Boiler Evaporation Tubes with Variable Inner Diameters
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Solution Overview
Problem
Conventional supercritical variable pressure once-through boilers face challenges in optimizing tube inner diameter and managing pressure drop, leading to increased auxiliary power, running costs, and reduced flow stability due to uniform tube diameters, which are not adaptable to varying heat flux conditions.
Innovation Solution
The boiler structure employs a combination of boiler evaporation tubes with varying wall thicknesses and inner diameters adjusted based on the furnace heat flux, using rifled tubes in high heat flux regions and smooth tubes in low heat flux regions to optimize tube inner diameters and reduce pressure drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the tube inner diameter is uniformly set large to reduce the overall velocity, then the frictional loss component of pressure drop is reduced and flow stability is improved, but the tube inner diameter cannot be optimized for regions with varying heat flux and auxiliary power increases
Solution Approach 1:
The patent applies local quality by varying the tube inner diameter according to the local heat flux conditions in different furnace regions. Tubes in high heat flux regions (burner area) have smaller inner diameters to maintain appropriate flow velocity and heat transfer characteristics, while tubes in low heat flux regions have larger inner diameters to reduce frictional loss and pressure drop. This localized optimization resolves the contradiction between maintaining flow stability and reducing auxiliary power consumption.
Solution Approach 2:
The patent changes the geometric parameter (tube inner diameter) along the flow direction to optimize performance. By progressively increasing the tube inner diameter from the burner region upward through the furnace, the design adapts to changing heat flux conditions, maintaining efficient heat transfer where needed while minimizing pressure drop and frictional losses in lower heat flux regions, thereby reducing auxiliary power requirements.
2Reliability
If the tube inner diameter is uniformly set small to increase the velocity, then the heat transfer characteristics are ensured, but the pressure drop increases and flow stability deteriorates
Solution Approach 1:
The patent applies local quality by setting smaller tube inner diameters specifically in regions where high heat transfer is required (burner and high heat flux zones), while using larger diameters in regions where heat transfer demands are lower. This ensures adequate heat transfer characteristics are maintained locally without incurring excessive pressure drop and energy losses throughout the entire tube system.
Solution Approach 2:
The patent changes the tube inner diameter parameter along the vertical direction of the furnace to balance heat transfer requirements against pressure drop considerations. The diameter is optimized at each section to provide sufficient velocity for heat transfer while limiting frictional losses, thereby reducing overall energy loss.
3Reliability
If the tube inner diameter is uniformly determined based on the highest heat flux region, then sufficient durability is ensured in high heat flux regions, but the pressure drop cannot be optimized and auxiliary power increases
Solution Approach 1:
The patent applies local quality by determining tube inner diameter based on local heat flux conditions rather than uniformly based on the maximum heat flux region. Tubes in high heat flux regions are sized to ensure durability and adequate heat transfer, while tubes in lower heat flux regions have larger diameters to minimize pressure drop and reduce auxiliary power consumption, optimizing the overall system performance.
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 approach reduces pressure drop, decreases auxiliary power requirements, and enhances flow stability and natural circulation characteristics by optimizing tube diameters according to heat flux variations, thereby improving operational efficiency and reducing boiler size and costs.
Implementation Method 1
water pumped into the boiler evaporation tubes from one end thereof flows in one direction without circulating therein and turns into steam
Implementation Method 2
water pumped into the boiler evaporation tubes from one end thereof flows in one direction without circulating therein and turns into steam
Implementation Method 3
it is preferable that the boiler evaporation tubes are appropriately used by using a rifled tube in a region with a high furnace heat flux
Data Source
AI summary
Provided is a boiler structure with which, by reducing the pressure drop in boiler evaporation tubes correspondingly to the heat flux, which varies in accordance with the distance in the boiler height direction, it is possible to reduce auxiliary power for a water feed pump and so forth, in addition to improving the flow stability and the natural circulation characteristics. The boiler structure includes a number of boiler evaporation tubes that are arranged on a wall surface of a furnace and that form a furnace wall, water pumped into the boiler evaporation tubes being heated in the furnace during flowing inside the tubes to produce steam, wherein the boiler evaporation tubes are formed by connecting tubes of a plurality of types, in which tube wall thicknesses are adjusted on the basis of furnace heat flux such that the higher the furnace heat flux in a region is, the smaller the tube inner diameter becomes.