchannel while maintaining the advantage of enhanced heat transfer. Cases 4, 5, and 6 exhibit significantly higher comprehensive heat transfer performance (η) than Case 0 (without electrodes), especially at low Re. While the inertial force at high Re suppresses vortex formation and heat transfer enhancement, η remains superior to Case 0. Notably, Case 5 maintains a minimum η of 1.18 even at Re = 1000. Furthermore, this paper proposes an equivalent slip drag reduction mechanism to elucidate the drag reduction effect of the increasing electrode size arrangement. Heat transfer augmentation and pressure drop reduction, as mentioned here in microchannels, are crucial for electronics cooling and microfluidic devices.

Enhancement of heat transfer characteristics in wavy microchannel heat sinks with streamlined micropins within convergent-divergent flow passages

In the current study, the heat transfer characteristics of a novel design microchannel with a wavy sinusoidal convergent-divergent wall structure featuring streamlined pins have been numerically investigated under laminar flow conditions. Various amplitudes, wavelengths, pin heights, and Reynolds numbers are considered as parameters. The thermal and hydraulic characteristics are analyzed in terms of Nusselt number, Fanning friction factor, and Performance Evaluation Criteria number (PEC), which evaluates the heat transfer enhancement against the associated pressure drop. It is revealed that increasing the amplitude and decreasing wavelength, along with moderate pin heights, significantly augment heat transfer. The streamlined pins effectively direct the flow, and the resulting secondary flow and chaotic advection considerably enhance heat transfer in the designed configuration. The study demonstrates that the heat transfer can be improved by a factor of 4.79 compared to a straight microchannel. Under these geometric and flow conditions, the pressure drop increases by a factor of 9.87, and the PEC is found to be around 2.23. A multi-objective optimization study using the Non-dominated Sorting Genetic Algorithm (NSGA-II) is conducted with Genetic Aggregation Response Surface Methodology to evaluate the impact of various parameters on thermal-flow performance and to identify the optimal design with material quantity variation. According to the optimal results, a 5 % increase in material can augment thermal-flow performance by approximately 206.6 % compared to traditional microchannels. Finally, practical correlations for the Nusselt number and friction factor, accounting for various parameters, have been developed to facilitate in designing of microchannel cooling systems.

Numerical investigation of the enhanced heat transfer characteristics in dimpled enhanced tube to shell-and-tube lube oil heat exchangers

Numerical investigation of the enhanced heat transfer characteristics in dimpled enhanced tube to shell-and-tube lube oil heat exchangers

Thermal analysis of constant surface area tapered helical Coils: Insights from numerical modelling

Helical coils are integral to numerous engineering and domestic applications, from room heaters and vehicle suspensions to nuclear reactors, owing to their high surface area-to-volume ratio that facilitates efficient heat transfer. This study investigates the natural convection heat transfer characteristics of tapered helical coils under radiative heat loss, focusing on both straight and inverted configurations, within an unconfined air medium. The numerical simulations were validated against experimental results with a maximum deviation of 5 % before proceeding to establish the numerical findings. The analysis considers geometric parameters such as non-dimensional pitch (p*), cone angle (θ), and emissivity (ε), along with Rayleigh number (Ra), to elucidate their impact on average Nusselt number (Nu), mass flow rate of air through the coil core, and heat transfer mechanisms. Results reveal distinct behaviors for straight and inverted coils, with varying Ra and θ influencing heat transfer dynamics and airflow patterns. Notably, inverted coils exhibit enhanced heat transfer characteristics compared to straight coils. For straight coils, Nu initially decreases with increasing θ at lower Ra but rises beyond a critical θ at higher Ra due to independent heat dissipation by the coil turns. When θ changes from 0° to 50° at p* = 6, the change in average Nu is approximately 3 % and 10 % for Ra = 108 and 104 respectively. In contrast, for inverted coils, Nu increases with θ across all Ra, owing to the wider top opening facilitating airflow. Furthermore, empirical correlations are developed to predict Nu based on key parameters, achieving high accuracy with deviations of ± 6 % and ± 4 % for straight and inverted coils, respectively. These correlations provide robust tools for optimizing thermal management in diverse applications. Overall, this study contributes significant insights into tapered coil performance, essential for advancing heat transfer technology and design optimization.

Analysis of LNG flow and enhanced heat transfer characteristics within tubes with structural enhancements

Analysis of LNG flow and enhanced heat transfer characteristics within tubes with structural enhancements

Numerical investigation on the enhanced heat transfer characteristics of non-Newtonian viscoelastic fluids in microchannel with chip arrays

Elastic turbulence is an efficient heat transfer method at microscale. In this work, we conduct a systematic investigation on the flow and heat transfer performances of viscoelastic polymer solutions in microchannels with chip arrays by means of high-fidelity numerical simulations. Focusing on the effects of fluid elasticity [i.e. polymer relaxation time (λ)] and flow Reynolds number (Re), we find that the synergistic interplay between inertial and elastic forces is strategically exploited to amplify convection, thereby facilitating an enhanced heat transfer performance. For highly elastic fluid, the Nusselt number (Nu) can be improved by 76.13 % compared to that of less elastic fluid, while the pressure drop is reduced appropriately. In addition, as the fluid elasticity increases, the pressure drop decreases and eventually converges to a constant. In the zone of elastic turbulence, the fluid reinforces the convective heat transfer, which can be ascribe to the deformation of long-chain polymer molecules. Particularly, we consider the effect of temperature-dependent λ on the heat transfer performance. Our results demonstrate that the increased temperature-dependent λ decreases the value of Nu, and the variation between values of variable and constant λ is reduced with increasing Re or λ. Hence, in some cases of large fluid elasticity or high Re, it is possible to safely ignore the impact of temperature-dependent λ with an acceptable accuracy. The present work provides important insights into the enhanced heat transfer via elastic turbulence, which could guide the applications in the field of chip cooling.

Heat transfer enhancement characteristics of sinusoidal corrugated tubes fabricated via laser powder bed fusion

Laser powder bed fusion (LPBF) has emerged as a powerful tool to develop heat transfer devices with higher efficiency. Corrugated tubes are commonly used components to achieve enhanced heat transfer in these devices. However, there still lacks a comprehensive study on the thermal-hydraulic performance of LPBF-fabricated corrugated tubes. In this work, we investigated the heat transfer enhancement characteristics of sinusoidal corrugated tubes (SCTs) fabricated via LPBF. SCTs with different amplitude-to-diameter ratios (A/D ratio) and wavelength-to-diameter ratios (S/D ratio) were designed and fabricated. The geometrical morphologies and surface roughness of LPBF-fabricated SCTs were characterized. Numerical simulations were performed to investigate the effects of A/D ratio and S/D ratio on the flow patterns and flow dynamics. A test system was developed to measure the pressure loss and thermal performance. Performance Evaluation Criterion were calculated to characterize the heat transfer enhancement. A/D ratio was found to have more significant impacts on the friction factor and Nusselt numbers than S/D ratio. Correlation models were developed to predict friction factors and Nusselt numbers based on the least square method. Mean prediction errors of ±3.3 % and ±5.3 % and maximum prediction errors of ±11.6 % and ±18.1 % were achieved for Nusselt numbers and friction factor, respectively.

Enhanced heat transfer characteristics using dimples in the receiving end of laser wireless power transmission system

Laser wireless power transmission is a method of transmitting energy using laser as the carrier and photovoltaic cell as the receiving end. The study of cooling of its receiving end is significant, which can improve the efficiency and extend the service life of the system. In this article, dimples and protrusions with different heights are designed as heat dissipation components, which is the first application to laser wireless power transmission. And numerical simulations are conducted using the standard k-ω model to analyze and compare the heat transfer characteristics and electrical characteristics of photovoltaic cooling system under different geometric parameters. The results show that, under the same flow rate, the backside temperature of the cells with dimples and protrusions packs is 1 ∼ 3 K lower and the average Nusselt number increases by 30 %∼54 % compared to that of the smooth flat plate. At the same geometric parameters of the heat sinks and the Reynolds numbers of 7207, 14413, and 28106, the power peaks are increased by 15.3, 16.7and 17.7 times compared to that of the cells without the heat sinks.

Modeling of magneto bioconvection Williamson nanoliquid through modified heat flux: The significance of entropy

The combination of microbes and nanofluids has noteworthy consequences for technological and engineering progress, particularly in the realm of heat transfer applications. This study explains radiative flow with chemical reactions affect the emergence of microorganisms in magnetic mixed convective Williamson nanofluid flow. The Cattaneo-Christov heat flux theory and the effects of heat source/sink have been examined about the energy equation. The prime idea of this analysis is to enhance heat and mass transport. The modelled equations have been converted to dimensionless by considering suitable alteration. The dimensionless expression is then numerically tackled using MATLAB's bvp4c approach. The graphs for different profiles—that is, momentum, temperature, concentration and concentration of microorganisms that move—are made visible for particular nondimensional factors. Furthermore, entropy generation minimization has been obtained through law of thermodynamics. The drag friction, heat and mass transfer rate, and microbe density are also computed in a tabular manner. The most important findings that are pertinent to this study are that an increase in the values of the Brownian motion, thermal radiation and thermophoresis significantly enhance heat transfer characteristics. A consistent pattern can be observed when comparing the current results with earlier research.

Heat Transfer and Fluid Flow Characteristics in a Micro Heat Exchanger Employing Warm Nanofluids for Cooling of Electronic Components

The heat transfer enhancement and hydrodynamic characteristics of nanofluid use in a micro heat exchanger is investigated for cooling electronic components working in hot climatic conditions. The cooling fluid employed was water and TiO2 nanoparticles at mass concentrations of 1% and 5%, the Reynolds numbers ranged from 400 to 2000, and the inlet temperatures ranged between 35 °C and 65 °C. At a nanofluid inlet temperature of 55 °C and a nanoparticle concentration of 1%, the Nusselt number increased by 23% up to 54% as the Reynolds number varied between 400 and 2000. At a nanoparticle concentration of 5%, the percentages that correspondingly enhanced the Nusselt number were 32% and 63%. The temperature of the electronic heating component decreased by 4.6–5.2 °C when the nanofluid concentration was increased from 0 to 5% at a Reynolds number of 400 and a nanofluid inlet temperature of 35 °C. Small increments in the pressure drop of about 6% and 13% were observed at nanofluid concentrations of 1% and 5%, respectively. With nanoparticle concentrations of 1% and 5%, a Reynolds number of 2000, and a nanofluid inlet temperature of 35 °C, performance evaluation criterion (PEC) values of 1.36 and 1.45 were obtained. When the nanofluid inlet temperature increased to 65 °C, the PEC parameter decreased to 1.02–1.10 for both concentrations.

Investigation of heat exchanger tube fitted with triangular perforated nail head twisted‐tape inserts

AbstractA numerical investigation of the Nusselt number, heat transfer augmentation efficiency, and friction factor in a laminar flow tube with triangular perforated nail head twisted tape (TPNHTT) is reported using ANSYS 19.2 Fluent. The effects of triangular cut (each side 3 mm) in the middle pitch of the tape along the height, diameter, and top diameter of the nail head (10, 2, and 2.5 mm, respectively) have been explored for (300 ≤ Re ≤ 1800) in a tube of 22 mm diameter. In this paper, implementation has been done with a TPNHTT varying width (14 ≤ b ≤ 20) twist ratio (TR) ranging from (3 ≤ TR ≤ 6), inserts in a tube for laminar flow. Twisted tape (TT) produces a swirl flow associated with fluid resulting in heat transfer enhancement and pressure drop characteristics other than that for the plain tube (PT). The performance of the Nusselt number and friction factor increased up to 123.62% and 495.30%, respectively, on the application of TPNHTT as compared with PT. A maximum thermal performance efficiency of 2.98 has been achieved using the twisted‐tape ratio of the current tube in laminar flow at a Reynolds number of 1700. In addition, correlation equations (11) and (12) have been developed for the friction factor and Nusselt number valid for 300 ≤ Re ≤ 1800, 14 ≤ b ≤ 20, and 3 ≤ TR ≤ 6. The study has proved that applying TT is an upgraded approach for laminar convection heat transfer. This novel work finding will be supportive for researchers to design the latest heat exchangers.

Structural optimization of thermal management system for bionic liquid cold battery based on fuzzy grey correlation analysis

An energy-efficient battery thermal management system with efficient enhanced heat transfer characteristics, low power consumption and backflow inhibition performance is of great importance for electric vehicle power batteries. Based on the design of the Tesla valve and inspired by bionics, a new type of bionic blade-like mini-channel liquid cold plate with high efficiency, low power consumption and certain anti-reverse flow performance was proposed. Firstly, the initial liquid-cooled plate thermal simulation model at 5C discharge was established by CFD method and its reliability was verified by experiment. Then, orthogonal tests and fuzzy correlation analysis (FGRA) were used as evaluation methods to analyze the effects of four structural parameters (inner angle α, circumcenter angle θ1, circumcenter angle θ2, and channel height d) on the average temperature, heat transfer coefficient, and friction coefficient. The results show that the variation of the channel height d had the highest degree of influence on the mean temperature (Tave) and friction coefficient f, and that the internal angle α had the highest correlation with the heat transfer coefficient h. Finally, based on the optimization results, a better model within the range of values of each factor was obtained. When α = 25°, θ1 = 90°,θ2 = 75°, and d = 1.2 mm, Nu was increased by 0.932 (95.08 %), and ΔP was decreased by 501.686 Pa (84.74 %).The results of the optimization were shown in the following table.

Experimental and numerical analysis of PV-PCM integrated with novel shaped corrugated fins

In this paper, performance of a PV-PCM system with novel internal corrugated fins is analysed by dynamic simulation and experiments for the inclinations of 0°, 15°, and 30° against a flux of 750 W/m2 using a solar simulator. The impact of fins (n) is investigated numerically, and the optimal number of fins is found. Performance parameters such as temperature, power output, and efficiency are compared for PV, PV-PCM, and finned PV-PCM systems. The validity of the numerical model is established by comparing the simulated and experimental PV temperatures, which reduces cost and time and allows the numerical models to optimise the design and performance of the system. Results showed that an increase in inclination leads to improved performance of the PV due to an increased convection heat transfer rate. The effect of the fins is pronounced at lower inclinations. Corrugated fins enhance the heat transfer rate compared to traditional flat fins, and the heat transfer enhancement characteristics of corrugated fins within the finned PV-PCM system can provide valuable insights for optimised performance. Compared to the PV-only system, the maximum PV temperature reductions for PV-PCM and finned PV-PCM systems are 30.1 °C and 38.6 °C for θ=0° and 25.23 °C and 34.1 °C for θ=30°. The optimal number of fins is 4 for all inclinations. The maximum efficiency enhancement for optimal systems decreased from 28.15 % at θ = 0° to 22.27 % at θ = 30°. Finally, the experimental performance of finned PV-PCM at a latitude corresponding to Calicut, India, is also conducted.

A numerical study of a novel centrally bifurcated mini-channel liquid cooling plate for enhanced heat transfer characteristics

Temperature rise and poor temperature consistency of lithium-ion batteries due to heat accumulation affect the safe application of batteries. Mini-channel structured liquid cooling plates (LCP) with excellent battery thermal management effects is investigated. In order to obtain a better temperature management effect and temperature consistency at lower pressure drops, a double-layer mini-channel structure LCP bifurcated from the center to the periphery is innovatively designed. Using the simulation software, the impact of the novel LCP's structural elements on battery thermal management efficiency is studied. According to research, the LCP with a double-inlet and double-outlet arrangement provides the best temperature control while requiring the lowest pressure drop. With a 25.7 Pa pressure drop, the LCP can decrease the maximum temperature and maximum temperature difference of the battery to 38.83 °C and 6.57 °C during discharging at 2C. Subsequently, the effects of main channel width, branch channel structural elements and inlet mass flow rate on the performance of the LCP are investigated. Compared to the structural elements, the inlet mass flow rate has more influence on the effectiveness of battery thermal management. However, when the inlet mass flow rate is increased to more than 0.8 g ·s−1, the influence gets less significant. Compared to the other four structural LCPs, the batteries maximum temperature and maximum temperature differences while discharging at 2C are the lowest at 0.8 g ·s−1 inlet mass flow rate with just 152 Pa pressure drop, 33.64 °C and 6.89 °C, respectively. All of these findings could be help to optimize the structure design of mini-channel liquid cooling plates used to battery thermal management.

Experimental Investigation of Local Nusselt Profile Dissemination to Augment Heat Transfer under Air Jet Infringements for Industrial Applications

An experimental study is presented in this paper to evaluate the enhancement of heat transfer characteristics. This includes the study of a steady air jet impinging on a planar aluminum plate with constant heat flux. Extensive industrial applications of heat transfer include electronic heat sinks, the food industry, automobiles, and heat exchangers. The magnitude of the local Nusselt number along the streamwise direction is determined through detailed experimental computation using the infrared radiometry technique. The range of Reynolds number was selected between 6500 ≤ Re ≤ 15000 and the air jet outlet-to-target surface spacing 2 ≤ Y/D ≤ 6. The objective is to develop a semi-empirical correlation that can be used to determine the distribution of local Nusselt numbers over a flat plate. Considering the objective function of the spacing between the air jet outlet and target surface spacing (Y/D), Reynolds number (Re), and non-dimensional number from stagnation point in the radial direction of the plate (r’/D), it was observed that the heat transfer rates are higher for the configuration Y/D = 4 for varying Reynolds numbers, a 5 percent increase was observed. The stagnation Nusselt number shows an increasing trend up to Y/D = 4, for Reynolds numbers 10,000 and 12,000 respectively, the corresponding stagnation Nusselt numbers are 110 and 115. In comparison to the stagnation Nusselt number, which is the same Reynolds number corresponds to, the transition field Nusselt number had heat transfer values that were 12% lower.