Turbulent Convective Heat Transfer Research Articles

Machine learning algorithms on predicting the turbulent mixed convection flow in a driven-cavity with two horizontal cylinders

Turbulent mixed convection flow and heat transfer properties in a driven cavity with two circular cylinders arranged one above another are analyzed numerically with the incorporation of a finite element scheme, based on the Galerkin method of weighted residuals. A comparison of streamlines, isotherms, and local, average Nusselt number is provided to illustrate how the Richardson number Ri, Reynolds number Re and the eddy viscosity ε affect the transport phenomena inside the cavity. The local and average Nusselt number have been evaluated and it is found that strong convection at the top wall causes the average Nusselt number to progressively rise with respect to Ri and ε, while steady or slightly varying profiles are seen with regard to Re. In order to predict the thermal distribution inside the cavity due to these hot cylinders, Artificial Neural Network (ANN) and Gaussian Process Regression (GPR) have been developed with these model parameters as input and average Nusselt Number as target values. Several plots have been depicted to come to a conclusion that both models have been trained very effectively with the minimal observed Mean Square Error (MSE) values of 0.0026018 and 0.0026428 for ANN and GPR, respectively. In support to these findings, the coefficient of determination R2 suggests that ANN (R2 = 0.89) outperforms GPR (R2 = 0.87) in testing accuracy, hence it is recommended for prediction task.

Modeling of Metal Matrix Concentrated Solar Receivers for sCO2 Power Blocks

Abstract Supercritical CO2 power blocks for Concentrating Solar Power (CSP) with novel metal matrix solar receivers have the potential to reduce operating expenses while improving overall system efficiencies. These concentrated solar receivers integrated with a metal matrix-based phase change (PCM) thermal storage medium provide the compounding effect of an efficient heat exchanger while also integrating thermal storage within the receiver. Detailed numerical modeling of such devices with enthalpy-porosity-based formulation for phase change and turbulent convective heat transfer for the sCO2 microchannels is described in the current work. With sCO2 power blocks operating at temperatures and pressures beyond 800°C and 200 bar, different high-temperature PCMs are studied. A detailed steady charging followed by discharge and charging transients is simulated to analyze the thermal performance of these devices. In the current work, the energy storage density of PCMs is studied, followed by an analysis of the movement of the melt-pool interface over the streamwise length of a high corrugation wavy microchannel. A scaling analysis is carried out to estimate the heat transfer coefficients while compare them with the numerical model predictions. The results from the current work can be utilized for sizing and detailed design of integrated solar receivers for high-temperature sCO2 power block applications.

A detailed thermohydraulic performance assessment of surface-modified silver nanofluids in turbulent convective heat transfer

This study investigates the thermohydraulic performance of surface-modified silver nanofluids in turbulent convective heat transfer applications. The primary objective is to evaluate the impact of citrate, lipoic acid, and silica surface modifications on heat transfer coefficients, pressure drops, and friction factors under turbulent flow conditions. Silver nanoparticles (50 nm) with the specified surface modifications were synthesized and dispersed in deionized water, ensuring stable nanofluid preparations. Experimental evaluations were conducted in a smooth brass tube with a uniform heat flux, covering Reynolds numbers from 3400 to 21,800, mass flow rates of 32 to 78 g s−1, and inlet temperatures of 26 °C, 31 °C, and 36 °C. Key findings indicate that the silica-shelled nanofluid (Ag/S) exhibited a significant 35% increase in the heat transfer coefficient compared to DI water, while citrate-coated (Ag/C) and lipoic acid-coated (Ag/L) nanofluids showed slight decreases of 0.2% and 2%, respectively. The mean Nusselt number for Ag/S also increased by 9%, demonstrating enhanced heat transfer capabilities. Surface-modified nanofluids experienced higher pressure drops and friction factors than the base fluid. Ag/C showed a 7.7% increase in pressure drop, Ag/L a 12.3% increase, and Ag/S a 12.5% increase, correlating with an 11.9% rise in viscosity. While surface-modified silver nanofluids, particularly silica-shelled, can significantly improve heat transfer performance, the associated increases in pressure drops and friction factors must be carefully balanced for specific applications. Future research should explore long-term stability, varying nanoparticle concentrations, and more complex geometries to optimize nanofluid formulations for targeted heat transfer applications.

Investigation of thermal performance at forced convection in plate-fin heat sink

Interest in studies on more effective and faster heat dissipation in microelectronic equipment has increased in recent years due to the cooling area and equipment size limitations. This study attempts to focus on the effect of different fin geometry parameters on pure forced convection heat transfer. Total surface areas of plate-fin heat sinks were kept constant and were carried out for ten different heat sinks in these analyses. The Ansys-Fluent 2023 R1 commercial package program was used to perform the thermal and hydrodynamic performance analyses. Three-dimensional turbulent forced convection heat transfer analyses at heat sinks were subjected to fluid flow (500≤Re≤3000). The effects of gap between fins, fin thickness, fin height, fin number, and air velocity on the heat transfer and the friction factor were obtained and discussed for heat sinks. It was observed that there was a maximum difference of 0.27 % between the maximum temperatures obtained as a result of this analysis and the experimental study results in the literature. Among the ten cases examined (from Case 1 to Case 10), the highest heat transfer coefficient was obtained in Case 2 (number of fins 6, gap between fins 4 mm, fin height 17 mm and fin thickness 2 mm) at Re = 3000. The heat transfer coefficient of Case 2 was 41.29 % higher than the heat transfer coefficient of Case 4 at Re = 3000; though, the friction factor of Case 2 is 55.93 % higher than Case 4. Also, a useful correlation for the heat transfer coefficient was generated for the fin geometric parameters and Reynolds number.

Retraction notice: Numerical investigation on turbulent convective heat transfer of nanofluid flow in a square cross-sectioned duct

Retraction notice: Numerical investigation on turbulent convective heat transfer of nanofluid flow in a square cross-sectioned duct

Numerical analysis of turbulent mixed convection heat transfer of molten salt in horizontal tubes with uniformly cooled heat flux

Molten salt is a widely used heat transfer medium in the field of energy systems. In the engineering design, mixed convection heat transfer often occurs in the high heat flux tube convection heat transfer process, which can significantly change the convective heat transfer capability. However, optimizing the heat exchange conditions can improve the heat transfer capacity of molten salt. In this study, turbulent mixed convection heat transfer characteristics of Hitec molten salt inside horizontal cooling tubes are investigated numerically using the Reynolds stress turbulence model. The results show that the secondary flow caused by buoyancy can lead to significant nonuniform in heat transfer and wall temperature on the wall surface of the horizontal tube cross section. In addition, the buoyancy parameter Bo is selected to characterize the buoyancy effect on Hitec mixed convection heat transfer inside a horizontally cooled circular tube, and within the Bo range from 2.82 × 10−8 to 1.61 × 10−5, as the Bo increases, the relative average Nusselt number for the upper half tube wall gradually increases, the relative average Nusselt number for the lower half tube wall decreases, and the relative average Nusselt number for the entire tube wall shows the combined results of the upper half wall and the lower half wall relative average Nusselt numbers, which slightly increases and then decreases. Furthermore, based on the numerical data, the critical buoyancy parameters Bocr,1 = 10−7 and Bocr,2 = 6.96 × 10−6 at which the buoyancy force starts to affect heat transfer and the average Nusselt number for the entire tube wall starts to decrease are proposed, and variations of the mixed convection heat transfer against the buoyancy parameter Bo are presented respectively for different regions of the horizontal cooling tubes. Based on this research, a reasonable and widely applicable buoyancy parameter selection criterion can be constructed to guide the future engineering designs.

Modulation of flow, heat, and mass transfer in turbulent double-diffusive convection

The present study addresses numerical simulations of the double-diffusive convection in a turbulent regime. The characteristic concentration and temperature Prandtl numbers (PrC = 700 and PrT = 7) correspond to the typical seawater properties. Here, we applied the Large-Eddy Simulation (LES) approach, with relatively simple subgrid turbulence closures of momentum, concentration, and temperature for the unresolved scales. The wall-resolved LES approach proved to work well on significantly coarser numerical mesh than used in recent Direct Numerical Simulation (DNS) studies of Yang et al. (2016) in the intermediate range of working parameters, 107 ≤ RaC ≤ 109, 0 ≤ RaT ≤ 106, which covers the quasi-Rayleigh-Bénard, fingering, and damping flow regimes. A good agreement between concentration and temperature Nusselt numbers is obtained. The instantaneous Nusselt numbers distribution revealed a significant impact of the imposed strong thermal stratification (RaT = 106) in comparison to the neutral case (RaT = 0).

Performance evaluation and enhancement of turbulent flow and convective heat transfer characteristics for turbine blade internal cooling

For turbine blade internal cooling, the performance of turbulent flow and convective heat transfer in the cooling channel is numerically investigated via the computational fluid dynamics method, where the cooling channel adopts the combination of transverse rib arrangements and round-edged rib configurations or the combination of oblique rib arrangements and round-edged rib configurations. Under these two combination conditions, the simulation result shows that in the wide Reynolds number range of Re = 20 000–80 000, the heat transfer enhancement and the flow loss reduction, such as the larger normalized Nusselt number of Nu/Nu0 and smaller normalized friction factor of f/f0, are simultaneously realized by the oblique rather than transverse rib arrangement. In the oblique rib channel, the relationship between turbulent flow and convective heat transfer is for the first time revealed by the relationship between secondary vortices and turbulent kinetic energies. Based on the relation between secondary vortices and turbulent kinetic energies, the overall performance of turbulent flow and convective heat transfer for the oblique rib channel is first optimized by various normalized rib height, e/Dh, and rib spacing, p/e, and then evaluated by both overall performance factors of OPT1 and OPT2. Both OPT1 and OPT2 are larger at e/Dh = 0.062 and p/e = 15.00 in the wide range of e/Dh = 0.047–0.101 and p/e = 10.00–15.00. As a result of the comprehensive evaluation of OPT1 and OPT2, the combination of e/Dh = 0.062 and p/e = 15.00 is eventually employed by the oblique rib channel.

Effect of porous fin parameters on the turbulent natural convection heat transfer in the side-heated cavity containing the internal heat source

In order to study the effect of porous fin parameters on the natural convection heat transfer in the side-heated cavity containing the internal heat source, the influence of the structural parameters of porous fins (length of porous fins l, installation position of porous fins s, Installation angle of porous fins θ) and the physical property parameters of porous fins (effective thermal conductivity Ke, Darcy number Da) on the natural convection heat transfer in the cavity was numerically analyzed by arranging a porous fin on the hot wall. The effect of the coupling effect of the structure parameters of porous fins was analyzed by the response surface method, and it was found that the coupling effect of the installation position and installation angle of porous fins had the most significant effect on the convective heat transfer in the cavity, the combination of the structural parameters of porous fins with the optimal convective heat transfer effect is l = 0.053 H, s = 0.373 H, and θ = 93.21°, which increases the average Nusselt number of the hot wall by 38.72% compared with no-fin structure; The effect of Darcy number and effective thermal conductivity of porous fins on the average Nusselt number of the hot wall surface is analyzed. The results of the study can guide the study of solar radiation in buildings, the internal temperature control of automobiles, and the study of the thermal performance of electronic components.

Opposing Mixed Convection Heat Transfer for Turbulent Single-Phase Flows

Convection, wherein forced and natural convections are prominent, is known as mixed convection. Specifically, when a forced convection flow is downward, this flow is called opposing flow. The objectives of this study are to gain a comprehensive understanding of opposing flow mixed convection heat transfer and to establish the prediction methodology by evaluating existing correlations and models. Several heat transfer correlations have been reported related to single-phase opposing flow; however, these correlations are based on experiments conducted in various channel geometries, working fluids, and thermal flow parameter ranges. Because the definition of nondimensional parameters and their validated range confirmed by experiments differ for each correlation reported in previous studies, establishing a guideline for deciding which correlation should be selected based on its range of applicability and extrapolation performance is important. This study reviewed the existing heat transfer correlations for turbulent opposing flow mixed convection and the single-phase heat transfer correlations implemented in the thermal–hydraulic system codes. Furthermore, the authors evaluated the predictive performance of each correlation by comparing them with the experimental data obtained under various experimental conditions. The Jackson and Fewster, Churchill, and Swanson and Catton correlations can accurately predict all the experimental data. The effect of the difference in the thermal boundary conditions, i.e., uniform heat flux and uniform wall temperature, on the turbulent mixed convection heat transfer coefficient is not substantial. The authors confirmed that heat transfer correlations using the hydraulic-equivalent diameter as a characteristic length can be used for predictions regardless of channel-geometry differences. Furthermore, correlations described based on nondimensional dominant parameters can be used for predictions regardless of the differences in working fluids. The authors investigated the extrapolation performance of the mixed convection heat transfer correlations for a wide range of nondimensional parameters and observed that the Jackson and Fewster, Churchill, and Aicher and Martin correlations exhibit excellent extrapolation performance with respect to natural and forced convection flows, indicating that they can be applied beyond the parameter range validated experimentally.

Flow and thermal fields modeling in jet impingement configurations using a Reynolds stress turbulence closure within the RANS and Sensitized-RANS framework

The flow and thermal field characteristics underlying turbulent convective heat transfer in two reference configurations, representing a jet exiting a planar slot and a circular tube and impinging on a heated wall, are studied computationally. The performance of a conventional Reynolds Stress Model (RSM) and its scale-resolving variant, employed in the context of a time-accurate Reynolds-Averaged Navier–Stokes (RANS) simulation, is investigated in conjunction with different modeling approaches for the turbulent heat flux uj′θ′¯, whose gradient represents the turbulence-induced heat source in the temperature transport equation. In this so-called Sensitized-RANS modeling strategy, employing an improved eddy-resolving instability-sensitive Reynolds Stress Model (IISRSM, Jakirlić and Maduta (2015)), the unresolved ‘sub-scale’ turbulent correlations represent the solutions of a set of corresponding transport equations for the entire stress tensor ui′uj′¯. The turbulent scalar-flux models follow from the classical gradient-diffusion approach with the diffusion-like coefficients formulated as a function of both the scalar eddy-viscosity and the anisotropic Reynolds stress tensor. The latter model expressions also take into account various non-linear relationships in terms of turbulent stress components. The computational results of the fully-developed channel flow, featured only by the mean shear and constant wall heat flux, representing a preliminary investigated flow configuration, agree very well with the corresponding DNS (Direct Numerical Simulation) database for both RSM versions in conjunction with all the turbulent heat flux models adopted. However, the study of the two flow impingement cases with the different structure of the impinging jet and nozzle-to-wall distance variations, characterized by a much more complex flow straining, using the considered conventional Reynolds stress model shows significantly different results for the Reynolds stress and thermal fields compared to the available DNS data, especially in the immediate impact region manifested by a significant overprediction of the turbulence intensity. In contrast, the IISRSM-relevant results for the mean flow and temperature fields, the associated integral characteristics, and the corresponding turbulence quantities are in very good agreement with the reference DNS data, due to the much higher predictive capabilities of this eddy-resolving turbulence model compared to its baseline counterpart.

Effect of particle size on second law of thermodynamics analysis of Al2O3 nanofluid: Application of XGBoost and gradient boosting regression for prognostic analysis

In this study, the current research delves into the influence of nanoparticle size on turbulent forced convective heat transfer, entropy generation, and friction factor. The investigation focused on three different sizes (30 nm, 50 nm, and 80 nm) of Al2O3 nanoparticles (NPs) suspended in a water-based nanofluid (NF) with a 1 vol% concentration flow in a circular tube. The nanoparticles (NPs) were characterized using various characterization techniques. The stability and pH of the NF were determined, and its viscosity (VST) and thermal conductivity (TC) were measured at a temperature of 60 °C. Heat transfer experiments were conducted with varying particle sizes and Reynolds number (Re), maintaining a fluid inlet temperature of 60 °C. The results indicated that the NF containing 30 nm particles exhibited higher VST and TC compared to the other samples and the base fluid. The maximum enhancement in Nu for Al2O3 (30 nm) and Al2O3 (80 nm) NFs is 60.7 and 18.5 % greater than that of base fluid, respectively. The maximum and minimum total entropy generation (Sgen,T) value of 0.499 and 0.286 observed for base fluid and Al2O3 NF (30 nm), respectively at low Re. The highest friction factor enhancement for Al2O3 NF (30 nm) exceeded by 9.4 % compared to the base fluid, and the maximum thermal performance factor observed for Al2O3 NF (30 nm) was 1.57. Finally, regression analysis was employed to establish correlations for estimating Nu and friction factor values. Prognostic models were developed using two sophisticated machine learning algorithms, XGBoost and Gradient Boosting Regression (GBR). Both models demonstrated exceptional prediction abilities, achieving over 99 % accuracy rates based on the experimental data.

A general approach for predicting convective heat transfer coefficients in turbulent systems

A generalized approach for predicting turbulent convective heat transfer coefficients using large eddy simulation is presented. This model is based on semi-empirical transport theory, which links the local convective heat transfer rate to the local energy dissipation rate within the near-wall boundary layer. We apply these approaches to agitated tanks, pipe flow systems, cylinders in crossflow, and tube bundles. We validate the generality and reliability of the theoretical model against expectations from experimentally derived empirical design correlations.

Numerical and experimental investigation of laminar and turbulent convective heat transfer in a coiled flow reverser with twisted tape insert

This paper presents a comprehensive investigation of heat transfer enhancement and pressure drop in a Coiled Flow Reverser (CFR) with a twisted tape insert. Both laminar (10 < Re < 2000) and turbulent (12,000 < Re < 18,000) regimes have been studied using both experimental and numerical methods. The effects of twist ratio of twisted tape, inlet Reynolds number, and perforating the twisted tapes have been investigated. The study found that the best performance in the laminar regime is achieved with a twisted tape with a twist ratio of 15.73 and no holes on it at a Reynolds number of 2000. In the turbulent regime, the same twisted tape performs the best at a Reynolds number of 17,000. The highest Thermal Performance Ratio (TPR) in laminar regime is 1.55 and in turbulent regime is 0.99. In comparison to the straight pipe, all types of CFRs show better performance in heat transfer enhancement. Also, as the Reynolds number increases, the friction coefficient decreases in all configurations. The study reveals that the twisted tape insert enhances heat transfer performance while increasing pressure drop. This study provides valuable insights into the design and optimization of heat exchangers with CFR. The findings can be used to improve the efficiency and performance of various industrial processes, such as refrigeration systems, air conditioning, and power plants.

Experimental and computational study of convective heat fluxes in swirling two‐phase flows

AbstractThe convective mode of heat transfer is mainly due to the bulk motion of the fluid. Its turbulent nature and enhanced heat transfer coefficients have always attracted the academic, scientific community, and industrialists for many decades. The current research is based on the experimental and theoretical investigations on the turbulent convective heat transfer in swirling (60–300 rpm) steam (1–3 bars) injection into cocurrently flowing water. An exponential increase in the convective heat transfers up till the most swollen part of the swirling steam‐water volume of fluids has been observed. However, the convective heat transfer of the remaining part of the steam's plume shows an almost stagnant decreasing trend. The range of Rayleigh number that supports the transition in trends of the convective heat fluxes is 2.84 × 1011–3.71 × 1011. This transition affects the magnitude of the convective heat fluxes and the extent of the effective momentum fluxes, which is evident in the dominant role of the flow instabilities acting across the length of the steam's plume. Computational Fluid Dynamic analysis also has supported the exhibition of the heat fluxes magnitudes under the influence of the interacting Kelvin–Helmholtz instabilities and inertial instabilities across and along with the cocurrently acting shear layer.

Numerical simulations of heat transfer phenomena with turbulent supercritical carbon dioxide flow in heated horizontal minichannels with different shapes

This study aims to clarify and evaluate the influence of buoyancy force on heat transfer to supercritical carbon dioxide flowing in horizontal minichannels. Numerical simulations are carried out on the turbulent mixed convective heat transfer of supercritical carbon dioxide in horizontal semicircular, circular, and rectangular minichannels (dh = 2 mm) for the low-pressure side of a closed Brayton system heat exchanger (p = 8 MPa, Tin = 303 K, G = 1200 kg‧m−2‧s−1, Rein = 42,521–42,860, q = 50–30 kW‧m−2). The heat transfer mechanism in different channels is analyzed and the effect of heat flux is investigated. The heat transfer in the bottom wall is stronger than that in the top wall due to the buoyancy force. The heat transfer at the corners of semicircular and rectangular channels is greatly reduced due to blockage compared to the circular channel. A transition in the heat transfer regime from enhanced to normal is found as the heat-to-mass flux ratio increases to 83.33 J·kg−1. Starting from q/G = 125 J‧kg−1, there is a significant heat transfer deterioration, and the difference between the top and bottom walls gradually becomes apparent under the influence of buoyancy. In addition, the applicability of three existing buoyancy parameters (Buc, BuJ, and BuP) is evaluated. The BuP buoyancy criterion agrees best with the simulation results. A comparative study with the case without gravity identifies a threshold value of 6.0 for BuP in the circular channel and a threshold value of 1.0 for BuP in the semicircular and rectangular channels. Above this threshold, natural convection will have a considerable effect on forced turbulent heat transfer.

Review and comparison of turbulent convective heat transfer in state-of-the-art 3D truss periodic cellular structures

To promote the development and application of periodic cellular structures (PCSs), this paper reviews and systematically compares the heat transfer and pressure drop of state-of-the-art 3D truss PCSs. Relative merits among these PCSs in the turbulent regime are clarified which have been fuzzy in the open literature. The topological and orientation effects on the thermo-fluids of the PCSs are also investigated. Twelve PCSs with the same height and porosity, separately in two different orientations, are evaluated by numerical simulations. These PCSs include the cubic lattice (CL), the body-centered cubic lattice (BCCL), the face-centered cubic lattice (FCCL), octet lattice (OL), circular pyramid lattice (CPL), rectangular pyramidal lattice (RPL), tetrakaidecahedron lattice (TL), X-lattice (XL), shifted X-lattice (SXL), circular tetrahedral lattice (CTL), rectangular tetrahedral lattice (RTL), and Kagome lattice (KL). It is found that the entry and exit effects on heat transfer and pressure drop are limited within the first four unit cells and the last unit cell, respectively. For a given Reynolds number within the range of 2692–11087, the SXL in orientation A (SXL-OA in abbreviation) exhibits the best overall heat transfer; and the SXL-OA also has the best endwall heat transfer. In addition, the OL-OA, XL-OA and SXL-OA show the best heat transfer on the PCS core. In terms of pressure drop for a given Reynolds number, the RTL-OA and RTL-OB exhibits the highest and the lowest pressure drop, respectively. For a given pumping power, the OL exhibits the best overall heat transfer. Thermo-fluidic mechanisms are also explored with representative PCSs. For the given porosity and range of Reynolds number, correlations for overall heat transfer, local heat transfer and pressure drop are presented, which are beneficial for engineers to quickly evaluate and compare the PCSs made of different materials. The systematic comparison in the turbulent regime extends the comparison in the laminar regime in the open literature, which is expected to promote reasonable development and application of PCSs in heat exchangers and thermal management systems. Applications of PCSs in different scenarios and future work are also commented.

Performance evaluation with turbulent flow and heat transfer characteristics in rectangular cooling channels with various novel hierarchical rib schemes

Turbulators, such as ribs, dimples, and pin-fins, play a vital role in the internal cooling efficiency of turbine blades. As a typical turbulator, various rib configurations using a uniform arrangement scheme have indicated high heat transfer enhancement but the friction loss is simultaneously subject to a great increase. In this work, a novel hierarchical arrangement scheme of ribs is developed aiming to improve the cooling efficiency. Adopting the uniform scheme as a baseline, the hierarchical scheme is implemented for six representative rib configurations (including transverse ribs, angled ribs, V-shaped ribs, inverted V-shaped ribs, M-shaped ribs, and inverted M-shaped ribs) and evaluated for its feasibility and generality. For different cooling designs, turbulent flow and heat transfer of the ribbed cooling channel are studied by three-dimensional numerical simulations based on the finite volume method with a constructed turbulence model. It is found that for all rib configurations, the hierarchical scheme can remarkably reduce the friction loss as desired, especially for the inverted V-shaped rib with a reduction of up to 50%. Due to the occurrence of flow separation, secondary flows offered by transverse ribs are characterized by a two-dimensional recirculation vortex behind the rib. For other rib configurations, secondary flows present a typical three-dimensional characteristic including the downwash flows along the inclined rib leg and the longitudinal vortices. The usage of the hierarchical scheme with small ribs strongly suppresses these secondary flows, which contributes to the significant decrease in form drag loss. Meanwhile, using the hierarchical scheme produces a slight heat transfer deterioration commonly, which is because the constrained secondary vortices weaken the turbulent mixing and convection heat transfer. Significantly, for the two W-shaped ribs, the limited secondary vortices but fully developed under the hierarchical scheme achieve a higher heat transfer enhancement. Finally, for all considered ribs, the hierarchical scheme can improve the overall performance factor of (Nu/Nu0)/(f/f0)1/3 by more than 10%, and up to 21.15% for the V-shaped rib. Adjusting design variables, including the decreasing ratio of the rib size and the initial rib size, the hierarchical scheme still provides even higher performance enhancement.

Heat transfer enhancement of a slot-confined and submerged impinging jet utilizing lamina-shaped CoFe3O2/water nanofluid

Designing a cooling system is crucial for the thermal management of many different types of energy applications, such as fuel cells, solar panels, electronic cooling, and many more. A higher local heat transfer coefficient is attained by impinging jets, making them a viable cooling option. This study investigates a two-dimensional numerical study into the turbulent convective heat transfer in a confined slot and submerged impinging jet by using water and a nanofluid for Reynolds numbers between 6000 and 24000. The nanofluid of lamina-shaped CoFe3O2/water has been studied, with the volume concentration of nanoparticles ranging from 2.0% to 4.0%. Using a finite volume technique based on the SIMPLE algorithm, the governing momentum, continuity, and energy equations are solved. A presentation and discussion of the influence of the nanoparticle's volume fraction and the Reynolds number on the flow and thermal properties are provided. Increasing the volume fraction of nanoparticles is shown to enhance the Nusselt number and the Darcy friction factor. Entropy generation increases with the increase of the Reynolds number for all working fluids.

Characteristics of turbulent forced convective nanofluid flow and heat transfer in a 2D axisymmetric corrugated pipe

Characteristics of turbulent forced convective nanofluid flow and heat transfer in a 2D axisymmetric corrugated pipe