scholarly journals Simulation of thermal processes in the lining of the ship's boiler

2021 ◽  
pp. 112-116
Author(s):  
В.А. Стенин ◽  
И.В. Ершова ◽  
В.А. Жуков
Keyword(s):  
Heat Exchange ◽  
Temperature Gradient ◽  
Convective Heat Exchange ◽  
Operating Conditions ◽  
Flue Gases ◽  
Working Fluid ◽  
Thermal Processes ◽  
Clear Understanding ◽  
Boiler Furnace ◽  
Stationary Heat

Судовой котлоагрегат подвергается воздействиям высокого давления рабочего тела и температуры дымовых газов. Кроме того работа его осложняется также быстрой и частой сменой нагрузки. Для продолжительной и надёжной работы котлов необходимо обеспечить прочность их конструкций, в частности, футеровки. Судовые котельные агрегаты футеруются огнеупорными материалами, во многом определяющими срок службы котла. При тепловом воздействии на теплоизоляционные материалы футеровки возникают термические напряжения, приводящие к деформации, растрескиванию и разрушению кирпичной кладки. Однако ввиду сложности постановки прямого физического эксперимента пока нет однозначного ответа на вопрос, какие условия способствуют разрушительному тепловому воздействию на футеровку котла. Потому авторы предлагают исследовать тепловые процессы в кирпичной кладке методами математического моделирования. В прикладном пакете ANSYS R17.2 WORKBENCH была создана твердотельная модель элемента футеровки (кирпича), на которой исследовались стационарные и нестационарные процессы теплообмена с граничными условиями первого и третьего рода. В результате экспериментов установлено, что разность деформаций соседних слоев огнеупора пропорциональна градиенту температуры, причём в нестационарных режимах теплообмена величина температурного градиента может значительно превышать его значение в стационарных условиях. Если учесть, что при форсированной нагрузке температура дымовых газов в топочном объёме достигает предельных значений, а интенсивность конвективного теплообмена существенно возрастает, то температурные напряжения, возникающие в футеровке котла, могут превысить предел прочности огнеупора. The ship's boiler unit is exposed to the high pressure of the working fluid and the temperature of the flue gases. The operating conditions are aggravated with rapid and frequent alternations in load. To ensure continuous and reliable operation, boiler and its elements, including lining, design needs to be strong. Ship boilers are lined with fire resistant materials, which lining basically defines lifetime of a boiler. Any heat impact to lining insulation will result in thermal stress that leads to deformation, cracking and destruction of brickwork. However, as direct physical experiment is difficult to conduct, there has been no clear understanding as to what conditions cause destructive thermal impact to the boiler lining. In light of this, the authors propose to investigate thermal processes in brickwork by mathematical modeling methods. Using ANSYS R17.2 WORKBENCH application package, the solid model of the lining element (brick) was created and stationary and non-stationary heat exchange processes with the boundary conditions of the first and third order were investigated. The experiments showed that the difference of deformations of neighboring lining layers was proportional to temperature gradient, yet in non-stationary heat exchange mode the temperature gradient can be significantly higher than that in stationary conditions. Considering that in forced loading mode the temperature of flue gases in boiler furnace can reach its limit and intensity of convective heat exchange increases significantly, the temperature stress that occurs in the boiler lining can exceed the strength of fire resistant brickwork.

DYNAMIC AND THERMAL INTERFERENCE EFFECTS ON TWO NEIGHBOURING BUILDING MODELS

2019 ◽  
Vol 21 (5) ◽  
pp. 138-150
Author(s):  
S. V. Korobkov ◽  
A. I. Gnyrya ◽  
V. I. Terekhov
Keyword(s):  
Heat Exchange ◽  
Mutual Effect ◽  
Convective Heat Exchange ◽  
Physical Models ◽  
Interference Effects ◽  
Total Contribution ◽  
Heat Flows ◽  
Building Models ◽  
Number Of Factors ◽  
Thermal Interference

The paper considers the dynamic and thermal interference effects on two neighbouring building models in the form of square prisms arranged at a short distance from each other. It is shown how relative positions of the models affect the specific phenomena caused by the airflow interactions.The aim of this paper is to experimentally study the dynamic and thermal interference of a tandem of two building models in the form of square prisms depending on their relative position.The phenomenon of wind loads on buildings and structures has always attracted great interest among engineers and researchers. With the accumulation of knowledge and technical capabilities, the potential for likely ways to study wind flows and their impact on different objects increased. In recent years, the world science has accumulated an extensive knowledge base on wind impacts on objects of various shapes, such as prisms, pyramids, cylinders, etc. Studies are carried out for their mutual impact of several objects on changes in both the wind load and heat exchange. Their mutual effect on the air motion and turbulence is considered.There are two main areas in the field of the wind impact. The first impact is the force load on building, the second is the wind as a source of convective heat exchange. The object of this study is the interference parameters allowing to assess the influence on the field of pressure and heat recoil of disturbances evoked in front of the barriers.At the first stage, physical models help to study the pressure field on different facets and ratios of the local and medium heat exchange under the forced convection conditions. The next step is to jointly consider the wind (dynamic) load and heat flows, attempting to detect the total contribution to changes depending on the reciprocal model arrangement. All experiments are performed in the aerodynamic tube, at the TSUAB department. It is shown that the dynamic and thermal interference ratios vary greatly in two building models. At the same time, the thermal interference is very conservative compared to the dynamic. Using the interference parameters, it is easy to analyze the extreme pressure and the heat flow on the model surface depending on a large number of factors, including their arrangement.

scholarly journals Large Eddy Simulations of Strongly Non-Ideal Compressible Flows through a Transonic Cascade

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 772
Author(s):  
Jean-Christophe Hoarau ◽  
Paola Cinnella ◽  
Xavier Gloerfelt
Keyword(s):  
Compressible Flows ◽  
Flow Behavior ◽  
Pressure Ratio ◽  
Organic Rankine Cycle ◽  
Ideal Gas ◽  
Operating Conditions ◽  
Large Eddy Simulations ◽  
Working Fluid ◽  
Viscous Effects ◽  
Large Eddy

Transonic flows of a molecularly complex organic fluid through a stator cascade were investigated by means of large eddy simulations (LESs). The selected configuration was considered as representative of the high-pressure stages of high-temperature Organic Rankine Cycle (ORC) axial turbines, which may exhibit significant non-ideal gas effects. A heavy fluorocarbon, perhydrophenanthrene (PP11), was selected as the working fluid to exacerbate deviations from the ideal flow behavior. The LESs were carried out at various operating conditions (pressure ratio and total conditions at inlet), and their influence on compressibility and viscous effects is discussed. The complex thermodynamic behavior of the fluid generates highly non-ideal shock systems at the blade trailing edge. These are shown to undergo complex interactions with the transitional viscous boundary layers and wakes, with an impact on the loss mechanisms and predicted loss coefficients compared to lower-fidelity models relying on the Reynolds-averaged Navier–Stokes (RANS) equations.

scholarly journals Sensitivity Analysis of OTEC-CC-MX-1 kWe Plant Prototype

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2585
Author(s):  
Jessica Guadalupe Tobal-Cupul ◽  
Estela Cerezo-Acevedo ◽  
Yair Yosias Arriola-Gil ◽  
Hector Fernando Gomez-Garcia ◽  
Victor Manuel Romero-Medina
Keyword(s):  
Sensitivity Analysis ◽  
Experimental Tests ◽  
Caribbean Sea ◽  
Ocean Model ◽  
Operating Conditions ◽  
Working Fluid ◽  
Ocean Energy ◽  
Mexican Caribbean ◽  
Water Temperature Data ◽  
Mass Flows

The Mexican Caribbean Sea has potential zones for Ocean Thermal Energy Conversion (OTEC) implementation. Universidad del Caribe and Instituto de Ciencias del Mar y Limnologia, with the support of the Mexican Centre of Innovation in Ocean Energy, designed and constructed a prototype OTEC plant (OTEC-CC-MX-1 kWe), which is the first initiative in Mexico for exploitation of this type of renewable energy. This paper presents a sensitivity analysis whose objective was to know, before carrying out the experimental tests, the behavior of OTEC-CC-MX-1 kWe regarding temperature differences, as well as the non-possible operating conditions, which allows us to assess possible modifications in the prototype installation. An algorithm was developed to obtain the inlet and outlet temperatures of the water and working fluid in the heat exchangers using the monthly surface and deep-water temperature data from the Hybrid Coordinate Ocean Model and Geographically Weighted Regression Temperature Model for the Mexican Caribbean Sea. With these temperatures, the following were analyzed: fluctuation of thermal efficiency, mass flows of R-152a and water and power production. By analyzing the results, we verified maximum and minimum mass flows of water and R-152a to produce 1 kWe during a typical year in the Mexican Caribbean Sea and the conditions when the production of electricity is not possible for OTEC-CC-MX-1 kWe.

scholarly journals Component-Oriented Modeling of a Micro-Scale Organic Rankine Cycle System for Waste Heat Recovery Applications

2021 ◽  
Vol 11 (5) ◽  
pp. 1984
Author(s):  
Ramin Moradi ◽  
Emanuele Habib ◽  
Enrico Bocci ◽  
Luca Cioccolanti
Keyword(s):  
Electric Power ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pump Efficiency ◽  
Micro Scale

Organic Rankine cycle (ORC) systems are some of the most suitable technologies to produce electricity from low-temperature waste heat. In this study, a non-regenerative, micro-scale ORC system was tested in off-design conditions using R134a as the working fluid. The experimental data were then used to tune the semi-empirical models of the main components of the system. Eventually, the models were used in a component-oriented system solver to map the system electric performance at varying operating conditions. The analysis highlighted the non-negligible impact of the plunger pump on the system performance Indeed, the experimental results showed that the low pump efficiency in the investigated operating range can lead to negative net electric power in some working conditions. For most data points, the expander and the pump isentropic efficiencies are found in the approximate ranges of 35% to 55% and 17% to 34%, respectively. Furthermore, the maximum net electric power was about 200 W with a net electric efficiency of about 1.2%, thus also stressing the importance of a proper selection of the pump for waste heat recovery applications.

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