Heat Transfer最新文献

The present paper explores the dynamics of ion-acoustic solitary waves (IASWs) within an unmagnetized, highly relativistic quantum plasma containing positive and negative ions alongside electrons, employing the quantum hydrodynamic model. The treatment accounts for the inertial characteristics of negative and positive ions, considering electrons as inertialess. The nonlinear nature of quantum IASWs is investigated through the derivation of the Korteweg–de Vries equation using the reductive perturbation method. The investigation highlights how wave propagation characteristics, whether compressive or rarefactive, are substantially modulated by several parameters, such as the quantum diffraction parameter $��\; ��\left(�\; �H�\; �\right)��$, relativistic effects $��\; ��(�\; �u_0�\; �/�\; �c�\; �)��$, equilibrium density $��\; ��\left(�\; �p�\; �\right)��$, and ion mass ratio $��\; ��\left(�\; �Q�\; �\right)��$. The analysis identifies the existence of both slow and fast wave modes, heavily influenced by the relativistic parameters involved. Our findings have significant implications for the understanding of both laboratory and space plasmas, especially in contexts where negative ions are present.

This paper investigates magnetohydrodynamic (MHD) boundary layer slip flow with heat transfer over a bullet shaped object. The study addresses a significant problem in fluid dynamics and heat transport with applications in various engineering and industrial domains, including aerospace, material processing, and energy systems. The governing equations are resolved using the bvp4c, an inbuilt MATLAB tool, and the arithmetic computation for the momentum and thermotic equations are executed. The results are exhibited graphically. Numerical outcomes are graphically depicted with the aid of velocity and temperature profiles for several model variables. The achieved results exhibit a promising agreement with the previously established findings available in the open literature. The heat transfer processes and fluid flow are remarkably influenced by means of the ratio of surface thickness and stretching potential. The results obtained designated that the Mixed convection parameter λ increases momentum BL thickness, whereas the temperature profile diminishes. Furthermore, momentum and temperature profile improve for surface thickness parameter $���s��$. The current investigation highlights the potential utility of heat transport rate and friction factor in the industrial divisions for regulating cooling rates and enhancing the quality of end products.

Roll coating plays a major role in industrial coating, including wallpapers, plastic and photographic films, sticky tapes, magnetic recordings, wrapping magazines and books, and so on. The current study proposes a mathematical model for a non-isothermal, incompressible Sutterby fluid flowing through a narrow gap between two heated, counterrotating rollers. Lubrication approximation theory is used to simplify nondimensional expressions. The perturbation technique provides exact results for velocity profile, temperature, flow rate, and pressure gradient, whereas the numerical technique (Simpson rule) is used to compute the pressure profile and flow rate, respectively. The effects of the involved parameters on various physical characteristics like pressure, flow rate, temperature, pressure gradient, force, and power input are depicted in graphs and tabular form. A mechanism for controlling the coating thickness, power input, flow rate, separation force, and pressure distribution is provided by the material properties involved. With variations to a Sutterby fluid parameter $���\beta ��$ and the velocity ratio K, both the pressure gradient and pressure decrease. It is significant to note that the temperature distribution is controlled by the velocities ratio and Brinkman number. Moreover, the separation point is shifted towards the nip area and the coating thickness on the web reduces with increasing velocities ratio K.

This study aims to investigate a two-phase subsonic ejector added to a flash evaporation desalination system to increase the system productivity of distilled water. The flash evaporation was of low-temperature condition that it could be powered by a flat and evacuated tube solar water heater. A parametric study of superheat degree (range 5°C–25°C), back pressure (range 10–30 kPa of absolute pressure), primary fluid flow rate (range 1–3 L/min), nozzle diameter (range 1–3 mm), and salinity concentration (range 0%–7%) were investigated to examine the system productivity and the ejector performance in terms of its entertainment ratio under different operating conditions. Results show that the inclusion of the ejector led to an average of 99% improvement in system productivity, primarily through the efficient secondary flow. Moreover, the effect of the studied parameter was more pronounced in the considered flash evaporation desalination system as it has two places where flash evaporation occurs, compared with the normal system where the flash evaporation occurs at one place. All in all, the application of the ejector could enhance the system's productivity significantly under different operating conditions.

The study aims to examine how duct length affects the performance of a solar air heater (SAH) with a D-shaped ribbed absorber plate, compared to a smooth absorber plate. The optimized D-shaped ribs from previous research investigations are utilized in the present work to explore the absorber plate's length influence on the Nusselt number. The study reveals a slight decrease in the Nusselt number as the length of the absorber plate with D-shaped ribs is increased. The observed behavior is attributed to the diminishing capacity of air to extract heat from the heated surface within the elongated duct. Moreover, the study calculates the pressure drop and thermo–hydraulic performance parameter (THPP) associated with the D-shaped ribs and formulates correlations to establish a quantitative understanding of the relationship between duct length and D-shaped rib performance. The maximum value of THPP was found to be 1.17 within the considered range of duct height. Furthermore, correlations have been derived for the Nusselt number and friction factor in terms of duct length to hydraulic diameter ratio and Reynolds number with maximum deviations of +1.7 and +2.13, respectively. These correlations serve as valuable tool for engineers and researchers seeking to optimize the design of SAHs, enabling them to balance the benefits of D-shaped ribs with the considerations of duct length. This research contributes to the growing body of knowledge of SAH design, offering insights into the trade-offs and intricacies of utilizing D-shaped ribs and adjusting duct length for improved THPP.

The computational study of power-law fluid flow, along with heat transfer attributes over a corrugated heated cylinder, is explored using ANSYS FLUENT (Version 18.0). Fluids power-law indices fall in the range of 0.25 ≤ n ≤ 1.5, and the Reynolds number spans in the range of 1 ≤ Re_N ≤ 40. The flow is two-dimensional, steady, and laminar. A wide range of Prandtl numbers (0.7 ≤ Pr_N ≤ 500) is used to cover the most industrially applied fluids. A domain height of 135D_h is used. A grid with the smallest element size of 0.04 m and 135,914 nodes was used. Flow and heat transfer attributes were studied using streamlines, isotherms, and local and average Nusselt numbers. The average Nusselt number increases with Re_N and/or Pr_N. The heat transfer rate is significantly lower in dilatant fluids and higher in pseudoplastic fluids than in Newtonian fluids. The onset of wake formation behind the cylinder takes place at Re_N = 10. The increase in Reynolds number (Re_N) and power-law index (n) causes an increase in wake size. Heat transfer increases with the Reynolds number and/or decrease in the power-law index. The enhancement in heat transfer due to corrugation is studied in detail in terms of average Nusselt number, which has not been studied for arched corrugated cylinder, even for Newtonian fluids in low Reynolds number range. A Nusselt number correlation is also developed for the given ranges of conditions.

India leads the world in jaggery production, with the jaggery industry being a vital rural-based sector. The jaggery plants in the country face challenges in effectively utilizing energy, resulting in varying efficiency levels ranging from 20% to 65% across different plants. To address this, a modified approach employing open pan heat exchangers (OPHEs) in jaggery plants is proposed to enhance overall performance. The effectiveness of the heat exchanger (HE) relies on factors such as heat transfer coefficient (HTC), surface contact area, and temperature differences between surfaces and the warm liquid. Circular conduits are predominantly favored in HE design, but this study delves into the impact of conduit shapes specifically circular, semi-circular, and square on the achievement of the HE. The study reveals that semi-circular conduits outperform circular conduits by 25%–28% in terms of HTC, while square conduits show a 21%–24% improvement. Moreover, comparing the efficiency of a conventional open pan jaggery plant with a circular conduit OPHE and a modified version featuring semi-circular conduits OPHE, significant improvements are noted. A one hp pump is enough to overcome the issue related to pumping power due to a change in conduit shape. Heat transfer rate (HTR) is very poor for circular conduit due to line contact, whereas HTR for semi-circular conduit is 38%–39% better than the square conduit. Efficiency increases from 24.36% for the conventional open pan to 62.5% for the circular conduit and further to 83.22% for the semi-circular conduit. Processing time for jaggery making also varies significantly, with 165 min for the conventional open pan, which is reduced by 33.33% for the circular conduit OPHE and 45.45% for the semi-circular conduit OPHE. As compared to circular conduit processing time of semicircular conduit OPHE is reduced by 18.18%.

The purpose of this article is to study the effect of electromagnetic (EM) stimulation on the pipeline, which has an electrical and thermal effect in addition to the chemical reaction on the crude oil and makes a sinusoidal wave on the wall. Modeling the crude oil as Carreau fluid is done. EM stimulation is an effective and safe technology that can be used to improve fluid movement in a variety of industrial applications. The flow analysis by applying EM may avoid blocking the crude oil pipeline which leads to a loss of production and capital investment. The basic partial differential equations of momentum, temperature and concentration are reduced to a system of nonlinear partial differential equations, which is solved numerically by using the Rung–Kutta–Merson method with Newton iteration in a shooting and matching technique under the assumption of long wavelength and the effect of physical implanted parameters is represented through charts for velocity, temperature, and concentration and numerical application.

Heat transfer characteristics in the electromagnetohydrodynamic flow of a third-grade fluid between parallel plates have already been examined by researchers, but studies on the effect of temperature-dependent viscosity on velocity, temperature, and heat transfer coefficients are very few. The present study investigates the heat transfer behavior of a third-grade fluid flow between large parallel plates, taking temperature-dependent viscosity when magnetic and electric fields are imposed externally. The plate walls are subjected to uniform temperatures. Consideration of temperature-dependent viscosity results in the formulation of the phenomenon by nonlinear, coupled differential equations, which are solved by applying the least-square method (LSM). Solving coupled, nonlinear equations by the LSM requires a great deal of modification in the implementation process. The obtained results in terms of dimensionless velocity are validated with the results of earlier studies and are also in a close match with the results of the Adomian decomposition method of the current study. Results indicate that for a higher value of the viscosity parameter, at first, velocity increases with an increase in the non-Newtonian parameter. Beyond a certain value of the non-Newtonian parameter, velocity starts reducing. Temperature, at all points of any cross-section, increases up to a certain non-Newtonian parameter and then reduces with the rise in the same parameter. For higher values of the viscosity parameter and low non-Newtonian parameters, the upper plate requires an enhanced rate of cooling. Whereas, for higher values of the non-Newtonian parameter at higher viscosity parameters, a lower heating rate is required. The results of the mathematical model can serve to be useful in the field of liquid metal flows in metallurgical industry, micropumps, medical and biological sectors, and microelectromechanical applications.

This study introduced a novel numerical modeling for the evaluation of a hybrid heat sink design by replacing the solid fins with aluminum foam fins (AFF) for the same thickness of 2 mm within a phase change material (PCM). This innovation is designed to enhance thermal performance in electronic cooling applications. Heat fluxes of 2, 3, and 4 kW/m² were applied to the base. The performance has been verified at set point temperatures (SPT) of 60°C, 70°C, and 80°C, encompassing a range relevant to various applications. Different AFF thicknesses (4 and 6 mm) and foam porosities (0.85, 0.90, and 0.95) were investigated. The study demonstrated that AFFs improve heat transfer by increasing fin surface area and by effectively raising the thermal conductivity of the PCM. Compared to the SF heat sink, the results show that the AFF design extended the operational time by 5%–8% for the range of heat fluxes. Notably, AFFs with a thickness of 6 mm achieved a significant 41% improvement in the operation time at a lower SPT (60°C). The metal foam porosity of ε = 0.85 exhibited superior thermal performance within the investigated temperature range. This research paves the way for optimizing hybrid heat sink designs using metal foam for efficient thermal management and reduction of weight.