Heat Transfer最新文献

This paper reports on a novel hybrid thermal management strategy. It uses secondary coolants (air and liquid) to withdraw heat simultaneously from the composite phase change material, resulting in increased heat extraction capability of the composite phase change material and improved thermal environment of the battery module. The significance of this strategy is that the fluid used in the liquid cooling stays stationary. Comprehensive experimental and numerical studies are performed, and parametric studies are conducted to reduce the volume of the phase change material, size of the air duct, and airflow Reynolds number. The numerical results showed that the maximum temperature was limited to 27.8°C, and a high-temperature uniformity of 0.4°C was obtained. Furthermore, the required volume of the composite phase change material is reduced by ~50%. Additionally, beyond a 6 mm height of the air duct, the reduction in maximum pressure drop is not significant enough, and it is considered the optimal height, and a Reynolds number of 1950 is considered the optimal airflow Reynolds number. Therefore, the proposed thermal management concept for the battery module can sustain the thermal environment needed for the effective operation of Lithium-ion batteries.

The investigation is about the effect of heat and mass transportation over a dragging out cylinder for Cross fluid flow in addition to free stream. This research is a notable effort to measure heat and mass transportation of the flow over an expanding cylinder with the imposition of the external flow. The system of complex partial differential equations is converted into highly nonlinear ordinary differential equations. The solution of the nonlinear system of equations is made with the numerical technique Runge-Kutta fifth order just after the implementation of the shooting technique with suitable conditions. MATLAB solver bvp4c has solved the problem of the flow over stretching cylinder very efficiently and presents the facts in the form of the graphs and numerical values. The results claim that for the values of gamma parameter from 0.1 to 0.5 the rate of heat transfer increases by 14% on the other lambda with values from 0.1 to 0.3 the heat transfer rate declines 11%. For the growing values of Schmidt number from 1.0 to 5.0 the rate of mass transfer decreases by 85%. The rate of heat transfer has fallen by 86% for the improving values of the Prandtl number from 1, 2, and 3.

The present investigation aims to study the comparative analysis of CNT, GO, and CNT + GO nanoparticle coatings on copper surfaces under a pool boiling situation. Coating on copper surfaces is performed using the dip coating method. Pool boiling experiments are conducted for all the coated surfaces at atmospheric pressure. Water is used as a working fluid. A comparison was made based on the coated surface characteristics and pool boiling behavior of the samples. The results show that CNT + GO coating on copper surfaces is better in terms of critical heat flux (CHF) and boiling heat transfer coefficient (BHTC). It is also observed that CHF and BHTC of the CNT + GO-coated surface are 129.19% and 194.75% higher, respectively, compared to the bare copper surface. Bubble dynamics studies were also performed for all the samples.

During the Stelmor air-cooling process, the temperature distribution has a significant impact on the wire loops' final mechanical properties. The temperature distribution during the air-cooling process is accurately solved by establishing three-dimensional model and numerical simulations. The heat transfer coefficient at the highly dense region is much smaller than that of wire loops at the low dense region, and changes periodically over time, according to a computational fluid dynamics simulation method. It is also found that the heat transfer coefficient on the cross-section of the wire loop is very different, with a difference of 70–100 W/m² K. Finally, the finite difference method is used to calculate the mathematical model of the temperature distribution during the Stelmor air-cooling process. Comparing the results with the measurement data, the simulation results and measurement data match up well.

The researchers explored the free convective flow of a hybrid nanofluid in a vertical microchannel with a rectangular cross-section. Notably, both channel walls were heated alternately, and a transverse magnetic field was applied across the channel. The channel walls had unique properties, one of which was nonslip and the other was exceedingly hydrophobic. The major purpose was to investigate the effects of magnetism and superhydrophobicity on important flow parameters. The differential equations in the investigation were solved, producing accurate results. The study yielded some significant discoveries. First, when heated, the magnetic parameter reduced skin friction on both sides. Second, in both heating conditions, the magnetic field reduced flow rate and velocity. The flow rates in the two reported situations were similar at a crucial temperature jump coefficient. Furthermore, for low-temperature jump coefficients, heating the superhydrophobic side reduced the Nusselt number whereas heating the nonslip side had no magnetic effect. The percentage change in the value of Nusselt number and velocity decreases continuously with increase in nonlinear density variation with temperature (NDT) parameter and magnetic parameter. The percentage increases in the value of skin friction with increase in temperature jump and slip length but decrease in the percentage of skin friction for the effect of magnetic term and NDT parameter. As the NDT parameter increases, the velocity percentage rises to 50.59% when the superhydrophobic surface is heated and to 84.30% when the nonslip surface is heated. The temperature jump is statistically significant for the value of the Nusselt number and skin friction for the no-slip surface condition. These discoveries have practical consequences for the design and management of both tiny and large-scale systems, with possible applications in microfluidics, microelectronics, nanoscience, and nanotechnology.

A hybrid flat solar collector was manufactured from basic materials to combine the effects of both water and air solar heaters. The reason is to increase the amount of heat delivered to water by doubling the heat sources, one from the direct beam of sun and the other from the hot air delivered by the air solar heater. In addition, the flow of water inside the solar heater is made in a thin layer so that much heat can be gained by water per unit time. The outlet hot air of the solar air heater enters air ducts that pass through the solar water heater. With a constant water flowrate of 0.0167 kg/s, three different air velocities (1.7, 2.1, and 2.4 m/s) were applied to determine the optimum air velocity that results in the maximum outlet water temperature and the maximum removal factor FR for the solar water heater. The experiment was run from 10:00 a.m. to 2:00 p.m. every day during June 2023 and the data was recorded every 15 min. The data obtained from the experiment showed that the lowest air speed (1.7 m/s) results in the highest outlet water temperature (63°C) and heat removal factor FR (0.74).

The current work is interested on investigating the impacts of thermal radiation, chemical reaction, and absorption radiation of a hydromagnetic convection-free mass and heat transfer flow in case of an electrically conducting fluid that passes through a vertical plate moving impulsively. The analytical solutions of the governing momentum, energy, and species concentration equations with the initial and boundary conditions are obtained by the Laplace transformation technique. Graphs for fluid characteristics are used to analyze the impact of changing parametric quantities such as M, N, Sc, Kc, Q, Gr, Gm, and t on the temperature, velocity, concentration, and Sherwood number. We derive the engineering curiosity expressions for the Nusselt number and stress, and at the end, we tabulate and discuss the consequences of new parameters. The magnetic field effect and the chemical reaction are seen to diminish the fluid velocity and concentration, respectively, but in contrast, the absorption radiation effect is seen to accelerate both velocity and temperature. It is closely studied that the Nusselt number and skin friction values for hydrogen consistently exceed those for carbon monoxide.

In this paper, the impact of nanolayer which shows the relationship between the nanoparticle and pure fluid is investigated on the fluid transport and thermal transfer through a rotating system. The nanolayer shows the relationship between the nanoparticle and base liquid, signifying a higher thermal conductivity than the nanoparticle and lower conductivity than the base fluid. Also, the effect of larger nanoparticle size and volume on fluid thermal distribution is considered. The nanoparticle raises the fluid thermal conductivity with the aim of conserving thermal transfer during fluid transport, consequently saving energy. The mechanics of the fluid is developed using a higher-order coupled system of nonlinear models, solved with the aid of the Homotopy perturbation method. Obtained results from the analysis show the impact of nanolayer expansion on thermal distribution increases boundary layer thickness. Also, the size of the nanoparticle when varied from 10 to 40 nm shows a heat transfer increase of 17.02% at the center of the disk. Particle size increase indicates temperature rise as nanolayer size encompassing the nanoparticle increases. Obtained results when compared against literature give good agreement. The study finds useful applications in coolant and lubricant processing amongst other practical applications.

The cooling and heating sector is responsible for the highest energy consumption in the building sector, comprising approximately 30% of the total. Extensive research has been conducted to address this issue and minimize energy consumption through the implementation of innovative technologies. Among these technologies, the passive earth-air heat exchanger (EAHE) has proven highly effective in reducing energy usage in the cooling and heating sector. This research focused on optimizing U-shaped EAHE systems and examined their functional and thermal-fluidic parameters through numerical analysis. The simulation employed COMSOL Multiphysics software, and the results obtained were in excellent agreement with experimental data. The study investigated a base case, as well as five optimized cases with varying inlet velocities, to evaluate performance. The findings revealed that increasing the working fluid's inlet velocity led to a decrease in the system's thermal efficiency. However, at higher velocities, the economic parameters for energy production showed improvements. Specifically, the system generated a maximum energy output of 9132 W in the fifth case, operating at a velocity of 2 m/s. Additionally, the system achieved an impressive performance coefficient of approximately 5.13 in the same case, with an inlet velocity of 0.46 m/s. Notably, the lowest recorded output temperature of the system was 22°C at the specified inlet velocity.

The onset of convective instability in an internally heated dielectric fluid-saturated porous layer under the influence of a uniform AC electric field for different types of boundary conditions is investigated. The flow in the porous medium is described by the Brinkman model with fluid viscosity different from effective viscosity. The lower adiabatic and the top with finite heat transfer coefficient to the external environment boundaries are considered to be either rigid or stress-free. The presence of a uniform volumetric heat source alters the conduction profile of the temperature field from linear to quadratic in the vertical coordinate. A modal linear stability analysis of the basic motionless state is carried out and the general regime of linear instability is investigated by solving the stability eigenvalue problem numerically using the Galerkin method of weighted residual technique. The neutral stability condition as well as the critical value of the thermal Rayleigh number is computed for rigid–rigid, free–free, and rigid–free boundaries for various values of governing parameters. It is seen that the nature of boundaries affect the stability of the system only quantitatively, though not qualitatively. The rigid–rigid boundaries offer a more stabilizing effect against convection in comparison with rigid–free and free–free boundaries. The study found that the effect of increasing thermal electric Rayleigh number and the Darcy number is to hasten the onset of instability, while the opposite trend is perceived with an increase in the ratio of viscosities and Biot number. The outcomes of this investigation are found to be in good agreement with past studies under the limiting cases.