Papers by Keyword: Nusselt Number

Abstract: Natural convective in enclosures are very important topics in thermal engineering because they find versatile industrial applications. An internal circular cylinder's vertical position and heat source on fluid flow and heat transfer in a triangular cavity are investigated. Numerical simulations were carried out to analyze variations in the average Nusselt number, streamline topology, temperature distribution, and velocity fields by using ANSYS Fluent. The results show that the Nusselt number rises from approximately 0.91–0.94 at lower positions (Y = 0.1–0.3) to a maximum of about 0.97 near Y = 0.4 driven by intensified thermal gradients and buoyancy-induced circulation. Within the upper-to-mid region (Y = 0.2–0.4) the formation of large adjacent vortices enhances macro-scale mixing, resulting in nearly a 4% improvement in heat transfer relative to the reference case. At mid-level positions (Y = 0.4–0.6) quasi-steady symmetric circulations are sustained, maintaining effective convection with Nu values of 0.95–0.97. In contrast, at higher locations (Y = 0.7–0.9), the weakening of vortex strength leads to flow stagnation and localized deterioration in heat transfer, reducing Nu to about 0.90–0.92. Overall, the findings underscore the critical importance of internal component placement in improving natural cooling performance, and further suggest that the most efficient thermal behavior is achieved when the cylinder and heat source are positioned within 0.2 < Y < 0.4, offering practical guidance for optimizing the thermal design of triangular enclosures.

Abstract: This work offerings a numerical study of natural convection heat transfer within a triangular enclosure having a centrally positioned cylindrical heating source. The effect of the heat source size is investigated by varying its non-dimensional diameter from 0.1 to 0.5. The eating source cylinder and enclosure are maintained at constant temperatures. The buoyancy-driven flow field is analyzed using streamline distributions, non-dimensional velocity magnitudes, and isotherm contours. Results reveal that the size of the internal heating source significantly affects the thermal performance of the combined structure. For small values of , the flow remains weak and localized, with limited convective motion. As increases to moderate values ≈0.3, recirculation regions intensify, velocity fields expand, and thermal plumes rise symmetrically, which indicates enhanced convective transport. However, additional increasing of values leads to flow constriction, reduced circulation strength, and causes less effective heat transfer. It is found that the average Nusselt number decreases with increasing due to diminished temperature gradients and restricted fluid motion despite the larger surface area provided by bigger cylinders. The results are applicable for the design of passive electronic cooling systems, solar thermal collectors, and other natural heat convection-based enclosures.

Abstract: The aim of this work is the numerical study of natural convection in a square enclosure filled with nanofluids, using (Cu-water) and (TiO₂- water) nanofluids. The finite volume method is used to solve the Navier-Stocks and energy equations. The effects of different relevant parameters, such as types of nanoparticles, volume fraction of nanoparticles (0-30%) and whose Rayleigh number varying from 10³ to 10⁶. It appears from this study that heat transfer increases by increasing the Rayleigh number and the volume fraction of the nanoparticles. The use of nanofluid enhances heat transfer, the highest heat transfer enhancement is observed in Cu-nanofluid. Consequently, the type of nanoparticle is a main factor for the enhancement of heat transfer. A comparison of our results with those of Barakos and Mitsoulis revealed a good agreement.

Abstract: An experimental study is performed on thermal fluid transport phenomenon in plate heat exchanger. Emphasis is placed on enhancement of heat transfer performance in plate heat exchanger with the aid of silica-nanofluid as a working fluid. A plate heat exchanger (PHE), manufactured by HISAKA company (RX-O15A-KNHJ-7), is used as the test section. The PHE has 3 stainless steel plates (271.3mm X 136.5mm) with a nominal gap of 2.5 mm between any two plates. Thermal energy of the hot working fluid is transferred to that of the cold one through the titanium plate in the test section. Here, hot and cold working fluids are supplied by the independent loops, i.e., hot and cold fluid loops, respectively. It is found that (i) heat transfer is enhanced due to particle suspension in comparison with the pure working fluid, and (ii) heat transfer performance is substantially intensified with an increase in volume fraction of nanoparticle and Reynolds number.

Abstract: The present numerical work, based on the finite volume method, deals with the characterization of natural convective flow and thermal fields inside differentially vertical heated square cavities filled with a nanofluid as well as the quantification of the convective exchanges. The investigation is devoted to study the influence of the hybrid nanofluid (Al₂O₃-Cu / water) on the flow’s general structure with a particular attention to the Nusselt number. An exhaustive parametric study is conducted considering different combinations of Al₂O₃ and Cu nanoparticles (NPs) dispersed in water for a range of Rayleigh numbers (Ra) and total volume fractions An appropriate agreement with experimental data was observed for the estimation of the hybrid nanofluid thermal conductivity. From the results, it is observed that the heat transfer intensifies by increasing the Ra number and the nanoparticles volume fraction. The hybrid nanofluid seems to be the most efficient nanofluid in comparison with a base fluid and a single nanofluid. This heat transfer enhancement becomes more convincing with the increase of the Cu NPs content (% in volume).

Abstract: This study aimed to investigate numerically the heat transfer improvement and pressure drop inside annular channel of a rotor-stator provided with fins mounted on the stator without and with Taylor number. The impact of mounting various types of fins (triangular, rectangular, trapezoidal shapes with small and large base) is studied by varying the fin width b from 0 to 14 mm. In the presence of axial air flow, numerical simulations are carried out by solving the governing continuity, momentum and energy equations of turbulent flow in cylindrical coordinates using the Finite Volume Method. The results obtained by Reynolds Stress Model RSM model have indicated that the heat transfer enhances as the surface area of the fins and the effective Reynolds number increase, while there is an increase in pressure drop. Furthermore, we have shown that the presence of Taylor number has a slight increase in Nusselt number and pressure drop compared to the case without Taylor number. Among the four geometries, it is found that the rectangular cavity is the best geometry which gives maximum heat transfer and minimum pressure loss.

Abstract: The present work deals with the numerical investigation of forced convection flow and heat transfer in a finned concentric annulus. The outer cylinder is axially finned while the rotating inner cylinder has a smooth surface. Our research focus on the impact of the fin inclination angle on heat transfer enhancement in rotating annular channels. Tests were carried out for different geometrical configurations using fins with inclined angle (α = 30°, 60°, 90° and 120°). Numerical study is based on effective Reynolds number and Taylor number. The results obtained using the code ANSYS-Fluent with SST k-ω turbulence model show a good agreement between the experimental and the numerical results. In the presence of rotational flow (Ta = 1.14 × 10⁶), the results indicate that α =120° is the optimal case which improves significantly the heat and mass transfer inside the finned channel.

Abstract: The present study relates to numerical investigation of natural convection heat transfer in a nanofluid filled square enclosure. One side of the enclosure is maintained at high temperature and the other side at a low temperature; while the top and bottom sides are adiabatic. The commercial CFD software ANSYS-FLUENT© was used to solve this numerical problem with the governing differential equations discretized by a control volume approach. nanofluids of Cu-water, Al₂O₃-water and TiO₂-water have been simulated for a range of Rayleigh numbers and volume fractions. The results were obtained in the form of streamlines and isotherms. Interpretations of the results are done based on heat transfer rates, volume fraction, Rayleigh number and Nusselt number. It is to be noted that addition of nanoparticles enhances the heat transfer rate. It is also observed that the Nusselt number is highly affected by volume fraction and Rayleigh number.

Abstract: In this work, the thermal behavior of a turbulent forced-convection flow of air in a rectangular cross section channel with attached W-shaped obstacles is investigated. The continuity, momentum and energy equations employed to control the heat and velocity in the computational domain. The turbulence model of k-ε is employed to simulate the turbulence effects. The finite volume method with SIMPLE algorithm is employed as the solution method. The results are reported temperature, local and average Nusselt numbers, and mean velocity contours. The subject is relevant and important for industrial applications.

Abstract: This paper theoretically examines the impact of thermal buoyancy on human skin tissue’s blood flow, heat exchange and their interaction with the surrounding environment using a two phase mathematical model that relies on continuity, momentum and energy conservation equations in continuum mechanics. The tissue blood flows and heat transfer characteristics are determined numerically based on Darcy’s Brinkman model for a saturated porous medium coupled with modified Pennes bioheat equation while analytical approach is employed to tackle the model of interacting surrounding environmental buoyancy driven air flow with heat sink. The influence of embedded biophysical parameters on the skin tissue’s blood flow rate and temperature distribution together with friction coefficient at skin tissue surface and Nusselt number are display graphically and discussed quantitatively. It is found that a boost in thermal buoyancy enhances skin tissue heat transfer and blood flow rates.