The heat transfer in power-law fluids across three corrugated circular cylinders placed in triangular pitch arrangement is studied computationally in a confined channel. Continuity, momentum and energy balance equations were solved using ANSYS FLUENT (Version 18.0). The flow is assumed to be steady, incompressible, 2D and laminar. A square domain of side 300 Dh is selected after detailed domain study. An optimized grid with 98187 cells is used in the study. The convergence criteria of 10 -7 for the continuity, x-momentum and y-momentum balances and 10 -12 for energy equation were used. Constant density and non-Newtonian power-law viscosity modules were used. Diffusive term is discretized using central difference scheme. Convective terms are discretized using Second Order Upwind (SOU) scheme. Pressure-velocity coupling between continuity and momentum equations was implemented using the SIMPLE (Semi-Implicit Method for Pressure Linked Equation) scheme. Streamlines show wake development behind the cylinders, which is much dominant at large ReN and n. Isotherm contours are cramped at higher values of ReN and PrN, implying higher heat transfer. Global parameters like Cd and Nu are computed for the wide ranges of controlling dimensionless parameters, such as power-law index (0.3 ≤ n ≤ 1.5), Reynolds (0.1 ≤ ReN ≤ 40) and Prandtl numbers (0.72 ≤ PrN ≤ 500). The NuLocal plot attains a pitch near corrugation of surface due to abrupt change in velocity and temperature gradients. Nu increases with ReN and/or PrN and decreases with n under otherwise identical situations. Nu is correlated with pertinent parameters, namely, ReN , PrN and n.

In this research, the radially increasing axisymmetric discharge of an electrically conducting fluid across a surface is accurately evaluated mathematically using the influence of Soret number. The surface is extended at an exponential speed in a radial direction, which causes flow trends. New similarity transformations are discussed in order to transform the governing, transform nonlinear partial differential equations into standard derivatives. The Successive Linearization Method is used to perform mathematical analysis for flow performing. The Chebyshev spectral technique is utilized to resolve the linear system in order to provide accurate solutions that converge effectively to the whole numerical solution. Comparisons with earlier research are conducted to evaluate the validity of the results on the distribution of velocity, temperature and concentration. Verify convergence and accuracy of the solution, the impacts of a few fluid factors are identified and explained.

Tüm dünyada fosil yakıtlar küresel ısınmaya neden olmaktadır.

The quest for augmenting dropwise condensation heat transfer performance has been the driving force behind the exploration of innovative techniques and approaches to fulfil the desired objective. Recent literature in condensation heat transfer unveils that dropwise condensation heat transfer improvements from Slippery Liquid Infused Porous Surfaces (SLIPSs) was central to the study of several researchers because these surfaces have shown excellent droplet mobility due to extremely low adhesion between the condensing liquid and the lubricant infused surface, thereby, promote dropwise condensation. As part of supplementing current research on SLIPSs, for the first time, the present study explores the potential of a semi-solid lubricant impregnated porous surface in enhancing the condensation heat transfer performance of a vertical condenser tube. The results of experiments conducted over a wide range of subcooling (5°C ≤ ΔT ≤ 65°C) in a saturated steam environment signify that Copper tubes with semi-solid lubricant impregnated porous surfaces are potential candidates for enhancing dropwise condensation heat transfer coefficient when compared to an untreated vertical Copper condenser tube. The highest enhancement is found to be 280% at a subcooling of 40°C. Also, the semi-solid lubricant impregnated porous surfaces are proficient in sustaining dropwise condensation for a time period of 72 hours without any degradation in the heat transfer performance. The method devised here for fabricating the semi-solid lubricant impregnated surfaces is simple, less expensive, and less time-consuming compared to the techniques reported earlier for fabricating the SLIPSs. Additionally, in this work an approach based on numerical optimization by a stochastic global optimization technique, namely, Genetic Algorithm, is proposed to retrieve the coefficients and the exponent in the mathematical expression of overall resistance, which in turn is used to compute the tube-side dropwise convection heat transfer coefficient.

We have explored the result of the activation energy, thermal conductivity, and variable viscosity, A vertical wavy surface is passed by heat sources during convective heat transfer. Coupled equations controlling the flow, the nonlinear, mass, and heat transferring an electrically conducting viscous fluid via a vertically wavy surface have been solved with the Runge-Kutta-Shooting approach. ( f′, f ) the velocities, (φ)concentration and (θ)temperature, Sherwood and Nusselt number were discussed for several variations of Ds, Dc, E1, δ, Rd, β, θr, A1, B1, a, ξ. It has been seen that axial velocity increases with rising values of Ds, Dc, E1, Nr and reduces with thermal radiation (Rd), and thermal conductivity (β). Nusselt number (Nu) reduces with temperature dispersion (Ds), variable viscosity(θr), thermal conductivity (β) and enhances with solutal dispersion (Dc), radiation (Rd). Space/temperature dependent heat sources (A1, B1).

The study aims to quantify the effect of Dufour number, on flow patterns and heat transfer rates in the exponentially accelerated vertical plate with MHD flow and chemical reaction. The unsteadiness of the flow suggests that time-dependent changes in velocity, temperature, and other relevant parameters are considered. MHD further complicates analysis with the electromagnetic interactions between the fluid and the field. The fluid, be characterized as a gray, absorbing/emitting radiation medium, indicating that it absorbs and emits thermal radiation but does not exhibit scattering behavior. Set of partial differential equations are then resolve using FEM. Graphical results are then discussed. Profiles vary with different, Dufour number, radiation, or temperature-dependent heat source/sink parameter. By varying the values of these governing parameters, on the skin-friction coefficient, Nusselt number, and Sherwood number are also analyzed.

This study examines turbulent convective heat transfer performance (CHTP) and entropy production rate (EPR) of distilled water flowing in outwardly corrugated converging pipes (CCPs) of various diameter ratios (DR). The SST k - ω turbulence models were used to simulate the flow of H 2O inside the pipe. The effects of Reynolds number ( 5 . 0 × 10 3 ≤ Re  ≤ 5 . 0 × 10 4 ), and DR ( 1 ≤ DR  ≤ 2 ) on average Nusselt number ( Nu ), Poiseuille number (fRe) thermal performance evaluation criterion (PEC), EPR, and thermal effectiveness number ( I ) Nu were investigated parametrically. The findings revealed a significant improvement in Nu in the modified pipe compared with the straight pipe. This improvement is attributed to flow acceleration and increases in the mixing rate of hot fluid near the wall with cold fluid at the core fluid zone. Also, Nu , fRe , and EPR increase with increasing Re and DR. However, the opposite is the case for PEC and   I . Finally, the values of PEC, and I revealed that the modified pipe is advantageous compared with a straight pipe at ( 5 × 10 3 ≤ Re ≤ 1 . 0 × 10 4 ) .

The study aims to find the optimal fin length distribution for improved heat transfer during melting and solidification in a tubular PCM heat exchanger designed for heat storage. Three types of horizontal PCM tabular heat exchangers, all with five longitudinal fins, were studied numerically. While maintaining a constant heat transfer area, each model depicts a unique fin length distribution design. The first model, which serves as the reference design, has a homogeneous fin length distribution and each fin is 30 mm long. The second model has shorter upper and side fins and longer lower fins (20 mm for the upper fin, 25 mm for the side fins, and 40 mm for the lower fins). The third model has long lower fins but shorter than that of second model, short side fins and no change in upper fin length with reference design (30 mm for upper fin, 25 mm for side fins and 35 mm for lower fins). The findings indicate that the second model exhibits the best heat transfer performance for the melting process, while the first model is most effective for solidification. Interestingly, the third design emerges as the optimum choice for both melting and solidification processes.

While a variety of solar concentrators have been studied for decades, the study of the spherical glass concentrator has never been reported, to the best of our knowledge. For that, this paper examines the optical characteristics of the novel solar spherical glass concentrator and identifies its performance and features. In addition, the thermal and exergetic performance of the concentrator are studied with three cavity receiver designs under various operating temperatures and different mass flow rates. More specifically, the examined receiver shapes: spiral, conical, and cylindrical. All the cavities are analyzed in order to determine the best design which maximizes the thermal efficiency of the solar collector. According to the results, the spherical collector can concentrate the heat flux up to 25 times the incident flux value. Also, the study is defined the best receiver dimensions that achieve optimum optical performance. Then, the optical analysis is conducted with an optical simulation in COMSOL Ray Optics to validate this work’s findings. Moreover, the best design is found to be the one with a spiral shape, while the conical is the next choice. The cylindrical is the third design in the performance sequence.