Steam Generator Mixing Chamber for Temperature Equalization
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Solution Overview
Problem
Once-through steam generators with two-pass boilers experience incomplete mixing of flow medium, leading to temperature imbalances and potential material damage due to high temperature stresses, which existing designs fail to adequately address through flow distribution and material selection.
Innovation Solution
The steam generator tubes are connected in a novel configuration where flow medium from lower heating surface segments is mixed with that from upper segments, increasing mass flow density and temperature equalization by using collectors and downpipes to distribute the flow medium across the combustion chamber walls, particularly enhancing cooling for the upper front and rear walls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the through-flow collector is used to connect lower and upper section tubes, then complete pressure equalization is achieved, but incomplete mixing of flow medium occurs leading to temperature imbalances
Solution Approach 1:
The system divides the flow medium distribution into separate pathways: one for pressure equalization (through-flow collector) and another for flow mixing (mixing chamber). This segmentation allows each function to be optimized independently, resolving the contradiction between maintaining pressure equality and achieving complete flow mixing.
Solution Approach 2:
A mixing chamber is introduced as an intermediary element between the lower and upper section tubes. This intermediary provides a dedicated space where flow medium from different tubes can mix completely before entering the upper sections, eliminating temperature imbalances while the through-flow collector separately handles pressure equalization.
2Strength
If higher-alloy materials like T23 or T24 are used for enclosing walls, then resistance to high temperature stresses is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The invention changes the flow distribution parameters (mass flow density, flow mixing) to achieve more uniform temperature distribution in the enclosing walls. By optimizing the hydraulic parameters through the mixing chamber and downpipe system, the thermal stress on materials is reduced, allowing the use of conventional materials instead of complex higher-alloy materials.
3Temperature
If mass flow density is increased to improve flow distribution, then temperature equalization improves, but risk of flow stagnation in upper vertical tubing increases
Solution Approach 1:
The mixing chamber performs preliminary mixing of flow medium from multiple lower section tubes before the combined flow enters the upper vertical tubing. This preliminary action ensures that the flow is already well-mixed and maintains momentum, preventing stagnation while achieving temperature equalization through the increased mass flow density in the upper sections.
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 configuration significantly improves cooling and reduces temperature imbalances, allowing for safer operation with lower outlet temperatures and reduced material stress, potentially eliminating the need for higher-alloy materials like T23 and T24, and enabling operation at higher live steam temperatures.
Implementation Method 1
the flow medium from lower heating surface segments is mixed with that from upper segments, increasing mass flow density and temperature equalization
Implementation Method 2
significantly improves cooling and reduces temperature imbalances, allowing for safer operation with lower outlet temperatures and reduced material stress
Data Source
Figure 1
AI summary
The invention relates to a continuous flow steam generator comprising a combustion chamber (1), which has a substantially rectangular cross-section and a lower and an upper combustion chamber region (11, 12), and comprising a horizontal gas pass (2) connected downstream of the combustion chamber (1) on the flue-gas side. Gas-tight and gas-permeable peripheral walls (S, F, R, N, G) of the continuous flow steam generator are completely or partly made of steam generator pipes (10) which are welded together and through which a flow medium can flow, and collectors (31-40) are arranged and connected to the steam generator pipes such that groups of steam generator pipes connected in parallel form heating surface segments (H1-H10) of the peripheral walls (S, F, R, N, G). First passage collectors (31, 33, 34) are arranged and connected such that the flow medium from first heating surface segments (H1, H2) of two parallel first peripheral walls of the lower combustion chamber region (11) can be mixed with the fluid medium from second heating surface segments (H9, H10) of second peripheral walls, standing perpendicular to the first peripheral walls, of the upper combustion chamber region (12).