Numerical Investigation Of Heat Transfer Research Articles

A numerical investigation of heat transfer and clogging in smooth and ribbed cooling channels of the GEF9’s first rotor blade

Analysis of heat transfer and the possibility of clogging in gas turbines play a crucial role in their design and material selection. Due to the high operating temperatures of gas turbine blades, internal blade cooling is utilized to reduce the damage of high temperatures and enhance the durability of gas turbines. Among these methods, the blades' internal cooling is one of the most common approaches. The main objective of this research is to investigate the feasibility of using ribs to increase the internal cooling rate and consequently reduce the surface temperature of the second rotor blade of the GEF9 turbine. Additionally, the experimental observations of damaged blades, proved that some of the internal cooling paths are blocked due to particle deposition of dusty cooling air. So, the main innovation of this research lies in simulating the dust trajectory of dust particles within the cooling channels using an Eulerian-Lagrangian approach to predict blockages in the cooling channels, as well as investigating erosion resulting from the impact of dust particles with the cooling passage walls. Based on the obtained results, ribs increase the convective heat transfer up to 40% but raise the pressure drop in other hands. With analysis of different types of geometrical parameters, the best thermal efficiency is about 0.76 (less than 1). The probability of clogging in the ribbed channels is 100 times more than smooth ones and also the rate of erosion in ribbed channels is 10% more than smooth channels which can increase the stress and reduce the durability of the blade. So using rib in this type of blade is not feasible. By comparing the volume fractions of dust particles near the internal walls in the smooth cooling channels, the first and fourth channels have the highest and lowest likelihood of blockages, respectively and it shows that front channels should be designed with higher diameter.

Numerical investigations of heat transfer and pressure drop in packed bed duct exposed to forced convection boundaries under local thermal non-equilibrium conditions

The present study is a 2-D numerical study which discusses the thermohydraulic performance of packed bed duct under local thermal non-equilibrium and steady state conditions exposed to forced convection boundaries (BC-6). The numerical model is well validated with the experimental work reported in the literature and found to be accurate enough to perform further parametric investigations. The analysis is done to see the effect of different ball diameter (5 mm, 9 mm and 11 mm), bed porosity, heat transfer fluid (air, water and engine oil - Pr = 0.70–645) and ball material (EPS, steel and bronze) on heat transfer and fluid flow characteristics in turbulent flow region of Reynolds number ranging from 900 to 14,320. The numerical results obtained using commercial CFD software COMSOL shows that, the heat transfer coefficient and pressure drop in packed bed increases with increase in ball diameter, thermal conductivity of ball and bed porosity which is exactly reverse as reported in literature for BC-1 to BC-5. The maximum thermal performance factor with bronze particles is 2.45 and 24.5 times more than stainless steel and EPS particles respectively for larger particle size and bed porosity. Engine oil exhibits significantly higher heat transfer coefficient (9.7 × 105 W/m2K) and pressure drop (3.3 × 106 Pa) compared to water (40,126 W/m2K and 2028 Pa) and air (600 W/m2K and 250 Pa) respectively. Overall, the combination of water as heat transfer fluid along with bronze particles of larger diameter and larger bed porosity emerges as the optimal choice for enhancing heat transfer in the packed duct exposed to forced convection boundary condition BC-6.

Thermal management of a battery pack using fin-embedded phase change material

Abstract The present study focuses on the numerical investigation of heat transfer from a battery cell surrounded by phase change material (PCM) with longitudinal fins embedded in it. Three-dimensional transient heat conduction equation is solved numerically in the battery domain, whereas the solidification-melting model adopting Enthalpy-Porosity approach is solved in PCM to obtain liquid fraction and temperature distribution. PCM with 16 fins was found to be quite effective in reducing the battery surface temperature compared to 12, 8, and 4 fins. However, the effectiveness of 16 fins is observed up to 1500 sec till the PCM completely melts into liquid. A maximum reduction of 25 K has been achieved at 1500 sec by adding 16 fins to PCM. Beyond 1500 sec, the temperature rises sharply, exceeding all other cases at 2200 sec. Fins play an essential role in augmenting heat transfer, which benefits in achieving the phase change process in less time to restrict the temperature rise; however, at the same time, when the phase change process completes, fins become detrimental to the system since the temperature of the battery starts rising sharply.

Editor's Note for article entitled “Numerical investigation of heat transfer and entropy generation in serpentine microchannel on the battery cooling plate using hydrophobic wall and nanofluid”

Editor's Note for article entitled “Numerical investigation of heat transfer and entropy generation in serpentine microchannel on the battery cooling plate using hydrophobic wall and nanofluid”

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 analysis of microchannel heat sink performance using delta vortex generator

The design of unique microsinks arises from the desire to provide efficient cooling at low pressure drop for a more compact miniaturized electronic equipment. Three-dimensional numerical investigations of heat transfer and fluid flow have been carried out with delta vortex generator (DVG) structures in the rectangular microchannel. A pair of delta vortex generators (DVGs) are placed symmetrically about the horizontal mid plane in rectangular microchannels. Performance variances are assessed on the basis of the average Nusselt number (Nu), friction factor (f), and thermal performance (TP) along with the thermal resistance (RT) and hydraulic resistance (RH) for the Reynolds number in the range of 93 to 746. The parametric variation has been carried out by altering geometric parameters such as the angle of DVGs with centerline (θ), the number of pair of DVGs (n), the length of DVGs (l), the distance of DVGs from the centerline (B), the position of DVGs from the inlet for first pair (L1), and the distance between the vortex generators (S). The objective is kept to maximize the TP, to minimize the value of thermal resistance, and to decrease the increase in the hydraulic resistance for the same geometrical variation. The highest thermal performance equal to 1.256 has been achieved with the combination of θ, n, l, B, S, and L1 equal to 45°, 3, 0.6 mm, 0.1 mm, 4.5 mm, and 5.334 mm, respectively. For the same geometrical parameters, a minimum thermal resistance equal to 0.98 K/W and a hydraulic resistance equal to 3.234 kPa-min/ml have been attained at Re about 745.66. By minimizing the thermal and hydraulic resistance of the microchannel with DVGs, it becomes possible that heat can be more effectively transferred across the interface and the desired cooling can be achieved with less power input. The implementation of DVGs enhances intermixing through the generation of longitudinal and transverse vortices, leading to a more evenly distributed temperature across the channel. This enhancement in the heat transfer reduces the thermal resistance. Additionally, the vortices generated by DVGs modify the velocity profile, thereby decreasing the pressure drop and the hydraulic resistance. The specific impact of longitudinal vortices on the enhancement of the heat transfer through adjustments in geometric parameters is thoroughly elucidated.

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

Experimental & numerical investigation of heat transfer using twisted tapes with rectangular cuts

The current work focuses on using rectangular inserts with water as the working fluid to investigate heat transfer experimentally and numerically in a horizontal circular tube [10]. The study considers variations in the number of rectangular slots within the same strip. The tube has dimensions of 0.0266 m diameter. Twisted tapes, featuring rectangular cuts, are constructed from a 3 mm thick Stainless-steel strip with a length of 1035 mm. For experimentation, two different types of rectangular inserts were considered: one with nine cuts and the other with eighteen cuts. The dimensions of the cuts were as follows: length of 1000 mm, width of 13 mm, depth of cut 8 mm, and thickness 3 mm. The heat flux applied to the horizontal tube was steady and uniform. The range of the Reynolds number was 9,000–19,000. A plain tube without an insert was used to compare the results. The horizontal tube along with rectangular insert was modelled in Ansys Fluent software with fine meshing and analysed. Initially, CFD analysis was done for plain tube with and without insert, and results have been verified by comparison with experimental values. A comprehensive comparison is established, evaluating different heat transfer parameters, including convective heat transfer coefficient (h), heat transfer rate (q), and Nusselt number (Nu).

Investigation of heat transfer and pressure drop in flexible metal hoses with corrugated surfaces

In this study, we conducted a numerical investigation of heat transfer and pressure drop in annular corrugated and 1-, 2-, and 3-start spiral-corrugated flexible metal hoses. To validate the numerical results for pressure drop, we established an experimental setup. The pressure drop results were verified through experimental data, while the numerical heat transfer results were validated against existing correlations in the literature. The results obtained using the corrugated flexible metal hoses were compared to those of a smooth tube, and all hoses along with the smooth tube were 1 meter long. The hydraulic diameters of the annular corrugated hose and the spiral corrugated hoses were 25 mm and 26.2 mm, respectively, with a corrugation depth of 3.2 mm for all hoses. Water, at an average temperature of 25?C, was used as the fluid, with a constant surface temperature of 70?C for the test tube. Analyses were conducted for Reynolds numbers ranging from 10000 to 50000. The results indicated that the fluid outlet temperature and pressure drop values for the annular corrugated hose were generally higher than those for the spiral corrugated hoses. Among the hoses tested, the 1-start spiral corrugated hose showed the highest friction factor, 7.83 times higher than that of the smooth tube. The 3-start spiral corrugated hose achieved the highest Nusselt number, 1.4 times higher than that of the smooth tube, at a Reynolds number of 20000. The performance evaluation criteria for all hoses ranged from 0.6 to 1.

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.