Serpentine Tube Heat Exchanger Layout for Compact Gas Furnaces
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Solution Overview
Problem
Existing heat exchangers in gas-fired furnaces, such as tubular and clamshell types, face challenges in achieving compactness and cost-effectiveness due to large tube diameters and complex manufacturing processes, leading to poor cost-effectiveness in shipping and installation, as well as high manufacturing costs.
Innovation Solution
A heat exchanger design featuring at least two heat exchange shell enclosures with three rows of tubes arranged along a furnace air flow path, where each tube has a leaving-tube-end and an entering-tube-end, connected sequentially to form a serpentine flue gas passage, allowing for a compact structure and reduced manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If tubular type heat exchanger uses large tube diameter to satisfy gas combustion space and heat transfer surface area requirements, then heat transfer efficiency is improved, but the height of gas-fired furnace increases and compactness deteriorates
Solution Approach 1:
The patent transitions from a single-row vertical tube arrangement to a multi-row horizontal arrangement where tubes are connected in series across multiple rows. This dimensional change allows the flue gas to traverse a longer path through multiple rows (first row, second row, third row, etc.) without increasing the vertical height, thereby maintaining heat transfer efficiency while reducing furnace height.
Solution Approach 2:
The patent implements a nested arrangement where multiple rows of tubes are positioned within a compact vertical space. The tubes in different rows are connected sequentially, creating a nested-like structure where the flue gas path winds through multiple levels. This allows the system to pack more heat transfer surface area into a smaller vertical envelope, reducing the overall furnace height while maintaining effective heat transfer.
2Strength
If tubular type heat exchanger uses large bend radius to avoid excessive stretching or compressing of tube metal, then tube strength is maintained, but compactness and cost-effectiveness deteriorate
Solution Approach 1:
The patent divides the heat exchanger into multiple discrete rows of tubes, each row containing multiple tube sections. The tubes are connected in series between rows through shell enclosures, creating segmented sections that can be manufactured and assembled independently. This segmentation allows for simpler, more compact tube configurations within each row while maintaining overall structural integrity through the series connection of multiple rows.
Solution Approach 2:
Instead of using large-radius bends within single vertical tubes, the patent redistributes the heat transfer path across multiple horizontal rows. The tube connections between rows are made through shell enclosures, effectively moving the turning points from within individual tubes to the inter-row connections. This dimensional redistribution allows for smaller, more compact tube sections while maintaining tube strength.
3Temperature
If clamshell type heat exchanger uses optimized clamshell surfaces for effective heat transfer and thermal stress management, then heat transfer efficiency is improved, but manufacturing costs and design cycle increase
Solution Approach 1:
The patent divides the heat exchanger into multiple rows of tubes that are connected through shell enclosures. Each row and shell enclosure can be manufactured as separate, standardized components. This segmentation simplifies the manufacturing process compared to forming complex optimized clamshell surfaces, as standard tube and shell components can be produced using conventional fabrication methods and then assembled together.
Solution Approach 2:
The patent changes the fundamental geometric parameters of the heat exchanger from complex curved clamshell surfaces to a simpler arrangement of straight tubes in multiple rows connected through shells. This parameter change from curved to linear geometries significantly reduces manufacturing complexity and cost while maintaining effective heat transfer through the increased surface area provided by multiple rows.
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 compact heat exchanger design reduces the height of the gas-fired furnace, enhances manufacturing efficiency, and lowers overall costs while improving heat transfer efficiency through staggered tube arrangements and varying tube diameters, resulting in improved air ventilation and reduced air flow resistance.
Implementation Method 1
The at least three rows of heat exchange tubes are connected in a leaving-tube-end to entering-tube-end fashion sequentially via the at least two heat exchange shell enclosures to define a substantially serpentine flue gas passage
Implementation Method 2
at least three rows of heat exchange tubes arranged along a furnace air flow path
Data Source
AI summary
A heat exchanger and a gas-fired furnace including the same are provided. The heat exchanger includes at least two heat exchange shell enclosures; and at least three rows of heat exchange tubes arranged along a furnace air flow path. Each of the heat exchange tubes defines a leaving-tube-end and an entering-tube-end, two adjacent rows are spaced from each other, the at least three rows of heat exchange tubes are connected in a leaving-tube-end to entering-tube-end fashion sequentially via the at least two heat exchange shell enclosures to define a substantially serpentine flue gas passage.