Computational Investigation Of Heat Transfer Research Articles

Experimental and computational investigation of heat transfer during quenching of semi-solid aluminum plates under hot cracking condition

The present work attempts to study the cooling characteristics of 7050 aluminium alloy under semi-solid conditions during the jet impingement quenching. An aluminium plate heated to 485℃ (10% liquid fraction) is prone to hot cracks, causing large fluctuations in the temperature data. The 2-D direct heat transfer problem is formulated with the finite element technique, and moving boundary conditions are applied to simulate the quenching process. The heat flux is estimated from the boiling curve parameters (Qmax, TDNB, TLeid) by matching the simulated and experimental temperature data. The cracks are incorporated as the interface elements in the finite element domain along with the phase change model to simulatethe heat transfer phenomena. The influence of phase change and hot cracks on heat transfer is studied in detail with static and dynamic cracking conditions. The parity plot reveals that experimental and simulation results are in good agreement for uncracked plates, with an error range of ± 3% and R2 = 0.9987. Phase change incorporation improves the simulation results for cracked plates, reducing the error range from ± 10% (without phase change) to ± 5% (with phase change) along with R2 values of 0.9929 and 0.9863, respectively. The Boiling curve parameters for the cracked plate are found to be Qmax: 7.2 MW/m2, TDNB: 190℃, and TLeid: 450℃. Further, the findings show that the crack originates in the impingement zone of the quenched side of the plate.

3D computational investigation of heat transfer and entropy generation due to cryogenic cooling of twin heaters

3D computational investigation of heat transfer and entropy generation due to cryogenic cooling of twin heaters

Computational Investigation of Heat Transfer and Mass Flow in GTA Welding of AA6061 Plates

Computational approach or numerical simulation is a trend in recent manufacturing technology, in the present study a computational approach is made for a pulse type GTAW to analyze the heat transfer and mass flow behavior using FEA software ANSYS 19.0. Transient thermal simulations are carried at three different heat inputs in the form of voltage and currents with the welding speed of 70mm/min. The heat source profiles are obtained with the different heat inputs from experimental investigations. The same heat source profiles are modeled using the Solid EDGE software and called in the ICEM CFD to generate grids with unstructured tetrahedral mesh and grids are also made for the workpiece by modelling for a dimension of 150mm × 100mm having 6mm thickness same as the experimental workpiece. The generated Finite element model is called in ANSYS Workbench for transient thermal simulations to obtain the temperature distributions and the heat source models are also called in ANSYS Fluent for velocity field. The heat source models selected and the temperature field obtained from the computational numerical simulations are in good agreement with the experimental results indicating validation of the simulation process made.

Computational investigation of heat transfer on the surface of engine cylinder with fins of different shapes and materials

In everyday life the use of vehicles has expanded immensely for some ventures and house hold applications, likewise the running time of engine cycle is exceptionally long. Thus because of the consistent running enormous measure of heat is produced. At the point when this heat isn't appropriately disseminated, the engine gets more fragile very soon and life of the engine declines because of the heat development. To build the life of the engine, heat dispersal is expanded by giving fins at external of engine chamber. The shape of the fins and the material used for the fin increases its heat dissipation capacity and in turn increases the cooling of the engine for proper functioning. The present work focuses on the design of fins of circular and tapered shapes for a 2-stroke engine. The temperature distribution and the heat dissipation along the fin surface of two shapes has been observed by a steady state thermal analysis. Alusil and Silumin has been selected as the fin materials and a computational evaluation has also been done using FEM. A better shape of the fin along with a suitable material has been selected based on the results observed by FEM and on comparison with the existing shape and material of the fin.

Computational investigation of heat transfer in a flow subjected to magnetohydrodynamic of Maxwell nanofluid over a stretched flat sheet with thermal radiation

AbstractThe main objective of this paper is to numerically investigate the results of a mathematical model for unsteady magnetohydrodynamics (MHD) boundary layer flow over a porous stretching surface. The analysis of non‐Newtonian Maxwell nanofluid is presented involving the influence of porous media, thermal radiation, viscous dissipation, and joule heating through the Keller box method. Partial slip and convective conditions are also enacted near the boundary. After using the similarity technique on the governing system of nonlinear partial differential equations, the Keller box method is then implemented to find out the numerical solution for copper–water Cu–H2O and molybdenum disulfide MoS2–H2O nanofluids. The impact of various governing flow parameters is interpreted numerically and illustrated graphically on the interaction of particles. Additionally, numerical results are further utilized to calculate the skin friction coefficient and heat transfer rate at the boundary. Finally, in a limiting case, the acquired numerical results are compared with existing results. The remarkable finding of the present study is that Cu–H2O based nanofluid is detected as a superior thermal conductor instead of MoS2–H2O based nanofluid.

Experimental and computational investigation of heat transfer in a microwave-assisted flow system

Microwave technology is gaining popularity as a tool for chemical process intensification and an alternative to conventional heating. However, in flow systems non-uniform temperature profiles are commonly encountered and hence methods to characterise and improve them are required. In this work, we studied the effects of various operational parameters - microwave power, inlet flow rate, tube orientation and pressure - on the electric field and temperature profiles of water flowing in a PTFE tube (2.4 mm internal diameter), placed in a commercial single-mode microwave applicator. A finite element model was developed to estimate the longitudinal temperature profiles and the absorbed microwave power, while in situ temperature monitoring was performed by a fibre optic probe placed at multiple locations inside the tube. The water temperature inside the tube increased by increasing the microwave power input and temperature profiles stabilised beyond 20 W, while the percentage absorbed microwave power showed the inverse trend. When changing the tube orientation or decreasing the inlet flow rate, microwave absorption decreased significantly. When the pressure was increased to 2.3 bara, water temperature increased by ∼20 °C. Results from this study provide valuable insights on achievable temperature profiles and energy efficiency of microwave-assisted flow synthesis systems.

Computational investigation of heat transfer and entropy generation rates of Al2O3 nanofluid with Buongiorno's model and using a novel TVD hybrid LB method

The present paper deals with the Buongiorno's model for nanofluids with a novel TVD11Total Variation Diminishing. Hybrid Lattice Boltzmann technique. It is well known that when the diffusion fluxes (with Dissipation behaviors) own negligible values regarding convective fluxes, almost all classical methods suffer serious instability errors. The Lattice Boltzmann method also is not an exception to this rule. In order to resolve this issue, many novel techniques and methods (e. g. MRT-LBM) are developed. Here we propose a novel TVD Hybrid LB method to solve Buongiorno's model for Al2O3-Water nanofluid in the presence of an elliptic cold obstacle. The Model naturally possesses small values of diffusion coefficients and thereby, explicit methods are not considered as primitive choices to be applied in the simulation of this model. But the TVD characteristics of the following Hybrid LB method made it a valuable asset in resolving these kinds of problems. Moreover, the heat transfer and entropy generation of a square cavity with sinusoidal temperature and concentration boundary conditions were numerically examined and different aspect ratio combinations, as well as different obstacle locations, were tested. The results indicated that for a moderate Ra number like Ra=105, total entropy generation of the system and the heat transfer rate from the walls are reduced with an increment in the obstacle size. In addition, it was found that site 4 presents the highest rate of entropy generation amongst all, yet still, the average Be number is not remarkably raised for this location.

Computational investigation of heat transfer and pressure drop in a typical louver fin-and-tube heat exchanger for various louver angles and fin pitches

In this study 3-D numerical simulations on heat transfer and pressure drop characteristics for a typical louver fin-and- double-row tube heat exchanger were carried out. The heat transfer improvement and the corresponding pressure drop amounts were investigated depending on louver angles, fin pitch and Reynolds number, and reported in terms of Colburn j -factor and Fanning friction factor f . The heat transfer improvement and the corresponding pressure drop amounts were investigated depending on louver angles between 20° ≤Ө≤ 30°, louver pitch of Lp =3.8 mm and frontal velocities of U between 1.22 m/s - 3 m/s. In addition, flow visualization of detailed flow features results, such as velocity vectors, streamlines and temperature counters have been shown to understand heat transfer enhancement mechanism. The present results indicated that louver angle and fin pitch noticeably affected the thermal and hydraulic performance of heat exchanger. It has been seen that increasing louver angle, increases thermal performance while decreasing hydraulic performance associated to pressure drop for fin pitches of 3.2 mm and 2.5 mm. Fin pitch determines the flow behaviour that for fin pitch of 2 mm, increasing louver angle decreased heat transfer and pressure drop. Velocity vectors and streamlines give considerable information about the flow whether it is duct directed or louver directed. For all conditions the flow is louver directed.

Experimental and computational investigation of heat transfer in channels filled by woven spacers

Models of woven-type spacer-filled channels were investigated by Computational Fluid Dynamics (CFD) and parallel experiments in order to characterize the performance of Membrane Distillation (MD) modules. The case of overlapped spacers was analysed in a companion paper.Experiments were based on a non-intrusive technique using Thermochromic Liquid Crystals (TLC) and digital image processing, and provided the distribution of the local convective heat transfer coefficient on a thermally active wall. CFD simulations ranged from steady-state conditions to unsteady and early turbulent flow, covering a Reynolds number interval of great practical interest in real MD applications. A specific spacer aspect ratio (pitch-to-channel height ratio of 2) and two different spacer orientations with respect to the main flow (0° and 45°) were considered.Among the existing studies on spacer-filled channels, this is one of the first dealing with woven spacers, and one of the very few in which local experimental and computational heat transfer results are compared. Results suggest a convenience in adopting the 45° orientation for applications that can be operated at very low Reynolds numbers, since convenience decreases as the Reynolds number increases.

Computational Investigation of Heat Transfer of Nanofluids in Domestic Water Heat Exchanger

Recent development of nanotechnology led to the concept of using suspended nanoparticles in the heat transfer fluids to improve the heat transfer properties of the base fluids. The heat transfer enhancement by nanofluids is the significant concerns in the efficiency of domestic water heat exchanger system. A computational investigation of the heat transfer in a domestic water heat exchanger is conducted on the water and water-based nanofluids. Copper (Cu) nanoparticle and Alumina (Al2O3) nanoparticle are selected in the water-based nanofluids. Volume fraction of nanoparticle in the nanofluids is set at 0.5 %, 1.0 %, 1.5 %, 2.0 %, 2.5 %, and 3.0 %. Heat exchanger has been invented for the heat transfer from one medium to another medium in many heat transfer systems. Domestic water heat exchanger can be used in a heat pump domestic water heating system. The density, the thermal conductivity, and the dynamic viscosity of the water base fluid are increased while the specific heat capacity of the water base fluid is reduced with the addition of copper as well as alumina nanoparticle. Addition of copper nanoparticle into the water-based heat transfer fluid significantly increases the domestic hot water temperature. The efficiency of domestic water heat exchanger system is optimum when 1.5 % copper or alumina nanoparticle is added into the water-based heat transfer fluid.

CFD modeling of particle–particle heat transfer in dense gas-solid fluidized beds of binary mixture

This paper presents a computational investigation of heat transfer, especially the direct particle–particle heat transfer between different particle classes in a dense gas–solid fluidized bed of binary particles using a computational fluid dynamics (CFD) method. A particle–particle heat transfer model between different particle classes is proposed in a gas–solid fluidized bed. By incorporating it into the multi-fluid model, a Eulerian–Eulerian CFD model is established. The heat transfer in a fluidized bed containing binary particles is thus investigated. The results indicated that particle–particle heat exchange coefficient between different particle classes increases with increasing large particle size and superficial gas velocity. However, it first increases and then decreases with increasing the large particle content in the fluidized bed. Gas–particle heat transfer is still the dominant heat transfer mode in the fluidized bed of binary particles. The ratios of particle–particle heat transfer to gas–particle heat transfer range from 1.27% to 3.09% for various operating conditions.