Simulation Of Heat Transfer Enhancement Research Articles

Numerical Simulation of Heat Transfer Enhancement of a Heat Exchanger Tube Fitted with Single and Double-Cut Twisted Tapes

Numerical Simulation of Heat Transfer Enhancement of a Heat Exchanger Tube Fitted with Single and Double-Cut Twisted Tapes

Three-dimensional numerical simulation of heat transfer enhancement of electronic devices by single crystal diamond rhombus-shaped pin fin microchannel heat sink

Pin fin microchannel heat sink is an excellent solution for enhancing the thermal dissipation for electronic devices with high integration and high-power density. The effect of the single crystal diamond (SCD) rhombus-shaped pin fin microchannel (RPFMC) heat sink with single-phase laminar fluid on the device heat transfer is investigated by three-dimensional numerical simulation, and geometrical parameters of the RPFMC heat sink are optimized and evaluated according to the performance evaluation criterion. The simulation results indicate that the thermal resistance of the device gets reduced by up to 81.6 % through using a SCD RPFMC heat sink instead of a silicon RPFMC heat sink with the same design, due to the superior thermal conductivity of SCD. Hotspot heat fluxes are evaluated to explore the tolerance of the SCD RPFMC heat sink which could withstand a heat flux of 2000 W/cm2 with the temperature increased by only 17.3 K. Geometric design evaluation suggests that the SCD RPFMC heat sink with the rhombus-shaped pin fin angle of 75° and duty ratio of 0.4 has the optimal overall thermal performance.

Numerical simulation of heat transfer enhancement from tubes surface to airflow using concave delta winglet vortex generators

Improvement of the convection heat transfer coefficient of the airflow has become a concern nowadays to increase the rate of heat transfer. Therefore, the present study is focused on evaluating the improvement of heat transfer numerically from several heated tubes to the airflow in the channel using vortex generators. Airflow into the channel is varied in the range of Reynolds number of 2100–11,200. The vortex generators used in this study are delta winglet pairs and concave delta winglet pairs with in-line or staggered configurations for one to three pairs of vortex generators. The results of the study showed that the installation of three pairs of concave delta winglet vortex generators with a staggered arrangement resulted in the best convection heat transfer improvements with the highest increase in convection heat transfer coefficients up to 53.58% than those from the baseline (without vortex generators). However, the increase in the convection heat transfer coefficient is accompanied by an increase in pressure drop of up to 69.69% against the baseline.

Numerical Simulation of Heat Transfer Enhancement in the Paths of Propulsion Systems with Single-Row Spherical and Oval Dimples on the Wall

Modeling the vortex intensification of turbulent heat transfer in narrow engine ducts using single-row dimples was carried out within the framework of multi-block computing technologies implemented in a special VP2/3 package. The cases of a rectangular section with the placement of vortex generators—single-row packages of oval and spherical dimples on the initial hydrodynamic section and the section of the stabilized flow are excluded. The connection between the generated vortex structures and the predominant increase in heat transfer compared to the increase in hydraulic losses for various dimple layouts has been established: zigzag, ladder, and centers shifted and in a longitudinal-transverse order. The superiority in heat removal from the thickness with inclined oval dimples is shown—1.23 times compared to spherical ones with a decay in hydraulic resistance by 1.16 times.

A Numerical Simulation of Heat Transfer Enhancement Using Al2O3 Nanofluid

Introduction: A numerical study is performed in which the friction factor and forced convection heat transfer is studied for Al2O3 nanoparticle dispersed in water as a base fluid. Methods: Four concentrations of nanofluids in the range of 0-2.5 vol% have been simulated. The Reynolds Number is varied in the range of 100-500 by varying inlet velocity. Cross flow of air is assumed over the pipe with air velocity of 2.2 m/s. Results: The results depict that the friction factor decreases with an increase in flow rate and increases with increase in volume concentration. The maximum deviation for friction factor obtained by simulation from that obtained using Darcy’s relation is about 21.5% for water. Nusselt number increases with increase in Reynolds Number and nanofluid volume concentration with a maximum of 7653.68 W/m2 at a nanoparticle concentration of 2.5% and Reynolds Number of 500. Heat transfer rate enhancement of upto 13.6% is obtained as compared to pure water. The maximum increase in Nusselt Number is about 13.07% for a nanoparticle concentration of 2.5%. Conclusion: The simulation results are compared with established relations obtained by other researchers and there is a good agreement in terms of trends obtained. The deviations from established relations are also depicted.

Numerical and Physical Simulation of Heat Transfer Enhancement Using Vortex Generators

Vortex generation and flow disruption in fluid ducts by means of surface modification is a widely used passive heat transfer augmentation technique. The present paper contains the results of numerical and experimental studies of the flow fields and heat transfer enhancement in the ducts with oval-trench and oval-arc shaped dimples applied to the heat transfer surface. The results of the numerical study of the flow over the dimpled surface with periodic boundaries are verified by experimental visualization of the flow and temperature fields. The influence of characteristic geometrical parameters of the dimples on the heat transfer, friction factor, and flow structure in heat-exchange ducts has been obtained. Preliminary results on the artificial neural networks application on heat transfer and friction factor assessment for the flow over dimpled surfaces are presented.

Numerical and Physical Simulation of Heat Transfer Enhancement Using Oval Dimple Vortex Generators—Review and Recommendations

Vortex generation and flow disruption in heat exchanger passages by means of surface modification is a widely used passive heat transfer augmentation technique. The present paper contains the results of numerical and experimental studies of the hydraulic resistance and heat transfer in the rectangle duct with oval-trench- and oval-arc-shaped dimples applied to the heat transfer surface. For the turbulent flow in the duct (Pr = 0.71, Red = 3200–9 × 104—for heat transfer determination and Red = 500–104—for the friction factor measurements), rational geometrical parameters of the oval-trench dimple were determined: relative elongation of dimple l/b = 5.57–6.78 and relative depth l/b = 5.57–6.78, while the value of the attack angle to the mean flow was fixed φ = (45–60)°. The comparison of the experimental and numerical modeling for the flow in the narrow duct over the surface with a single- and multi-row dimple arrangement has revealed a good agreement. It was found that the average heat transfer coefficient magnitudes in such ducts could be increased 1.5–2.5 times by means of single and multi-row dimple application on the heat transfer surface. The heat transfer augmentation for the surfaces with the oval-arched dimples was found to be 10% greater than the one for the oval-trench dimples. The corresponding friction factor augmentation was found to be 125–300% in comparison to the smooth surface duct. The obtained experimental data were used for the data generalization. Derived generalized equation allows for predicting the friction factor and heat transfer coefficient values for the flow over the single-row oval-trench simple arrangement. The maximal deviation of the experimental data from the proposed equations was found to be 20%. The application of the artificial neural networks for predicting the hydraulic resistance and heat transfer augmentation in such ducts was presented.

CFD simulation of heat transfer enhancement in circular tube with twisted tape insert by using nanofluids

Abstract Heat transfer enhancement using nano-fluids has gained significant attention over the past few years. Nano-fluids are potentially applicable as alternative coolants for many areas such as electronics, automotive, air conditioning, power generation and nuclear applications. Heat transfer coefficient and the friction factor characteristics of SiC/water nanofluid will have been numerically investigated using ANSYS FLUENT 14.0. The Nanofluid was employed in a circular tube equipped with modified Horizontal Wing Twisted Tapes (HWTT) with different twist ratio (y = 2.0, 4.4, 6.0) were used for simulation and compared with Plain Twisted Tapes (PTT). The results of CFD investigations of heat transfer Coefficient and friction characteristics are presented for the HW-TT with Different twist ratio in comparison with the P-TT case.

Numerical simulation of heat transfer enhancement in a plate-fin heat exchanger using a new type of vortex generators

In this work, the effect of different vortex generators on fin-plate heat exchanger performance with a triangular channel cross-section is examined. The analysis is done using finite volume method. The effects of vortex generators in a channel are investigated by consideration of channel temperature and heat transfer coefficient. Six different vortex generators including a simple rectangular vortex generator (SRW), rectangular trapezius vortex generator (RTW), angular rectangular vortex generator (ARW), Wishbone vortex generators (WW), intended vortex generator (IVG) and wavy vortex generator (WVG) have been investigated. The observations suggest that simple rectangular vortex generator increases the heat transfer of fin-plate heat exchanger more than other models. This vortex generator increases heat transfer in the heat exchanger by 7%. However, vortex generators increase the pressure drop in heat exchanger. In addition, by increasing the height of the vortex generators the heat transfer rate is increased and the best angle of attack for the installation of vortex generator is 45°.

Numerical Simulation of Heat Transfer Enhancement over a Surface-mounted Rib with Active Control

A numerical study of heat transfer with external perturbation over a surface-mounted rib is performed using Large-Eddy Simulation (LES). The Reynolds number, based on the rib height and the inflow velocity, is 4500. A zero mass-flux jet is chosen as the manipulated perturbation with a frequency at St = fh/U0=0.08. The purpose of this study is to elucidate the effect of perturbation on the enhancement of heat transfer. Due to perturbation, the mean reattachment length shows a reduction of 13%, while the maximum mean Nusselt number on the heated wall has an augment of 10%.

Simulation of heat transfer enhancement in nanofluids using dissipative particle dynamics

The current paper applied dissipative particle dynamics (DPD) approach to investigate heat transfer within nanofluids. The DPD approach was applied to study natural convection in a differential heated enclosure by considering the viscosity and the thermal conductivity of the nanofluid to be dual function of temperature and volume fraction of nanoparticles. Experimental data for viscosity and thermal conductivity are incorporated in the current DPD model to mimic energy transport within nanofluids. This incorporation is done through the modification of the dissipative weighting function that appears in the dissipative force vector and the dissipative heat flux. For the entire range of Rayleigh number considered in this study, it was found that the DPD results show a deterioration in heat transfer in the enclosure due to the presence of nanoparticles for φ>4%. However, some slight enhancement is shown to take place for small volume fraction of nanoparticles, φ≤4%. The DPD results experienced some degree of compressibility at high values of Rayleigh number Ra ≥105.

Numerical simulation of heat transfer enhancement by elastic turbulence in a curvy channel

Although many investigations on elastic turbulence have been conducted in recent years, two major research topics still call for in-depth mechanistic investigations. Specifically, one is heat transfer performance affected by elastic turbulence; the other is so-called high Weissenberg number problem (HWNP) in numerical simulation of viscoelastic fluid flow. Taking these two topics into account simultaneously, the coupled problem becomes heat transfer characteristic of viscoelastic fluid in elastic turbulence at high Weissenberg number (Wi) and very low Reynolds number (Re). In this work, we implement numerical simulations by embedding log-conformation reformulation algorithm into the open-source software OpenFOAM. The heat transfer process of viscoelastic fluid flow in a three-dimensional (3D) curvy channel is simulated over a wide range of Wi. For the first time, significant heat transfer enhancement induced by elastic turbulence in a curvy channel at high Wi was identified numerically. When Wi is above the critical value of O(1), the heat transfer performance is found to be dramatically improved by elastic turbulence and then approaches a saturation. From the transient analysis of flow motions in the axial and cross sections, it can be seen that the flow twists and wiggles in the curvy channel and the field synergy effect of viscoelastic fluid flow becomes more intensive than that of Newtonian fluid flow. These effects give rise to the extremely irregular flow motions in the cross section and consequently lead to heat transfer enhancement.

Simulation of heat transfer enhancement in tube flow with twisted tape insert

Heat transfer behaviour in a tube with inserted twisted tape swirl generator is investigated numerically, for different values of the twist ratio and diameter ratio and for Reynolds numbers within the range 100-20,000. The transition-SST model is used as the turbulence model. The computational model is validated, first, on a plain tube, where a good agreement is achieved with the correlations. The subsequent analysis of the tube with twisted tape indicates that the use of twist tape enhances heat transfer generally, which is accompanied by a higher pressure drop. It is observed that an improvement of the thermal-hydraulic performance can only be observed for certain configurations and Reynolds numbers.

Numerical simulation of heat transfer enhancement for natural convection in a cubical enclosure filled with Al2O3/water and Ag/water nanofluids

ABSTRACTIn the present study, the natural convective heat transfer in a cube filled with Al2O3/H2O and Ag/H2O nanofluids is investigated numerically. Commercial CFD code FLUENT has been used to simulate water-based nanofluid considering it as a single-phase fluid. The influence of different parameters, such as the Rayleigh number and the nanoparticle volume fraction, is studied. The velocity vectors and the isotherm profiles are plotted. The variation of the Average Nusselt number at the hot wall and the variation of y-component of velocity are presented and discussed. The numerical results show a decrease in the heat transfer with the increase in the particle volume fraction and the same trend in the increase of the Nusselt number with the Rayleigh number.

Numerical Simulation of Heat Transfer Enhancement in Periodic Converging-diverging Microchannel

Heat transfer performance and fluid flow in three-dimensional converging–diverging microchannel of circular cross-section are studied numerically. Three different types of microchannel, diameter 100μm and length 6.125mm each are used for simulation for the Reynolds number range of 50 to 1000. The effect of Reynolds Number, converging/diverging angle and converging-diverging cross-section length on pressure drop and heat transfer in proposed microchannels are investigated and discussed. The result indicated that the flow in the converging-diverging cross-section induces stronger recirculation and flow separation, which decreases with decreasing the converging and diverging angle and increases with increasing aspect ratio. However, the local and global heat transfer performances in the channels are improved by the converging-diverging cross-section at the expense of higher pressure drop compared to the straight channel with the same cross-section. Conversely, special attentions are given to analyze the thermal performance of microchannels through variation of thermal resistance with pumping power.

CFD simulation of heat transfer enhancement of Al2O3/water and Al2O3/ethylene glycol nanofluids in a car radiator

The present numerical study simulated turbulent and laminar flow heat transfer in nanofluids (Al2O3 particles in water and ethylene glycol-based fluid) passing through a flat tube in 3D using computational fluid dynamics (CFD) for single and two-phase approaches. The advantages over pure base fluids were evaluated. Empirical correlations were used to calculate nanofluid viscosity and thermal conductivity as a function of the volumetric concentration of the nanoparticles. First, the Nusselt numbers of the pure water and pure ethylene glycol in flat tubes were compared with the experimental data. Next, the Nusselt numbers for both approaches were compared with those for experimental data at the same Reynolds number for different concentrations of nanoparticles. A small difference in the friction factors of the tube was observed between the two approaches and the Nusselt number for the two-phase model was markedly different from that for the single-phase model; however, the volumetric flow for the same heat transfer rate decreased and less pumping power was required for the nanofluids.

Simulation of heat transfer enhancement by longitudinal vortex generators in dimple heat exchangers

A three-dimensional DDF-MRT-LBE (double distribution function multi-relaxation-time lattice Boltzmann equation) is presented to study the flow and heat transfer in dimple heat exchangers. Results are obtained for periodically fully-developed laminar flow in parallel-plate channels with spherical dimples symmetrically opposing onto both walls. Both the heat transfer and flow resistance are discussed. Furthermore, to enhance the heat transfer with low pressure penalty, a small crescent-shape protrusion was added as a LVG (longitudinal vortex generator). And a grooved LVG was developed to reduce the drop loss caused by the crescent-shape protrusion. The streamline contours, isotherms, Nusselt numbers and friction coefficients at various Reynolds numbers are presented. The results show that the thermal performance of the LVG cases is higher than that of the dimple cases with similar flow characteristics. Moreover, from the viewpoint of energy saving, LVG cases perform better than the dimple cases.

Analytical and numerical prediction of heat transfer and pressure drop in open-cell metal foams

Enhanced cooling methods are needed for advanced power systems. A promising method is using an open-cell metal foam to improve the heat transfer rates. However, the pressure drop induced by the metal foams is relatively higher and thus becomes a critical issue in engineering applications. The focus of this research is the modeling and simulation of heat transfer enhancement and corresponding pressure drop. A simplified analytical model based on diamond-shaped unit cells has been developed to predict the heat transfer capability of a foamed channel. The heat transfer rates predicted by the analytical model have been compared with available experimental data from other researchers and favorable agreements have been obtained. To evaluate the pressure drop in metal foams, a unit-cell CFD model was built using software package Fluent. The model is based on a structure of sphere-centered open-cell tetrakaidecahedron, which is very similar to the actual microstructure of an aluminum metal foam. Flow patterns and grid independence are investigated and simulation results are shown to agree well with experimental data.

Numerical simulation of heat transfer enhancement in wavy microchannel heat sink

In this paper, heat transfer and water flow characteristics in wavy microchannel heat sink (WMCHS) with rectangular cross-section with various wavy amplitudes ranged from 125 to 500 μm is numerically investigated. This investigation covers Reynolds number in the range of 100 to 1000. The three-dimensional steady, laminar flow and heat transfer governing equations are solved using the finite-volume method (FVM). The water flow field and heat transfer phenomena inside the heated wavy microchannels is simulated and the results are compared with the straight microchannels. The effect of using a wavy flow channel on the MCHS thermal performance, the pressure drop, the friction factor, and wall shear stress is reported in this article. It is found that the heat transfer performance of the wavy microchannels is much better than the straight microchannels with the same cross-section. The pressure drop penalty of the wavy microchannels is much smaller than the heat transfer enhancement achievement. Both friction factor and wall shear stress are increased proportionally as the amplitude of wavy microchannels increased.