Explore the vast range of titles available.

Many passive heat controlling technologies are based on the use of phase change materials. As a rule, at low operation temperatures, close to environmental conditions, paraffins or fatty acids with melting points of 20–90 °C are used. However, the low thermal conductivity of these materials requires the development of various heat transfer enhancers satisfying technical requirements. In this work, the possibility of nanoparticle application to the heat transfer augmentation inside a closed copper radiator filled with pure n-octadecane, depending on the thermal conditions of the local heater and other system parameters, are numerically investigated.

Nowadays, the heat transfer enhancement in electronic cabinets with heat-generating elements can be achieved using the phase change materials and finned heat sink. The latter allows to improve the energy transference surface and to augment the cooling effects for the heat sources. The present research deals with numerical analysis of phase change material behavior in an electronic cabinet with an energy-generating element. For an intensification of heat removal, the complex finned heat sink with overall width of 10 cm was introduced, having the complicated shape of the fins with width of 0.33 cm and height H = 5 cm. The fatty acid with melting temperature of 46 °C was considered as a phase change material. The considered two-dimensional challenge was formulated employing the non-primitive variables and solved using the finite difference method. Impacts of the volumetric heat flux of heat-generating element and sizes of the fins on phase change material circulation and energy transference within the chamber were studied. It was shown that the presence of transverse ribs makes it possible to accelerate the melting process and reduce the source temperature by more than 12 °C at a heat load of 1600 W/m. It should also be noted that the nature of melting depends on the hydrodynamics of the melt, so the horizontal partitions reduce the intensity of convective heat transfer between the upper part of the region and the lower part.

Low-power electronic devices are suitably cooled by thermogravitational convection and radiation. The use of modern methods of computational mechanics makes it possible to develop efficient passive cooling systems. The present work deals with the numerical study of radiative-convective heat transfer in enclosure with a heat-generating source such as an electronic chip. The governing unsteady Reynolds-averaged Navier–Stokes (URANS) equations were solved using the finite difference method. Numerical results for the stream function–vorticity formulation are shown in the form of isotherm and streamline plots and average Nusselt numbers. The influence of the relevant parameters such as the Ostrogradsky number, surface emissivity, and the Rayleigh number on fluid flow characteristics and thermal transmission are investigated in detail. The comparative assessment clearly emphasizes the effect of surface radiation on the overall energy balance and leads to change the mean temperature inside the heat generating element. The results of the present study can be applied to the design of passive cooling systems.

Development of modern electronic devices demands a creation of effective cooling systems in the form of active or passive nature. More optimal technique for an origination of such cooling arrangement is a mathematical simulation taking into account the major physical processes which define the considered phenomena. Thermogravitational convection in a partially open alumina-water nanoliquid region under the impacts of constant heat generation element and heat-conducting solid wall is analyzed numerically. A solid heat-conducting wall is a left vertical wall cooled from outside, while a local solid element is placed on the base and kept at constant volumetric heat generation. The right border is supposed to be partially open in order to cool the local heater. The considered domain of interest is an electronic cabinet, while the heat-generating element is an electronic chip. Partial differential equations of mathematical physics formulated in non-primitive variables are worked out by the second order finite difference method. Influences of the Rayleigh number, heat-transfer capacity ratio, location of the local heater and nanoparticles volume fraction on liquid circulation and thermal transmission are investigated. It was ascertained that an inclusion of nanosized alumina particles to the base liquid can lead to the average heater temperature decreasing, that depends on the heater location and internal volumetric heat generation. Therefore, an inclusion of nanoparticles inside the host liquid can essentially intensify the heat removal from the heater that is the major challenge in different engineering applications. Moreover, an effect of nanosized alumina particles is more essential in the case of low intensive convective flow and when the heater is placed near the cooling wall.

PurposeThis paper aims to study the mathematical modeling of passive cooling systems for electronic devices. Improving heat transfer is facilitated by the correct choice of the working fluid and the geometric configuration of the engineering cavity; therefore, this work is devoted to the analysis of the influence of the position of the heat-generating element and the tilted angle of the electronic cabinet on the thermal convection of a non-Newtonian fluid.Design/methodology/approachThe area of interest is a square cavity with two cold vertical walls, while the horizontal boundaries are adiabatic. An element of constant volumetric heat generation is placed on the lower wall of the chamber. The problem is described by Navier–Stokes partial differential equations using dimensionless stream function and vorticity. The numerical solution is based on the developed computational code using the finite difference technique and a uniform rectangular grid.FindingsThe key conclusions of this work are the results of a detailed analysis of streamlines and isotherms, the average Nusselt number and profiles of the average heater temperature. It was found that more intensive cooling of the heat-generating element occurs when the cavity is filled with a pseudoplastic fluid (n < 1) and not inclined (α = 0). The Rayleigh number of Ra = 105 and the thermal conductivity ratio of k = 100 are characterized by the most positive effect.Originality/valueThe originality of the research lies in both the study of thermal convection in a square chamber filled with power-law fluid under the influence of a volumetric heat production element and the analysis of the influence of geometric and thermophysical parameters characterizing the considered process.

The issue of thermal control plays an important role in the development of technical systems of computing and radio equipment. Temperature conditions are an important factor in the performance and durability of devices. New models of heat sink containing materials with phase transitions “solid body–liquid” are appeared. In the present paper, the numerical study of natural convection melting/solidification of phase change material inside a finned heat sink with a local heater having time-dependent volumetric heat flux has been carried out. An unsteady conjugate phase change problem has been solved taking into account natural convection in the melt, in the presence of a heat-dissipating copper profile. The energy equation has been formulated using a special smoothing function of temperature. The equations of hydrodynamics have been formulated using non-primitive variables, namely the stream function and vorticity. The system of transient differential equations of natural convection, taking into account the melting process and the heat-generating and heat-conducting element, has been solved using the finite-difference method. Analysis has been performed for different values of the volumetric heat generation within the heater and the periodic volumetric heat generation frequency. Obtained results have shown that a rise of the volumetric heat generation frequency leads to an increase in the amplitude of the average temperature within the heater that can have a negative effect on the system operation.Graphic abstract

Purpose The purpose of this study is a numerical analysis of transient natural convection in a square partially porous cavity with a heat-generating and heat-conducting element using the local thermal non-equilibrium model under the effect of cooling from the vertical walls. It should be noted that this research deals with a development of passive cooling system for the electronic devices. Design/methodology/approach The domain of interest is a square cavity with a porous layer and a heat-generating element. The vertical walls of the cavity are kept at constant cooling temperature, while the horizontal walls are adiabatic. The heat-generating solid element is located on the bottom wall. A porous layer is placed under the clear fluid layer. The governing equations, formulated in dimensionless stream function, vorticity and temperature variables with corresponding initial and boundary conditions, are solved using implicit finite difference schemes of the second order accuracy. The governing parameters are the Darcy number, viscosity variation parameter, porous layer height and dimensionless time. The effects of varying these parameters on the average total Nusselt number along the heat source surface, the average temperature of the heater, the fluid flow rate inside the cavity and on the streamlines and isotherms are analyzed. Findings The results show that in the case of local thermal non-equilibrium the total average Nusselt number is an increasing function of the interphase heat transfer coefficient and the porous layer thickness, while the average heat source temperature decreases with the Darcy number and viscosity variation parameter. Originality/value An efficient numerical technique has been developed to solve this problem. The originality of this work is to analyze unsteady natural convection within a partially porous cavity using the local thermal non-equilibrium model in the presence of a local heat-generating solid element. The results would benefit scientists and engineers to become familiar with the analysis of convective heat transfer in enclosures with local heat-generating heaters and porous layers, and the way to predict the heat transfer rate in advanced technical systems, in industrial sectors including transportation, power generation, chemical sectors and electronics.

In the present study, the time-dependent magnetohydrodynamic (MHD) convective flow of a hybrid alumina–silver/water nanoliquid within a wavy-walled trapezoidal cavity which contains a solid heat-generating and rotating cylinder is considered . The mass transport and convective heat transfer within the hybrid nanofluid are described using a two-phase approach, which accounts for Brownian and thermophoretic effects. The penalty finite element technique is employed so that a numerical approximation for the model equations is obtained, and the impacts of alumina and silver nanoparticle sizes and cylinder size on the isotherms, streamlines, mean Nusselt number and nanoparticle concentration distributions are explored. From the numerical results, it was determined that the temperature of the nanoliquid and non-uniformity of the nanoparticle distribution are enhanced with increased cylinder size and reduced nanoparticle diameters. Furthermore, the heat transfer rate on the cylinder surface increases when the cylinder size is increased and the nanoparticle diameters are decreased.

This research exploration emerged from the critical need to revolutionize heat transfer techniques, particularly in pivotal domains like nuclear technologies, electronics and energy-efficient systems. The motivation for this study endeavour stemmed from the complex interrelation among nanofluids, magnetic fields and their potential for enhancing heat exchange. A pragmatic numerical approach is utilized to examine the Cu–H 2 O nanofluid flow situation within an enclosure featuring cooled vertical walls and a heat-generating source, while ensuring insulation for the remaining edges. The evaluation analyses the contribution of entropy, including total, viscous and thermal entropies, establishing a connection to real-world heat transfer challenges. The Galerkin finite element algorithm is utilized to solve the partial differential system of the modelled problem. The phenomena of entropy generation, fluid flow and heat transfer are studied under the influence of parameters such as the Hartmann number, Rayleigh number, magnetic field inclination angle and nanoparticle volume fraction. The study reveals that irreversibility increases with the magnetic field inclination angle, while entropy generation decreases with an increase in the Hartmann number. The primary innovation of this study is uncovering new dimensions with widespread practical implications by deciphering the complex dynamics of nanofluid convection with entropy generation and inclined magnetic influence. This research holds significant potential for advancing heat transfer applications in water treatment and resource management, aligning with the journal’s focus on sustainable and innovative water solutions.

This paper deals with the influence that the internal shape of open ‘cavities’ exerts on the Constructal design of a heat generating body. Several shapes of cavity are studied; triangular, elliptical, trapezoidal and Y-shaped cavities intruding into a trapezoidal shaped solid with uniform heat generation. The trapezoidal solid is commonly used in round electronic devices. The geometric aspect ratios of the cavities and the solid are free to vary while the total volume occupied by the solid and the cavity are fixed. The objective is minimizing the peak (hot spot) temperature with respect to the geometrical parameters of the system. Finite element method is employed to calculate the peak temperature of the solid. With respect to the Constructal thermal design, the numerical results prove that, utilizing the triangular and Y-Shaped cavities can result more reliable and effective rather than other studied cavities.