Mathematical Models for Assessing the Thermal Engineering Reliability of Boiler Units of Power Complexes

2021 ◽  
Vol 64 (6) ◽  
pp. 88-93
Author(s):  
Alexander Belov ◽  
◽  
Dmitry Shaforost ◽  
Viktor Chebotarev ◽  
◽  
...  
Keyword(s):  
Natural Circulation ◽  
Spatial Localization ◽  
Hot Water ◽  
Ultrahigh Pressure ◽  
Thermal Engineering ◽  
Safety Factors ◽  
Direct Flow ◽  
Thermal Failure ◽  
Mathematical Properties ◽  
Boiler Units

The analysis is carried out and the definitions of the concept of thermal engineering reliability, the determining parameter and the determining function of boiler units, are given. A classification has been developed for the determining parameters of steam and hot water boilers by level in the chain of cause-and-effect relationships in the event of a thermal failure. It is proposed to divide the determining parameters and functions of boilers according to their spatial localization into integral and local. A lot of models for defining functions with different mathematical properties (for example, the presence or absence of discontinuities of the second kind) are considered. The defining functions (reliability criteria) currently used in boiler construction have been identified. The analysis of the safety factors for overturning and stagnation in direct-flow and drum boiler units is carried out. The incorrectness of the currently used dependence is shown. A formula has been proposed for these coefficients using internal useful heads, which is especially relevant for boilers with natural circulation at ultrahigh pressure.

Dynamic Behaviour of a Vertical Natural Circulation Two Pressure Stage HRSG Behind a Heavy Duty Gas Turbine

2000 ◽  
Author(s):  
Georg N. Stamatelopoulos ◽  
Karl Ponweiser ◽  
Heimo Walter ◽  
Wladimir Linzer ◽  
Hubert Neßler ◽  
...  
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Dynamic Behaviour ◽  
Natural Circulation ◽  
Operational Reliability ◽  
Combined Cycle ◽  
Thermal Engineering ◽  
Simulation Code ◽  
Pressure Stage ◽  
Cold Starts

Modern combined cycle gas turbines are highly flexible in their operation, concerning start up, load change and shut down. Heat Recovery Steam Generators (HRSG) arranged downstream of the Gas Turbine (GT) are forced to operate in such a way, that the gas turbine operation is not restricted by them. Therefore, they should be designed for a high cycling capability with typical values in the range of 200 to 250 cold starts, 1000 warm and 2500 hot starts for their typical 25 year life span. Cold starts are defined as a standstill period of over 120 hours, warm starts to a weekend shutdown and hot starts to an overnight shut down. AE Energietechnik GmbH (AE), a Babcock Borsig Power company has specialized in designing, erecting and commissioning vertical natural circulation multiple pressure stage HRSGs. The vertical design combines simplicity and low investment costs with performance reliability and high availability. In order to forecast the dynamic behaviour of such a HRSG, AE has supported the development of a dynamic simulation code at the Institute of Thermal Engineering (ITW) located at the Vienna University of Technology. This finite volume code enables the prediction of velocities, pressures and temperatures for several dynamic processes of the HRSG. In the present paper computational results of starts and load changes will be presented for a vertical natural circulation HRSG. Furthermore, several design optimization changes which where made in order to increase operational reliability and availability will be demonstrated. Finally, practical applications of already constructed HRSG will be discussed and conclusions will be drawn.

Analysis and Research on Natural Circulation Capacity of HFETR

2016 ◽  
Author(s):  
Taozhong Xu ◽  
Caiyu Deng ◽  
Yuxin Xiang
Keyword(s):  
Pressure Vessel ◽  
Cold Water ◽  
Flow Direction ◽  
Natural Circulation ◽  
Reactor Power ◽  
Hot Water ◽  
Forced Circulation ◽  
The Core ◽  
Establishment Process ◽  
Residual Heat

Natural circulation is being used as an important circulation to remove reactor residual heat. In the core of High Flux Engineering Trial Reactor of China (HFETR), the coolant is driven by pumps normally and flows from upside to downside in the core. When HFETR is shut down or runs in low power, the natural circulation between the hot water in the core and the cold water in the reflector inside the pressure vessel is established to cool down the core. Since the natural circulation processed only in the pressure vessel, the accident pumps need to be turned on periodically to remove reactor residual heat. The inversion of flow direction in HFETR and internal natural circulation lead to a different natural circulation establishment process from traditional reactor in which coolant flows form down to top normally. In this paper the transition between the natural circulation and forced circulation is analyzed by RELAP5/MOD3 code. The results showed that the accident pump could be turned off in the power of 850kW; The time, at which the accident pump needs to be turned on to transit the natural circulation to forced circulation, is decided by the temperature of the water in top of pressure vessel, and a formula between temperature of the water in the top of pressure vessel and the reactor power was obtained. The research results have theoretical and practical value to the full use of the natural circulation ability, as well as the safety of the engineering reactors or similar test facilities.

scholarly journals Update and Analysis of Current Boiler Operations Used for the Generation of Steam Heat and Electricity

2017 ◽  
Vol 7 (1) ◽  
pp. 23
Author(s):  
Jack Fuller ◽  
Yang Guo
Keyword(s):  
Natural Gas ◽  
Thermal Energy ◽  
Environmental Protection Agency ◽  
Hot Water ◽  
Protection Agency ◽  
Boiler Units ◽  
Insight Into ◽  
Steam Heat ◽  
Current Operating ◽  
The U.S

According to the U.S, Environmental Protection Agency (EPA), the number of boilers in the U.S. devoted to the production of steam, electricity, and heat is approximately 1.5 million. This study analyzes boilers burning natural gas, coal, wood, oil, or other fuels to recover thermal energy in the form of steam or hot water to produce electricity or heat. The focus of this research paper will be to assess the compliance status of the boilers which were in the original EPA major source Boiler MACT group to provide insight into the current operating status of these boiler units.

Complex Efficiency of Using Wood Pellets in Power Plants

2021 ◽  
pp. 159-172
Author(s):  
Victor K. Lyubov ◽  
◽  
Aleksandr M. Vladimirov ◽  
Keyword(s):  
Combustion Chamber ◽  
Environmental Performance ◽  
Hot Water ◽  
Wood Pellets ◽  
Combustion Chambers ◽  
Wood Pellet ◽  
Carbon And Nitrogen ◽  
Boiler Units ◽  
Secondary Air ◽  
By Products

In advanced countries, the dramatic impact of greenhouse gases on the global climate is reduced by replacing fossil fuels with biofuels. This method is being actively encouraged. However, by-products of logging, processing and conversion of wood are classified as difficult to burn fuels due to their high moisture content, low energy density and extremely heterogeneous granulometric composition. A promising direction to increase the energy density and transportability of the timber industry by-products is their granulation. Wood pellet fuel burning in heat-generating plants results in significant increase in their energy and environmental performance. The purpose of the paper is an experimental and calculation study of the energy and environmental performance of 4 MW hot water boilers produced by Polytechnik Luft- und Feuerungstechnik GmbH in the process of burning pine and spruce wood pellets obtained from by-products woodworking. When performing studies, the components of the boiler’s heat balance, gas release, and particulate emissions were determined. Numerical modeling of thermochemical and aerodynamic processes taking place in the boiler combustion chamber was carried out by using the Ansys Fluent three-dimensional simulation software. Together with industrial-operational tests it showed the possibility to reduce the total share of flue gas recirculation into combustion chambers of boiler units to values not exceeding 0.45, in providing an acceptable temperature of combustion products at the combustion chamber outlet and maintaining minimum emissions of carbon and nitrogen monoxides. At the same time, the share of gases fed by recirculation smoke exhausters to the over-bed area of the burner should have higher values than under the reciprocating grates of boilers. Guidelines for comprehensive improvement of wood pellet combustion efficiency in combustion chamber of 4 MW hot water boilers have been developed and implemented. The priorities are: using the air passed through the cooling channels of the setting as secondary air; reducing the rarefaction in the combustion chambers to 30–70 Pa; optimizing the ratio of primary and secondary air, herewith, the share of primary air in the total flow should be 0.26–0.35. Implementation of the developed guidelines allowed to increase the boiler gross efficiency by 0.5–1.8 %, to reduce the aerodynamic resistance of the gas path by 15–20 % and to ensure consistently low emissions of carbon and nitrogen monoxides and soot particles. When designing boiler units for burning wood pellet fuel it is advisable to place heating surfaces in the combustion chamber, included in the circulation circuit of the boiler. This will increase the efficiency and life cycle of the boiler unit.

scholarly journals Experimental investigation on the performance of thermosyphon solar water heater in the South Caspian Sea

2011 ◽  
Vol 15 (2) ◽  
pp. 447-456 ◽  
Author(s):  
Abdollah Riahi ◽  
Hessam Taherian
Keyword(s):  
Experimental Investigation ◽  
Dynamic Response ◽  
Flat Plate ◽  
Caspian Sea ◽  
Natural Circulation ◽  
Hot Water ◽  
Solar Water Heater ◽  
Water Heater ◽  
Solar Insolation ◽  
Solar Water

In the present study, a natural circulation closed thermosyphon flat plate solar water heater has been tested at the Faculty of Engineering of University of Mazandaran located in Babol city (36N, 52E). Data were collected for several sunny and cloudy days. Dynamic response of the system to variations in solar insolation was studied and analyzed. It was found that such systems can provide ample energy to satisfy the demand for hot water, contrary to misperception among locals.

Simulation Study for the Performance of a Large Solar Hot Water System Constructed by Natural Circulation Solar DHW System Modules

2012 ◽  
Author(s):  
Ru Yang ◽  
Kuan-Hsiang Yu
Keyword(s):  
Numerical Simulation ◽  
Simulation Study ◽  
System Performance ◽  
Natural Circulation ◽  
Water System ◽  
Hot Water ◽  
Operating Parameters ◽  
Theoretical Support ◽  
System Operating

This research is aimed to study the system performance for a large solar hot water system constructed by connecting a series of small domestic natural-circulation systems. This type of large solar hot water system has been recently installed in Taiwan without either practical or theoretical support. There are few studies on this type of large solar hot water system available. This paper presents the numerical simulation study for the control and the system operating parameters effects on the system performance to provide important information both for users and system designers.

scholarly journals Research on solar water heating system based on TRNSYS simulation optimization

2021 ◽  
Vol 69 (4) ◽  
pp. 132
Author(s):  
Yan Yan ◽  
Liyan Zhang ◽  
Yuhan Li ◽  
Xiangyu Xu ◽  
Zhencheng Jiang ◽  
...  
Keyword(s):  
Solar Energy ◽  
Optimal Allocation ◽  
Natural Circulation ◽  
Water System ◽  
Energy System ◽  
Hot Water ◽  
Circulation System ◽  
Water Tank ◽  
Construction Technology ◽  
Forced Circulation

In this paper, the typical system of solar energy system: natural circulation system and forced circulation system are analyzed. The two systems are simulated on the TRNSYS platform, and the configuration of the system itself has been discussed. The purpose is to provide reference for the scientific implementation of solar energy architecture integration. On the basis of summarizing the solar energy construction technology, the natural circulation system and the forced circulation system of solar hot water system have been discussed emphatically. The simulation experiment is designed on the TRNSYS platform. The influence of different heat collection area and water tank volume on solar energy guarantee rate and system efficiency has been discussed by simulation data. Finally, the optimal allocation scheme of natural constraints of natural circulation and forced circulation has been obtained.

scholarly journals Development of the boiler for combustion of agricultural biomass by products

2010 ◽  
Vol 14 (3) ◽  
pp. 707-714 ◽  
Author(s):  
Valentina Turanjanin ◽  
Dejan Djurovic ◽  
Dragoljub Dakic ◽  
Aleksandar Eric ◽  
Branislav Repic
Keyword(s):  
Renewable Energy Sources ◽  
Hot Water ◽  
Electricity Production ◽  
Thermal Engineering ◽  
Total Biomass ◽  
Test Results ◽  
Agricultural Biomass ◽  
Thermal Output ◽  
By Products ◽  
Made In

Republic of Serbia consumes about 15 million tons of equivalent oil per year (Mtoe). At the same time potential of the renewable energy sources is about 3,5 Mtoe/year. Main renewable source is biomass, with its potential of about 2,6 Mtoe/year, and 60% of the total biomass source is of agricultural origin. Mainly, that type of biomass is collected, transported and stored in form of bales. At the same time in one of the largest agricultural companies in Serbia (PKB) there are over 2000 ha of soya plantations, and also 4000 t/year of baled soya straw available, none of which being used for energy purposes. Therefore, efforts have been made in the Laboratory for Thermal Engineering and Energy of the "Vinca" Institute to develop a technology for utilizing bales of various sizes and shapes for energy production. Satisfactory test results of the 1 MW experimental facility - low CO levels and stable thermal output - led to the building-up of a 1.5 MW soya straw bales-fired hot water boiler, with cigarette type of combustion, for the purposes of greenhouse and office heating in the PKB. Further more, achieving good results in exploitation of that hot water boiler, the next step is building up the first combined heat and power (electricity) production facility (CHP), which will use agricultural biomass as a fuel, in Serbia.

Numerical Simulation Study on Supercritical Natural Circulation Flow and Heat Transfer in Narrow Rectangular Channels

2013 ◽  
Author(s):  
Mingqiang Song ◽  
Tao Zhou ◽  
Jingjing Li ◽  
Juan Chen ◽  
Wanxu Cheng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Supercritical Water ◽  
Subcritical Water ◽  
Natural Circulation ◽  
Fluid Velocity ◽  
Engineering Calculation ◽  
Thermal Engineering ◽  
Ansys Cfx ◽  
Rectangular Channels ◽  
Study Parameter

When the model of natural circulation in vertical rectangular channels with gap 1 mm was created, considering the character of supercritical water, the distribution of fluid velocity, temperature and density were obtained with the help of ANSYS CFX. The conclusion is that supercritical density is much lower than that of subcritical water in this study parameter and that the heat transfer ability of supercritical water is higher than that of subcritical water. Futuremore, narrow rectangular channels contribute supercritical fluid to transfer heat, which lay the foundation of accurate supercritical thermal engineering calculation.

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