Forced-flow steam generator tube throttle design
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Solution Overview
Problem
Once-through steam generators with vertical steam generator tubes experience impermissibly high temperatures due to insufficient heat dissipation, leading to potential tube wall destruction, caused by low mass flow and incomplete mixing of the water-steam mixture, especially in corner tubes with low heat input and low steam content.
Innovation Solution
Incorporating a throttle device, designed as an orifice plate, in each steam generator tube downstream of the through-flow header to increase frictional pressure loss and ensure sufficient heat dissipation by weakening the natural circulation characteristic and maintaining a sufficient pressure difference for flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If steam generator tubes are arranged vertically with through-flow headers for natural circulation, then ease of operation is improved, but temperature distribution becomes uneven causing impermissibly high temperatures in individual tubes
Solution Approach 1:
The patent applies local quality by installing individual throttle devices in specific steam generator tubes, particularly in corner tubes and tubes with unfavorable flow conditions. This localized intervention creates different flow resistance characteristics in specific tubes to balance the overall temperature distribution while preserving natural circulation in the system.
Solution Approach 2:
The patent changes the flow resistance parameter by introducing throttle devices with specific opening sizes and positions. This parameter modification alters the pressure drop characteristics in individual tubes, redistributing the flow to achieve more uniform heat dissipation and temperature distribution across all tubes.
2Temperature
If throttle devices are installed in steam generator tubes to increase frictional pressure loss, then temperature uniformity is improved, but device complexity increases
Solution Approach 1:
Rather than uniformly installing throttle devices in all tubes, the patent applies them selectively in specific locations where flow imbalance and temperature issues occur, such as corner tubes and tubes with low steam content. This targeted approach achieves temperature uniformity while minimizing the increase in device complexity.
3Temperature
If mass flow in steam generator tubes is increased to improve heat dissipation, then temperature control is improved, but pressure difference required for flow increases
Solution Approach 1:
The patent modifies the pressure drop parameter by introducing controlled frictional losses through throttle devices. This parameter change allows the system to maintain adequate mass flow for heat dissipation while operating within the available pressure difference, effectively decoupling the direct proportionality between flow rate and pressure requirement.
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
The arrangement of throttle devices in steam generator tubes prevents excessive temperatures and ensures adequate heat dissipation, thereby extending the service life and reducing repair susceptibility of the steam generator.
Implementation Method 1
the respective throttle device (18) arranged at the upper outlet of the enclosing wall (4) and designed as a screen. This allows a particularly simple local reduction in the nominal width of the relevant steam generator pipe and thus a simple increase in the frictional pressure loss
Implementation Method 2
insufficient dissipation of the incoming heat through the flow medium
Implementation Method 3
pressure equalization is achieved between the steam generator tubes connected in parallel
Data Source
Figure 1
Figure 2
AI summary
A forced-flow steam generator (1) having a surrounding wall (4) formed from steam generator pipes (2) which are welded in a gas-tight fashion and traversable by flow in the vertical direction, in which within the surrounding wall (4) there is arranged a passage collector (14) by means of which the outlet side of a first multiplicity of steam generator pipes (2) in parallel configuration is connected at the flow medium side to the inlet side of a second multiplicity, in series configuration with and downstream of the first multiplicity, of steam generator pipes (2) in parallel configuration, should have a particularly long service life and particularly low susceptibility to faults, independently of the operating state. For this purpose, the steam generator pipes (16) arranged downstream of the passage collector (14) have in each case one restrictor device (18).