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Hyperthermia is one of the non-invasive therapy of an Abdominal Aortic Aneurysm (AAA), which is achieved by applying a heat source upon the AAA without surgical operation. This research paper considers laminar flow and heat transfer in a heated abdominal aortic aneurysm using an isothermal boundary condition. Heat is added to explicate the thermal treatment of a diseased artery. The blood is assumed as a non-Newtonian fluid based on the shear-thinning Carreau model. Two unequal aneurysms are assumed in the lower wall to simulate bulges or a disordered artery. Flexible wall segments are assumed in the upper wall and opposing to each aneurysm. The transient momentum and energy equations are solved based on the fluid–structure interaction (FSI) using the Arbitrary-Lagrangian–Eulerian (ALE) method. It is found that the shear stress is much higher for a higher index of the power-law fluid governing the blood viscosity and hence, it is strictly recommended to reduce the viscous nature of the blood in diseased vessels. It is found also that the thermal energy can be greatly transported across the blood at a higher Reynolds number, this means that the hyperthermia therapy becomes effective when blood flows violently through the aortic. [ABSTRACT FROM AUTHOR]

In this paper an attempt has been made with experimental as well as theoretical analysis to find the variation in heat transfer coefficient with Reynolds number and numerical simulation attempt has also been done with different turbulence models in forced convection turbulent flows. Experimental analysis was carried out by using forced convection experimental setup at constant power supply to the heater and by varying the different flow rates of air with the help of a blower. The tube heat exchanger is fully insulated. In turbulent flows, the heat transfer coefficient is greatly affected by the turbulence, hence in this paper numerical analysis was carried out with different turbulence models and analysis has been done with both experimental and theoretical values to find the best turbulence model. [ABSTRACT FROM AUTHOR]

• Unsteady wake dynamics past a blunt headed cylinder at incidence is studied. • Determined critical Reynolds number (Re) based on primary stability analysis. • Identification of various flow regimes during vortex shedding. • Evaluation of forced convective heat transfer for various Re and angles of incidence. • Entropy generation optimization at different Re and angles of incidence. In the present paper, a numerical investigation has been carried out to study the forced convective flow and heat transfer characteristics past a blunt-headed cylinder in crossflow. Employing air as an operating fluid, calculations are carried out for a range of Reynolds number (Re) from 40 to 160. The angle of incidence is varied in the range of 0∘ ≤ α ≤ 180 ∘. The thermofluid features of flow and heat transport are analysed in detail for different angles of incidence. To analyse the aerodynamic characteristics, several parameters such as drag and lift coefficients, moment coefficient, Strouhal number, recirculation length, and local time-averaged vorticity flux have been calculated. Furthermore, a stability analysis has been undertaken by using the Stuart Landau equation to enumerate the critical Reynolds number at each angle of incidence. Heat transfer characteristics are studied by computing local and time-averaged values of Nusselt numbers. When compared to a rectangular cylinder, a blunt-headed cylinder exhibits an enhanced heat transfer rate. In the end, an entropy generation analysis has been carried out to study the effects of Re and angle of incidence on the efficiency of thermofluid transport characteristics. [ABSTRACT FROM AUTHOR]

• The heat transfer process of NH 4 Cl fouling was studied experimentally. • The local heat transfer characteristics around tube wall was analyzed. • The effects of flow rates and temperature on heat transfer process were investigated. • The fouling resistance and average fouling thickness on the HET wall were obtained. The crystallization fouling of ammonium chloride (NH 4 Cl) often occurs on heat exchange tube bundles in petroleum refining equipment, which seriously reduces the heat transfer and operational efficiency of the equipment. In this paper, the heat transfer characteristics of heat exchange tube (HET) with NH 4 Cl crystallization fouling was studied experimentally. The effects of velocity, temperature and mass flow rate of hot and cold fluids on the overall and local heat transfer characteristics were analyzed. The results indicate that the local heat transfer coefficient around the tube wall decreases first and then increases with the increase of the circumferential angle (θ) under clean condition. At the position of 0°-45°, the local heat transfer coefficient is the largest. At 90°-135°, the local heat transfer coefficient is the smallest. Under fouling condition, the local heat transfer coefficient increases with the increase of circumferential angle. In the region of 0°-45°, the local heat transfer coefficient is the smallest. The region with the largest local heat transfer coefficient is 135°-180° The heat transfer coefficient (h), fouling resistance (R f) and average fouling thickness increase with the increase of Reynolds number (Re), temperature of hot fluid (T h) and mass flow rate of cold fluid (q m,c), but decrease with the increase of temperature of cold fluid (T c). [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract In the process of drilling, the tubing-casing annulus are easily to be eccentric. Heat transport phenomenon occurring in such tubes and annulus can be complex, and this paper investigates forced convection in a vertical eccentric annulus with different radius ratios and eccentricity (normalized by the radius difference). Physical experiments and numerical simulation have been conducted with constant inner tube inlet temperature and flow rate of hot water. Results show that with the increase of radius ratios, the convection heat transport coefficient increases. For a radius ratio of 1.875, the heat transport coefficient increases as the eccentricity increases when the Re > 2000 and it decreases when the Re < 2000. For a radius ratio of 2.25 and Re < 1500, the influence of eccentricity is trivial, but for Re > 1500, the increase of eccentricity strengthens the heat convection. For a radius ratio of 3.06, the heat transport coefficient increases as the eccentricity increases. An empirical correlation for Nusselt number is derived as a function of Reynolds number, Prandtl number and eccentricity. Highlights • For D o / D i = 1.875, the effect of eccentricity is identified into two zones. • For D o / D i = 3.06, the increase of eccentricity enhances the convective heat transport. • The increase of radius ratio strengthens the heat transport of annular channels. • With low eccentricity and low Reynolds number, the increase of radius ratio can hardly improve the heat exchange efficiency. • Three kind of empirical correlations are regressed through parametric analysis. [ABSTRACT FROM AUTHOR]

The study of the forced convection in a channel has many practical applications. In this paper, the forced convection heat transfer from surface mounted blocks attached to the bottom wall of a horizontal channel with nanofluid is numerically studied by the second-order lattice Boltzmann method (LBM). The effects of Reynolds numbers and geometrical parameters of the blocks in different aspect ratios on the flow field and temperature distribution for various volume fractions of nanofluid (φ = 0, 0.01, 0.03 and 0.05) are analyzed. Also, the influence of these parameters is investigated on the local and average Nusselt numbers. It is concluded that heat transfer in channels can be enhanced by using the block on the walls and adding nanoparticles. There is a maximum value of 39.04% increase in average heat transfer coefficient for all the examined cases compared to the base fluid (i.e., water). [ABSTRACT FROM AUTHOR]

In this paper, nanofluid forced convection heat transfer is investigated in existence of magnetic field. Three dimensional simulations are presented by means of Lattice Boltzmann Method. Koo-Kleinstreuer-Li (KKL) model is considered to estimate the properties of nanofluid. Roles of Hartmann number, Reynolds number, Al 2 O 3 volume fraction are illustrated graphically. Outputs are depicted in forms of velocity, isokinetic energy, streamlines, isotherms contours and Nusselt number. Results demonstrate that velocity of nanofluid augments with rise of Reynolds number and Al 2 O 3 volume fraction but it reduces with increase of Hartmann number. Convection mode reduces with enhance of Lorentz forces. Temperature gradient over the moving wall augments with augment of hot surface velocity and Al 2 O 3 volume fraction. [ABSTRACT FROM AUTHOR]

In this paper, the forced convective heat transfer of water-Fe 3 O 4 nanofluid in an enclosure with moving and sinusoidal walls is investigated. New numerical method is chosen namely CVFEM. Influences of Reynolds, Hartmann numbers and volume fraction of Fe 3 O 4 on hydrothermal characteristics are presented. Results indicated that temperature gradient is an enhancing function of lid velocity and volume fraction of Fe 3 O 4 but it is a reducing function of Lorentz forces. Besides, heat transfer improvement augments with enhance of Reynolds number but it reduces with augment of Hartmann number. [ABSTRACT FROM AUTHOR]

• Effect of novel positioned dual splitter plates on heat transfer is investigated. • Wake topology and its effect on heat transfer for dual splitter plates is discussed. • A mixed effect of the dual plates on the fluid forces around square cylinder is observed. • Substantial enhancement of 46% on the overall heat transfer is noticed. • Novel combined thermo-fluid regime is defined for the square cylinder with dual plates. In various applications of flow over a cylinder, the convective heat transfer is required to be enhanced for better operation by maintaining the operating temperature. In this paper, the influence of splitter plates on the fluid forces and heat transfer around a square cylinder is discussed thoroughly. The placement of the splitter plates is novel in its kind as these are placed at the top and bottom surfaces of a square cylinder instead of the conventional position i.e. downstream or upstream of the cylinder. Effect of this novel position of the splitter plates on the heat transfer along with the wake topology for a range of Reynolds number (Re) (60 ≤ Re ≤ 150) is not available in the previous study and accordingly, a rigorous investigation of the flow physics is presented here. Two splitter plates are utilized of the same geometry with varying lengths, locations, and orientations. It is found that the primary recirculation length decreases with increasing Re by introducing the splitter plates compared to a bare cylinder and the corresponding primary separation angle, ψ S1 is significantly affected by the geometry of the splitter plates. The splitter plates have a mixed effect on the fluid forces and heat transfer rate for all the considered Re. A maximum percentage of reduction on the mean drag coefficient and R.M.S (root mean squared) lift coefficient is found as 9% and 20%, respectively. Whereas, a maximum percentage enhancement of 40.7% is obtained on the heat transfer rate by introducing the splitter plates. However, the splitter plate geometry and its location can be decided according to the requirement of the heat transfer rate based on the application and the corresponding demand on the fluid forces. [Display omitted] [ABSTRACT FROM AUTHOR]

The airflow pattern close to a moving human is proved to be a combined free-forced convection due to the temperature difference between the moving human and the environment. In this paper, theoretical analysis was conducted to study the effects of human movement on the mixed convective heat transfer, expressed by Nusselt, Reynolds and Grashof numbers. The correlations of these non-dimensional numbers for each segment of the human have been established. It can be demonstrated that the increasing values of the Reynolds (forced convection) and Grashof (natural convection) numbers take a positive effect on the total rate of convective heat transfer, and the proportions of the forced and natural convection are on the same level. The heat transfer of the mixed convection is affected by the specific geometry characteristic of the different body segments. For the windward and leeward body segments, the heat transfer of mixed convection is more obvious during the human movement than other segments, while the heat transfer of mixed convection for the upper limbs by the body sides are much less obvious. In addition, a detailed information of the flow field around the moving body can be speculated from the correlation equations of the mixed convection for 18 body segments. [ABSTRACT FROM AUTHOR]

This paper investigates experimentally the effects of laminar nanofluid flow over the microscale backward-facing step (MBFS) and forward-facing step (MFFS) on the heat transfer characteristics. The experiments were implemented on MBFS and MFFS with a step height of 600 μm. Both MBFS and MFFS have the upstream and downstream lengths of 0.1 m and 0.15 m respectively. The Reynolds number ranged of 280–480. The concentrations of SiO 2 nanoparticle valued at 0.005 and 0.01 with a diameter of 30 nm were immersed in a distilled water. The experimental results revealed that the concentration of 0.01 water–SiO 2 nanofluid recorded the highest Nusselt number. The comparison between MBFS and MFFS revealed that the highest Nusselt number is obtained through the use of the MFFS, which is approximately twice that of MBFS. However, the friction factor recorded a higher value for MFFS. The experimental results were in a good agreement with the numerical published results. [ABSTRACT FROM AUTHOR]

In this paper, 3D analysis of forced convection of Newtonian and non-Newtonian nanofluids through a horizontal pipe using single- and two-phase mathematical models is performed. The models include the Newtonian single-phase model, non-Newtonian single-phase model, Newtonian two-phase mixture model and finally non-Newtonian two-phase mixture model. The geometry of the problem is a horizontal pipe that is filled with Al 2 O 3 /water nanofluid. The effects of particle volume fraction and the Reynolds number on the heat transfer and hydrodynamic characteristics of the flow are examined. Results indicate that for the volume fraction of 0.01, the non-Newtonian mixture model gives more accurate results in comparison with the other models. By increasing the solid volume fraction, the mixture models give a higher heat transfer coefficient in comparison with that of the corresponding single-phase model; however, by comparing the results of Newtonian and the corresponding non-Newtonian models, no meaningful relationship can be obtained. Furthermore, for all the investigated models, the Nusselt number is increased with increasing the Reynolds number. [ABSTRACT FROM AUTHOR]

• Forced convection heat transfer from rectangular straight fins have been experimentally measured. • Three-dimensional conjugate heat transfer simulations are conducted. • The relationship between the Nusselt and Reynolds numbers is approximately linear. • Shorter fin channels were more effective in heat transfer than longer ones. • The heat transfer rate decreased linearly with the increase in channel length but remained approximately constant with the increase in number of fins. • Laminar and transitional-turbulent flows are characterized. This paper presents an experimental and numerical study of forced convection heat transfer from straight rectangular fins on a horizontal surface at low Reynolds numbers ranging from 2600 to 6800. Heat transfer for a fixed number of fins, fin spacing, and length was measured in a wind tunnel for varying inlet air velocity and heat input. Three-dimensional conjugate heat transfer simulations were also conducted to characterize important features of heat transfer and flow of the fin array and the effects of fin channel length on heat transfer. A maximum relative error of about 4.28% was found between the experimental and the numerical results for the average Nusselt number. The experimental results showed that forced convection heat transfer is characterized by an approximately linear relationship between the Nusselt and Reynolds numbers, which also agreed reasonably well with the available correlations for fully developed turbulent convective heat transfer for tubes with uniform heat flux. Further investigations of the effects of fin geometry were made numerically. Shorter fin channels, where the flow is thermally and hydrodynamically developing, were more effective in heat transfer than longer ones, where the flow approaches or reaches full development. It is shown that heat transfer rate per channel decreases linearly with the increase in channel length, but remains approximately constant with the increase in number of fins. It is also shown that the contributions of natural convection and radiation were negligible for the specific fin design and the range of inlet flow conditions and maximum fin temperature investigated here. [ABSTRACT FROM AUTHOR]

• Investigating forced convection of a nanofluid through a wavy-sinusoidal minitube using two-phase model. • Evaluation of the effect of geometrical and thermal parameters to achieve the most advantageous geometry. • Wavy amplitude, wavelength and phase shift have serious impact on wavy-wall minitube PEC. • PEC amount for optimum tube is about 1.670. In present study heat transfer and forced convection flow of non-Newtonian two-phase ethylene-glycol/water mixture based nanofluid through a wavy-sinusoidal minitube has been investigated. The 2D governing system of equations is solved numerically in the computational field using the Control-Volume-Approach founded on the SIMPLE technique. Flow velocities or Reynolds numbers are varied in the turbulent regime range from Re =6000 to Re =15,000 and the tube walls boundary condition is uniform temperature. The optimization was conducted considering five different constant and variable α(x) amplitudes, five various constant and variable λ(x) wavelengths and five various phase shifts in order to achieve the most advantageous geometry in view of the highest thermal-hydraulic performance evaluation criterion index. From obtained results in present paper, it has been realized that the wavy-wall minitube thermal-hydraulic performance is seriously affected with varying the wavy amplitude, wavelength and phase shift. The highest thermal-hydraulic PEC has been obtained for the amplitude of α=0.5 mm with increasing wavelength and phase shift of θ=90° at Re =6000 Reynolds number. After opting of the optimum geometry, Silicon-Carbide (SiC) nanoparticles were added to base fluid in volume fraction of 4% and sizes of 16 to 90 nm. Based on results, the PEC of EG/water based nanofluid with nanoparticle diameter of d np =90 nm has been conducted to be the most efficient among all models during investigated range of flow velocities. PEC amount for optimum tube using EG/water based SiC nanofluid with volume fraction of ϕ=4% and nanoparticle diameter of d np =90 nm at Re =15,000 is about 1.670. [ABSTRACT FROM AUTHOR]

The experimental system: (a) Schematic diagram. (b) Physical diagram. • Effects of round hole diameter on the flow and heat transfer are studied. • Effects of pitch-row on the flow and heat transfer are studied. • Thermal and exergy efficiency for thermo-hydraulic performances are studied. For investigating the thermal and hydraulic characteristics of water-based SiO 2 nanofluids in a triangular tube with different turbulators, an experimental system has been designed and verified in this paper. The effects of different round hole diameters (d = 3 mm, 4 mm, 5 mm) and round hole pitch-rows (l = 5 cm, 10 cm, 15 cm) of perforated turbulators on the thermo-hydraulic characteristics are researched. Meanwhile, the influences of Reynolds numbers (Re = 400–8000) and nanoparticles mass fractions (D-I water, ω = 0.1%, 0.3%, 0.5%) are also studied. These experimental results show that, under the same circumstance, the nanofluids in the triangular tube with ω = 0.5% have the largest positive influence on the heat transfer enhancement ratio which is up to 16.73%. For a comprehensive study of the flow and heat transfer, thermal efficiency (comprehensive performance index) and exergy efficiency are adopted. It can be found that the larger the diameter and the smaller the pitch-row of the holes is, the greater the comprehensive evaluation index can be. In addition, all working conditions exhibit the superior exergy efficiency. The highest exergy efficiency can be got when Re = 6000 and ω = 0.5%. [ABSTRACT FROM AUTHOR]