Editorial

3 pages, 162 KiB

Open AccessEditorial

Numerical Simulation of Convective Heat Transfer

by Mikhail A. Sheremet

Energies 2023, 16(4), 1761; https://doi.org/10.3390/en16041761 - 10 Feb 2023

Cited by 3 | Viewed by 995

Convective heat transfer as an energy transport phenomenon occurs in various engineering and natural systems such as heat exchangers, chemical reactors and solar collectors, cooling systems, transportation of contaminant in urban landscape and air pollution, motion of sea or ocean waves and others [...] Read more.

Convective heat transfer as an energy transport phenomenon occurs in various engineering and natural systems such as heat exchangers, chemical reactors and solar collectors, cooling systems, transportation of contaminant in urban landscape and air pollution, motion of sea or ocean waves and others [...] Full article

(This article belongs to the Special Issue Numerical Simulation of Convective Heat Transfer)

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13 pages, 2488 KiB

Open AccessArticle

Correlations for Convective Laminar Heat Transfer of Carreau Fluid in Straight Tube Flow

by Sun Kyoung Kim

Energies 2022, 15(7), 2368; https://doi.org/10.3390/en15072368 - 24 Mar 2022

Cited by 1 | Viewed by 1618

Abstract

Correlations for the Nusselt number for the fully-developed laminar flow of Carreau fluids through circular pipe subject to a uniform heat flux have been sought. Based on the mathematical expression, the Nusselt number could be obtained by numerical integration. To evaluate the Nusselt [...] Read more.

Correlations for the Nusselt number for the fully-developed laminar flow of Carreau fluids through circular pipe subject to a uniform heat flux have been sought. Based on the mathematical expression, the Nusselt number could be obtained by numerical integration. To evaluate the Nusselt number for many conditions, an efficient integration method has been proposed. Using the obtained Nusselt number for different material constants and flow conditions, an improved correlation method has been proposed. The proposed correlation could reduce the maximum error from 3% to 0.9%. Full article

(This article belongs to the Special Issue Numerical Simulation of Convective Heat Transfer)

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13 pages, 33397 KiB

Open AccessArticle

Cooling Effect of Water Channel with Vortex Generators on In-Wheel Driving Motors in Electric Vehicles

by Jae Chang Bae, Hyeon Rae Cho, Saurabh Yadav and Sung Chul Kim

Energies 2022, 15(3), 722; https://doi.org/10.3390/en15030722 - 19 Jan 2022

Cited by 7 | Viewed by 2454

Abstract

Designing an effective cooling system for high-power-density in-wheel motors of electric vehicles is required to avoid the irreversible demagnetization of the permanent magnet due to a rise in its temperature. In this study, a water-cooling channel was used between the stator and housing [...] Read more.

Designing an effective cooling system for high-power-density in-wheel motors of electric vehicles is required to avoid the irreversible demagnetization of the permanent magnet due to a rise in its temperature. In this study, a water-cooling channel was used between the stator and housing to evaluate the cooling performance of a 25 kW in-wheel motor utilizing the commercially available software Ansys Fluent 19.2. Initially, cooling channels with a single or pair of vortex generators have been used with varying heights for pressure drop evaluation considering the allowable pressure drop of 0.7 bar for a water pump. The results indicates that both a single and a pair of vortex generators satisfy the limit of a pressure drop at the height of 4 and 3 mm, respectively, and the cooling performances of two vortex generators were evaluated at these heights. It has been found that the cooling performance of a permanent magnet is enhanced by 4.1% and 6.5% using a single and a pair of vortex generators, respectively, compared to the cooling channel without a vortex generator. Furthermore, considering the ram air effect on water-cooling channels of in-wheel motors under high-speed conditions, the temperature of the permanent magnet is decreased by about 2.1 °C and was found to be 148.8 °C under the temperature limit of demagnetization of the permanent magnet. Full article

(This article belongs to the Special Issue Numerical Simulation of Convective Heat Transfer)

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17 pages, 2316 KiB

Open AccessArticle

Effective Condensing Dehumidification in a Rotary-Spray Honey Dehydrator

by Marcin Morawski, Marcin Malec and Beata Niezgoda-Żelasko

Energies 2022, 15(1), 100; https://doi.org/10.3390/en15010100 - 23 Dec 2021

Cited by 2 | Viewed by 3058

Abstract

This paper presents a mathematical model of the heat and mass transfer processes for a rotary-spray honey dehydrator with a heat pump and a closed air circuit. An analytical calculation model, based on the energy balance equations of the dehydrator and heat pump, [...] Read more.

This paper presents a mathematical model of the heat and mass transfer processes for a rotary-spray honey dehydrator with a heat pump and a closed air circuit. An analytical calculation model, based on the energy balance equations of the dehydrator and heat pump, was used to model the transient dehydration process of honey in a dehydrator. The presented article includes a different approach to modelling both the dryer and the heat pump assisting the drying process. The novel quality of this study lies in the use of original equations to determine the heat and mass transfer coefficients between honey and air and using an actual model of a cooling unit to model the honey dehydration process. The experimentally verified calculation algorithm enables an analysis of the effects of air flow rate, mixer rotation speed, and cooling unit power on the efficiency of the drying process. The dehydrator calculation model was used to minimize the drying time by selecting the optimal evaporative temperature values of the cooling unit. For fixed mixer speed and air flow rates, optimal values of evaporation temperatures allow for 8–13% reduction in honey drying time and an increase in the specific moisture extraction rate (SMER) by 4–32%. Full article

(This article belongs to the Special Issue Numerical Simulation of Convective Heat Transfer)

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17 pages, 7567 KiB

Open AccessArticle

Non-Isothermal Vortex Flow in the T-Junction Pipe

by Tatyana A. Baranova, Yulia V. Zhukova, Andrei D. Chorny, Artem Skrypnik and Igor A. Popov

Energies 2021, 14(21), 7002; https://doi.org/10.3390/en14217002 - 26 Oct 2021

Cited by 4 | Viewed by 1542

Abstract

The numerical simulation approach of heat carrier mixing regimes in the T-junction shows that the RANS approach is beneficial for a qualitative flow analysis to obtain relatively agreed averaged velocity and temperature. Moreover, traditionally, the RANS approach only predicts the averaged temperature distribution. [...] Read more.

The numerical simulation approach of heat carrier mixing regimes in the T-junction shows that the RANS approach is beneficial for a qualitative flow analysis to obtain relatively agreed averaged velocity and temperature. Moreover, traditionally, the RANS approach only predicts the averaged temperature distribution. This mathematical model did not consider the temperature fluctuation variations important for the thermal fatigue task. It should also be emphasized that unlike the LES approach, the steady RANS approach cannot express a local flow structure in intense mixing zones. Nevertheless, apparently the adopted RANS approach should be used for assessing the quality of computational meshes, boundary conditions with the purpose to take LES for further numerical simulation. Full article

(This article belongs to the Special Issue Numerical Simulation of Convective Heat Transfer)

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20 pages, 624 KiB

Open AccessArticle

A Fibonacci Wavelet Method for Solving Dual-Phase-Lag Heat Transfer Model in Multi-Layer Skin Tissue during Hyperthermia Treatment

by Hari Mohan Srivastava, Mohd. Irfan and Firdous A. Shah

Energies 2021, 14(8), 2254; https://doi.org/10.3390/en14082254 - 17 Apr 2021

Cited by 19 | Viewed by 1813

Abstract

In this article, a novel wavelet collocation method based on Fibonacci wavelets is proposed to solve the dual-phase-lag (DPL) bioheat transfer model in multilayer skin tissues during hyperthermia treatment. Firstly, the Fibonacci polynomials and the corresponding wavelets along with their fundamental properties are [...] Read more.

In this article, a novel wavelet collocation method based on Fibonacci wavelets is proposed to solve the dual-phase-lag (DPL) bioheat transfer model in multilayer skin tissues during hyperthermia treatment. Firstly, the Fibonacci polynomials and the corresponding wavelets along with their fundamental properties are briefly studied. Secondly, the operational matrices of integration for the Fibonacci wavelets are built by following the celebrated approach of Chen and Haiso. Thirdly, the proposed method is utilized to reduce the underlying DPL model into a system of algebraic equations, which has been solved using the Newton iteration method. Towards the culmination, the effect of different parameters including the tissue-wall temperature, time-lag due to heat flux, time-lag due to temperature gradient, blood perfusion, metabolic heat generation, heat loss due to diffusion of water, and boundary conditions of various kinds on multilayer skin tissues during hyperthermia treatment are briefly presented and all the outcomes are portrayed graphically. Full article

(This article belongs to the Special Issue Numerical Simulation of Convective Heat Transfer)

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15 pages, 3102 KiB

Open AccessArticle

Influence of the Fin Shape on Heat Transport in Phase Change Material Heat Sink with Constant Heat Loads

by Nadezhda S. Bondareva, Mohammad Ghalambaz and Mikhail A. Sheremet

Energies 2021, 14(5), 1389; https://doi.org/10.3390/en14051389 - 03 Mar 2021

Cited by 7 | Viewed by 2503

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Numerical Simulation of Convective Heat Transfer)

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24 pages, 1227 KiB

Open AccessArticle

Thermoelectric Generation with Impinging Nano-Jets

by Fatih Selimefendigil, Hakan F. Oztop and Mikhail A. Sheremet

Energies 2021, 14(2), 492; https://doi.org/10.3390/en14020492 - 18 Jan 2021

Cited by 5 | Viewed by 1753

Abstract

In this study, thermoelectric generation with impinging hot and cold nanofluid jets is considered with computational fluid dynamics by using the finite element method. Highly conductive CNT particles are used in the water jets. Impacts of the Reynolds number of nanojet stream combinations [...] Read more.

In this study, thermoelectric generation with impinging hot and cold nanofluid jets is considered with computational fluid dynamics by using the finite element method. Highly conductive CNT particles are used in the water jets. Impacts of the Reynolds number of nanojet stream combinations (between (Re

_{1}

, Re

_{2}

) = (250, 250) to (1000, 1000)), horizontal distance of the jet inlet from the thermoelectric device (between (r

_{1}

, r

_{2}

) = (−0.25, −0.25) to (1.5, 1.5)), impinging jet inlet to target surfaces (between w

_{2}

and 4w

_{2}

) and solid nanoparticle volume fraction (between 0 and 2%) on the interface temperature variations, thermoelectric output power generation and conversion efficiencies are numerically assessed. Higher powers and efficiencies are achieved when the jet stream Reynolds numbers and nanoparticle volume fractions are increased. Generated power and efficiency enhancements 81.5% and 23.8% when lowest and highest Reynolds number combinations are compared. However, the power enhancement with nanojets using highly conductive CNT particles is 14% at the highest solid volume fractions as compared to pure water jet. Impacts of horizontal location of jet inlets affect the power generation and conversion efficiency and 43% variation in the generated power is achieved. Lower values of distances between the jet inlets to the target surface resulted in higher power generation while an optimum value for the highest efficiency is obtained at location z

_{h}

= 2.5w

_{s}

. There is 18% enhancement in the conversion efficiency when distances at z

_{h}

= w

_{s}

and z

_{h}

= 2.5w

_{s}

are compared. Finally, polynomial type regression models are obtained for estimation of generated power and conversion efficiencies for water-jets and nanojets considering various values of jet Reynolds numbers. Accurate predictions are obtained with this modeling approach and it is helpful in assisting the high fidelity computational fluid dynamics simulations results. Full article

(This article belongs to the Special Issue Numerical Simulation of Convective Heat Transfer)

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16 pages, 398 KiB

Open AccessArticle

A Study on the Numerical Performances of Diffuse Interface Methods for Simulation of Melting and Their Practical Consequences

by Andreas König-Haagen, Erwin Franquet, Moritz Faden and Dieter Brüggemann

Energies 2021, 14(2), 354; https://doi.org/10.3390/en14020354 - 11 Jan 2021

Cited by 3 | Viewed by 1327

Abstract

This work is the final one in a series of three papers devoted to shedding light on the performance of fixed grid methods, also known as enthalpy methods, for the modeling and the simulation of solid/liquid phase transition. After a detailed analysis of [...] Read more.

This work is the final one in a series of three papers devoted to shedding light on the performance of fixed grid methods, also known as enthalpy methods, for the modeling and the simulation of solid/liquid phase transition. After a detailed analysis of five of the most common enthalpy methods for conductive-dominated and conductive-convective problems and then a study concerning the formulation of the advective term in the energy balance equation, the aim of the present paper is to extend the above-mentioned studies by an investigation of the numerical performance. Such a goal is achieved by comparing the required iterations and, even if it is shown to be only a rough guide, the simulation time of each method, for a great variety of parameter variations. In terms of contribution, the main conclusions of this overall work are to demonstrate that almost all solvers give similar results when stable. However, there are still distinctive deviations with the experiments, highlighting the need for a proper validation experiment. The second important assessment concerns resilience: almost all solvers work well, with only the applied apparent heat capacity method being the major exception as it often leads to unrealistic results. As a rule of thumb, models are more resilient when only the sensible enthalpy is advected. As far as the average of the required iterations is concerned, the so-called optimum approach needs the least. The order of the other solvers depends on the advective formulation, whereas source-based methods perform averagely and the tested apparent heat capacity method poorly. Cases with only sensible enthalpy advected need fewer iterations for four of the five solvers and less computational time for all solvers. Full article

(This article belongs to the Special Issue Numerical Simulation of Convective Heat Transfer)

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