scholarly journals Thermal-hydraulic modeling of the steady-state operating conditions of a fire-tube boiler

2009 ◽  
Vol 24 (1) ◽  
pp. 29-37 ◽  
Author(s):  
Ahmed Rahmani ◽  
Ahmed Dahia
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Hydraulic Modeling ◽  
Sensitivity Study ◽  
Operating Conditions ◽  
Saturated Steam ◽  
Operating Pressure ◽  
Operating Data ◽  
Boiler Operation ◽  
Calculation Results

In this work, we are interested to simulate the thermal-hydraulic behavior of three-pass type fire-tube boiler. The plant is designed to produce 4.5 tons per hour of saturated steam at 8 bar destined principally for heating applications. A calculation program is developed in order to simulate the boiler operation under several steady-state operating conditions. This program is based upon heat transfer laws between hot gases and the fire-tube internal walls. In the boiler combustion chamber, the heat transfer has been simulated using the well-stirred furnace model. In the convection section, heat balance has been carried out to estimate the heat exchanges between the hot gases and the tube banks. The obtained results are compared to the steady-state operating data of the considered plant. A comparative analysis shows that the calculation results are in good agreement with the boiler operating data. Furthermore, a sensitivity study has been carried out to assess the effects of input parameters, namely the fuel flow rate, air excess, ambient temperature, and operating pressure, upon the boiler thermal performances.

Heat transfer characteristic modelling and the effect of operating conditions on re-cooled cycle for a scramjet

2011 ◽  
Vol 115 (1164) ◽  
pp. 83-90 ◽  
Author(s):  
W. Bao ◽  
J. Qin ◽  
W. X. Zhou
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Transfer Characteristic ◽  
Cooling Capacity ◽  
Sensitivity Study ◽  
Performance Model ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Fuel Flow ◽  
Temperature And Pressure

Abstract A re-cooled cycle has been proposed for a regeneratively cooled scramjet to reduce the hydrogen fuel flow for cooling. Upon the completion of the first cooling, fuel can be used for secondary cooling by transferring the enthalpy from fuel to work. Fuel heat sink (cooling capacity) is thus repeatedly used and fuel heat sink is indirectly increased. Instead of carrying excess fuel for cooling or seeking for any new coolant, the cooling fuel flow is reduced, and fuel onboard is adequate to satisfy the cooling requirement for the whole hypersonic vehicle. A performance model considering flow and heat transfer is build. A model sensitivity study of inlet temperature and pressure reveals that, for given exterior heating condition and cooling panel size, fuel heat sink can be obviously increased at moderate inlet temperature and pressure. Simultaneously the low-temperature heat transfer deterioration and Mach number constrains can also be avoided.

Thermo-structural analysis of a honeycomb-type volumetric absorber for concentrated solar power applications

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Masoud Behzad ◽  
Benjamin Herrmann ◽  
Williams R. Calderón-Muñoz ◽  
José M. Cardemil ◽  
Rodrigo Barraza
Keyword(s):  
Heat Transfer ◽  
Thermal Stress ◽  
Steady State ◽  
Discrete Model ◽  
Continuum Model ◽  
Transient State ◽  
Operating Conditions ◽  
Steady State Condition ◽  
Content Type ◽  
The Continuum

Purpose Volumetric air receivers experience high thermal stress as a consequence of the intense radiation flux they are exposed to when used for heat and/or power generation. This study aims to propose a proper design that is required for the absorber and its holder to ensure efficient heat transfer between the fluid and solid phases and to avoid system failure due to thermal stress. Design/methodology/approach The design and modeling processes are applied to both the absorber and its holder. A multi-channel explicit geometry design and a discrete model is applied to the absorber to investigate the conjugate heat transfer and thermo-mechanical stress levels present in the steady-state condition. The discrete model is used to calibrate the initial state of the continuum model that is then used to investigate the transient operating states representing cloud-passing events. Findings The steady-state results constitute promising findings for operating the system at the desired airflow temperature of 700°C. In addition, we identified regions with high temperatures and high-stress values. Furthermore, the transient state model is capable of capturing the heat transfer and fluid dynamics phenomena, allowing the boundaries to be checked under normal operating conditions. Originality/value Thermal stress analysis of the absorber and the steady/transient-state thermal analysis of the absorber/holder were conducted. Steady-state heat transfer in the explicit model was used to calibrate the initial steady-state of the continuum model.

scholarly journals Test Results of a Polymer Radiator of MTZ-80 Tractor Cooling System

2020 ◽  
Vol 14 (1) ◽  
pp. 55-60
Author(s):  
O. N. Didmanidze ◽  
R. T. Khakimov ◽  
E. P. Parlyuk ◽  
N. A. Bol’shakov
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Cooling System ◽  
Operating Mode ◽  
Aerodynamic Characteristics ◽  
Operating Conditions ◽  
Hydrodynamic Resistance ◽  
Measuring Instruments ◽  
Research Areas ◽  
In Series

Global car manufacturers wish to increase the number of manufactured products, reduce their cost and labor input. The choice of research areas, design and technological developments in radiator construction is an extremely important and urgent task, due to the mass production of radiators for tractors and automobiles on the one hand, and the favorable development prospects of these interrelated industries, on the other. (Research purpose) To substantiate theoretically and experimentally the use of a combined cooling system containing both aluminum and polymeric water radiators and similarly liquid-oil heat exchangers based on the four principles listed above on automobiles and tractors. (Materials and methods) The authors performed bench tests using a special wind tunnel to study the thermal and aerodynamic characteristics of a prototype tractor radiator with a polyurethane core. After reaching the steady-state operating mode of the installation, the experimental values were determined for the control and measuring instruments. (Results and discussion) The authors carried out measurements of all parameters of both coolants in series at each steady-state operating mode of the bench. They obtained the main indicators dependences (reduced heat transfer, aerodynamic and hydraulic drag) of the heat exchanger, close to the operating conditions of the vehicles. (Conclusions) A prototype MTZ-80 radiator with a polyurethane core has great prospects as a future alternative radiator. An increase by 10-15 percent in the radiator heat transfer is possible by using aluminum fi ns on the surface of the polyurethane plate. A 15-20 percent reduction in hydrodynamic resistance is achieved by increasing the diameter of the capillary throughput in a polyurethane plate and the number of plates themselves in the radiator cell.

Jet Engine Gas Path Analysis Based on Takeoff Performance Snapshots

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
A. Putz ◽  
S. Staudacher ◽  
C. Koch ◽  
T. Brandes
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Performance Model ◽  
Operating Conditions ◽  
Medium Size ◽  
Jet Engines ◽  
Transient Effects ◽  
Steady State Analysis ◽  
Simulation Results ◽  
State Analysis

Current engine condition monitoring (ECM) systems for jet engines include the analysis of on-wing gas path data using steady-state performance models. Such data, which are also referred to as performance snapshots, usually are taken during cruise flight and during takeoff. Using steady-state analysis, it is assumed that these snapshots have been taken under stabilized operating conditions. However, this assumption is reasonable only for cruise snapshots. During takeoff, jet engines operate in highly transient conditions with significant heat transfer occurring between the fluid and the engine structure. Hence, steady-state analysis of takeoff snapshots is subject to high uncertainty. Because of this, takeoff snapshots are not used for performance analysis in current ECM systems. We quantify the analysis uncertainty by transient simulation of a generic takeoff maneuver using a performance model of a medium size two-shaft turbofan engine with high bypass ratio. Taking into account the influence of the preceding operating regimes on the transient heat transfer effects, this takeoff maneuver is extended backward in time to cover the aircraft turnaround as well as the end of the last flight mission. We present a hybrid approach for thermal calculation of both the fired engine and the shutdown engine. The simulation results show that takeoff derate, ambient temperature, taxi-out (XO) duration and the duration of the preceding aircraft turnaround have a major influence on the transient effects occurring during takeoff. The analysis uncertainty caused by the transient effects is significant. Based on the simulation results, we propose a method for correction of takeoff snapshots to steady-state operating conditions. Furthermore, we show that the simultaneous analysis of cruise and corrected takeoff snapshots leads to significant improvements in observability.

Validation of Hydrodynamic Stability of Supercritical Once-Through Boiler

2008 ◽  
Author(s):  
Bing Wei ◽  
Dong Zhou
Keyword(s):  
Flow Instability ◽  
Hydrodynamic Instability ◽  
Pressure Head ◽  
Operating Conditions ◽  
Hydrodynamic Characteristics ◽  
Boiler Operation ◽  
Calculation Results ◽  
Low Mass ◽  
The Stability ◽  
Heating Loads

Operating safety is one of the most important things to supercritical once-through boilers. To study the hydrodynamic characteristics of fluid in water walls of supercritical once-through boilers and to find out the instable factors will be of great significance to boiler operation. In this paper the mathematical models for hydrodynamic characteristics of fluid in water walls are established. With an example of 600MW boiler, by using the calculation program, the hydrodynamic characteristics curves without and with the throttles at the inlets of the water walls at different operating conditions are presented, the fluid flow instability and the reasons are analyzed. The calculation results show that the boiler operates stably and safely at 100% MCR (Maximum Continuous Rating) condition, the hydrodynamic instability exists at low heating loads of 30% MCR. The method of installing the throttles at the inlets of the water wall pipes will increase the parabola characteristics, help to improve the fluid instability to a certain stable extent, but due to the small curve slopes at low mass flowrates, still need to pay more attention to the low heating loads operation. The existence of gravity pressure head is good to the stability of the vertical upward flow.

scholarly journals Steady state CFD analysis of heat transfer coefficient in pressurised pipes of super-heater of OP210 steam boiler

2018 ◽  
Vol 240 ◽  
pp. 05008 ◽  
Author(s):  
Mariusz Granda
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Heat Transfer Coefficient ◽  
Steady State ◽  
Transfer Coefficient ◽  
Saturated Steam ◽  
Steam Boiler ◽  
Cfd Analysis ◽  
Convergence Criteria ◽  
Super Heater

The aim of the paper is Computational Fluid Dynamics (CFD) analysis of Wall Heat Transfer Coefficient (WHTC) of pressurized pipe as a part of super-heater of the OP210 boiler. The object of the investigation is convection from saturated steam to the wall of the pipe, which works under high pressure and high temperature. The analysis is an approach to obtain exact solutions of WHTC according to the third type boundary condition compared to direct results from CFD analysis. The paper consists of three-step approach typical for CFD analysis: (i) Pre-Processing, the most elaborated part of the analysis where knowledge about super-heaters, turbulence, velocity profile is important to 3D model, mesh and boundary condition definition. (ii) Simulation of steady state turbulent flow until convergence criteria are met. (iii) Post-Processing where different approaches to the WHTC are shown in comparison. Also, the investigation includes two different types of meshes (where a different number of inflation layers are used) and comparison between k-epsilon and Solid Shear Stress (SST) turbulence model.

Modeling of Heat Transfer in a Moving Packed Bed: Case of the Preheater in Nickel Carbonyl Process

2005 ◽  
Vol 73 (1) ◽  
pp. 47-53 ◽  
Author(s):  
Redhouane Henda ◽  
Daniel J. Falcioni
Keyword(s):  
Heat Transfer ◽  
Packed Bed ◽  
Outer Wall ◽  
Volume Averaging ◽  
Equation Model ◽  
Operating Conditions ◽  
Design Parameters ◽  
Gas Phases ◽  
Calculation Results ◽  
The Difference

Heat transfer in a two-dimensional moving packed bed consisting of pellets surrounded by a gaseous atmosphere is numerically investigated. The governing equations are formulated based on the volume averaging method. A two-equation model, representing the solid and gas phases separately, and a one-equation model, representing both the solid and gas phases, are considered. The models take the form of partial differential equations with a set of boundary conditions, some of which were determined experimentally, and design parameters in addition to the operating conditions. We examine and discuss the parameters in order to reduce temperature differences from pellet to pellet. The calculation results show that by adopting a constant temperature along the preheater outer wall and decreasing the velocity of the pellets in the preheater, the difference in temperature from pellet to pellet is reduced from ∼120°C to ∼55°C, and the thermal efficiency of the preheater is tremendously improved.

Cylindricity Sensitivity Thermal Model of the AGR-5/6/7 Experiment in the Advanced Test Reactor

2020 ◽  
Author(s):  
Grant L. Hawkes
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Thermal Model ◽  
National Laboratory ◽  
Sensitivity Study ◽  
Operating Conditions ◽  
Department Of Energy ◽  
Easy Method ◽  
Gas Gap ◽  
Test Reactor

Abstract The AGR-5/6/7 experiment is currently being irradiated in the Advanced Test Reactor (ATR) at the Idaho National Laboratory and is approximately 70% complete. Several fuel and material irradiation experiments have been planned for the U.S. Department of Energy Advanced Gas Reactor Fuel Development and Qualification Program, which supports the development and qualification of tristructural isotropic (TRISO)-coated particle fuel for use in high-temperature gas-cooled reactors. The goals of these experiments are to provide irradiation performance data to support fuel process development, qualify fuel for normal operating conditions, support development of fuel performance models and codes, and provide irradiated fuel and materials for post-irradiation examination and safety testing. Originally planned and named as separate fuel experiments, but subsequently combined into a single test train, AGR-5/6/7 is testing low-enriched uranium oxycarbide TRISO fuel. The AGR-5/6/7 test train has five capsules with thermocouples and independent gas control mixtures. Unique to this paper is a sensitivity study concerning the cylindricity of the graphite holders containing the fuel compacts and their eccentricity in relation to the stainless-steel capsule walls. Each capsule has small nubs on the outside used for centering the graphite holder inside the stainless-steel capsule with a small gas gap used to control temperature. Due to machining tolerances of these nubs, and vibration wearing the nubs down when the experiment is running in the reactor, the possibility exists that the holder may move around radially. Each capsule is equipped with several thermocouples placed at various radii and depths within each graphite holder. This paper will show the sensitivity of offsetting the graphite holder for various radii in 45-degree increments around the circle with the objective of minimizing the difference between the measured thermocouples and the modeled thermocouple temperatures. Separate gas mixtures of helium/neon are introduced into this gas gap between the holder and capsule wall and changed as necessary to maintain the desired thermocouple temperatures to keep the fuel compacts at a constant temperature as the nuclear reactor conditions change. The goal of the sensitivity study is to find a radius and an angle to offset the holder from perfectly centered for each of the five capsules separately. The complex thermal model includes fission heating, gamma heating, radiation heat transfer, and heat transfer via conduction and radiation across the control gaps. Subroutines linked to the thermal model offer an easy method to offset the graphite holder from the capsule walls without remeshing the entire model.

Enhanced Heat Transfer Structure Design for Ion Dump of EAST-NBI System Based on Hypervapotron

2017 ◽  
Author(s):  
Ling Tao ◽  
Chundong Hu ◽  
Yuanlai Xie
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Energy Deposition ◽  
High Energy ◽  
Operating Conditions ◽  
Quasi Steady State ◽  
Enhanced Heat Transfer ◽  
Steady State Operation ◽  
The Future ◽  
Transfer Structure

Ion dump is an important functional component of the Neutral Beam Injection (NBI) system of Experimental Advanced Superconducting Tokamak (EAST) for absorbing un-neutralized particles deflected by deflection magnets during neutralization, and by means of the corresponding measurement and analyzing method on it, the total energy deposition value and instantaneous energy deposition distribution of the deflected ion beam can be obtained. According to the operation mechanism of the NBI system, ion dump is directly subjected to high-energy particle bombardment for long time, the corresponding heat-loaded on its plates is high, so the temperature rise control is demanding. In order to realize the running power of 2–4MW and running pulse length of more than 100s or even 1000s in the future NBI system, the structure of the ion dump must be designed in accordance with the quasi-steady state operation requirements to provide the guarantee for the steady state operation of EAST system. The Hypervapotron structure based on the subcooled boiling principle is used as an alternative structure to enhance the heat transfer of this high-heat-flux component. According to the operating requirements, space requirements, measurement requirements and beam power distribution characteristics, the engineering design and implementation of ion dump based on the enhanced heat transfer structure is realized for the future long pulse quasi-steady NBI system. The computational results of the heat-fluid-solid coupling simulation based on the two-phase heat transfer are also confirmed the feasibility of the proposed ion dump structure under quasi-steady-state operating conditions. This study is of great significance to explore the optimal heat transfer structure for quasi-steady ion dump to realize the high current, quasi-steady state and high power operation of EAST-NBI system.

scholarly journals Impingement Density Analysis on Heat Transfer and the Appearance of Edge Cracks in Conventional Slab Using Hydraulic Nozzles

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 108
Author(s):  
Alfonso Ruiz-Pineda ◽  
Alicia Aguilar-Corona ◽  
Constantin Alberto Hernández-Bocanegra ◽  
José Ángel Ramos-Banderas ◽  
Gildardo Solorio-Díaz ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Continuous Casting Machine ◽  
Casting Machine ◽  
Major Axis ◽  
Operating Conditions ◽  
Heat Extraction ◽  
Opening Angle ◽  
Operating Pressure ◽  
Density Maps ◽  
Edge Cracks

In this work, the fluid dynamics and heat transfer of two hydraulic nozzles used in the secondary cooling of the conventional slab continuous casting machine were analyzed. Impingement density maps, the jet opening angle and heat flux associated with different operating conditions (impingement distance, pressure) were experimentally determined. The opening angle and impingement density footprint were found to vary considerably in shape and magnitude with varying operating pressure and distances. Finally, it was found that when short operating distances are used, a greater heat extraction gradient occurs in the major axis of the impingement footprint, which promotes edge-cracks in the slab in plant.

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