Alternating Notch Heat Transfer Sheets for Rotary Preheaters
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Solution Overview
Problem
Conventional rotary regenerative air preheaters suffer from low heat transfer efficiency and increased pressure drop due to uninterrupted high-velocity flow and flow stagnation areas, which reduce overall efficiency and require higher fan power, especially with heavy heat transfer sheet assemblies.
Innovation Solution
The use of heat transfer sheets with alternating notch configurations, featuring first and second lobes connected in a common flow channel, and transition regions that create turbulent flow and mitigate stagnation areas, enhancing heat transfer efficiency while maintaining structural support and minimizing pressure loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional sheet spacing features are used to position adjacent sheets apart, then structural integrity is maintained, but heat transfer efficiency remains low due to uninterrupted high-velocity flow
Solution Approach 1:
The patent applies local quality by creating asymmetric notch configurations with varying depths and positions on different sheets. Specific notches are strategically placed to generate controlled turbulence in high-heat-transfer zones while maintaining smooth flow in other areas, thereby improving heat transfer efficiency without significantly increasing pressure drop
Solution Approach 2:
The patent employs curved and rounded notch features rather than sharp angular configurations. The rounded notches create gradual flow transitions that induce turbulence beneficial for heat transfer while avoiding abrupt flow separation that would increase pressure drop and create stagnation zones
2Loss of energy
If turbulent flow is induced through channels to increase heat transfer efficiency, then heat transfer improves, but pressure drop increases
Solution Approach 1:
The patent creates localized turbulence only in specific regions where heat transfer benefits are maximized, rather than inducing turbulence throughout the entire flow path. The asymmetric notch configurations are positioned to generate vortices and mixing in high-temperature zones while maintaining streamlined flow in lower-temperature regions, thus improving heat transfer efficiency without proportionally increasing pressure drop
Solution Approach 2:
The patent applies partial action by inducing turbulence only to the extent necessary for improved heat transfer. The notch configurations are designed with specific dimensions and spacing that generate sufficient turbulence for enhanced heat transfer while avoiding excessive turbulence that would cause unacceptable pressure losses
3Loss of energy
If abrupt contour changes are made in heat transfer sheets to create turbulence, then heat transfer efficiency increases, but flow stagnation areas accumulate particles
Solution Approach 1:
The patent uses rounded and curved notch configurations instead of sharp angular features. The rounded contours create gradual flow transitions that induce beneficial turbulence for heat transfer while preventing flow separation and stagnation zones where particles would accumulate. The smooth curved surfaces guide flow continuously without creating dead zones
Solution Approach 2:
The patent strategically positions notches with specific curvature radii and depths in locations where turbulence is most beneficial for heat transfer, while avoiding configurations that would create stagnation zones. The asymmetric design ensures that turbulence-generating features are placed in high-velocity regions where particle accumulation is less problematic
4Strength
If heavy heat transfer sheet assemblies are used to provide structural support, then structural integrity is maintained, but fan power requirements increase
Solution Approach 1:
The patent modifies the geometric parameters of the sheet spacing features, creating asymmetric notches with optimized depths, widths, and positions. These parameter changes reduce the material required for spacing features while maintaining their structural function, thereby reducing overall assembly weight and fan power requirements without compromising structural integrity or heat transfer 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
The proposed heat transfer sheets achieve improved heat transfer efficiency and reduced pressure drop, leading to increased energy savings and lighter, more efficient preheater designs.
Implementation Method 1
The heat transfer sheets absorb heat from the flue gas stream and transfer this heat to the combustion air stream
Implementation Method 2
The hot flue gas stream and combustion air stream are simultaneously directed through respective sectors. The rotor rotates the flue gas and combustion air sectors in and out of the flue gas stream and combustion air stream to heat and then to cool the heat transfer sheets
Implementation Method 3
The use of heat transfer sheets with alternating notch configurations, featuring first and second lobes connected in a common flow channel, and transition regions that create turbulent flow and mitigate stagnation areas, enhancing heat transfer efficiency
Data Source
Figure 1
Figure 2A
Figure 2B~2C
AI summary
A heat transfer sheet for a rotary regenerative heat exchanger includes a plurality of rows of heat transfer surfaces each being aligned with a longitudinal axis extending between first and second ends thereof. The heat transfer surfaces have a height relative to a central plane of the heat transfer sheet. The heat transfer sheet includes one or more notch configurations for spacing the heat transfer sheets apart from one another. Each of the notch configurations are positioned between adjacent rows of heat transfer surfaces. The notch configurations include one or more lobes connected to one another, positioned in a common flow channel and extending away from the central plane and one or more lobes extending away from the central plane in an opposite direction and being coaxial. The lobes have height a relative to the central plane that is greater than the height of the heat transfer surfaces.