Condensing boiler for use with non-condensing stacks
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Solution Overview
Problem
The high cost and labor involved in replacing non-condensing boiler stacks with condensing stacks due to their different pressure and corrosion resistance requirements, making it economically unfeasible to upgrade to more efficient condensing boilers.
Innovation Solution
A condensing boiler design incorporating a combination of lower and higher efficiency heat exchanger tubes, allowing it to produce drier and hotter flue gas suitable for non-condensing stacks, maintaining efficiency and reducing the need for stack replacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a condensing boiler is used with a non-condensing stack, then the boiler efficiency is improved, but the stack corrosion resistance deteriorates
Solution Approach 1:
The heat exchanger is segmented into two distinct types of tubes: condensing tubes and non-condensing tubes. This segmentation allows different portions of the flue gas to be treated differently - some condensed to extract heat, others maintained above dew point to prevent corrosion. The segmented approach resolves the contradiction by enabling high efficiency heat extraction in specific zones while protecting the stack in other zones.
Solution Approach 2:
Different regions of the heat exchanger are assigned different functional qualities. Condensing tubes are positioned where maximum heat recovery is needed, while non-condensing tubes are positioned to maintain flue gas temperature above the dew point. This local differentiation of quality allows the system to achieve high overall efficiency while locally preventing the corrosive conditions that would damage the stack.
2Reliability
If a condensing stack is installed, then the corrosion resistance is improved, but the cost increases
Solution Approach 1:
The invention creates a functional copy of a condensing stack's corrosion protection capability within the heat exchanger itself. By incorporating non-condensing tubes that maintain flue gas temperature above the dew point, the system replicates the corrosion-resistant environment of a dedicated condensing stack, eliminating the need for expensive specialized stack materials while achieving the same protective effect.
Solution Approach 2:
The invention uses standard, inexpensive heat exchanger tube materials instead of expensive stainless steel condensing stack materials. By achieving corrosion protection through the heat exchanger design rather than through expensive stack materials, the system replaces costly long-lived components with cheaper, easily replaceable heat exchanger tubes, significantly reducing installation costs.
3Ease of manufacture
If a non-condensing stack is used, then the installation cost is reduced, but the flue gas temperature must be maintained higher
Solution Approach 1:
The system dynamically adjusts flue gas temperature at different locations and times within the heat exchanger. Flue gas is allowed to cool to condensing temperatures in the condensing tube sections for maximum heat recovery, while simultaneously maintaining above-dew-point temperatures in non-condensing tube sections. This dynamic temperature management enables the use of inexpensive non-condensing stacks while achieving condensing-level 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
Enables the use of condensing boilers with existing non-condensing stacks, providing significant cost savings and encouraging the adoption of more efficient systems without compromising performance.
Implementation Method 1
The heat exchanger includes a combination of lower efficiency heat exchanger tubes and higher efficiency heat exchanger tubes... directing combustion gases into first ends of the heat exchanger tubes, directing water through the heat exchanger and outside of the tubes
Data Source
AI summary
A condensing boiler for use with a non-condensing stack, including a heat exchanger with a combination of higher efficiency heat exchanger tubes and lower efficiency heat exchanger tubes.