scholarly journals Design of a natural circulation circuit for 85 MW steam boiler

2017 ◽  
Vol 21 (3) ◽  
pp. 1503-1513 ◽  
Author(s):  
Konstantin Pleshanov ◽  
Ekaterina Khlyst ◽  
Mikhail Zaichenko ◽  
Kirill Sterkhov
Keyword(s):  
Natural Circulation ◽  
Steam Pressure ◽  
Point Of View ◽  
Steam Boiler ◽  
Heat Absorption ◽  
Simple Circuit ◽  
Two Phase ◽  
Circulation Circuit ◽  
Boiler Designer ◽  
Research And Design

The paper describes research and design of fluidized bed steam boiler natural circulation circuit. The capacity of the drum boiler is 85 MW, superheated steam pressure is 98 bar. There are two variants research results of the designed circulation circuit. The first circulation circuit variant was designed as a complex circuit with a common downcomers and risers for the boiler evaporating screen. In the second variant the flow is separately supplied to and discharged from the evaporator that is divided into independent sections. We have researched and described the influence of heat absorption inequality on the furnace evaporation pads using the Boiler Designer software. We also have calculated main characteristics of the two-phase flow in the evaporation pads and evaluated reliability of the natural circulation. The circulation circuit is optimized from point of view of reliability and metal expenses. Results demonstrate that the specific quantity of metal of complex and simple circuit variants is approximately the same with equal reliability.

Numerical Aspects on the Prediction of Stability Boundaries of Two-Phase Natural Circulation Circuits, Considering Flashing Evaluation

2005 ◽  
Vol 73 (6) ◽  
pp. 911-922
Author(s):  
P. Zanocco ◽  
D. Delmastro ◽  
M. Giménez
Keyword(s):  
Numerical Integration ◽  
Natural Circulation ◽  
Stability Limit ◽  
Linearization Method ◽  
Test Case ◽  
Implicit Methods ◽  
Two Phase ◽  
Circulation Circuit ◽  
Wide Range ◽  
The Stability

In this work, the stability of a two-phase, natural circulation circuit is analyzed, using a specially developed model. This thermohydraulic model results in a set of coupled, nonlinear, first-order partial differential equations, which are solved by means of the up-wind finite difference method, using combinations of explicit and implicit methods for the numerical integration of the different balance equations. An adaptive nodalization scheme is implemented, minimizing the error of the propagation of small perturbations through the discretized volumes and especially the ones having two-phase flow regime. A linearization method is implemented by means of numerical perturbations. Frequency domain calculations are carried out, allowing a rapid visualization of the stability of the linearized system. Two cases are analyzed: a test case, where the code is compared in a wide range of qualities with an analytical model, and an application case, where the model is used to analyze the stability of an integral reactor cooled by natural circulation. The CAREM prototype is taken as a reference. In both cases, the numerical diffusion and integration errors are analyzed in the stability limit prediction by means of a convergence analysis using different nodalization and numerical integration criteria.

Experimental study on saturated boiling of two phase natural circulation under low pressure in narrow rectangular channels

Kerntechnik ◽  
2017 ◽  
Vol 82 (6) ◽  
pp. 631-636
Author(s):  
Li Zi-chao ◽  
Qi Shi ◽  
Zhou Tao ◽  
Li Bing ◽  
Muhammad Ali Shahzad ◽  
...  
Keyword(s):  
Experimental Study ◽  
Natural Circulation ◽  
Low Pressure ◽  
Two Phase ◽  
Rectangular Channels ◽  
Saturated Boiling

The REPAS Study: Reliability Evaluation of Passive Safety Systems

2002 ◽  
Author(s):  
M. E. Ricotti ◽  
F. Bianchi ◽  
L. Burgazzi ◽  
F. D’Auria ◽  
G. Galassi
Keyword(s):  
Initial Conditions ◽  
Natural Circulation ◽  
Quantitative Information ◽  
External Input ◽  
Passive System ◽  
Two Phase ◽  
Passive Safety Systems ◽  
Safety Systems ◽  
Physical Laws ◽  
Physical Phenomena

The strategy of approach to the problem moves from the consideration that a passive system should be theoretically more reliable than an active one. In fact it does not need any external input or energy to operate and it relies only upon natural physical laws (e.g. gravity, natural circulation, internally stored energy, etc.) and/or “intelligent” use of the energy inherently available in the system (e.g. chemical reaction, decay heat, etc.). Nevertheless the passive system may fail its mission not only as a consequence of classical mechanical failure of components, but also for deviation from the expected behaviour, due to physical phenomena mainly related to thermalhydraulics or due to different boundary and initial conditions. The main sources of physical failure are identified and a probability of occurrence is assigned. The reliability analysis is performed on a passive system which operates in two-phase, natural circulation. The selected system is a loop including a heat source and a heat sink where the condensation occurs. The system behavior under different configurations has been simulated via best-estimate code (Relap5 mod3.2). The results are shown and can be treated in such a way to give qualitative and quantitative information on the system reliability. Main routes of development of the methodology are also depicted.

Experimental Investigation on Droplet Behavior in a Transonic Compressor Cascade

2014 ◽  
Vol 137 (3) ◽  
Author(s):  
Niklas Neupert ◽  
Birger Ober ◽  
Franz Joos
Keyword(s):  
Experimental Investigation ◽  
Gas Turbines ◽  
Surface Film ◽  
Flow Channel ◽  
Point Of View ◽  
Compressor Cascade ◽  
Two Phase ◽  
Transonic Compressor ◽  
Droplet Behavior ◽  
Industrial Gas Turbines

In recent years, overspray fogging has become a powerful means for power augmentation of industrial gas turbines (GT). Most of the studies concerning this topic focus on the problem from a thermodynamic point of view. Only a few studies, however, were undertaken to investigate the droplet behavior in the flow channel of a compressor. In this paper, results of experimental investigation of a water laden flow through a transonic compressor cascade are presented. A finely dispersed spray was used in the measurements (D10 < 10 μm). Results of the droplet behavior are shown in terms of shadowgraphy images and images of the blade surface film pattern. The angle of attack, the incoming velocity, and the water load were varied. The qualitative observations are related to laser Doppler and phase Doppler anemometer (LDA/PDA) data taken in the flow channel and at the outlet of the cascade. The data represent a base for numerical and mean line models of two-phase compressor flow.

A Natural Circulation Model of the Closed Loop, Two-Phase Thermosyphon for Electronics Cooling

2001 ◽  
Author(s):  
S. I. Haider ◽  
Yogendra K. Joshi ◽  
Wataru Nakayama
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Closed Loop ◽  
Two Phase Flow ◽  
Natural Circulation ◽  
Saturation Temperature ◽  
Electronics Cooling ◽  
Phase Flow ◽  
Two Phase

Abstract The study presents a model for the two-phase flow and heat transfer in the closed loop, two-phase thermosyphon (CLTPT) involving co-current natural circulation. Most available models deal with two-phase thermosyphons with counter-current circulation within a closed, vertical, wickless heat pipe. The present research focuses on CLTPTs for electronics cooling that face more complex two-phase flow patterns than the vertical heat pipes, due to closed loop geometry and smaller tube size. The present model is based on mass, momentum, and energy balances in the evaporator, rising tube, condenser, and the falling tube. The homogeneous two-phase flow model is used to evaluate the friction pressure drop of the two-phase flow imposed by the available gravitational head through the loop. The saturation temperature dictates both the chip temperature and the condenser heat rejection capacity. Thermodynamic constraints are applied to model the saturation temperature, which also depends upon the local heat transfer coefficient and the two-phase flow patterns inside the condenser. The boiling characteristics of the enhanced structure are used to predict the chip temperature. The model is compared with experimental data for dielectric working fluid PF-5060 and is in general agreement with the observed trends. The degradation of condensation heat transfer coefficient due to diminished vapor convective effects, and the presence of subcooled liquid in the condenser are expected to cause higher thermal resistance at low heat fluxes. The local condensation heat transfer coefficient is a major area of uncertainty.

Analysis of Hydrodynamics and Mass Transfer of Gas-Liquid and Liquid-Liquid Taylor Flows in Microchannels

2019 ◽  
pp. 1-49
Author(s):  
Rufat Abiev
Keyword(s):  
Mass Transfer ◽  
Point Of View ◽  
Process Conditions ◽  
Two Phase ◽  
Physical Point ◽  
Micro Channels ◽  
Liquid Systems ◽  
Simplifying Assumptions ◽  
Liquid Flows ◽  
Solid Liquid

Analysis of hydrodynamics and mass transfer Taylor flows in micro channels of both gas-liquid and liquid-liquid systems on the basis of classical theoretical approach with some simplifying assumptions was performed. Results of theoretical analysis for description of hydrodynamic parameters and mass transfer characteristics were confirmed by comparison with the author's own and available in literature experimental data. It was shown that the main parameters of two-phase Taylor flows could be quite precisely described theoretically: mean bubble/droplet velocity, liquid film thickness, real gas holdup (which is always smaller than so-called dynamic holdup), pressure drop. Peculiarities of liquid-liquid flows compared to gas-liquid Taylor flows in capillaries are discussed. Wettability effect on hydrodynamics was examined. Tools of mass transfer intensification of gas-liquid and liquid-liquid Taylor flow in micro channels are analyzed. Three-layer model for heat and mass transfer has been proposed and implemented for the case of solid-liquid mass transfer for gas-liquid Taylor flows; optimal process conditions for this process are found theoretically and discussed from physical point of view.

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