Improving HEAT TRANSFER in thermal systems has become a focus of many research studies due to the critical need for efficient waste of residual HEAT. The regulation of HEAT TRANSFER between components in thermal systems has a direct impact on their efficiency and performance. As a result, effective HEAT management is critical to improving the efficiency of thermal systems and extending the life of their components. It should be noticed that baffles are important structural components widely used in various industrial applications like HEAT exchangers, solar collectors, electronic cooling, etc. In addition, baffles enhance fluid mixing and HEAT TRANSFER behaviors. Most industrial systems do not operate in a steady state. In particular, transient phases occur during start-up and shut-down or during the control phase of controlled systems. Thus, in laminar flow, baffles induce flow unsteadiness or help the flow to bifurcate from a steady state to an unsteady flow. This paper treated the effects of different baffle shapes incorporated in channels on HEAT TRANSFER rate, efficiency and friction factor in mixed and FORCED CONVECTION cases. Various experimental and numerical studies have been carried out on this topic to examine HEAT TRANSFER enhancement compared to the flow energy. It was noticed that increasing the Reynolds number, blockage ratio and decreasing the Grashof number can achieve an increase in HEAT TRANSFER. The maximum HEAT TRANSFER enhancement was obtained for higher blockage ratio and higher Reynolds number in FORCED convective flow. The highest HEAT TRANSFER improvement was obtained for the 45° angled baffles (between 150% and 850%). In mixed convective flow, the highest rate of HEAT TRANSFER was obtained for transverse baffles (2.8 times compared to a similar channel with no baffles). Finally, This comprehensive review is beneficial for researchers focused on flow and HEAT TRANSFER applications to use other baffle designs and fluids beyond air.

In his research article, several models of HEATsink were optimally designed in fin length, width and height along with pin placement which consists of 4 pin fin HEATsink models HEATsink (including square with different pin angles, circular, truncated cone, and cone pin HEATsinks and one model of the plate-fin HEATsink (PFHS)) in order to achieve better thermal performance as well as less energy consumption and were numerically investigated under high air velocity and HEAT fluxes. Different parameters such as peak temperature, Nusselt number, HEAT resistance, pressure drop, and energy consumption were compared. The results show that the square PPFHS with the pin angle of 45 degrees has the highest thermal performance compared to the rest of the models while also having the highest pressure drop and energy consumption between the models consuming more than 255 and 358 percent more energy in order to have the same air velocity in the pathway, while the truncated and the fully formed cone model despite having 25% and 30% less thermal performance, have the least pressure drop between the pin models of the HEATsinks and therefore consume the least energy out of the PPFHS.

This research study presents a numerical study on FORCED CONVECTION HEAT TRANSFER of an aqueous ferrofluid passing through a circular copper tube in the presence of an alternating magnetic field. The flow passes through the tube under a uniform HEAT flux and laminar flow conditions. The primary objective was to intensify the particle migration and disturbance of the boundary layer by utilizing the magnetic field effect on the nanoparticles for more HEAT TRANSFER enhancement. Complicated CONVECTION regimes caused by interactions between magnetic nanoparticles under various conditions were studied. The process of HEAT TRANSFER was examined with different volume concentrations and under different frequencies of the applied magnetic field in detail. The convective HEAT TRANSFER coefficient for distilled water and ferrofluid was measured and compared under various conditions. The results showed that applying an alternating magnetic field can enhance the convective HEAT TRANSFER rate. The effects of magnetic field, volume concentration and Reynolds Number on the convective HEAT TRANSFER coefficient were widely investigated, and the optimum conditions were obtained. Increasing the alternating magnetic field frequency and the volume fraction led to better HEAT TRANSFER enhancement. The effect of the magnetic field in low Reynolds numbers was higher. The results showed that the modeling data were in a very good agreement with experimental data. The maximum error was around 10%.

The present paper describes a two-dimensional finite volume numerical simulation of flow and HEAT TRANSFER in airflow windows by free and FORCED CONVECTION techniques. The governing equations are the fully elliptic, Reynolds-averaged Navier-Stokes equations. The simple algorithm is employed to correct the pressure term. The second-order upwind scheme is used to discretize the CONVECTION terms. The (k-e/RNG) turbulence model is applied for the flow simulation. The mesh used is the body-fitted, multi-plane grid system. Results on the variations of velocity and temperature profiles with geometrical parameters, at different temperature and velocity, for HEAT TRANSFER by free and FORCED CONVECTION techniques are presented. Comparisons of the present results on temperature distribution for FORCED CONVECTION and for free CONVECTION with the available experimental FORCED CONVECTION data indicate that the airflow-influenced FORCED CONVECTION methods are considerably enhanced.

A theoretical solution is presented for the FORCED CONVECTION HEAT TRANSFER of a viscoelastic fluid obeying the Giesekus constitutive equation in a concentric annulus under steady state, laminar, and purely tangential flow. A relative rotational motion exists between the inner and the outer cylinders, which induces the flow. A constant temperature was set in both cylinders, in this study. The fluid properties are taken as constants and axial conduction is negligible, but the effect of viscous dissipation is included. The dimensionless temperature profile, the normalized bulk temperature, and the inner and outer Nusselt numbers are derived from solving non-dimensional energy equation as a function of all relevant non-dimensional parameters. The effects of Deborah number (De), mobility factor (a), Brinkman number (Br) and velocity ratio (b) on the normalized temperature profile and Nusselt number are investigated. The results indicate the significant effects of these parameters on the dimensionless temperature distribution and Nusselt number.

A strong magnetic field provides a new method of HEAT TRANSFER with high HEAT flux. A numerical simulation for a HEAT sink with high HEAT flux under an external uniform magnetic field in three different directions is used to investigate the flow field and displacement HEAT TRANSFER between liquid metal and hot surfaces. Due to its high density and large thermal and electrical conductivity coefficients, gallinsten liquid metal has been used as a working fluid. Discretization of the Navier-Stokes equations is performed by the upstream second-order finite volume method. The results show that the effect of applying a magnetic field in the Y and Z directions (perpendicular to the flow axis) on the HEAT sink with a Hartmann number of 88, improves the displacement HEAT TRANSFER coefficient by 15% and 8%, respectively. The best efficiency in increasing the HEAT TRANSFER was obtained by applying the magnetic field in the Y direction. By applying the magnetic field in the Y direction to the HEAT sink, the displacement HEAT TRANSFER coefficient was increased by 11. 9% for Hartman number of 44, 15% for Hartman number of 88, and 17. 7% for Hartman number of 132, compared to zero Hartman number. By applying the magnetic field in Z direction to the HEAT sink, the displacement HEAT TRANSFER coefficient was increased by 4. 3% for Hartmann number of 44, 8% for Hartmann number of 88, 11. 4% for Hartmann number of 132 and 22. 1% for Hartmann number of 330, compared to Hartmann number of zero. Also, the results show that the effect of applying a magnetic field perpendicular to the flow axis has increased the velocity gradient. As a result, the pressure drop and friction coefficient of the HEAT sink have increased.

In this paper, HEAT TRANSFER in a sinusoidal channel filled with nanofluid under magnetic field effect is investigated numerically. The magnetic field transversely applied to the channel. Water as a base fluid and copper as nano particles were considered .The Maxwell-Garnetts model and Brinkman model for HEAT conduction coefficient and dynamic viscosity were used respectively. The effects of changing some parameters such as shape 0≤a≤0.3, volume fraction 0≤f≤0.05, Hartmann number 0≤Ha≤20 and Reynods number 100≤Re≤500 were considered. The results show that increasing in all mentioned parameters lead to increasing in Nusselt number. Volume fraction is mainly affect on maximum local Nusselt number in each channel's wave while Hartmann number is affected minimum and maximum Nusselt number.

FORCED CONVECTION HEAT TRANSFER in metal foams in the presence of radiation HEAT TRANSFER is studied using the homotopy perturbation method (HPM). To see wall effects, Darcy-Brinkman model for the flow in porous media is used. A constant HEAT flux is imposed at the wall and the radiation HEAT TRANSFER is modeled by a temperature-dependent conductivity. In the present study the case of conjugate CONVECTION and radiation HEAT TRANSFER is analyzed by a semi-analytical approach for the first time. Effects of the radiation parameters (λ, Tr) and porous medium shape parameter (s) on the Nusselt number and dimensionless temperature profile are investigated. Moreover, a discussion on the accuracy and limitations of the HPM method will be presented.

Up to now, the HEAT TRANSFER coefficient for a number of non-Newtonian fluids in various combinations of vessel/agitator has been investigated. These types of fluids have a wide variety of applications and uses in the industry. Among these applications, exothermic polymerization reactions, production of resins and lacquers and many other applications require HEAT TRANSFER to non-Newtonian fluids either for chemical reaction or for reduction of viscosity in the process. Therefore, knowledge of HEAT TRANSFER coefficient in these systems is important in the design and operation of such systems. In the present investigation, using an experimental set up consisting of a jacketed vessel, a pitched turbine agitator with variable speed motor, a 2000 W electric HEATer situated in the middle of the vessel as the source of HEAT for the system and instrumentation, systems for the measurement of cooling water flow rate and local and bulk temperatures, HEAT TRANSFER coefficient for non-Newtonian fluids has been measured. All thermocouples have bean calibrated according to BSEN 60751- 1996 standards and proved to have an error of ±0.1°C. Parameters such as the concentration of Zanthan gum in water (non-Newtonian fluid solution of 0.2, 0.3 and 0.5%) and the speed of rotation of the agitator (200, 300, 400, 500 and 600 rpm) have been varied and the findings of various experiments were noted giving special attention to the viscosity of the solution and its effects. A power law relation was derived for the apparent viscosity of the non-Newtonian fluid as a function of the rotation speed and the temperature. By the use of dimensional analysis, an empirical equation was derived relating Reynolds, Prandtl and viscosity numbers to the Nusselt number and hence the variation of HEAT TRANSFER coefficient was indicated as a function of the most important operating parameters. The investigation included Reynolds number in the range 300 - 66000. Correlation is in the usual form of Nusselt number as a function of multiplications of Reynolds, Prandtl and viscosity number. The power of Prandtl number has been taken as 0.33 which is according to what has been indicated in most of the literature for similar cases. However, the power for Reynolds and viscosity numbers as well as the correlation constant was determined from the experimental data. The final from of this experimental correlation is Nu=0.935 Re 0.62 Pr 0.33 vi 182 This correlation shows a good agreement (over 90%) with the experimental data.

HEAT TRANSFER and pressure drop in Al2O3-water nanofluid flow through an internally ribbed pipe is studied numerically. The governing conservation equations in cylindrical coordinates for laminar incompressible flow are solved using well-known SIMPLE algorithm based on finite-volume method. The effects of flow parameters, the distance between the pipe ribs, and the volume fraction of nanoparticles, on HEAT TRANSFER and friction coefficient are investigated. The obtained results illustrate that increasing nanoparticles volume fraction makes the thermal entrance length decrease, and consequently, the HEAT TRANSFER gets increased. It also reveals that 5% of increment in nanoparticles volume fraction may lead to 28-percent rise in local Nusselt number and about 11-percent rise in average Nusselt number. In this case, the friction factor will also increase about 1.5 times in comparison with the pure fluid ones. The results also show that increasing the pipe ribs distance by five times in Re=100, will make the average Nusselt number increase by 2.45 times.