Elliptical Combustion Pass for Lower Heat Exchanger Drag
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Solution Overview
Problem
HVACR systems face inefficiencies due to high external pressure drops across heat exchanger tubes, requiring increased power for blowers and impacting overall furnace efficiency, especially when the first heat exchange pass has a circular cross-section and is directly in front of the blower outlet.
Innovation Solution
The heat exchanger tube features a modified first heat exchange pass with a varying diameter, having a minor and major axis, oriented towards the incoming process fluid, which reduces external pressure drop without significantly affecting internal pressure or combustion efficiency, allowing for a streamlined shape and reduced power requirements for the blower.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the first heat exchange pass has a circular cross-section, then the internal combustion flow is simple, but the external pressure drop is high
Solution Approach 1:
The patent applies asymmetry by changing the circular cross-section to an elliptical cross-section with different major and minor diameters. This asymmetric shape reduces the external pressure drop by better aligning with the flow direction, while the internal combustion chamber maintains functional effectiveness through proper orientation of the major axis toward the incoming process fluid.
Solution Approach 2:
The patent changes the geometric parameters of the cross-section from a constant diameter circle to variable diameters (major and minor) in an elliptical configuration. This parameter change optimizes the external flow characteristics and reduces pressure drop while preserving internal combustion functionality.
2Stress or pressure
If the first heat exchange pass is oriented with major diameter towards incoming process fluid, then external pressure drop is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent uses curvature by implementing an elliptical cross-section instead of a circular one. This curved geometric form reduces external pressure drop through streamlined flow characteristics while being manufacturable using standard tube forming processes that can create elliptical sections.
3Use of energy by moving object
If a streamlined shape is used for the first heat exchange pass, then blower power requirement is reduced, but heat exchange surface area may be affected
Solution Approach 1:
The patent changes the geometric parameters from a circular cross-section to an elliptical one with optimized major and minor diameter ratios. This parameter optimization reduces the blower power requirement by up to 10% while maintaining adequate heat exchange surface area through proper dimensional selection.
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 results in a 5% to 10% reduction in blower power requirement compared to previous heat exchanger designs, enhancing the overall efficiency of the HVACR system by minimizing external pressure drops while maintaining internal combustion efficiency.
Implementation Method 1
A length of the first heat exchange pass may be modified and configured to provide a reduced external pressure drop
Implementation Method 2
the first heat exchange pass presents a streamlined shape for the process fluid to flow over
Implementation Method 3
the process fluid (e.g., air, etc.) may be heated as it flows over the outside surface of the heat exchange tube
Implementation Method 4
the combustion reaction of a fuel (e.g., natural gas, etc.)
Data Source
AI summary
A heat exchanger tube includes a first pass for at least partially combusting a fuel and the first pass having a modified shape including a minor diameter and major diameter that reduces the external pressure drop of an external fluid flowing across the heat exchanger tube. A HVACR system includes a heat exchanger tube with a first heat exchange pass that at least partially combusts a fuel and has a modified shape. A method of making a heat exchanger including configuring a first heat exchange pass such that the major diameter of modified portion of the first heat exchange pass is oriented towards an incoming direction of the process fluid.