The two-phase Eulerian–Eulerian model is used to analyze a hybrid slurry consisting of micro-encapsulated phase change material (MEPCM) and copper (Cu) nanoparticles suspended in water inside a differentially heated enclosure under natural convection. The governing equations for each phase and their interaction terms are discretized using finite difference methods, along with sixth-order accurate compact schemes employed for nonlinear terms. After validating the solver with experimental and numerical results, a parametric study is conducted for different temperature differences across walls(4–16 K), solid phase volume fractions (1%–15%), and MEPCM/Cu particle mixture ratios (95:5, 90:10, 80:20), focusing on melting dynamics, flow behavior, and heat transfer characteristics. Adding Cu nanoparticles improves the slurry’s thermal conductivity, accelerating heat diffusion from the hot wall and promoting faster MEPCM melting, which in turn intensifies natural convection and improves heat transfer performance. At a temperature difference of 12 K (Corresponding Grashof number of 1.98 × 106) and 5% solid phase volume fraction with a mixture ratio of 80:20 (MEPCM:Cu), the average Nusselt number increases by 11.7% and 39.71% over MEPCM-water and water, respectively. Further increasing solid phase volume fraction up to the optimum value of 15% enhances thermal conductivity and latent heat capacity, thereby intensifying buoyancy-driven flow and improving heat transfer performance.

We study the thermo-fluid dynamic interaction of two buoyant plumes emanating from an anti-symmetrically heated cylinder pair within a square enclosure. Closed-cavity mixed convection due to the rotation of a single heated cylinder was well-explored. The present configuration introduces a cold cylinder above the hot cylinder, and their axes lie on the vertical mid-plane of the enclosure. The hindrance offered by the cold cylinder is examined by varying the Rayleigh number ( Ra ), rotational Reynolds number ( Re ω ), dimensionless inter-cylinder distance and Prandtl number. The Richardson number is kept near 1 to observe the transition regime between free and forced convection dominance. Our study elucidates some primary and secondary flow field symmetries under static conditions, perturbed by rotation and, more seriously, by co-rotation. We demonstrate that the double symmetry of pressure distribution around static cylinders is interrupted by rotation: the vertical symmetry is affected more prominently for counter-rotation. Unlike the two pressure-minima around static cylinders, the rotating cylinders exhibit only one minimum. We identify two particular θ -locations on the cylinders ( θ = 18 ° and θ = 162 ° on the heated one) where the near-wall pressure remains insensitive to changes in radial distances. Investigating the characteristic changes of the shear stress components on the cylinders (viz. τ x and τ y ) with rotation, we demonstrate three distinct fluid dynamic zones demarcated by the changes in the sign of τ y confined to one-half of the cylinder, while the other half preserves the static cylinder behavior. One of the three fluid dynamic zones characterized by τ y > 0 vanishes with increasing Re ω , interlinked to the transition from mixed to forced convection. A differential Nusselt number ( Δ Nu ) is invoked to illustrate the impact of rotation on heat transfer. The result reveals insignificant enhancement of the Δ Nu for counter-rotation. On the contrary, co-rotation enhances ( Δ Nu co / Δ Nu counter ∼ O ( 10 2 )) this metric with increasing Re ω and Ra .

Internally threaded tubes are high-efficiency heat transfer components crucial for all-aluminum residential air conditioning systems. This study systematically investigates the effects of geometric parameters—number of threads, thread height, thread apex angle, and helix angle—on thermal–hydraulic performance in 5 mm aluminum internally threaded tubes using numerical simulations. Using the friction factor and performance evaluation criterion as metrics, we optimize the tube configuration. Empirical correlations are developed for rapid evaluation of the heat transfer and flow resistance across parameters and operating conditions. Results show that the thread apex angle (40°–60°) most significantly impacts heat transfer performance. The number of threads (35–55) and helix angle (14°–26°) exhibit notable enhancement effects when the Reynolds number exceeds 5200. The optimal parameter combination is 50 threads, thread height of 0.23 mm, thread apex angle of 40°, and helix angle of 26°, yielding an average 6.52% performance improvement over conventional copper tubes. Computational correlations for the Nusselt number and friction factor, developed via multivariate nonlinear regression of simulation data, limit prediction deviation to within 10%. These results guide structural and performance optimization for small-diameter (5 mm) aluminum tubular heat exchangers, providing theoretical support for enhancing heat transfer efficiency while managing flow resistance in compact thermal systems.

The apparatus of modern aircraft engines are subjected to increasingly difficult operating situations, particularly the blades of high-pressure turbines. To improve the efficiency and performance of aeroengines and gas turbines, turbine inlet temperatures are gradually increased. To ensure the safe operation of turbine blades under these extremely high-temperature conditions, it is essential to develop effective cooling technologies. To this end, a new method has been used to improve heat transfer in energy-efficient engine blades. Microstructured surfaces created using biomimetic engineering can efficiently and cost-effectively enhance thermal and aerodynamic characteristics, aiding applications in the energy sector. The first-stage turbine blade of a turbofan engine with internal cooling for three different microstructure geometries (scallop, diamond, and sharkskin) was used to study the effect of these techniques on the boundary layer flow and heat transfer characteristics of the blade. The numerical simulation results show a decrease in the average temperatures distributed through the blade by a maximum ratio of 22.8% for the diamond geometry. The presence of a microstructure clearly enhances the heat transfer through the blade for all geometries. In addition, in terms of aerodynamics, there is an improvement in the flow characteristics and boundary layer control of the microstructured surfaces, represented by the distribution of pressure, wall shear stress, and drag reduction. The microstructure achieved 34.4% and 29.7% drag reduction for scallop and diamond geometries, respectively. The evaluation of heat transfer and flow parameters show the advantage of scallop and diamond geometries in comparison with sharkskin geometry for gas turbine blades applications.

The integration of photovoltaic (PV) panels with a phase change material (PCM) represents an innovative approach for thermal energy storage and cooling of PV panels. The objective of this research is to determine the optimum fin spacing that improves the rate of heat transfer within a PCM and consequently facilitates the rapid melting of the PCMs during the sunshine time. The optimum number of fins is defined as the number of fins that is if increased by 1 result in a decrease in the melting time by less than 2%. A transient 3D numerical model has been developed to simulate the melting process of the PCMs as a function of the fin spacing using ANSYS Fluent, and the numerical results have been validated experimentally. The numerical simulations have been applied for two different types of PCMs, which are paraffin wax and the inorganic salt, calcium chloride hexahydrate. The optimum number of fins is a function of the PCM material, such that it is equal to 12 for Paraffin wax, which corresponds to a fin spacing of 1.8 cm, while in case of the inorganic salt it is 7 fins, which corresponds to a 3.3 cm spacing. The optimum number of fins is lower in case of the inorganic salt than in case of the wax, and that is due to the high thermal diffusivity of the salt, which has resulted in a faster heat transfer and melting of the inorganic salt as compared to wax for the same number of fins.

This study compares two numerical modeling approaches, Eulerian-Eulerian and Eulerian-Lagrangian, to model air/water mist jet impingement on a flat plate at constant heat flux. A parametric analysis investigates the effects of air Reynolds number (4,500–10,000), mist loading fraction (0.5%–1.2%), and non-dimensional nozzle-to-plate distance (20–40) on flow and heat transfer characteristics. The Eulerian-Lagrangian approach showed significant inaccuracies, with heat transfer coefficient errors up to 35% compared to experimental results. The results of the present investigation, predicted by the Eulerian-Eulerian technique, have a maximum error of 8% and are well within the experimental uncertainty. Heat transfer increases with Reynolds number and loading fraction, with maximum increases of 78.28% and 22.96%, respectively. Heat transfer decreases with nozzle-to-plate distance, with a maximum decrease of 44.5%.

This study investigates the transient heating characteristics of mini-channel heat sinks (MCHS), addressing a gap in existing research which predominantly focuses on steady-state analyses. Through comprehensive numerical simulations, three distinct mini-channel geometries are examined: conventional mini-channels, pin fin mini-channels, and strip fin mini-channels. Transient heating is modeled using functional forms, specifically cosine and step functions, to ensure consistent heating amplitude throughout each thermal cycle. The primary objective is to compare these geometrical configurations based on their responses to functional heating profiles. The analysis evaluates key performance metrics, including temperature distribution and thermal cooling efficiency at the base of the heat sink. Results indicate that strip fin mini-channels outperform both conventional and pin fin designs by maintaining lower temperatures, thereby enhancing thermal cooling performance. Although pin fin mini-channels demonstrate the highest thermal efficiency, they are associated with a significant pressure penalty, particularly at high flow rates, which may limit their practical application in scenarios requiring elevated flow conditions. These findings provide valuable insights for the design and optimization of MCHS, emphasizing the tradeoffs between thermal performance and pressure requirements in different mini-channel configurations.

The performance of a fuel cell is greatly affected by various parameters, with bipolar plates being a key component. The design of flow channels within these plates, whether serpentine, parallel, or interdigitated, directly impacts reactant distribution, water management, and pressure regulation. These aspects are essential for optimizing the fuel cell’s efficiency and functionality. In this study, six different designs of bipolar plate flow fields with serpentine patterns are explored, and these designs are simulated using computational fluid dynamics. The designs include various configurations, including serpentine flow with 1, 2, 3, 4, and 5 channels and a quadrant serpentine flow. Through analysis of pressure and velocity distributions, the serpentine flow, the 2-channel design emerges as the most efficient, providing balanced pressure distribution and low velocity. Subsequently, these bipolar plates are fabricated using milling centers and tested in a computerized fuel cell workstation, with results compared to those of a conventional single serpentine bipolar plate. Experimental findings reveal that the serpentine flow, 2-channel design exhibits a 5% improvement in performance compared to the traditional single-channel fuel cell design.

A linear Fresnel collector is a line-focused concentrator that creates a line focus onto a fixed receiver. Among all solar concentrating technologies, the linear Fresnel collector has the lowest performance. Progressive study reveals that various novel efforts are taken to combat the drawbacks of linear Fresnel collector. In the current work, a concept of combined focus technology i.e., integration of line and point focus is implemented to improve the thermal performance of linear Fresnel collector. This research work aims to compare the thermal performance of standard and combined focus technology based linear Fresnel collector. Both collectors are tested simultaneously under similar climatic and operating conditions. Performance of point focus integrated linear Fresnel collector is observed better than conventional linear Fresnel collector. It is noted that there is an improvement in the temperature difference of working fluid, heat generation and collector efficiency by 12.37%, 5.10% and, 3.52% respectively. The findings of this work provides vital information to the concerned researchers.

The present paper discusses the comparative assessment of four machine learning models to predict the thermo-electric behavior of a 24-Ah Lithium-ion Phosphate battery module arranged in 4-series and 4-parallel. The models considered are random forest regression (RFR), k-nearest neighbors regression, decision tree regression, and linear regression. Input variables include charging rate (0.5 C, 0.75 C, and 1 C), discharging rate (1, 2, and 3 C), state of charge (0-100%), and ambient temperature (30 °C, 40 °C, and 50 °C). The predicted outputs are temperature, voltage, and current. The prediction accuracy is evaluated using mean squared error and coefficient of determination. The investigation reveals that both K-nearest neighbors regression and random forest regression show potential for predicting thermal and electrical attributes of battery module with heat sink and without heat sink. These models appear suitable for applications in battery thermal management systems. Among them, the K-nearest neighbors regression model demonstrates superior forecasting capabilities for intermediate unseen data discharging conditions (1.5 and 2.5 °C) at ambient temperature of 30 °C and 40 °C.