Study of circulation ratio for natural circulation in water-tube boiler at different operating conditions.
01 Feb 2020-Vol. 1473, Iss: 1, pp 012026
TL;DR: In this paper, the authors identify the desired circulation ratio for the natural circulation of water tube boilers in different operating conditions, which is one of the most important design parameters as other design parameters like critical heat flux and skin temperature are mainly derived from the circulation ratio.
Abstract: The basic objective of the paper is to identify the desired circulation ratio for the natural circulation of water tube boilers in different operating conditions. This requires the basic study of heat flux and the mode of the boiling heat transfer, and the phenomenon like departure from nucleate boiling and tube overheating. The parameters, which need to be studied are heat flux, pressure, dryness fraction, void fraction, liquid velocity and their impact on the required circulation ratio. For a natural circulation boiler, the circulation ratio is one of the most important design parameters as the other design parameter like critical heat flux and skin temperature are mainly derived from the circulation ratio. The required circulation ratio can vary with the boiler pressure, liquid velocity and maximum heat flux. This study is intended to provide input for the safe and optimum design of a natural circulation boiler.
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TL;DR: In this paper, the authors present a developed computational procedure capable of sizing and analyzing the performance of natural circulation package boilers to meet a specific load, and determine the impact of heat flux, friction factor and tube plugging on the circulation ratio and wall temperature.
Abstract: The published literature on natural circulation in package boilers lacks a model that performs calculations for each circuit and determines circulation parameters for all circuits. This study presents a developed computational procedure capable of sizing and analyzing the performance of natural circulation package boilers to meet a specific load. Also; the study identifies the most critical circuit of a package boiler and determines the impact of heat flux, friction factor and tube plugging on the circulation ratio and wall temperature. The model was validated by comparing its results with experimental data. The results revealed that the Circuit 3 (The D-Tubes) is the most critical circuit. Plugging some of these tubes reduces the circulation ratio and increases the tube wall temperature significantly. The results indicate that the circulation ratio decreased by 20% and the wall temperature increased by 9.6% as a result of increase in the heat flux by 24%.
2 citations
TL;DR: In this paper, the critical situations in a furnace of a subcritical drum boiler were investigated and it was shown that by moving to higher altitudes of the investigated furnace, its water wall tubes were more sensitive to heat flux distribution, which consequently increased the possibility of dryness phenomenon and failure of the tubes.
1 citations
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TL;DR: A review of flow instabilities in boiling natural circulation systems has been carried out in this article, where an attempt has been made to classify the instabilities occurring in natural circulation system similar to that in forced convection boiling systems.
Abstract: Several decades have been spent on the study of flow instabilities in boiling two-phase natural circulation systems It is felt to have a review and summarize the state-of-the-art research carried out in this area, which would be quite useful to the design and safety of current and future light water reactors with natural circulation core cooling With that purpose, a review of flow instabilities in boiling natural circulation systems has been carried out An attempt has been made to classify the instabilities occurring in natural circulation systems similar to that in forced convection boiling systems The mechanism of instabilities occurring in two-phase natural circulation systems have been explained based on these classifications The characteristics of different instabilities as well as the effects of different operating and geometric parameters on them have been reviewed
75 citations
TL;DR: In this article, the authors describe the design of fluidized bed steam boiler natural circulation circuit and the main characteristics of the two-phase flow in the evaporation pads and evaluated reliability of the natural circulation.
Abstract: 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.
11 citations