Heat Transfer最新文献

The study and application of cilia flow have implications across a wide range of disciplines, from medicine and biology to engineering and robotics, contributing to advancements in healthcare, biotechnology, and fluid dynamics research. Motivated by these applications, a numerical simulation is performed to investigate the mixed convective cilia flow of MHD hyperbolic tangent fluid in a curved channel. The analysis is performed in the presence of viscous dissipation. The curvilinear coordinates are used due to the curved nature of flow geometry in the derivation of flow equations. The fluid motion arises from the metachronal waves generated by the cilia. The constitutive equations are simplified by the hypothesis of the lubrication approximation and then solved numerically using the Keller Box method. Comprehensive investigation of velocity, temperature, pumping phenomena, streamlines, skin friction, and Nusselt number are graphed and analyzed. The results obtained from the analysis convey that the fluid velocity decreases with an increase in the magnetic field and increases with a rise in the Weissenberg number. The Nusselt number increases with the Brinkman number while the reverse observations are predicted for curvature parameter. Streamlines show fluid movement driven by cilia oscillations. Furthermore, the skin friction and Nusselt number at the channel walls are determined for a variety of critical parameter assessments. Potential applications of the current work include mucus clearance from the respiratory tract, microfluidics, oesophageal transport, biofluid mechanisms, and other fields of physiology.

The current study aims to precisely solve the problem of three-dimensional (3D) magnetohydrodynamics (MHDs) natural convective flow of a viscous, incompressible, electrically conducting, nongray, optically thick fluid past a uniformly moving porous vertical plate with variable sinusoidal suction in the slip flow regime, considering thermal diffusion, diffusion-thermo, and thermal radiation. The incorporation of variable sinusoidal suction with variable amplitude in a slip flow regime in 3D MHD natural convective flow across a uniformly moving porous vertical plate is the novelty of the present work. Into the fluid region, a uniform transverse magnetic field is applied. Using Rosseland approximation, the flux appearing in the energy equation can be described. At the plate, solutal, thermal, and momentum slip are taken into account. The equations governing the flow model are solved using the asymptotic series expansion method. Since sinusoidal suction creates a 3D flow, the flow is 3D. Through figures and tables, we discuss the effects of different parameters on flow and transport characteristics. The magnetic body force, or Lorentz force, is produced when a magnetic field and fluid velocity interact. Because of this force's resistance to the flow, the fluid's velocity drops. A greater amount of mass diffusivity results in an increase in the concentration profile. An increase in thermal diffusivity raises the temperature field. The rate of heat transmission is reduced by higher thermal diffusivity. The mass transfer accelerates as fluid viscosity rises because the fluid's viscosity increases along with the Schmidt number. Skin friction reduces by 0.5% when the Soret number rises by one unit. The rate of mass transfer is enhanced with a growing Reynolds number or low viscosity.

The heat transfer and the hydraulic performance of laminar flow using water–CuO nanofluid and pure water in smooth and complex channels with embedded hollow half-spheres are numerically studied over a range of Reynolds numbers. Pure water is first used as the coolant for all selected configurations, followed by low-volume fractions (3% and 5%) of water–CuO nanofluid in the optimal configuration. Three configurations are evaluated by varying the number and diameter of the opposing half-spheres. The results show that the heat transfer coefficient for microchannels with half-spheres increases, reaching up to 3.5 times that of smooth microchannels. Additionally, within the same Reynolds number range, the friction factor increases by up to 50%. The use of nanofluids results in a 6% and 14% increase in the heat transfer coefficient for concentrations of 3% and 5%, respectively, compared with pure water. These enhancements are directly correlated with the increase in thermal conductivity of the nanofluids relative to water.

Solar air heater (SAH) is a widely employed technology for harnessing solar thermal energy in numerous applications. Contemporary research optimizes designs within identical spatial constraints to maximize energy output. However, there is a recognized need to conduct analytical validation to stimulate the experimental setup and formulate an artificial neural network (ANN) model to govern and predict the operation system. This investigation involved developing and assessing an evacuated tube solar air heater (ETSAH) integrated with annulus-filled heat storage media. Furthermore, this study introduced an ANN model and analytical solution to predict performance parameters, representing a noteworthy contribution. The proposed ANN model achieved its optimal validation performance with a mean square error of 5.4018 × 10⁻⁶ after 11 epochs within 31 of training. Also, correlation findings show that the optimal architecture of a feed-forward backpropagation is achieved when the 5-40-40-40-2 model architecture is used. In this case, there are five neural nodes in the input layer that represent timing, temperature, radiation, and airflow rate. The power output of the ETSAH device shows a strong correlation with the flow rate, reaching its peak at 0.05 kg/s with a value of 2261 W and dropping to 368 W at 0.006 kg/s. Correspondingly, the greatest energy efficiency was measured at airflow rates of 0.05, 0.01, and 0.006 kg/s, accounting for 48.38%, 27.32%, and 19.65%, respectively.

Electronic components require faster propagation of heat to prevent overheating as well as to maintain a stable operating condition. Incorporating phase change materials (PCMs) in fin heat sinks (FHSs) can be a viable solution to enhance natural convection. In the present work, an extensive investigation has been carried out on three types (square, circular, and triangular) of FHSs filled with PCMs to find the best combinations for the thermal cooling of a heat sink. To increase the thermal conductivity of the PCMs, Cu–water nanofluid is added. The effects of three types (paraffin wax, stearic acid, and polyethylene glycol) of PCMs have been studied. Nondimensional equations have been solved numerically by using Galerkin's finite element method. A parametric investigation has been conducted by varying the Rayleigh number within the range of 10³–10⁶ to calculate the Nusselt number. Results reveal that a heat sink with PCMs can reduce the temperature rise by 6.41% and increase the Nusselt number by 4.6% compared to a heat sink without PCMs. As the height of the fins increases from 10 to 16 mm, thermal efficiency increases. Moreover, square FHSs show the best thermal performance by reducing the temperature rise by as much as 13.41% compared to circular and triangular FHSs. Therefore, this comparative study shows that the dimensional configurations of FHSs with varying PCMs have a great impact on thermal performance and thus provide one the opportunity to obtain an effective arrangement of heat sinks.

Thermal energy storage systems using PCM offer promising solutions for efficient thermal applications. This study aims to provide valuable insights into the PCM melting process and compare the thermal performance of different heat exchanger models. The experimental rig is carefully designed to simulate a shell and tube heat exchanger with five longitudinal copper fins at specific conditions. Three distinct models of the heat exchanger, labeled Models A, B, and C, were examined for their heat transfer efficiency during the melting process. Numerical simulations were conducted for the three models and compared with experimental results. Model A represented the benchmark model. It had uniform fin length, location, and angle. Model B was the modified design aimed at enhancing melting progress. These modifications included a longer lower fin, a shorter side fin compared to the reference, and a lower fin angle to optimize heat transfer performance. Model C incorporates further design modifications, with a longer lower fin, a shorter top fin, and different lower fin location. Numerical simulations and experimental observations revealed significant differences in heat transfer performance among the three models. The average heat transfer rates, measured up to the critical decline point, are crucial parameters for practical applications. A comparison among the three models showed that Model B surpassed the average heat transfer rate up to the critical point of Models A and C by 10% and 4%, respectively, demonstrating its superior practical applicability.

In arid regions facing challenges of limited access to potable water and electricity, solar desalination stands out as a promising solution for producing clean water from brackish sources. This research intends to examine and enhance an innovative and sustainable solar desalination system. A computational study is conducted on a pyramid solar still (PSS) combined with a phase-change material incorporated with nanoparticles, with a variety of absorber fins. The study investigates three configurations: a traditional pyramid–shaped solar still, one with square absorber fins, and another with circular fins. Paraffin wax mixed with Al₂O₃ nanoparticles is used beneath the absorber fins. Conservation equations are solved using COMSOL Multiphysics. Simulation outcomes demonstrate that the incorporation of finned absorbers, coupled with elevated water temperatures, significantly enhances the yield of the improved PSS compared with its conventional counterpart. The square-finned absorber PSS exhibits a substantial increase in total accumulated productivity over the conventional design. Moreover, the PSS with square-finned absorbers demonstrates an impressive average peak daily thermal efficiency improvement of 49.19% compared with a conventional solar still. This study highlights the effectiveness of the modified PSS as a superior option for household water generation.

India's rooftop solar photovoltaic (PV) installations are experiencing rapid growth due to favorable regulations. As climate change becomes a growing concern, researchers are turning their attention to the effects of weather patterns on the performance of rooftop solar panels, and also to optimize their efficiency in a changing environment. Consequently, industry players in the solar sector have been conducting performance validation and feasibility assessments of these plants. A 375 kWp rooftop PV plant is studied as a case example from April 1, 2022 to March 31, 2023, generating 543,666 kWh annually for the grid. The NMBE and MBE were assessed using simulation tools like PVGIS and PV Watts. In addition, a cost–benefit analysis of carbon credits was conducted with and without their inclusion. The energy payback time is calculated at 4.5 years post-inclusion. Over a 25-year lifespan, the embodied energy of the PV plant amounts to 2,552,265 kWh. This plant can mitigate CO₂ emissions annually by 10,173.57 tons which is equivalent to INR 5,464,925. The current study highlights both environmental and economic benefits by incorporating carbon credits into the project. Further advancement in simulation tools, PV technologies, climate change adaptations are expected which will improve the rooftop system efficiency with shorten pay pabck periods and maximum reductions in CO₂ emissions.

An analytical solution for unsteady, incompressible, laminar MHD fluid flow involving mass and heat transfer along a semi-infinite vertical moving flat plate in a porous medium have been studied in this paper. Effects of heat radiation and absorption, Joule heating, Dufour, thermal and solutal buoyancy, and first order chemical reaction of are discussed under suitable physical conditions. It is postulated that the plate will migrate in the fluid's motion's direction due to the presence of a uniform magnetic field normal to the porous surface. The regular perturbation technique is used to solve the dimensionless governing equations. The mathematical derivations for fluid velocity, temperature, and concentration are evaluated; apart from that, skin friction, rate of mass and heat transfer at the plate are also expressed. The present outcomes are compared with previously obtained results and are found to be in excellent agreement. It is observed that the fluid velocity and temperature enhanced with thermal and solutal buoyancy forces as well as the Dufour effect. Also, with an increase in chemical reaction parameter, there is a decrease in fluid velocity, temperature, and concentration. Skin friction and Nusselt number increase with higher heat absorption parameter values. Schmidt number and chemical reaction parameter both lead to a rise in Sherwood number. Applications for these models have been observed in a number of industrial and technical methods.

This paper introduces a novel approach to enhance the heat transfer efficiency of a plate-fin heat exchanger. The metaheuristic hybrid approach combines particle swarm optimization (PSO) with the genetic algorithm (GA). Seven critical design parameters are used as variables. The research demonstrates the effectiveness of this hybrid method through a case study based on existing literature. The numerical results show the superior performance of the hybrid genetic algorithm particle swarm optimization over conventional GA and PSO techniques. The hybrid method achieves an optimal configuration with increased accuracy in a shorter computational time, offering significant time and cost savings in the design process.