Numerical Investigation Of Heat Transfer Research Articles

Numerical Investigation of Heat Transfer and Development in Spherical Condensation Droplets.

This study establishes thermodynamic assumptions regarding the growth of condensation droplets and a mathematical formulation of droplet energy functionals. A model of the gas-liquid interface condensation rate based on kinetic theory is derived to clarify the relationship between condensation conditions and intermediate variables. The energy functional of a droplet, derived using the principle of least action, partially elucidates the inherent self-organizing growth laws of condensed droplets, enabling predictive modeling of the droplet's growth. Considering the effects of the condensation environment and droplet heat transfer mechanisms on droplet growth dynamics, we divide the process into three distinct stages, marked by critical thresholds of 105 nm3 and 1010 nm3. Our model effectively explains why the observed contact angle fails to reach the expected Wenzel contact angle. This research presents a detailed analysis of the factors affecting surface condensation and heat transfer. The predictions of our model have an error rate of less than 3% error compared to baseline experiments. Consequently, these insights can significantly contribute to and improve the design of condensation heat transfer surfaces for the phase-change heat sinks in microprocessor chips.

Numerical investigation of heat transfer and temperature distribution in a Microwave-Heated Heli-Flow reactor and experimental validation

Microwave-heated flow systems (MWFSs), offering improved process control, enhanced product yields, and the potential for scalable and sustainable manufacturing routes, have gained significant popularity in continuously manufacturing nanomaterials and their hybrids. Temperature control in a microwave zone can maintain fine control over the manufactured materials' properties; however, the current state-of-the-art designs lack monitoring of the temperature distribution throughout the flow reactor. Herein, a unique model of numerical estimations of temperature distribution in a microwave-heated system featuring a helical flow milli-reactor, Heli-Flow, is described and validated by experimentally acquired temperature profiles. The proposed numerical model accurately predicts the temperature profile along the Heli-Flow and the steady-state outlet temperature at the MW cavity's exit. The helical design of the reactor promotes homogeneous heating and eliminates orientation-related discrepancies. The maximum outlet temperatures achieved at different microwave powers and FRs align well with expected trends. The modeled temperatures closely match the experimental and analytical measurements, indicating the effectiveness of the simulation approach. This research contributes to understanding temperature distribution in MWFSs and offers insights for optimizing nanomaterial synthesis and other applications.

Numerical investigation of heat transfer in wire and tube-based phase change material heat exchanger

The utilization of latent heat storage units with their high energy density and isothermal heat transfer behavior can enhance the performance of thermal energy systems. This study aims to investigate the effect of fin placement on the melting time of a wire and tube-based Phase Change Material (PCM) heat exchanger using numerical simulations. The study introduces a new complex geometry for the heat exchanger, and numerical analysis of heat transfer was conducted in Ansys Fluent software using an established solidification and melting model. The numerical results were validated against experimental data, and it was found that the position of the tubes and fins had a significant impact on heat transfer within the PCM. The model was able to predict temperature data with a maximum discrepancy of 3%.

Thermophysical Properties of SWCNT Nanofluid

AbstractThe current paper has the objective of exploring the thermophysical properties (TPPs) of single walled carbon nanotube (SWCNT) nanofluids (NFs) for heat transfer applications. The effect of dispersing the nanotubes in conventional heat transfer fluids (HTFs) has been investigated. Carbon nanotubes (CNTs) have exceptionally high thermal conductivities. Using the effective medium theory, density, specific heat, thermal conductivity, and viscosity has been evaluated as functions of volume fractions. The base fluids considered in this work are water, ethylene glycol, engine oil, and kerosene oil as these are the commonly used HTFs for industrial applications. Theoretical predictions from this study show an increase in density, thermal conductivity, and viscosity with volume fraction while there is a decrease in specific heat with volume fraction. The effect of the aspect ratio (AR) of CNTs on the thermal conductivity of NF is also investigated. For low volume fractions of SWCNT, the thermal conductivity has been found to increase with AR. Further, this study has been extended for a real‐world application of heat transfer using SWCNT. In this paper, a numerical investigation of heat transfer in a square enclosure with differentially heated vertical walls, filled with SWCNT‐water NF under natural convection is carried out. Due to low concentrations of SWCNT in water, single phase flow is assumed. Velocity and temperature distributions are obtained as solutions to the energy and Navier–Stoke's equations. A comparison of the temperature and velocity profile has been represented by simulating the system over a range of Rayleigh numbers.

Numerical investigation of heat transfer and thermo-hydraulic performance of solar air heater with different ribs and their machine learning-based prediction

Numerical investigation of heat transfer and thermo-hydraulic performance of solar air heater with different ribs and their machine learning-based prediction

Numerical investigation of heat transfer in spirally coiled corrugated pipes: Assessment of turbulence models

The Archimedean spiral coil made of a transversely corrugated pipe represents the radiant heat absorber of a parabolic dish solar concentrator. The main advantage of the considered design is the coupling of two passive methods for heat transfer enhancement: coiling the flow channel and changing the surface roughness. The aim of this numerical study is to assess the capability of RANS models of different complexity (realizable k-?, SST k-?, and RSM linear pressure-strain) to adequately represent the heat transfer phenomena in the considered complex flow geometry for wide ranges of Reynolds and Prandtl numbers. The obtained results indicate that the realizable k-? model with enhanced wall treatment is inadequate to simulate the heat transfer for all flow conditions, while both SST and RSM slightly overestimate experimental data in the turbulent region and are able to predict laminarisation at low Reynolds numbers. The SST model predictions are more accurate in the transitional and at the beginning of the turbulent region, irrespective of the curvature ratio. The RSM predictions are generally more accurate in the turbulent region. Numerically obtained circumferential distributions of local Nusselt number reveal that considered turbulence models are unable to completely anticipate the interactions between the complex flow in the basic section of the pipe and the vortex flow within the corrugations.

NUMERICAL INVESTIGATION OF HEAT TRANSFER AND TURBULENT FLUID FLOW FOR TRANSVERSE VORTEX GENERATORS WITH NANOPARTICLES

This paper proposes a simple design and easy-to-install vortex generator (VG) for heat exchangers to enhance heat transfer rates. The aim is to maintain low pressure drops and high heat transfer rates. The effects of the VG's geometrical parameters on thermal performance and pressure drop are investigated in this paper for divergent and convergent schemes using commercial software Comsol Multiphysics version 6. The effects of Reynolds number, VG angle, and the quantity of VGs on the response (i.e., Nusselt number and pressure drop) are investigated based on variance analysis. The nanoparticle concentration varies from 1 to 6%. The results indicate that the quantity of VGs is the most significant factor affecting pressure drop. The critical factor for heat transfer enhancement of divergent and convergent VGs are the Reynolds number and the quantity of VGs, respectively. Finally, the optimal conditions are predicted by the response surface methodology (RSM). The optimal requirements for using VG type A are β = 0°, the quantity is two, and the Reynolds number should be 9160. Furthermore, the optimal conditions for VG type B are β = 0°, Reynolds number is 10,000, and the number of VGs is two. The VG proposed in this study has a simple structure that can be efficiently designed and installed on heat exchangers. It is more efficient and applicable than the designs suggested in the literature.

Enhancing heat transfer in tube heat exchanger containing water/Cu nanofluid by using turbulator

Abstract In the current essay, the numerical investigation of heat transfer in an exchanger containing nanofluid with Cu nanoparticles in the presence of a new inserter is carried out. The equations governing the turbulent fluid flow have been solved utilizing single-phase models with the aid of the finite volume method in ANSYS-FLUENT software using the k-ε turbulence model for the Re number ranging from 4000 to 8000. Furthermore, the influence of Reynolds number, nanoparticle volume fraction, and geometric characteristics of turbulator on the friction factor and Nusselt number have been scrutinized. Outcomes reveal that the newly introduced inserter performs well and increases the Nusselt number by roughly 34–54 times and the friction coefficient by approximately 1.8–3.2 times compared to the smooth tube. It is also observed that a 2 % increase in the nanoparticles volume fraction has resulted in a rise in the Nusselt number by around 92 %. To attain the optimal performance of the presented turbulator, the longitudinal distance between the inserters is recommended as S/D = 5.27, for which Performance evaluation criteria values in the range of 3.01–9.23 in the Reynolds range under investigation are acquired.

Enhancing heat exchanger efficiency with novel perforated cone-shaped turbulators and nanofluids: a computational study

Abstract The present paper presents a numerical investigation of heat transfer in an exchanger fitted with a modified conical-shaped turbulator containing water/Fe2O3 nanofluid. The study aims to address the critical need for improved heat exchanger efficiency, a vital component in various industries, including the chemical, power generation, and food industries. The work focuses on achieving enhanced heat transfer performance within a smaller volume, a primary goal of modern technology and industrial processes. The innovation in this study lies in the design and analysis of a novel conical turbulator, which has not been explored extensively in the context of heat exchangers fitted with nanofluids. Unlike traditional methods, which often rely on active or semi-active means to enhance heat transfer, this research introduces a passive approach through the incorporation of turbulators. Specifically, the study investigates the use of perforated cone-shaped turbulators in conjunction with nanofluids to boost heat transfer performance. The research employs state-of-the-art computational fluid dynamics (CFD) models, allowing for a comprehensive evaluation of the turbulator’s performance across a wide range of Reynolds numbers (Re = 4000–20,000). It further examines the influence of various turbulator parameters, nanoparticle content, and geometry on heat transfer efficiency. Key findings indicate that the modified turbulator exhibits exceptional performance, increasing Nusselt numbers by 3.4–5.4 times and friction coefficients by 2.3–1.8 times compared to smooth pipes. Particularly noteworthy is the 92 % increase in the Nusselt number achieved with a mere 2 % increase in the Fe2O3 nanoparticle content. The present study introduces a novel passive heat transfer enhancement method using perforated cone-shaped turbulators and nanofluids, filling a significant gap in existing research. The innovative turbulator design and its substantial performance improvements offer promising prospects for achieving higher heat exchanger efficiency, making it a valuable contribution to thermal systems and heat transfer engineering.

Numerical heat transfer investigation of a single impingement jet with combined V-ribs and preliminary optimization of V-rib configuration in initial crossflow

The heat transfer performance of a single jet impingement configuration with V-ribs on the impingement plate and V-ribs on the target plate was numerically investigated for turbomachinery applications. The geometrical parameters of the impingement wall ribs were kept constant. The effects of the height and the rib-to-jet distance of the target wall ribs were analyzed in detail. The studied jet Reynolds number was Re = 35,000, the separation distance was H/D = 3, and the velocity of jet-to-crossflow ratio was R = 1–5. Based on the numerical results, taking the heat flow rate as the objective, the rib geometry was optimized by the Differential Evolution (DE) algorithm. The optimized rib configuration was then numerically simulated to validate whether the DE algorithm can be utilized for similar applications. The results of the optimized configuration were compared to those of the sample cases to verify the effectiveness of the optimization. The pressure differences between the inlet of the main jet and the outlet, and between the inlet of the initial crossflow and the outlet were computed to evaluate the pressure loss introduced by the ribs. Thus, this work provides another perspective on designing high efficient anti-crossflow cooling configurations for turbomachinery applications.

Numerical investigation of heat transfer in aluminum nitride ceramics with engineered microstructures

We present a comprehensive investigation into the thermal conduction behavior of aluminum nitride (AlN) ceramics with engineered microstructures. A finite element method is employed to investigate the impact of grain boundaries, secondary phases, pores, and inclusion of reinforcement additives on the thermal conductivity of polycrystalline AlN ceramics. Our numerical approach is built upon experimental observations that provide geometric and materials-based understanding for numerical modeling. Our model accurately predicts the thermal conductivity of hot-pressed AlN ceramics, which underwent systematic microstructure engineering through fine-tuning sintering parameters. This numerical approach provides valuable insights into microstructure engineering and a broader understanding of heat transfer in AlN ceramics.

Numerical investigation of heat transfer and melting process of phase change material in trapezoidal cavities with different shapes and different heated tube positions

Numerical investigation of heat transfer and melting process of phase change material in trapezoidal cavities with different shapes and different heated tube positions

Numerical Investigation of Heat Transfer and Flow Characteristics of Supercritical CO2 in Solar Tower Microchannel Receivers at High Temperature

Using supercritical CO2 as a heat transfer fluid in microchannel receivers is a promising alternative for tower concentrating solar power plants. In this paper, the heat transfer and flow characteristics of supercritical CO2 in microchannels at high temperature are investigated by numerical simulations. The effects of microchannel structure, mass flow rate, heat flux, pressure, inlet temperature and radiation are analyzed and discussed. The results show that higher mass flow rate obtains poorer heat transfer performance with larger flow resistance of supercritical CO2 in microchannels at high temperature. The fluid and wall temperatures, average heat transfer coefficient and pressure drop all increase nearly linearly with the increases in heat flux and inlet temperature in the high-temperature region. Moreover, high pressure contributes to great hydraulic performance with approximate thermal performance. The effect of radiation on thermal performance is more pronounced than that on hydraulic performance. Furthermore, the optimized structures of inlet and outlet headers, as well as those of the multichannel in the microchannels, are proposed to obtain good temperature uniformity in the microchannels with relatively low pressure drop. The results given in the current study can be conducive to the design and application of microchannel receivers with supercritical CO2 as a heat transfer fluid in the third generation of concentrating solar power plants.

Experimental and numerical investigation of heat transfer and flow of water-based graphene oxide nanofluid in a double pipe heat exchanger using different artificial neural network models

In this study, a water-based graphene oxide nanofluid was utilized in a counter-current flow double pipe heat exchanger (DPHE). The inner pipe carried the hot fluid (deionized water-based fluid). In the outer pipe, the cold fluid was flown, in which the experiments were performed once for deionized water-based fluid and once for graphene oxide nanofluid. These experiments were conducted at various inlet hot fluid temperatures of 35, 45, and 55 °C, volumetric concentrations of 0.01, 0.055, and 0.1% for nanofluid, and cold fluid flow rates of 14.4, 18.9, and 23.4 ml/s to evaluate the thermohydraulics of the DPHE. The results demonstrated that an increase in the flow rate and concentration of nanoparticles led to an improvement in the heat transfer coefficient (HTC) . It is also observed that inlet hot fluid temperature had a negligible effect on this coefficient compared to the concentration and flow rate. Additionally, the results showed that the friction factor and pressure drop of nanofluid were higher than those of the basefluid and their values were increased by increasing the concentration. The maximum increase compared to the basefluid was 72% for the friction factor and 111%, for the pressure drop. Besides, radial basis function neural network (RBFNN) and multi-layer perceptron neural network (MLPNN) models were designed for estimating the HTC. Both models accurately predicted the coefficient, but the RBFNN model exhibited higher accuracy than the MLPNN model. The results further indicated that the nanofluid outperformed the basefluid in terms of HTC. Due to the exceptionally high thermal conductivity of graphene nanoparticles, the HTC of the nanofluid was improved by up to 85% compared to the basefluid. The optimum value of HTC was achieved at a temperature of 55 °C, a volume concentration of 0.1%, and a flow rate of 23.4 ml/s.

Numerical investigation of heat transfer and pressure drop characteristics on the hot fluid side of the plate-fin precooler under negative pressure conditions

Plate-fin heat exchangers are widely employed in aerospace and many other fields due to the advantage of high efficiency and low resistance. However, they usually operate at atmospheric or high-pressure conditions. In this study, The commercial CFD solver Fluent 16.0 was used to evaluate the overall performance of the plate-fin precooler whose hot fluid is nitrogen under negative pressure and high temperature conditions. The characteristics of the hot fluid flow field inside the precooler with and without fins were investigated. The effect of fin number on the heat transfer and pressure drop characteristics of the hot fluid side was analyzed. Furthermore, the comprehensive performance of the precooler under different pressure conditions was compared quantitatively. The results showed that under negative pressure conditions, the hot fluid flow field features inside the precooler without fins was regular, while that of the precooler with fins took on a “<” shaped flow features, indicating the evolving of thermal boundary layer. It was also found that the comprehensive performance of the precooler did not increase with an increase in the number of fins when the hot fluid was in a low-density and high-speed flow state. Moreover, pressure conditions did not affect the heat transfer performance of the precooler but had a significant impact on the pressure drop performance.

The Numerical Investigations of Heat Transfer and Bubble Behaviors of R22 in Subcooled Flow Boiling in Casing Tubes

Amidst the background of “double carbon”, energy saving and emission reduction is a popular direction in the current refrigeration industry. Therefore, the research on the boiling heat transfer of gas–liquid two-phase flow is helpful to strengthen the heat transfer and design a more efficient heat exchanger. In this paper, a research method combining numerical simulation and experimental verification is adopted. Firstly, an experimental platform used for the subcooled flow boiling of refrigerant in casing tubes is introduced and experiments are carried out to obtain experimental data, which provides a theoretical basis for the development of numerical simulation and verifies the feasibility of numerical simulation. A numerical model of subcooled flow boiling in R22 was established and the grid independence test was carried out. Based on the simulation results, three factors affecting the boiling heat transfer of R22 are analyzed: First, the boiling heat transfer coefficient of R22 increases with the increase of the mass flow rate of R22, but the increase decreases when the mass flow rate increases from 0.018 kg/s to 0.020 kg/s. Second, the boiling heat transfer coefficient of R22 increases significantly with the increase of hot water flow rate. Third, the influence of R22 subcooling on boiling heat transfer is more complex. When the subcooling is 5 °C and 1 °C, heat transfer can be enhanced; high subcooling at 5 °C can enhance convective heat transfer and low subcooling at 1 °C can accelerate the arrival of saturated boiling. In this paper, three kinds of bubble behaviors affecting heat transfer in supercooled flow boiling, including sliding, polymerization, and bounce are also studied, which provides a basis for further research on heat transfer mechanism of supercooled flow boiling.

Experimental and numerical investigations of heat transfer and flow characteristics during flow boiling in straight and diverging PDMS microchannel

Recent trends of miniaturization and densely packed circuits have necessitated the development of novel cooling methods, especially for emerging fields like flexible microelectronics, biotechnology, and nanotechnology. A polydimethylsiloxane (PDMS) based microchannel flow boiling heat sink can be used for these applications due to its unique properties as such as unique mechanical properties, biocompatibility, optical transparency, etc. PDMS microchannels are fabricated using soft lithography techniques, which involve using a mould to pattern the PDMS material. The mould is created using photolithography, and the PDMS is poured over the mould and cured to create the microchannels. In this study, an effort is made to compare the flow and heat transfer performance of a PDMS microchannel heat sink with different channel shapes, i.e. straight and diverging microchannel heat sinks for different heat flux and mass flux conditions. The PDMS microchannel was fabricated using the soft lithography technique and a flexible laser-induced graphene heater was fabricated and integrated with the developed PDMS microchannel to act as a heat source. Experimentally, the parameters like bubble pattern, pressure drop, exit vapour quality, and corresponding heat transfer coefficient were determined at varying mass and heat flux ranging from 19 to 114 kg m−2s−1 and from 13.3 to 156.6 kW m−2 respectively for both the microchannels. It was observed that the flow in the diverging microchannel is more stable and has a 13% higher heat transfer coefficient value compared to the straight microchannel under similar conditions. Further, a 3D numerical study was carried out to corroborate and elaborate on the results. The heat transfer, flow characteristics, and bubble pattern results show an excellent agreement with experimental results. This work has significant relevance in designing flexible microchannel heat sinks.

Numerical Investigation of Heat Transfer and Pressure Drop Characteristics in a Double Pipe Heat Exchanger with Corrugated Tubes and Rod Baffles at Various Reynolds Numbers

Numerical Investigation of Heat Transfer and Pressure Drop Characteristics in a Double Pipe Heat Exchanger with Corrugated Tubes and Rod Baffles at Various Reynolds Numbers

Numerical Investigations of Heat Transfer and Fluid Flow Characteristics in Microchannels with Bionic Fish-Shaped Ribs

Microchannel cooling technology is an effective method to solve local thermal stacking. In this paper, four innovative microchannels with bionic fish-shaped rib arrangements (CM-O, CM-R, CM-H, and CM-G) are designed by imitating geese and fish clusters. The heat transfer and flow characteristics of the microchannels are simulated numerically at different Reynold’s numbers (Re = 200 − 1600). The liquid water temperature and flow field in the four innovative microchannels with bionic ribs are analyzed. The results show that the ribs’ arrangement has an influence on the thermal performance of microchannels. Compared to the smooth microchannel (CM), the of the Nu microchannels with the bionic fish-shaped ribs increases by 33.00–53.26% while the fave increases by 28.63–34.93% at Re = 1200. The vortices around the ribs are clearly observed which improves the temperature gradient. The performance evaluation criterion (PEC) of CM-H is higher than that of the others. This indicates that the rib arrangement of CM-H is superior for heat dissipation application.

Numerical investigation of heat transfer and entropy generation in serpentine microchannel on the battery cooling plate using hydrophobic wall and nanofluid

Battery cooling is essential in electronic devices since the performance of batteries is negatively influenced by the increase in temperature of batteries. This paper investigates the significance of a serpentine microchannel that is situated on the surface of the battery. The nanofluid flow and thermal behavior are simulated through numerical methods in the serpentine microchannel and battery surface. The results confirmed that the present nanofluid is able to increase heat transfer between serpentine microchannel and battery by up to 20 %. Moreover, the most effective parameter on the heat transfer improvement was the Reynolds number so when the Reynolds number varies from 25 to 150 the heat transfer increased from 6.34 to 12.75. More importantly, the hydrophobic walls of microchannels lead to a 14.4 % enhancement in heat transfer compared with a conventional wall.