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Enhancement of Heat Transfer in Power Plants

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "J1: Heat and Mass Transfer".

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 25937

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Prof. Dr. Victor Terekhov

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Laboratory of Thermal and Gas Dynamics, Kutateladze Institute of Thermophysics, Siberian Branch of Russian Academy of Sciences, Acad. Lavrent’ev Avenue 1, 630090 Novosibirsk, Russia
Interests: heat and mass transfer in power plants; heat transfer enhancement; heat transfer with phase transitions; theory of the boundary layer; separated, vortex, and highly turbulent flows; heat exchange control methods; complex turbulent and two-phase flows; near-wall and impact jets; problems of building thermophysics and energy and resource conservation; experimental methods of aerodynamic and thermophysical studies

Special Issue Information

Dear colleagues,

The purpose of this Special Issue is to collect recent achievements in the extremely important and interesting field of energy and thermal physics, including enhancement of heat and mass transfer processes in power plants. This topic of science and technology is of great interest that has recently intensified due to a significant increase in the parameters of work processes (temperatures, heat and mass fluxes, etc.), which are now reaching extreme values. New areas of industrial technology have emerged, including microelectronics, and plasma and laser technologies, where the levels of heat fluxes can far exceed megawatts per square meter. All the advancements have necessitated the rapid growth of experimental and numerical studies in this field.

Papers that analyze aspects related to the enhancement of heat and mass transfer, useful for increasing the knowledge on energy systems, on the basis of one or more of the following topics, are welcome in this Special Issue:

Methods of intensification of heat and mass transfer;
Enhanced heat transfer during phase transformations (evaporation, boiling, condensation);
Vortex and tornado-like methods of enhancement;
Separated flows, ribs, steps, etc.
Physics flows and heat transfer;
Heat transfer on the walls with dimples, cavities, trenches, and protrusions;
Vortex generators;
Enhancement of heat transfer in impact jets and multiple jets;
Heat transfer and hydrodynamics in two-phase gas droplet, gas–liquid, and gas-dispersed flows;
Surface modification in two-phase systems; and
Features of enhancing heat transfer in mini- and micro-channels and micro-jets.

This list is not exhaustive. Therefore, works focused on other research areas that related to this Special Issue are also appreciated and invited.

Prof. Dr. Victor Terekhov
Guest Editor

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Keywords

enhancement of heat transfer
fluid flow
high turbulence
phase transitions
evaporation
boiling
condensation
vortex and tornado-like flows
separated flows
ribs
steps
dimples
cavities
trenches
protrusions
vortex generators
impact jets
two-phase flows
surface modification
micro-channels
micro-jets

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Published Papers (9 papers)

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Research

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18 pages, 4831 KiB

Open AccessArticle

Multi-Objective Constructal Optimization for Marine Condensers

by Huijun Feng, Wei Tang, Lingen Chen, Junchao Shi and Zhixiang Wu

Energies 2021, 14(17), 5545; https://doi.org/10.3390/en14175545 - 5 Sep 2021

Cited by 32 | Viewed by 2081

Abstract

A marine condenser with exhausted steam as the working fluid is researched in this paper. Constructal designs of the condenser are numerically conducted based on single and multi-objective optimizations, respectively. In the single objective optimization, there is an optimal dimensionless tube diameter leading to the minimum total pumping power required by the condenser. After constructal optimization, the total pumping power is decreased by 42.3%. In addition, with the increase in mass flow rate of the steam and heat transfer area and the decrease in total heat transfer rate, the minimum total pumping power required by the condenser decreases. In the multi-objective optimization, the Pareto optimal set of the entropy generation rate and total pumping power is gained. The optimal results gained by three decision methods in the Pareto optimal set and single objective optimizations are compared by the deviation index. The optimal construct gained by the TOPSIS decision method corresponding to the smallest deviation index is recommended in the optimal design of the condenser. These research ideas can also be used to design other heat transfer devices. Full article

(This article belongs to the Special Issue Enhancement of Heat Transfer in Power Plants)

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22 pages, 10253 KiB

Open AccessArticle

Computer Technologies of 3D Modeling by Combustion Processes to Create Effective Methods of Burning Solid Fuel and Reduce Harmful Dust and Gas Emissions into the Atmosphere

by Aliya Askarova, Saltanat Bolegenova, Valeriy Maximov, Symbat Bolegenova, Nariman Askarov and Aizhan Nugymanova

Energies 2021, 14(5), 1236; https://doi.org/10.3390/en14051236 - 24 Feb 2021

Cited by 6 | Viewed by 3528

Abstract

Using numerical methods, studies have been carried out to determine the effect of the introduction of the technology of two-stage combustion of high-ash Karaganda coal on the main characteristics of heat and mass transfer processes in the furnace of the BKZ-75 boiler at Shakhtinskaya TPP (Kazakhstan). Various regimes of supplying additional air into the combustion space, the volume of which varied from 0% (traditional basic version) to 30% of the total volume of air required for fuel combustion, have been investigated using 3D computer modeling methods. The performed computational experiments made it possible to obtain the distributions of the total velocity vector, temperature fields, concentration fields of carbon monoxide CO and nitrogen dioxide NO₂ over the entire volume of the furnace and at the outlet from it. The introduction of the two-stage combustion technology made it possible to optimize the combustion of high-ash coal, since in this case there is an increase in the temperature in the torch core and a decrease in it at the outlet from the furnace, which has a significant effect on the chemical processes of the formation of combustion products. Based on the results obtained, it can be concluded that an increase in the percentage of air supplied through additional injectors to 18% leads to a decrease in the concentrations of carbon monoxide CO by about 36%, and nitrogen dioxide NO₂ by 25% compared to the base case. A further increase in the volume of additional air leads to a deterioration in these indicators. The results obtained will make it possible to optimize the combustion of low-grade fuel in the furnace of the BKZ-75 boiler, increase the efficiency of fuel burnout, reduce harmful emissions into the atmosphere, and introduce a two-stage combustion technology at other coal-fired TPPs. Full article

(This article belongs to the Special Issue Enhancement of Heat Transfer in Power Plants)

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19 pages, 8789 KiB

Open AccessArticle

Impact of Heat Transfer on Transient Stress Fields in Power Plant Boiler Components

by Jerzy Okrajni, Mariusz Twardawa and Krzysztof Wacławiak

Energies 2021, 14(4), 862; https://doi.org/10.3390/en14040862 - 7 Feb 2021

Cited by 4 | Viewed by 2177

Abstract

In boilers operating in modern power plants, thick-walled elements of complex shapes, such as valves, superheater headers, T-pipes, Y-pipes, four-way pipes, and elbows, are especially prone to fatigue processes. Higher operation parameters and more frequent startups may speed up fatigue damage in these elements. Such damage is a local phenomenon and is caused by thermomechanical fatigue (TMF). This paper presents a method designed for predicting the behavior of components subjected to variable temperature and mechanical loading conditions. This method combines the results of measurements of operating parameters of devices under industrial conditions with those obtained using finite element modeling (FEM). Particular attention was given to the influence of the time-dependent heat transfer coefficient on the local thermomechanical stress–strain behavior of the material. It was stated that heat transfer conditions have a significant impact on local transient stresses and depend on the operation parameters of boilers. Consistency of the temperature changes as a function of time, determined in industrial conditions and calculated on the basis of the model approach, was obtained. This developed and described in the work approach enables defining the conditions of heat transfer on the surface of models of considered components. Full article

(This article belongs to the Special Issue Enhancement of Heat Transfer in Power Plants)

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24 pages, 41182 KiB

Open AccessArticle

Application of a Magnetic Field in Saturated Film Boiling of a Magnetic Nanofluid (MNF) under Reduced Gravity

by Kaikai Guo, Fucheng Chang and Huixiong Li

Energies 2021, 14(3), 634; https://doi.org/10.3390/en14030634 - 27 Jan 2021

Cited by 6 | Viewed by 1731

Abstract

To overcome the problem of abnormally large bubbles and the large reduction of heat flux under low gravity, the computational model of magnetic nanofluid (MNF) boiling flow was used to systematically study the thermodynamic characteristics of an MNF-saturated film boiling with and without the magnetic field. This study found that in the absence of a magnetic field, the decrease of the gravity level makes the bubble size increase and the bubble departure time increase, and the lower the gravity level, the worse the boiling heat transfer. However, after applying the magnetic field, bubble size decreases significantly and the bubble departure time is shortened. As the magnetic field intensity increases, the difference in bubble size and heat transfer characteristics between different gravity levels becomes smaller and smaller, which shows that for the boiling flow of MNF under low gravity levels, applying a magnetic field can effectively avoid the appearance of abnormally large bubbles, enhance heat transfer, and improve the safety of related heat transfer equipment. Full article

(This article belongs to the Special Issue Enhancement of Heat Transfer in Power Plants)

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18 pages, 6304 KiB

Open AccessArticle

Heat Transfer Enhancement of Circular- and Petal- Shaped Double-Tube-Type Heat Exchangers by Triple Ones

by Toshihiko Shakouchi, Kazuma Yamamura, Koichi Tsujimoto and Toshitake Ando

Energies 2020, 13(24), 6590; https://doi.org/10.3390/en13246590 - 14 Dec 2020

Cited by 2 | Viewed by 1930

Abstract

Conventional circular double or triple tube type heat exchanger, DHE or THE, is one of the compact heat exchangers; a large number of studies have been performed to improve their heat transfer performance. The authors demonstrated that a petal-shaped special DHE with a large wet perimeter yields a high heat transfer efficiency, η. In this study, the DHE with six or five petals-, five shallow petals-, and circular-inner tubes were used. To further improve the η of the DHE, a THE with a petal-shaped inner tube along with the middle and outer circular tubes were used. Hot water flowed through the inner tube and cold water flowed through the middle and outer tubes as a counter current flow. The heat transfer was approximately equal; however, the flow resistance (pressure loss) of the outer tube of the DHE could be decreased using the middle and outer tubes under the same amount of cold water as the DHE; consequently, the η could be improved. In addition, the effect of changing the flow path of the hot- and cold-water flows on the η was examined. Full article

(This article belongs to the Special Issue Enhancement of Heat Transfer in Power Plants)

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22 pages, 5543 KiB

Open AccessArticle

Innovative Turbine Intake Air Cooling Systems and Their Rational Designing

by Andrii Radchenko, Eugeniy Trushliakov, Krzysztof Kosowski, Dariusz Mikielewicz and Mykola Radchenko

Energies 2020, 13(23), 6201; https://doi.org/10.3390/en13236201 - 25 Nov 2020

Cited by 34 | Viewed by 5468

Abstract

The efficiency of cooling ambient air at the inlet of gas turbines in temperate climatic conditions was analyzed and reserves for its enhancing through deep cooling were revealed. A method of logical analysis of the actual operation efficiency of turbine intake air cooling systems in real varying environment, supplemented by the simplest numerical simulation was used to synthesize new solutions. As a result, a novel trend in engine intake air cooling to 7 or 10 °C in temperate climatic conditions by two-stage cooling in chillers of combined type, providing an annual fuel saving of practically 50%, surpasses its value gained due to traditional air cooling to about 15 °C in absorption lithium-bromide chiller of a simple cycle, and is proposed. On analyzing the actual efficiency of turbine intake air cooling system, the current changes in thermal loads on the system in response to varying ambient air parameters were taken into account and annual fuel reduction was considered to be a primary criterion, as an example. The improved methodology of the engine intake air cooling system designing based on the annual effect due to cooling was developed. It involves determining the optimal value of cooling capacity, providing the minimum system sizes at maximum rate of annual effect increment, and its rational value, providing a close to maximum annual effect without system oversizing at the second maximum rate of annual effect increment within the range beyond the first maximum rate. The rational value of design cooling capacity provides practically the maximum annual fuel saving but with the sizes of cooling systems reduced by 15 to 20% due to the correspondingly reduced design cooling capacity of the systems as compared with their values defined by traditional designing focused to cover current peaked short-term thermal loads. The optimal value of cooling capacity providing the minimum sizes of cooling system is very reasonable for applying the energy saving technologies, for instance, based on the thermal storage with accumulating excessive (not consumed) cooling capacities at lowered current thermal loads to cover the peak loads. The application of developed methodology enables revealing the thermal potential for enhancing the efficiency of any combustion engine (gas turbines and engines, internal combustion engines, etc.). Full article

(This article belongs to the Special Issue Enhancement of Heat Transfer in Power Plants)

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15 pages, 4198 KiB

Open AccessArticle

Numerical and Physical Simulation of Heat Transfer Enhancement Using Oval Dimple Vortex Generators—Review and Recommendations

by Alexander Mironov, Sergey Isaev, Artem Skrypnik and Igor Popov

Energies 2020, 13(20), 5243; https://doi.org/10.3390/en13205243 - 9 Oct 2020

Cited by 11 | Viewed by 2239

Abstract

Vortex generation and flow disruption in heat exchanger passages by means of surface modification is a widely used passive heat transfer augmentation technique. The present paper contains the results of numerical and experimental studies of the hydraulic resistance and heat transfer in the rectangle duct with oval-trench- and oval-arc-shaped dimples applied to the heat transfer surface. For the turbulent flow in the duct (Pr = 0.71, Re_d = 3200–9 × 10⁴—for heat transfer determination and Re_d = 500–10⁴—for the friction factor measurements), rational geometrical parameters of the oval-trench dimple were determined: relative elongation of dimple l/b = 5.57–6.78 and relative depth l/b = 5.57–6.78, while the value of the attack angle to the mean flow was fixed φ = (45–60)°. The comparison of the experimental and numerical modeling for the flow in the narrow duct over the surface with a single- and multi-row dimple arrangement has revealed a good agreement. It was found that the average heat transfer coefficient magnitudes in such ducts could be increased 1.5–2.5 times by means of single and multi-row dimple application on the heat transfer surface. The heat transfer augmentation for the surfaces with the oval-arched dimples was found to be 10% greater than the one for the oval-trench dimples. The corresponding friction factor augmentation was found to be 125–300% in comparison to the smooth surface duct. The obtained experimental data were used for the data generalization. Derived generalized equation allows for predicting the friction factor and heat transfer coefficient values for the flow over the single-row oval-trench simple arrangement. The maximal deviation of the experimental data from the proposed equations was found to be 20%. The application of the artificial neural networks for predicting the hydraulic resistance and heat transfer augmentation in such ducts was presented. Full article

(This article belongs to the Special Issue Enhancement of Heat Transfer in Power Plants)

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13 pages, 5702 KiB

Open AccessArticle

RANS Simulation of the Effect of Pulse Form on Fluid Flow and Convective Heat Transfer in an Intermittent Round Jet Impingement

by M. A. Pakhomov and V. I. Terekhov

Energies 2020, 13(15), 4025; https://doi.org/10.3390/en13154025 - 4 Aug 2020

Cited by 6 | Viewed by 2794

Abstract

The of effect pulse form (rectangular, sinusoidal and triangular) on the fluid flow and heat transfer of an intermittent jet impingement was studied numerically. It was shown in a non-steady-state jet, both an increase and decrease in heat transfer are possible compared with steady-state jet for all investigated pulse forms. For small distances between the pipe edge and obstacle (H/D ≤ 6) in the pulsed jet, heat transfer around the stagnation point increases with increasing pulse frequency, while for H/D > 8 an increase in frequency causes a heat transfer decrease. A growth in the Reynolds number causes a decrease in heat transfer, and data for all frequencies approach the steady-state flow regime. The numerical model is compared with the experimental results. Satisfactory agreement on the influence of the form and frequency of pulses on heat transfer for the pulsed jet on the obstacle surface is obtained. Full article

(This article belongs to the Special Issue Enhancement of Heat Transfer in Power Plants)

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Review

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24 pages, 5090 KiB

Open AccessReview

Heat Transfer in Highly Turbulent Separated Flows: A Review

by Viktor I. Terekhov

Energies 2021, 14(4), 1005; https://doi.org/10.3390/en14041005 - 14 Feb 2021

Cited by 18 | Viewed by 2995

Abstract

The study of flows with a high degree of turbulence in boundary layers, near-wall jets, gas curtains, separated flows behind various obstacles, as well as during combustion is of great importance for increasing energy efficiency of the flow around various elements in the ducts of gas-dynamic installations. This paper gives some general characteristics of experimental work on the study of friction and heat transfer on a smooth surface, in near-wall jets, and gas curtains under conditions of increased free-stream turbulence. Taking into account the significant effect of high external turbulence on dynamics and heat transfer of separated flows, a similar effect on the flow behind various obstacles is analyzed. First of all, the classical cases of flow separation behind a single backward-facing step and a rib are considered. Then, more complex cases of the flow around a rib oriented at different angles to the flow are analyzed, as well as a system of ribs and a transverse trench with straight and inclined walls in a turbulent flow around them. The features of separated flow in a turbulized stream around a cylinder, leading to an increase in the width of the vortex wake, frequency of vortex separation, and increase in the average heat transfer coefficient are analyzed. The experimental results of the author are compared with data of other researchers. The structure of separated flow at high turbulence—characteristic dimensions of the separation region, parameters of the mixing layer, and pressure distribution—are compared with the conditions of low-turbulent flow. Much attention is paid to thermal characteristics: temperature profiles across the shear layer, temperature distributions over the surface, and local and average heat transfer coefficients. It is shown that external turbulence has a much stronger effect on the separated flow than on the boundary layer on a flat surface. For separated flows, its intensifying effect on heat transfer is more pronounced behind a rib than behind a step. The factor of heat transfer intensification by external turbulence is most pronounced in the transverse cavity and in the system of ribs. Full article

(This article belongs to the Special Issue Enhancement of Heat Transfer in Power Plants)

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