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12 pages, 6317 KiB

Open AccessArticle

Assessment of the Condition of Pipelines Using Convolutional Neural Networks

by Yuri Vankov, Aleksey Rumyantsev, Shamil Ziganshin, Tatyana Politova, Rinat Minyazev and Ayrat Zagretdinov

Energies 2020, 13(3), 618; https://doi.org/10.3390/en13030618 - 1 Feb 2020

Cited by 26 | Viewed by 3923

Abstract

Pipelines are structural elements of many systems. For example, they are used in water supply and heat supply systems, in chemical production facilities, aircraft manufacturing, and in the oil and gas industry. Accidents in piping systems result in significant economic damage. An important [...] Read more.

Pipelines are structural elements of many systems. For example, they are used in water supply and heat supply systems, in chemical production facilities, aircraft manufacturing, and in the oil and gas industry. Accidents in piping systems result in significant economic damage. An important factor for ensuring the reliability of energy transportation systems is the assessment of real technical conditions of pipelines. Methods for assessing the state of pipeline systems by their vibro-acoustic parameters are widely used today. Traditionally, the Fourier transform is used to process vibration signals. However, as a rule, the oscillations of the pipe-liquid system are non-linear and non-stationary. This reduces the reliability of devices based on the implementation of classical methods of analysis. The authors used neural network methods for the analysis of vibro-signals, which made it possible to increase the reliability of diagnosing pipeline systems. The present work considers a method of neural network analysis of amplitude-frequency measurements in pipelines to identify the presence of a defect and further clarify its variety. Full article

(This article belongs to the Special Issue Advances in Design, Modelling, and Applications of Heat Transfer Equipment)

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20 pages, 5071 KiB

Open AccessArticle

Online Ash Fouling Prediction for Boiler Heating Surfaces based on Wavelet Analysis and Support Vector Regression

by Shuiguang Tong, Xiang Zhang, Zheming Tong, Yanling Wu, Ning Tang and Wei Zhong

Energies 2020, 13(1), 59; https://doi.org/10.3390/en13010059 - 20 Dec 2019

Cited by 30 | Viewed by 6170

Abstract

Depending on its operating conditions, traditional soot blowing is activated for a fixed time. However, low-frequency soot blowing can cause heat transfer efficiency to decrease. High-frequency soot blowing not only wastes high-pressure steam, but also abrades surface pipes, reducing the working life of [...] Read more.

Depending on its operating conditions, traditional soot blowing is activated for a fixed time. However, low-frequency soot blowing can cause heat transfer efficiency to decrease. High-frequency soot blowing not only wastes high-pressure steam, but also abrades surface pipes, reducing the working life of a heat exchange device. Therefore, it is necessary to design an online ash fouling monitoring system to perform soot blowing that is dependent on the status of ash accumulation. This study presents an online monitoring model of ash-layer thermal resistance that reflects the degree of ash fouling. A wavelet threshold denoising algorithm was applied to smooth the thermal resistance of the ash layer calculated by the heat balance mechanism model. Thus, the variation in thermal resistance becomes more visible, which is more conducive to optimizing the operation of soot blowing. The designed Support Vector Regression (SVR) model could achieve the online prediction of thermal resistance denoising for low-temperature superheaters. Experimental analysis indicates that the prediction accuracy was 98.5% during the testing phase. By using the method proposed in this study, online monitoring of heating surfaces during the ash fouling process can be realized without adding complicated and expensive equipment. Full article

(This article belongs to the Special Issue Advances in Design, Modelling, and Applications of Heat Transfer Equipment)

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21 pages, 9333 KiB

Open AccessArticle

Numerical Investigation on Heat-Transfer and Hydromechanical Performance inside Contaminant-Insensitive Sublimators under a Vacuum Environment for Spacecraft Applications

by Lijun Gao, Yunze Li, Huijuan Xu, Xin Zhang, Man Yuan and Xianwen Ning

Energies 2019, 12(23), 4562; https://doi.org/10.3390/en12234562 - 29 Nov 2019

Cited by 7 | Viewed by 2668

Abstract

The contaminant-insensitive sublimator (CIS) is a novel water sublimator in development, which uses two porous substrates to separate the sublimation point from the pressure-control point and provide long-life effective cooling for spacecraft. Many essential studies need to be carried out in the field. [...] Read more.

The contaminant-insensitive sublimator (CIS) is a novel water sublimator in development, which uses two porous substrates to separate the sublimation point from the pressure-control point and provide long-life effective cooling for spacecraft. Many essential studies need to be carried out in the field. To overcome the reliability issues such as ice breakthrough caused by large temperature or pressure differences, the CIS development unit model, the mathematical models of heat and mass transfer and the evaluation coefficient have been established. Numerical investigations have been implemented aiming at the impacts of physical properties of porous substrate, physical properties of working fluid, orifice layouts and orifice-structure parameters on the characteristics of flow field and temperature field. The numerical investigation shows some valuable conclusion, such as the temperature uniformity coefficient at the bottom surface of the large pore substrate is 0.997669 and the pressure uniformity coefficient at the same surface is 0.85361267. These numerical results can provide structure and data reference for the CIS design of lunar probe or spacesuit. Full article

(This article belongs to the Special Issue Advances in Design, Modelling, and Applications of Heat Transfer Equipment)

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20 pages, 8340 KiB

Open AccessArticle

Lightweight Equipment for the Fast Installation of Asphalt Roofing Based on Infrared Heaters

by Efrén Díez-Jiménez, Alberto Vidal-Sánchez, Alberto Barragán-García, Miguel Fernández-Muñoz and Ricardo Mallol-Poyato

Energies 2019, 12(22), 4253; https://doi.org/10.3390/en12224253 - 8 Nov 2019

Cited by 1 | Viewed by 2589

Abstract

A prototype for mechanizing the asphalt roofing process was developed. In this manuscript, we present the design, manufacturing, preliminary thermal test, and operation test of the equipment. The innovation is sustained by the use of infrared radiators instead of fuel burners. Infrared heaters [...] Read more.

A prototype for mechanizing the asphalt roofing process was developed. In this manuscript, we present the design, manufacturing, preliminary thermal test, and operation test of the equipment. The innovation is sustained by the use of infrared radiators instead of fuel burners. Infrared heaters provide optimal clean heat transfer to asphalt rolls in comparison to fuel burner automated systems since the latter generates a significant amount of CO₂, SO₂, and other non-ecofriendly emissions close to workers. Moreover, the equipment has several advantages with respect to manual installation, such as roofing capacity, cleanness, safety, uniformity, and environment-friendliness. It demonstrates an installation speed of 1 m/min, on average, for 3 kg/m² rolls, which leads to around 400–420 m² per person a day, more than the usual manual roofing rate. However, there are some issues that need to be resolved, such as inaccurate unrolling and/or bad adhesion gaps. Full article

(This article belongs to the Special Issue Advances in Design, Modelling, and Applications of Heat Transfer Equipment)

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24 pages, 7670 KiB

Open AccessArticle

Effect of Saturated Steam Carried Downward on the Flow Properties in the Downcomer of Steam Generator

by Yan Liu, Hui-lie Shi, Chun Gui, Xian-yuan Wang and Rui-feng Tian

Energies 2019, 12(19), 3650; https://doi.org/10.3390/en12193650 - 24 Sep 2019

Cited by 1 | Viewed by 3028

Abstract

The saturated water separated by the steam separator in a natural circulation steam generator may carry a small amount of saturated steam into the downcomer. The steam contacts subcooled water and condenses directly in the downcomer causing the variations in the pressure and [...] Read more.

The saturated water separated by the steam separator in a natural circulation steam generator may carry a small amount of saturated steam into the downcomer. The steam contacts subcooled water and condenses directly in the downcomer causing the variations in the pressure and steam quality and likely affecting the stability of the water cycle in the secondary loop. It is not conducive to core heat extraction and thus affects nuclear safety. The mathematical model of the downcomer was established in this study based on the internal structures of a natural circulation steam generator. The volume-of-fluid (VOF) and large-eddy-simulation (LES) models were used for analysis on FLUENT software (ANSYS, Pittsburgh, PA. USA) platform. The influence of direct contact condensation of top-down flowing steam on the flow properties in the downcomer of the steam generator under high pressure was studied. The trend of the temperature, pressure, and the void fraction were obtained by combining these models with the condensation model. Further, a one-dimensional calculation program based on the differential drop was also developed to assess the flow field in the downcomer. The calculation results are in good agreement with the experimental results which indicated that, when affected by the saturated steam carried downward, the flow temperature close to the exit of the downcomer rises slightly due to the absorption of the heat released by the steam condensation. Furthermore, the density corrected by the pressure-drop is more reliable than that corrected by the temperature. After the velocity in the downcomer has increased to a certain value, the sensitivity of steam quality to the subcooling degree in the downcomer begins to decline. The results in this paper can be used to perform stability analyses and to design steam generators. The results of research are helpful to the stability analysis and the design of a steam generator, and to improve the accuracy of the measurement of the steam generator operating parameters, thus enhancing the safety of Pressurize Water Reactor operating system. Full article

(This article belongs to the Special Issue Advances in Design, Modelling, and Applications of Heat Transfer Equipment)

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22 pages, 5178 KiB

Open AccessArticle

Influence of the Spacing of Steam-Injecting Pipes on the Energy Consumption and Soil Temperature Field for Clay-Loam Disinfection

by Zhenjie Yang, Xiaochan Wang and Muhammad Ameen

Energies 2019, 12(17), 3209; https://doi.org/10.3390/en12173209 - 21 Aug 2019

Cited by 8 | Viewed by 2670

Abstract

Soil steam disinfection (SSD) technology is one of the effective means to eliminate soil-borne diseases, especially under the condition of clay-loam soil cultivation for facility agriculture in Yangtze River delta (China). With the fine particles, small pores and high density of [...] Read more.

Soil steam disinfection (SSD) technology is one of the effective means to eliminate soil-borne diseases, especially under the condition of clay-loam soil cultivation for facility agriculture in Yangtze River delta (China). With the fine particles, small pores and high density of the soil, the way of steam transport and heat transfer are quite different from those of other cultivation mediums, and when using SSD injection method, the diffusion of steam between pipes will be affected, inhibiting the heat transfer in the dense soil. Therefore, it is necessary to explore the influence of steam pipe spacing (SPS) on the energy consumption and soil temperature (ST) for clay-loam disinfection. The best results are to find a suitable SPS that satisfies the inter-tube steam that can be gathered together evenly without being lost to the air under limited boiler heating capacity. To this purpose, we first used a computational fluid dynamics model to calculate the effective SPS to inject steam into deep soil. Second, the ST, ST rise rate, ST coefficient of variation, and soil water content variation among different treatments (12, 18, 24, or 30 cm pipe spacing) were analysed. Finally, the heating efficiency of all treatments depending on the disinfection time ratio and relative energy consumption was evaluated. The result shows that in the clay-loam unique to Southern China, the elliptical shape of the high-temperature region obtained from the numerical simulation was basically consistent with the experiment results, and the ratios of short diameter to long diameter were 0.65 and 0.63, respectively. In the SPS = 12 and 18 cm treatments, the steam completely diffused at a 0–20 cm soil layer depth, and the heat transfer was convective. However, at an SPS = 12 cm, steam accumulation occurred at the steam pipe holes, causing excessive accumulation of steam heat. The relative energy consumptions for SPS = 30, 24, and 12 cm were above 2.18 kJ/(kg·°C), and the disinfection time ratio was below 0.8. Thus, under a two-pipe flow rate = 4–8 kg/h, the inter-tube steam was found to be completely concentrated with a uniform continuous high temperature distribution within the soil for an appropriate SPS = 18–22 cm, avoiding the unnecessary loss of steam heat, and this method can be considered for static and moving disinfection operations in the cultivated layer (−20–0 cm) of clay loam soil. However, for soil with higher clay contents, the SPS can be appropriately reduced to less than 18 cm. For soil with lower clay contents and higher sand contents, the SPS can be increased to more than 22 cm. Full article

(This article belongs to the Special Issue Advances in Design, Modelling, and Applications of Heat Transfer Equipment)

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21 pages, 7138 KiB

Open AccessArticle

Design and Test of Cryogenic Cold Plate for Thermal-Vacuum Testing of Space Components

by Efrén Díez-Jiménez, Roberto Alcover-Sánchez, Emiliano Pereira, María Jesús Gómez García and Patricia Martínez Vián

Energies 2019, 12(15), 2991; https://doi.org/10.3390/en12152991 - 2 Aug 2019

Cited by 4 | Viewed by 4230

Abstract

This paper proposes a novel cryogenic fluid cold plate designed for the testing of cryogenic space components. The cold plate is able to achieve cryogenic temperature operation down to −196 °C with a low liquid nitrogen (LN₂) consumption. A good tradeoff [...] Read more.

This paper proposes a novel cryogenic fluid cold plate designed for the testing of cryogenic space components. The cold plate is able to achieve cryogenic temperature operation down to −196 °C with a low liquid nitrogen (LN₂) consumption. A good tradeoff between high rigidity and low thermal conduction is achieved thanks to a hexapod configuration, which is formed by six hinge–axle–hole articulations in which each linking rod bears only axial loads. Thus, there is not any stress concentration, which reduces the diameter of rod sections and reduces the rods’ thermal conduction. This novel design has a unique set of the following properties: Simple construction, low thermal conduction, high thermal inertia, lack of vibrational noise when cooling, isostatic structural behavior, high natural frequency response, adjustable position, vacuum-suitability, reliability, and non-magnetic. Additionally, the presented cold plate design is low-cost and can be easily replicated. Experimental tests showed that a temperature of at least −190 °C can be reached on the top surface of the cold plate with an LN₂ consumption of 10 liters and a minimum vibration frequency of 115 Hz, which is high enough for most vibration tests of space components. Full article

(This article belongs to the Special Issue Advances in Design, Modelling, and Applications of Heat Transfer Equipment)

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Review

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27 pages, 5162 KiB

Open AccessReview

Review of Design and Modeling of Regenerative Heat Exchangers

by Bohuslav Kilkovský

Energies 2020, 13(3), 759; https://doi.org/10.3390/en13030759 - 9 Feb 2020

Cited by 11 | Viewed by 7701

Abstract

Heat regenerators are simple devices for heat transfer, but their proper design is rather difficult. Their design is based on differential equations that need to be solved. This is one of the reasons why these devices are not widely used. There are several [...] Read more.

Heat regenerators are simple devices for heat transfer, but their proper design is rather difficult. Their design is based on differential equations that need to be solved. This is one of the reasons why these devices are not widely used. There are several methods for solving them that were developed. However, due to the time demands of calculation, these models did not spread too much. With the development of computer technology, the situation changed, and these methods are now relatively easy to apply, as the calculation does not take a lot of time. Another problem arises when selecting a suitable method for calculating the heat transfer coefficient and pressure drop. Their choice depends on the type of packed bed material, and not all available computational equations also provide adequate accuracy. This paper describes the so-called open Willmott methods and provides a basic overview of equations for calculating the regenerative heat exchanger with a fixed bed. Based on the mentioned computational equations, it is possible to create a tailor-made calculation procedure of regenerative heat exchangers. Since no software was found on the market to design regenerative heat exchangers, it had to be created. An example of software implementation is described at the end of the article. The impulse to create this article was also to broaden the awareness of regenerative heat exchangers, to provide designers with an overview of suitable calculation methods and, thus, to extend the interest and use of this type of heat exchanger. Full article

(This article belongs to the Special Issue Advances in Design, Modelling, and Applications of Heat Transfer Equipment)

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