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This study aims to undertake a comprehensive examination of heat transfer by convection in porous systems with top and bottom walls insulated and differently heated vertical walls under a magnetic field. For a specific nanofluid, the study aims to bring out the effects of different segmental heating arrangements.

An existing in-house code based on the finite volume method has provided the numerical solution of the coupled nondimensional transport equations. Following a validation study, different explorations include the variations of Darcy–Rayleigh number (Ra_m = 10–10⁴), Darcy number (Da = 10^–5–10^–1) segmented arrangements of heaters of identical total length, porosity index (ε = 0.1–1) and aspect ratio of the cavity (AR = 0.25–2) under Hartmann number (Ha = 10–70) and volume fraction of φ = 0.1% for the nanoparticles. In the analysis, there are major roles of the streamlines, isotherms and heatlines on the vertical mid-plane of the cavity and the profiles of the flow velocity and temperature on the central line of the section.

The finding of a monotonic rise in the heat transfer rate with an increase in Ra_m from 10 to 10⁴ has prompted a further comparison of the rate at Ra_m equal to 10⁴ with the total length of the heaters kept constant in all the cases. With respect to uniform heating of one entire wall, the study reveals a significant advantage of 246% rate enhancement from two equal heater segments placed centrally on opposite walls. This rate has emerged higher by 82% and 249%, respectively, with both the segments placed at the top and one at the bottom and one at the top. An increase in the number of centrally arranged heaters on each wall from one to five has yielded 286% rate enhancement. Changes in the ratio of the cavity height-to-length from 1.0 to 0.2 and 2 cause the rate to decrease by 50% and increase by 21%, respectively.

Further research with additional parameters, geometries and configurations will consolidate the understanding. Experimental validation can complement the numerical simulations presented in this study.

This research contributes to the field by integrating segmented heating, magnetic fields and hybrid nanofluid in a porous flow domain, addressing existing research gaps. The findings provide valuable insights for enhancing thermal performance, and controlling heat transfer locally, and have implications for medical treatments, thermal management systems and related fields. The research opens up new possibilities for precise thermal management and offers directions for future investigations.

The purpose of this paper is to analyze numerically the nanofluid natural convection inside a square enclosure with two L-shaped heaters using lattice Boltzmann method.

An environmentally friendly nanofluid, clove-treated graphene nanoplatelet (CGNP), is used to study the enhancement of heat transfer. Six various heaters configurations are considered and effects of nanoparticle concentration (0–0.1%) and Rayleigh number (10^3–10^6) on streamlines, isothermal lines and heat transfer parameters are studied. The developed computational code has been validated using mesh sensitivity analysis and numerical data of other authors.

It is observed that in contrast to distilled water, CGNP/water nanofluid is an efficient coolant and the Nusselt number is increased as the nanoparticle concentration and Rayleigh numbers increment. The nanoparticle concentration cannot change the flow pattern inside the enclosure. However, the Rayleigh number and heaters configuration can change the flow pattern significantly. Several heaters configurations (Cases 1–4) related to the symmetry of geometrical shape and corresponding boundary conditions, illustrate the symmetry of streamlines and isotherms about the vertical line (X = 0.5). The formation of vortices inside the enclosure is affected by the raising heat plume above the heaters. Moreover, at different Rayleigh numbers, the relative magnitude of average Nu for various cases is different. At Ra = 103, the energy transport characteristic depends on the relative location of heaters and cold walls, and the order of average Nusselt number is Case 3 ˜ Case 4 ˜ Case 6 > Case 1 ˜ Case 2 ˜ Case 5. However, at Ra = 106, an influence of thermal convection mechanism on heat transfer is significant and the ranking of average Nusselt number is Case 1 ˜ Case 4 > Case 5 > Case 6 > Case 2 > Case 3.

The originality of the research lies in both the study of thermogravitational convection in a closed chamber with two L-shaped heaters, and the analysis of the influence of control parameters for an environmentally friendly nanoliquid on electronics cooling process.

This paper aims to compute demand, consumption and other avoidance saving by replacing existing geysers with split and integrated type air source heat pump (ASHP) water heaters, to prove the potential of both ASHP water heaters in both winter and summer by virtue of their coefficient of performance (COP) during the vapour compression refrigeration cycles and to demonstrate that despite the viability of both split and integrated ASHP system, the latter exhibits a better performance in terms of its COP and achievable savings and load factor.

This research emphasised the use of the data acquisition system housing various temperature sensors, power metres, flow metre, ambient temperature and relative humidity sensor to determine electrical energy consumption and useful thermal energy gained by the hot water in a geyser and storage tanks of residential ASHP water heaters. The load factors, average power and electrical energy consumptions for the 150 L high-pressure geyser, a 150 L split and integrated type ASHP water heaters were evaluated based on the controlled volume (150, 50 and 100 L) of daily hot water drawn off.

The results depicted that the average electrical energy consumed and load factors of the summer months for the geyser, split and integrated type ASHP water heaters were 312.3, 111.7 and 121.1 kWh and 17.9, 10.2 and 16.7 per cent, respectively. Finally, the simple payback period for both the split and integrated type ASHP water heaters were determined to be 3.9 and 5.2 years, respectively. By the application of the Eskom’s projected tariff hikes over the years, the payback periods for the split and integrated ASHP water heaters could be reduced to 3.3 and 4.1 years, respectively.

The experiments were conducted in a controlled outdoor research facility as it was going to be of great challenge in conducting both experiments simultaneously in a specific home. The category of the different types of ASHP water heaters was limited to one due to the cost implication. The experiment was also conducted at a single location, which is not a full representation of all the ambient conditions of the different regions of South Africa.

The experiments were done with a specific controlled volume of hot water drawn off from each of the three hot water heating devices. The experiments was structuring controlled to a specific volume of hot water drawn off and at specific period of the day and hence to not cater for random drawers and intermittent drawn off.

The findings help to assure homeowners that irrespective of the type of ASHP water heaters installed in their residence, they can be guarantee of year-round performance and a favourable payback period provided their hot water consumption is over 200 L per day. Also, although the split type ASHP water heater performed better than the integrated system the cost of installation and maintenance will be higher in a split type in comparison to the integrated type. Finally, by successful implementation of either of the ASHP water heaters the home owner can substantially save of his hot water bill.

The experimental design and methodology is the first of its kind to be conducted in South Africa. The results and interpretation were obtained from original data collected from the set of experiments conducted. Also, the authors are able to show that the introduction of back up element in an ASHP unit to run simultaneously with the vapour compression refrigeration cycles of the ASHP can reduce the COP of the overall system.

The main objective of the present study is to investigate the effects of various lengths and different locations of the heater on the left sidewall in a square lid‐driven cavity.

The non‐dimensional equations are discretized by the finite‐volume method. The upwind scheme and the central difference scheme are implemented for the convection and the diffusion terms, respectively.

On increasing the Richardson number, the overall heat transfer is increased whether the length and the location of the heater is considered or not. Among the various lengths of the heater considered, the total heat transfer is better only for the length LH=1/3 of the heater if it is extended from top or bottom of the cavity. In the case of location of the heater, the average heat transfer enhances for center location of the heater. Existence of the magnetic field suppresses the convective heat transfer and the fluid flow.

The results can be used in the cooling of electronic devices and heat transfer improvement in heat exchangers.

The numerical results obtained here focus on the detailed investigation of flow and temperature field in a discretely heated lid‐driven square cavity. The findings will be helpful in many applications such as heat exchangers and cooling of electronic devices.

The purpose of the paper is to study natural convection within porous square and triangular geometries (design 1: regular isosceles triangle, design 2: inverted isosceles triangle) subjected to discrete heating with various locations of double heaters along the vertical (square) or inclined (triangular) arms.

Galerkin finite element method is used to solve the governing equations for a wide range of modified Darcy number, Da_m = 10⁻⁵–10⁻² with various fluid saturated porous media, Pr_m = 0.015 and 7.2 at a modified Rayleigh number, Ra_m = 10⁶ involving the strategic placement of double heaters along the vertical or inclined arms (types 1-3). Adaptive mesh refinement is implemented based on the lengths of discrete heaters. Finite element based heat flow visualization via heatlines has been adopted to study heat distribution at various portions.

The strategic positioning of the double heaters (types 1-3) and the convective heatline vortices depict significant overall temperature elevation at both Da_m = 10⁻⁴ and 10⁻² compared to type 0 (single heater at each vertical or inclined arm). Types 2 and 3 are found to promote higher temperature uniformity and greater overall temperature elevation at Da_m = 10⁻². Overall, the triangular design 2 geometry is also found to be optimal in achieving greater temperature elevation for the porous media saturated with various fluids (Pr_m).

Multiple heaters (at each side [left or right] wall) result in enhanced temperature elevation compared to the single heater (at each side [left or right] wall). The results of the current work may be useful for the material processing, thermal storage and solar heating applications.

The heatline approach is used to visualize the heat flow involving double heaters along the side (left or right) arms (square and triangular geometries) during natural convection involving porous media. The heatlines depict the trajectories of heat flow that are essential for thermal management involving larger thermal elevation. The mixing cup or bulk average temperature values are obtained for all types of heating (types 0-3) involving all geometries, and overall temperature elevation is examined based on higher mixing cup temperature values.

This paper's purpose is to review the design of a flip chip thermal test vehicle.

Design requirements for different applications such as thermal characterization, assembly process optimization, and product burn‐in simulation are outlined and the design processes of different thermal test chip structures including the temperature sensor and passive heaters are described in detail. The design of fireball heater, a novel test chip structure used for evaluating the effectiveness of heat spreading of advanced thermal solutions, is also explained.

Describes the design considerations and processes of the package substrate and printed‐circuit board with special emphasis on the physical routing of the thermal test chip structures. These design processes are supported with thermal data from various finite‐element analyses carried out to evaluate the capability and limitations of thermal test vehicle design.

The validation and calibration procedures of a thermal test vehicle are presented in this paper.

The purpose of this paper is to describe a heating system for the selective inhibition sintering (SIS) process that will produce uniform heat and minimize the polymer powder waste.

This research was conducted in two areas: the first was the production of uniform heat distribution. For this task, a lighting design software was used for the initial heater design. The result was then validated by thermal images, point‐by‐point temperature measurement, and physical part fabrication. The second area was the minimization of polymer powder waste. For this task, a finger‐based masking mechanism was designed, prototyped, and tested.

The lighting design software output illustrates that the square, crossed, and parallel patterns have very low variation and seem to be acceptable alternatives for the heating system pattern. Also, results show that the temperature variation for the ceramic heater is lower (therefore better) than the wire heater. Also, the study reveals that a finger‐based masking system design and prototype is very promising from the polymer powder waste‐saving standpoint.

Owing to the software limitation, radiation is the only source of heat transfer in this research (convection and conduction were not considered). Also, a limited number of patterns were examined for the heater design; this number can be expanded in future research.

A new design and development method has been proposed for the heating system for the SIS process that could lead to better heaters and waste‐reducing mechanisms for the SIS process and similar applications.

The purpose of this paper is to deal with an identification of a novel ink-jet printing sensor fabrication technology for fabricating flexible carbon heaters of macro and micro sizes, carbon interdigitated (IDT) electrodes and silver IDT electrodes. The technology involved in the proposed ink-jet printing method and materials used for the formulation of homemade nano-conductive inks (digital inks) are discussed in detail. The ink-jet printed flexible carbon heaters of different sizes (macro and micro) and carbon IDT electrodes and flexible silver IDT electrodes can be used as the flexible sensing layers in electrochemical gas sensors for sensitive and selective gas sensing applications. The characterization of ink-jet printed carbon heaters on Kapton substrate and its results are discussed. Similarly, the results of formulation of silver nano-conductive ink and printing of silver IDT electrodes on Kapton and its characterization are reported here for the first time.

Flexible carbon heaters of different sizes (macro and micro), carbon micro-IDT electrodes and silver IDT electrodes patterns were developed using AutoCAD 2D and printed on the Kapton (polyimide sheet) flexible substrate using the home-made nano-conductive inks with the help of EpsonT60 commercial piezo-head-based drop-on demand technology printer with standard printing options.

The proposed novel method is able to print heater patterns and IDT electrode patterns of approximately 12 µm and approximately 1 µm thickness, respectively, on flexible substrate using the home-made nano-conductive inks of carbon and silver by using a commercial low-cost printer. The home-made nano-conductive inks can be re-used for multiple prints up to six months shelf life. The resistance of the carbon heater was measured as 88 O under normal atmospheric condition. The novel flexible carbon heater was tested for its functionality and found to be satisfactory. The resistance of the silver IDT flexible electrodes was measured as 9.5 O which is better than the earlier works carried out in this paper.

The main challenge is associated with cleaning of printing ink ejection system in the existing commercial printers. The customization of the existing printer in the near future can minimize the printing challenges.

The novel ink-jet printing technology proposed in this work is cost-effective, capable of achieving bulk production of flexible sensor elements, and consumes the least device fabrication time and high material yielding. The printing can be done with commercial piezo-head-based ink-jet printers with custom-prepared nano-conductive inks. There is a huge market potential for this paper.

Both the carbon heaters and silver IDT electrodes were printed on Kapton flexible substrate by using the commercial printer for the first time. The paper is promising the revolution in flexible low-cost sensor fabrication for mass production, and it is an alternate for thin film and thick sensor fabrication methods. The future of sensor fabrication technology will be the ink-jet printing method. In this paper, the research developments of flexible carbon heaters and flexible silver IDT electrodes for the time are reported. The characterization of carbon heaters and silver IDT electrodes were carried out and confirmed that the results are favourable for gas sensor applications.

Because of their widespread use in industry, induction through‐heaters of various metal products must be of high effectiveness not only in “quasi” steady‐state operation but in different transient modes as well. Nowadays, they are usually designed to provide the required characteristics in “quasi” steady‐state operation mode mainly. The purpose of this paper is to examine numerical simulation of transient processes in induction through‐heating lines generally and investigate dynamic temperature fields during the first start of the heaters particularly.

The research methodology is based on coupled numerical electromagnetic and thermal analyses using FEM approach. ANSYS simulations are supported with the developed tools for imitation of mass transfer effects in continuous induction heating lines.

The results show that transient temperature fields in the heated strip or slab significantly differ from their “quasi” steady‐state descriptions. Local temperature variations acquired in longitudinal as well as transverse flux induction heaters during the first start have been predicted.

The received results can be used for design of induction through‐heaters and improvement of their characteristics in dynamic operation modes.

Investigation of dynamic characteristics of the heaters in dynamic modes can be only done by numerical modelling based on special algorithms providing a time loop additional to coupling between electromagnetic and thermal analyses. Such algorithms have been developed and used for investigation of two types of induction installations: through‐heaters of cylindrical billets for forging and heating lines of strip or thin slab for rolling mills.

The purpose of this paper is to investigate natural convective heat transfer in a cubical cavity with the heat source of a trapezoidal form having a constant temperature.

The domain of interest is a cubical cavity with two isothermal opposite vertical walls, while other walls are adiabatic. A discrete heater of a trapezoidal shape is located at the bottom wall of the cavity. Governing equations formulated in dimensionless vector potential functions, vorticity vector and temperature with corresponding initial and boundary conditions have been solved numerically using a developed computational code based on the finite difference method.

The results show that the variation of geometric parameters, such as height, length and size of the local heater, significantly influences the evolution of a temperature field and fluid flow inside the enclosure. The effects of Rayleigh number and time on streamlines, isotherms and average Nusselt number have been studied.

The originality of this work is to explore three-dimensional (3D) natural convection in a cubical cavity with a local heat source of trapezoidal shape, to analyze the effects of heater geometric parameters and to compare obtained 3D data with two-dimensional results.