Coiled Flue Tube Venting for Natural-Draft Gas Water Heaters
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Solution Overview
Problem
Conventional gas water heaters face challenges in efficiently utilizing natural convection for exhaust of combustion products, often requiring complex venting systems and prone to fatigue failures due to multiple welds in the flue tubes.
Innovation Solution
A gas water heater design featuring a power burner, a coiled flue tube, and an exhaust plenum that allows products of combustion to exhaust under natural convection, reducing pressure and eliminating the need for positive pressure venting, while using a seamless flue tube to minimize welds and potential fatigue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional venting systems are used for gas water heaters, then positive pressure venting can be achieved, but the system becomes complex and prone to fatigue failures due to multiple welds
Solution Approach 1:
The patent extracts the complex positive pressure venting system and replaces it with a natural convection exhaust system. The flue tube is designed to extend through the combustion chamber and exit at the top of the tank, allowing combustion products to exhaust naturally without requiring complex positive pressure venting components, thereby reducing system complexity and potential failure points
Solution Approach 2:
The flue tube is segmented into functional zones: a lower portion extending through the combustion chamber, a middle section forming loops within the tank, and an upper portion exiting at the top. This segmentation allows the system to achieve both reliable combustion product removal and natural convection exhaust while minimizing welds through continuous tube construction
2Ease of manufacture
If multiple welds are used in flue tubes, then assembly is easier, but fatigue failures occur more frequently
Solution Approach 1:
The flue tube is designed and positioned before final assembly, with inlet and outlet ends configured to receive connections from the burners and exhaust system. This preliminary configuration allows for minimal welding or connection points, reducing fatigue failure risk while maintaining ease of assembly
Solution Approach 2:
The flue tube features localized functional zones with different geometries: straight sections for connection points, looped sections for heat exchange and natural convection, and extended sections for exhaust. This local quality optimization allows the tube to perform multiple functions while minimizing the number of welds required
3Device complexity
If natural convection exhaust is implemented, then system simplicity increases, but combustion product removal efficiency may be reduced
Solution Approach 1:
The flue tube is configured to extend vertically through the combustion chamber and exit at the top of the tank, utilizing the vertical dimension to create natural convection currents. This dimensional arrangement allows combustion products to rise naturally through the flue tube and exhaust externally, maintaining removal efficiency while simplifying the system
Solution Approach 2:
The flue tube incorporates looped sections within the tank that create curved flow paths for combustion products. These curves enhance turbulent mixing and heat exchange while maintaining flow direction toward the exhaust, improving combustion product removal efficiency without requiring complex mechanical systems
4Use of energy by moving object
If flue tube is extended through combustion chamber, then heat exchange improves, but scale buildup increases
Solution Approach 1:
The continuous flow of combustion products through the flue tube creates periodic turbulence and flow variations that prevent scale deposition. The natural convection currents and flow dynamics within the extended flue tube maintain a self-cleaning effect, reducing scale buildup while preserving heat exchange efficiency
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 design enhances thermal efficiency, reduces scale buildup, and extends the life of the tank by allowing natural convection exhaust, while being cost-effective and capable of retrofitting into existing systems with increased capacity and efficiency.
Implementation Method 1
permit natural convection exhaust of products of combustion
Implementation Method 2
a heat exchanger having an inlet end and an outlet end, the inlet end secured in one of the first and second holes and the outlet end secured in the other of the first and second holes
Data Source
AI summary
A gas water heater includes a power burner, a flue tube, an exhaust plenum, and a draft hood. The flue tube includes a portion that describes at least a 360° loop. Products of combustion are forced through the flue tube under the influence of the power burner, and enter the exhaust plenum. In the exhaust plenum, the pressure of the products of combustion drops such that the products of combustion flow into the draft hood substantially entirely under the influence of natural convection. In one embodiment, the power burner fires down into the flue tube through a side wall of the water heater, the loop of the flue tube is near the bottom of the water heater, and the plenum is in the top of the water heater.