Rotary Heat Exchanger Elements With Angled Notches to Limit Fouling
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Solution Overview
Problem
Conventional rotary heat exchangers designed for coal-fired boilers do not fully utilize the cleaner and higher thermal potential of natural gas, leading to fouling and back-end corrosion issues, necessitating improvements for efficient heat transfer in natural gas-fired systems.
Innovation Solution
The heat transfer elements feature elongate notches and undulations or dimples oriented at specific angles to maintain spacing and induce turbulence, enhancing heat exchange, particularly suitable for natural gas-fired systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional heat transfer elements are used in rotary heat exchangers for natural gas-fired systems, then the existing design is compatible with coal-fired boilers, but the cleaner natural gas flow and higher thermal potential are not fully utilized, leading to fouling and back-end corrosion
Solution Approach 1:
The heat transfer element is segmented into multiple functional zones along the gas flow direction: a leading edge portion with first notches and first undulations, and a trailing edge portion with second notches and second undulations. This segmentation allows different sections to perform specialized functions - the leading edge focuses on inducing turbulence to prevent fouling, while the trailing edge optimizes heat transfer efficiency, thereby resolving the contradiction between reliability and harmful factors
Solution Approach 2:
Different portions of the heat transfer element are given different geometric characteristics tailored to their specific functional requirements. The leading edge portion has notches and undulations configured to maximize turbulence induction for fouling prevention, while the trailing edge portion has different configurations optimized for heat transfer. This local differentiation allows each zone to address specific problems, resolving the overall contradiction between preventing fouling and maintaining heat transfer efficiency
2Productivity
If heat transfer elements with notches and undulations are used to induce turbulence, then heat exchange efficiency is improved, but fan power increases due to increased turbulence
Solution Approach 1:
Turbulence-inducing features (notches and undulations) are applied partially rather than uniformly across the entire heat transfer element. The leading edge portion has aggressive turbulence-inducing geometry, while the trailing edge portion has different configurations. This partial application achieves sufficient turbulence to improve heat exchange efficiency without excessively increasing pressure drop and fan power requirements, resolving the contradiction between productivity and energy use
3Adaptability or versatility
If heat transfer elements are designed for coal-fired boilers, then they are compatible with existing coal-fired systems, but they do not take full advantage of the cleaner, lower emission gas flow and higher thermal potential of natural gas
Solution Approach 1:
The heat transfer element design incorporates features that serve multiple functions: the notches and undulations simultaneously induce turbulence to prevent fouling, enhance heat transfer efficiency, and maintain structural integrity. This multi-functionality allows the element to adapt to natural gas-fired systems while maintaining compatibility with existing rotary heat exchanger configurations, resolving the contradiction between adaptability and reliability
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
Significantly reduces flue gas exit temperatures and minimizes fouling, offsetting any slight fan power increase due to increased turbulence, resulting in improved heat transfer efficiency.
Implementation Method 1
the plurality of elongate undulations in the second plate may be oriented crosswise relative to the plurality of elongate notches in the first plate to define a spacing between the plates, and the plurality of undulations in the second plate may be oriented crosswise relative to the plurality of elongate undulations in the first plate to induce turbulence in the gas flows in order to improve heat transfer
Implementation Method 2
a rotary heat exchanger having a housing with a first opening in fluid communication with a first gas flow and a second opening in fluid communication with a second gas flow
Data Source
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AI summary
A rotary heat exchanger for preheating air using waste heat comprises a plurality of heat transfer elements movable between first and second openings in a housing to exchange heat between heated exhaust gases and a stream of fresh air. At least one heat transfer element comprises a first plate having a plurality of elongate notches formed therein at spaced intervals and oriented at a first angle relative to the flow direction. The plate further comprises a plurality of elongate undulations formed therein at spaced intervals and oriented a second angle relative to the flow direction, wherein the first angle is different than the second angle. A first height of each of said plurality of elongate notches is larger than a second height of each of said plurality of elongate undulations. The heat transfer elements may be stacked in a container for installation in the rotary heat exchanger.