Turbulent Tube Flow Research Articles

دراسة عددية لتعزيز انتقال الحرارة للتدفق المضطرب في ال نابيب المدملة

The importance of heat transfer enhancement has gained greater significance in many engineering applications, and a great amount of effort has been devoted to the use different techniques to improve the thermal performance of flowing fluids in pipes. Dimpled tubes were used for this purpose in this study. In this investigation, the heat transfer-flow characteristics of turbulent flow in dimpled tubes subjected to uniform heat flux are numerically investigated. The rate of heat transfer, friction factor, and performance evaluation criterion were determined for various designs of dimpled tubes and compared with smooth tubes. The considered cases are conducted in the Reynolds number range of 3000 to 12,000. The ANSYS Fluent R19 is used for this purpose. The Reynolds-averaged Navier-Stokes equations(RANS) are used to model the governing flow equations. The realizable k-ε turbulence model is used with enhanced wall conditionsto simulate turbulent flow adjacent to the inner wall surface. The results revealed that the rate of heat exchange in dimpled tubes higher than that of smooth ones. but with additional pressure loss. Moreover, the heat transfer performance of the staggered arrangement is higher than the inline arrangement by 17 %. Also, the performance evaluation criteria (PEC) increases with the increasing in dimples diameter, and decreases with increasing in relative pitch spacing, the maximum enhancement reaches 31% for d = 5 mm, and relative pitch spacing S/D = 2 at Re = 4000.

Numerical investigation of hydrogen ignition induced by unsteady flow phenomena

The purpose of the present study is to evaluate the possibility of using a gas dynamic heater as an igniter of the combustible gas mixtures. The impacts of some operating and geometrical parameters on average temperature of the gas dynamic heater are investigated by numerical simulation of axisymmetric turbulent flow in the resonance tube. The operating gas of the heater is air which is completely decoupled from the ignition chamber. The combustible mixtures under consideration is stoichiometric hydrogen-oxygen at atmospheric pressure, in which the ignition is studied solving the governing equations for one dimensional reacting flow using detailed chemistry. The finite volume method is used in the presently developed flow solver for numerical simulations. The results show that despite highly fluctuating temperature of the end wall of the resonance tube as a hot surface, it can provide proper condition for gas mixture ignition in the chamber, by adjusting an inlet pressure and geometry of the gas dynamic heater. The end wall average temperature depends on the nozzle inlet pressure and convergence angle of the resonance tube, and the results demonstrate that the characteristics of temperature time history of repeating cycles are so effective on ignition process.

Numerical Investigation of Turbulent Airflow in Heat Exchanger Tube Equipped with Perforated Conical Rings (NOZZLES)

Numerical investigation of turbulent air flow in heat exchanger tube equipped with perforated conical rings (nozzles). The main aim of this project to conduct thermal analysis on heat exchanger tubes to find the Reynolds number and rate of heat transfer and overall heat transfer coefficient by equipping it with perforated conical rings (nozzles). Nozzles, conical rings are popular heat transfer enhancement tools due to their simple installation, low cost and efficient performance. They can simply improve the thermal efficiency of the system and also used to investigate thermal characteristics of heat exchanger tube. This can be achieved by sending the air with turbulence into the heat exchanger tube equipped with nozzles and 3d simulation is conducted to analyses and compare with the standard values. Key Words: Heat exchanger, Perforated rings, Reynolds number, Overall heat transfer coefficient.

New insight into the heat transfer and pressure drop correlations for laminar and turbulent flow in a circular tube with a twisted-tape insert: A discriminated dimensional analysis

Discriminated dimensional analysis combined with the scale analysis has been implemented to obtain new correlations describing the dimensionless pressure drop as Hagen number and Nusselt number for laminar and turbulent swirl flow in a circular tube with a classical twisted-tape insert. The new insight into the phenomenon revealed that the swirl parameter Swh, as a criterion of similarity, governs the process in the entire region of swirl fluid flow in a circular tube with a classical twisted-tape insert. The validity of the analysis has been demonstrated by an excellent agreement between a large experimental data set for isothermal pressure drop and Nusselt number from many different sources with the predictions of the Hgh+−Swh and Nuh+−Swh correlations.

Conjugate heat transfer of a turbulent tube flow of water and GaInSn with azimuthally inhomogeneous heat flux

An experimental study of the conjugate heat transfer in a turbulent tube flow with azimuthally homogeneous and inhomogeneous heat flux distribution, where the tube is heated with a constant heat flux only over the half circumference, is presented. Using two fluids with clearly different Prandtl numbers (water and a liquid metal alloy), thermohydraulic effects that occur when fluids with very low Prandtl number are used in contrast to ordinary fluids (e.g. water with Pr≈1) are discussed. The test section is validated with water (Pr=5−7.4) for a Reynolds number in the range of 5·103<Re<4.2·104. The experimental data agree excellently with literature data. The maximum nondimensional temperature at the inner surface of the tube is expressed using a simple relationship based on the efficiency of a fin with an adiabatic tip. A near eutectic alloy of gallium, indium and tin (GaInSn, Pr=0.03) is used for the liquid metal experiments. The Péclet number is varied within the range of 240<Pe<3·103. Based on the experimental data of this work, an adapted correlation for the Nusselt number in a turbulent liquid metal tube flow with azimuthally homogeneous heat flux is provided:Nu=4.364+0.0276·Pe0.803The experimental data underlines, that the azimuthally averaged Nusselt number for an azimuthally inhomogeneous heat flux distribution can also be calculated with this correlation with an acceptable level of accuracy. Remarkably, the ratio of the local convective heat transfer coefficient to the azimuthally averaged value for GaInSn reaches a value up to 0.6 at the location of the maximum wall temperature. This is in strong contrast to water, where this ratio is close to unity.

Numerical investigation of entropy generation of turbulent flow in twisted tri-lobed tubes

Twisted tri-lobed tubes have garnered attention due to their exceptional heat transfer efficiency and straightforward fabrication. Existing literature lacks comprehensive assessments of the overall heat transfer performance of twisted tri-lobed tubes from the perspective of energy loss and irreversibility. This research aims to investigate entropy generation during turbulent water flow within twisted tri-lobed tubes, examining the influence of geometric parameters on local and average entropy production. Findings indicate that larger small circle radius (r) and straight lengths (l), coupled with smaller transition circle radius (R) and twist pitch lengths (p), result in diminished local and average heat transfer entropy production while enhancing local and average frictional entropy production, with heat transfer entropy generation dominating the overall entropy production. Additionally, with increasing Reynolds numbers, all twisted tubes demonstrate an increasing trend in average frictional entropy production, except for some cases (Case 1-Case 4) that exhibit an initial rise followed by a decline in average heat transfer entropy generation. Among the examined Reynolds range, Case 4 displays lower overall irreversibility compared to a plain tube. Following the second law of thermodynamics, Case 4 is preferred. The findings and methodology contribute to enhancing the thermodynamic evaluation of convective heat transfer in twisted tri-lobed tubes.

Investigating the Performance and Thermal Characteristics of Turbulent Flow in a Heat Exchanger Tube with Gridded Oval Slant Inserts

Investigating the Performance and Thermal Characteristics of Turbulent Flow in a Heat Exchanger Tube with Gridded Oval Slant Inserts

Heat transfer analysis of turbulent forced-convection flow in a wavy absorber tube containing a molten salt-based hybrid nanofluid filled with a porous material

The thermal performance of turbulent forced-convection flow was investigated in a wavy absorber tube containing a hybrid nanofluid consisting of salt molten filled with a porous material. The nanoparticles dispersed in the working molten salts are Al2O3 and graphene, which have a spherical shape and a diameter of less than 100 nm. The assessments were performed under turbulent forced convection flow conditions using k--ε model with enhanced wall treatment. The effects of porous media features, nanoparticle concentrations, and molten salt type on flow, thermal exchange, drop pressure, pumping power, skin friction factor, and efficiency are discussed. Outcomes indicated that boosting the values of increases friction coefficient, drop pressure, pumping power, and and system efficiency. Molten Hitec salt has a lower friction coefficient and pressure loss than Hitec XL and solar salt. The use of solar salt improved the heat transfer rate by and compared to Hitec and Hitec XL, respectively.

Effect of High Solid Concentration on Friction in a Transitional and Turbulent Flow of Bioliquid Suspension

Some suspensions in nature have a complex structure and demonstrate a yield shear stress and a non-linear relationship between the shear rate and the shear stress. Kaolin clay suspension is such an example in engineering, whereas in nature it is blood. This study represents an innovative approach to simulate bioliquid flow, similar to that of blood when the solid concentration is high. The objective of this study is to examine the influence of high solid concentration of bioliquid, similar to blood, on energy losses and velocity profiles in turbulent and transitional flow in a narrow tube. Using the analogy between the suspension of kaolin clay and blood, the physical model and the mathematical model were formulated. The mathematical model comprises continuity and time-averaged momentum equations, a two-equation turbulence model for low Reynolds numbers, and a specially developed wall damping function, as such suspensions demonstrate the damping of turbulence. Experimental data on blood rheology for solid concentrations equal to 43% and 70% by volume, gathered from the literature, were used to establish a rheological model. The results of the simulations indicated that an increase of solid concentration in bioliquid suspension from 43% to 70% causes an increase in wall shear stress to approximately 10% and 6% for transitional and turbulent flow, respectively, and changes in velocity profiles. Such simulations are important if an inserted stent or a chemical additive to the bioliquid suspension is considered, as they can influence the shear stress. The results of the simulations are presented in graphs, discussed, and conclusions are formulated.

Thermal performance and exergy analysis in a round tube with louvered trapezoidal winglets

An experiment was performed to investigate the influence of inserting a louver-punched trapezoidal-winglet (LPTW) into a uniform heat-fluxed tube in order to create a longitudinal vortex generator. This research aims to maximize both the thermal performance to increase energy savings, and the relative Nusselt number (NuR) at the optimal performance to reduce heat exchanger sizes. Therefore, the experimental result was emphasized on the thermal and pressure loss characteristics including entropy, and exergy analysis of the turbulent tube flow for Reynolds numbers (Re) that extended from 4760 to 29,280. The LPTWs were arranged by letting V-tip direct downstream with three attack angles (α = 30°, 45° and 60°) and five louver angles (θ1 = 0°, 25°, 30°, 45° and 90°), all at a single relative winglet pitch (PR = 1.0) and height (BR = 0.25). According to the findings, it revealed that the friction factor (f) and Nusselt number (Nu) of the LPTW at α= 60° and θ1 = 0° are, respectively, up to 29.1 and 5.5 times above those of the plain tube. With decreasing Re and θ1, the entropy generation (S˙′gen) was reduced to a lower value and the maximum exergy efficiency (ηEx) was obtained for the LPTW at α = 60° and θ1 = 0° The peak thermal performance around 2.5 together with NuR = 4.68 was found at a= 60°, θ1 = 45° and the lowest Re. However, the optimal condition at α= 60°, θ1 = 30° was preferable because it provides the greatest NuR = 5.04 at TEF = 2.47. Additionally, correlations for f and Nu were derived and presented for the range of parameters that were taken into consideration.

Entropy generation analysis of turbulent flow in conical tubes with dimples: a numerical study

Minimizing the entropy generation rate is one of the key performance indicators for enhancing the thermal design of heat exchangers. This paper introduces a comprehensive numerical entropy generation analysis of turbulent water flow inside—newly proposed—conical tubes with dimples subjected to a constant heat flux. The effect of different tube diameter ratios (DR = 1, 1.5, 2, 3, and 5) and flow modes (convergent and divergent tube configurations) on the thermal, viscous, and total entropy generation rates is investigated within Reynolds number (Re) range of 3 × 103–40 × 103 using ANSYS-Fluent package. Realizable k-ε (RKE) turbulence model is adopted in this study. A well-validated 3D model was adopted to estimate the dimensionless indices: Bejan number (Be), enhanced entropy generation ratio (Ns,en), and the irreversibility distribution ratio ({phi }_{mathrm{s}}) to characterize the entropy generation performance and to compare conical dimpled tubes to smooth ones. The results showed that total entropy production rate values for dimpled tube geometries are lower than those for the corresponding smooth ones, especially for convergent dimpled tubes. Convergent dimpled tubes with DR in the range of 1.5–3 achieved the lowest total entropy production values over the whole Re range, with an average value of 0.20 W K−1, as compared to an average value of 0.34 W K−1 for the smooth configurations. The average Ns,en values for dimpled convergent tubes with DR = 1.5–3 are 0.46 and 0.80 at Re = 3000 and 40,000, with reductions of 50.54% and 3.61% at both Re values, respectively. The study also showed that the entropy generation analysis could provide an effective tool to highlight the optimal design of tube heat exchangers based on the minimum entropy generation and the enhanced entropy generation ratio.

Numerical study on heat transfer characteristics of molten salt in a flat tube with circular helical wire

The combination of a new type of irregular-shaped helical wire and flat tube is used to further enhance heat transfer of molten salt for the first time due to the demands of efficient utilization of molten salt. The thermo-hydraulic performance of turbulent flow in a flat tube with irregular-shaped helical wire under constant wall temperature condition is investigated using Fluent software. The effects of helical pitch, wire diameter, gap width between the tube wall and helical wire, different fluids and inlet Reynolds number ranging from 1500 to 8500 are evaluated. It is found that adding irregular-shaped helical wire insert in flat tube can reduce greatly the lengths of flow and thermal entrance regions. The maximum heat transfer performance of flat tube with irregular-shaped helical wire is 400% that of smooth flat tube. The heat transfer performance increases with the wire diameter and decreases with the gap width and helical pitch. The maximum thermal performance factor with a value of 1.72 is observed based on a constant pumping power. Besides, the heat transfer performance of flat tube with irregular-shaped helical wire is 24.0%-40.2% larger than that of circular pipe with helical wire at low Reynolds number.

Study of the Internal Cyclonic Flow Characteristics of Cyclones with Different Guide Vane Heights

To investigate the influence of the guide vane height on the cyclonic flow characteristics of guide vane cyclones, this paper mainly adopts a combination of numerical simulation and physical experiments, taking the guide vane height as the research object, analysing the internal spiral flow generation law through the flow velocity distribution in each section of the cyclone and the change trend along the course and comparing the tangential velocity, radial velocity and axial velocity characteristics of the cyclone at different guide vane heights. The results show that the tangential velocity increases with the increase in the guide vane height on the cyclone and then decreases. When the ratio between the height of the guide vane and the inner radius of the cyclone is in the range of 0.5–0.7, a higher−strength and more stable spiral flow can be produced, and the tangential velocity reaches the maximum when the guide vane height is 30 mm and the height−to−diameter ratio is around 0.6. As the height of the guide vane increases, the radial velocity area towards the wall of the tube increases, while the radial velocity area towards the tube axis decreases. The overall distribution of axial flow velocity is similar to that of turbulent flow in a circular tube, and the velocity increases with increasing height of the guide vane. The conclusion of this paper provides a theoretical basis for further optimisation of the cyclone structure parameters.

Particle Distribution and Heat Transfer of SiO2/Water Nanofluid in the Turbulent Tube Flow.

In order to clarify the effect of particle coagulation on the heat transfer properties, the governing equations of nanofluid together with the equation for nanoparticles in the SiO2/water nanofluid flowing through a turbulent tube are solved numerically in the range of Reynolds number 3000 ≤ Re ≤ 16,000 and particle volume fraction 0.005 ≤ φ ≤ 0.04. Some results are validated by comparing with the experimental results. The effect of particle convection, diffusion, and coagulation on the pressure drop ∆P, particle distribution, and heat transfer of nanofluid are analyzed. The main innovation is that it gives the effect of particle coagulation on the pressure drop, particle distribution, and heat transfer. The results showed that ∆P increases with the increase in Re and φ. When inlet velocity is small, the increase in ∆P caused by adding particles is relatively large, and ∆P increases most obviously compared with the case of pure water when the inlet velocity is 0.589 m/s and φ is 0.004. Particle number concentration M0 decreases along the flow direction, and M0 near the wall is decreased to the original 2% and decreased by about 90% in the central area. M0 increases with increasing Re but with decreasing φ, and basically presents a uniform distribution in the core area of the tube. The geometric mean diameter of particle GMD increases with increasing φ, but with decreasing Re. GMD is the minimum in the inlet area, and gradually increases along the flow direction. The geometric standard deviation of particle diameter GSD increases sharply at the inlet and decreases in the inlet area, remains almost unchanged in the whole tube, and finally decreases rapidly again at the outlet. The effects of Re and φ on the variation in GSD along the flow direction are insignificant. The values of convective heat transfer coefficient h and Nusselt number Nu are larger for nanofluids than that for pure water. h and Nu increase with the increase in Re and φ. Interestingly, the variation in φ from 0.005 to 0.04 has little effect on h and Nu.

Numerical study on pressure drop characteristics for turbulent flow in conical spiral tubes

The study of pressure drop characteristics in a curved tube is important as it has extensive application in coiled tube heat exchangers, hydraulic and pneumatic systems. The literature review suggests that the pressure drop characteristics at the coil level as well as at local level for the curved tubes with varying curvature i. e. conical spiral tubes require further investigations. The objective of the present work is to investigate the flow resistance characteristics of turbulent fluid flow in conical spiral tubes with uniform wall temperature heating with the numerical simulation approach using ANSYS Fluent. The conical spiral tubes with different curvature and cone taper angle ranging from 10° to 60° were modelled and simulated for the Reynolds number range of 104 to 105. The CFD results reveal that the total pressure drop and the local cross-flow pressure loss coefficient increased with Reynolds number, cone taper angle and curvature ratio. The results also show that the friction factor and the cross-flow coefficient increased significantly in the tube at a cone taper angle of 60° due to an enhancement in the secondary flow and hence the pressure loss. For the given curvature radius and tube diameter of the conical spiral tube there exists an optimum Reynolds number at which the dimensionless cross-flow pressure coefficient has an optimum value. A correlation to predict the friction factor as a function of Reynolds number and cone taper angle is proposed for the turbulent flow in conical spiral tubes. For the usual practically applicable curvature ratio of less than 0.1 in curved tubes, the pressure drop prediction using the proposed correlation is found to be within ±10% of the numerical simulation results.

Forced convection heat transfer of nanofluids in turbulent flow in a flat tube of an automobile radiator

Nanofluids are fluids that can be applied in devices to obtain better performances (i.e. energy, heat transfer and others). Latest up to date literatures on nanofluids show that they can be used in engine cooling systems, solar water heating, cooling of electronics, to improving diesel generator efficiency, to improve heat transfer efficiency of chillers, in nuclear reactor and defense and space.This paper focuses on the numerical study of the performance of two nanofluids (Al2O3-water and TiO2-water) in heat transfer by forced convection in a flat tube of an automobile radiator In the computational simulations it was considered that the nanofluids have a constant velocity and a temperature of 363.15 K at the entrance of the tube. The tube wall is at a constant temperature of 303.15 K. This study is restricted to turbulent flows with Reynolds numbers equal to 5000, 10000, 15000 and 20000. The 3D computer simulations were performed using the Fluent software. The characteristic parameters of heat transfer from nanofluids subjected to forced convection were obtained for nanoparticle concentrations up to 10% and were compared with the base fluid (water). The numerical results were validated, comparing the friction coefficient and the Nusselt number with empirical correlations for the turbulent regime, available in the literature. The results for the heat transfer coefficient and the heat flux along the tube, for the studied conditions, are presented. Average values of some parameters associated with heat transfer and fluid flow were also determined, such as heat transfer coefficient, heat flux, Nusselt number, Prandtl number, wall shear stress, pressure drop, density, viscosity, thermal conductivity and specific heat, all of which were found to increase with the concentration of nanoparticles. The heat transfer enhancement with the nanoparticles concentrations up to 10% was also investigated. Furthermore, both nanofluids show the same behavior, for instance, for Re = 5000 the heat transfer enhancement rise 32.7% whereas for Re = 20000 the growth drops slightly to 31.3% with the concentration of Al2O3.

Numerical investigation of the thermal-hydraulic characteristics of turbulent flow in conical tubes with dimples

Innovative designs of heat exchangers are crucial to increase the heat transfer effectiveness for the purpose of compactness, energy savings, and emission reductions, among others. In this paper, the thermal-hydraulic performance of turbulent flow inside dimpled and conical tubes under a constant heat flux of 40 kW/m 2 is numerically investigated using Ansys-Fluent. The proposed novel design and the associated performance analysis were not covered before in the specialized research works of the related literature. Different geometrical and operational parameters (tube diameter ratio/flow modes) are varied to generate key performance indices for the dimpled and conical configurations compared to the traditional smooth heat exchanger case. The model was well-validated against both cases of dimpled and smooth tube configurations. Thermal-hydraulic performance parameters, mainly Nusselt number and friction factor, and performance evaluation criteria (PEC) are investigated for different diameter ratios (DR) of various conical tube heat exchangers of smooth and dimpled surfaces within a range of Reynolds number from 3000 to 40,000. The results for conical tubes with dimples showed considerable enhancements in heat transfer and the overall thermal-hydraulic performance compared to traditional smooth geometrical configurations. The study showed that convergent tube with dimples (DR = 1.5) presents the maximum value of PEC with 29.54% enhancement compared to the smooth geometry with DR = 1. The average-values of PEC over the whole studied range of Re with 8.03% enhancement compared to the smooth geometry at DR = 1, of all studied cases. In addition, convergent tube with dimples (DR = 1.5) presents a maximum percentage of the increase in Nusselt number ratio Nu r (2.72 at Re = 3000) with 121.4% enhancement compared to the corresponding smooth one. Hence, it can be considered as a promising technique in terms of energy-saving, especially at low values of Reynolds number. It can also be deduced that the newly proposed design of convergent tube HEX with dimples has positive energy efficiency operational characteristics and environmental impacts in terms of potential CO 2 reductions.

Artificial neural networks application on friction factor and heat transfer coefficients prediction in tubes with inner helical-finning

A study presents new model of the artificial neural network to predict friction factor and heat transfer coefficients for the turbulent flow in tubes with inner helical-finning. A fin geometry differs in its form, shape and fabrication method. The generalized equations, correlating thermal performance in such tube, available in earlier works by other authors primarily apply to a single type of inner helical-finning. In present work, we compile experimental results of other authors to an extended database that has been used further for artificial neural network training procedure. The presented model of artificial neural network applies to all types of inner helical tube finning. The mean average percent error values of 11.8% for friction factor and 16.3% for Nusselt number values for the ANN model over the whole database have been achieved. The performance validation of the obtained model was based on a comparison of predicted data with the independent experimental results obtained by authors, yielding excellent accuracy. • Extended database of Nusselt number and friction factor in helicallyfinned tubes. • Novel generalization model of artificial neural network. • Systematic analysis and validation of obtained artificial neural network model.

Numerical investigation on turbulent flow and heat transfer characteristics of ferro-nanofluid flowing in dimpled tube under magnetic field effect

• This is the first study on dimpled tube under magnetic field effect. • Effects of dimple geometry and magnetic field on the thermal and hydrodynamic behaviour have been investigated. • The Nu enhances with increasing volume fraction of magnetic nanoparticle. • The highest PEC is obtained for Ha = 75, magnetic nanoparticle fraction of 2.5 vol% and dimpled tube with P 2 /d = 7.5. For the aim of increasing the heat transfer enhancement, a hybrid method in which active and passive heat recovery techniques have been used together. The usage of nanofluid, MHD and dimpled fins tube have not been utilized together so far. Regarding this issue, this study is the first numerical study to determine effect of usage of three effects together comprehensively. In this study, thermo-hydraulic performance of Fe 3 O 4 /H 2 O nanofluid (ferro-nanofluid) flow inside dimpled tube under magnetic field effect has been examined numerically. The main purpose of the study is to obtain numerical data for turbulent flow in the spherical dimpled tubes providing some aid to design a highly efficient thermal energy storage devices. Dimple geometry with nondimensional pitch ratio ( P/d = 3.75, 7.50 and 11.25 ), Hartmann number ( Ha = 75, 150, 225) and nanoparticle volume fraction ( φ = 0.5, 1.0 and 2.5 vol % ) are the parameters investigated in this study. The numerical analyses have been carried out Reynolds number ranging from 10,000 to 50,000 at a constant heat flux at 20 kW/m 2 . The simulations have been built up by Realizable k- ε turbulence model and single-phase approach. Also, “MagnetoHydroDynamic” ( MHD ) module has also been activated for defining magnetic field effect. The results showed that Nusselt number increases with increasing Reynolds number and decreasing pitch ratio. The dimple geometry type of P/d = 7.50 has been determined as the most efficient dimple geometry type. In the case of highest magnetic field intensity, the highest Nusselt number increment (72.48%) has been obtained for φ = 2.5 vol% compared to the base fluid of distilled water using as the working fluid for smooth tube. The highest PEC value was also obtained as 1.126 for the case of P/d = 7.5, φ = 2.5 vol% and Ha = 75. In addition, the effect of magnetic field intensity on velocity and temperature distributions has been presented with contour graphs.

Estimation of local heat flux for turbulent flow in a helical coil tube by conjugate gradient method

Estimation of local heat flux is challenging in a helical coil tube heat exchanger due to the complex flow field developed by tube curvature. The heat flux has uneven distribution in the angular direction of the tube cross-section. The current research aims to estimate the local heat flux at the fluid-solid interface for the turbulent flow of water in a helical coil tube by solving the inverse heat conduction problem (IHCP). Conjugate gradient method (CGM) with an adjoint problem is used as an inverse algorithm. First, the commercial CFD software ANSYS FLUENT is used for solving the governing equations of continuity, momentum, and energy for turbulent flow to obtain the heat flux at the fluid-solid interface. This heat flux is used to determine the temperature distribution at the outer surface of the tube. The heat flux is then considered unknown and it is estimated by CGM algorithm with the developed in-house code in MATLAB. The result shows that the estimation of heat flux by CGM is very accurate.