Steam Generator Preheating Layout to Prevent Tube Overheating
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Solution Overview
Problem
In steam generators with high steam outputs and pressures, uneven distribution of partially evaporated medium to downstream steam generator tubes can lead to overheating and pipe damage due to excessive vapor content in the intermediate collector, reducing the service life and increasing repair needs.
Innovation Solution
The flow medium at the inlet of the inner wall upstream of the intermediate collector has a lower temperature than at the inlet of the enclosing wall, achieved through a preheating device design with different heat inputs for the inner and surrounding walls, using bypass lines and preheaters to control the temperature and prevent two-phase mixtures in the intermediate collector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the flow medium is preheated uniformly before entering the evaporator, then the efficiency of the steam generation process is improved, but vapor content in the intermediate collector increases causing uneven distribution and overheating of tubes
Solution Approach 1:
The preheating device is designed to provide different heat inputs to different flow paths. The first preheating device heats the flow medium for the enclosing wall to a higher temperature, while the second preheating device heats the flow medium for the inner wall to a lower temperature. This local differentiation prevents excessive vapor content in the intermediate collector while maintaining overall efficiency.
Solution Approach 2:
The preheating device is segmented into at least two separate preheating units with different heating capacities. The first preheating device is connected to the flow medium inlet for the enclosing wall, and the second preheating device is connected to the flow medium inlet for the inner wall. This segmentation allows independent temperature control for each path.
2Productivity
If inner walls are arranged inside the combustion chamber to increase heat exchange area, then steam output is improved, but intermediate collector becomes necessary causing flow distribution problems
Solution Approach 1:
Different temperature control strategies are applied to different parts of the system. The enclosing wall receives higher temperature flow medium, while the inner wall receives lower temperature flow medium. This local quality differentiation allows the intermediate collector to function properly without causing overheating, enabling the complex multi-wall configuration to achieve high steam output reliably.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively prevents overheating of steam generator tubes, ensuring a longer service life and higher efficiency while maintaining structural simplicity, allowing for reliable operation in both subcritical and supercritical pressure conditions.
Implementation Method 1
The preheating device (16) is designed in such a way that the flow medium intended for the entry of the inner wall (4) upstream of the intermediate collector (6) experiences a lower heat input than the flow medium intended for the entry of the enclosing wall (2)
Implementation Method 2
these steam generator tubes initially form an evaporator into which unevaporated medium is introduced and evaporated
Implementation Method 3
the flow medium—usually water—is located in steam generator tubes
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a steam generator (1) comprising a combustion chamber having a peripheral wall (2) formed at least partially from gas-proof, welded steam generator pipes, at least two additional inner walls (4, 8) formed at least partially from additional steam generator pipes which are arranged inside the combustion chamber, and said inner walls are connected one behind the other on the flow medium side by an intermediate collector (6). The aim of the invention is to provide a steam generator which has a particularly high service life and is particularly reliable. Said flow medium on the inlet (12) of the inner wall (4) upstream of the intermediate collector (6) has a lower temperature than that of the flow medium on an inlet (10) of the peripheral wall (2).