Condensing Heat Exchanger Layout for Dual-Burner Flexibility
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Solution Overview
Problem
Existing condensation heat exchangers for gas or oil boilers face challenges in achieving optimal efficiency and compactness across a wide range of powers, particularly when operating with a single burner or both burners at different power levels and start/stop times, while maintaining safety and efficiency.
Innovation Solution
A triple heat exchanger design with two main exchangers exposed to hot gases and a secondary exchanger, where the secondary exchanger is positioned between the primary exchangers, allowing for efficient heat recovery from both burners and enabling operation with either burner independently, using helical tube bundles with a flattened oval section and a partition to manage gas flow and fluid circulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a double exchanger design is used, then heat exchange efficiency is improved, but the device cannot operate with a single burner or two burners at different powers
Solution Approach 1:
The heat exchanger is divided into two independent primary exchangers (each with its own burner and heat exchange path) and a shared secondary exchanger. This segmentation allows each primary exchanger to operate independently, enabling flexible operational modes (single burner or dual burners at different powers) while maintaining efficient heat recovery through the common secondary exchanger.
2Use of energy by moving object
If the secondary exchanger is positioned between primary exchangers, then heat recovery from both burners is enabled, but gas flow management becomes complex
Solution Approach 1:
A partition wall with a communication orifice acts as an intermediary element between the two primary exchangers. This partition manages gas flow by directing it through the secondary exchanger while maintaining pressure balance and preventing short-circuiting, thereby enabling heat recovery from both burners without excessive complexity in gas flow management.
3Area of stationary object
If helical tube bundles with flattened oval section are used, then heat exchange surface area is increased, but manufacturing complexity increases
Solution Approach 1:
The tubes are designed with a helical configuration and flattened oval cross-section, which increases the heat exchange surface area and improves heat transfer efficiency. The curved helical path and oval shape maximize contact between the hot gases and tube surfaces, enhancing thermal exchange while the standardized geometry facilitates manufacturing through conventional tube bending and forming processes.
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 solution enhances heat exchange efficiency, allows for a broader power range (25 to 500 kW) with optimal efficiency and safety, and maintains compactness by utilizing the secondary exchanger to recover heat from both burners without disturbing the operation, ensuring efficient heating of water across varying power conditions.
Implementation Method 1
These hot gases contain a certain quantity of water in the form of vapors which are likely to condense when they come to lick the wall of the secondary exchanger, since this is below the dew point temperature
Implementation Method 2
This condensation has the effect of supplying additional calories to the water circulating in the secondary exchanger, these additional calories corresponding to the latent heat of vaporization
Implementation Method 3
The water, or any other fluid to be heated, circulates in whole or in part in this exchanger against the current of the flue gases, that is to say passing first through the secondary exchanger, where it undergoes preheating, then in a primary exchanger, where it undergoes actual heating
Data Source
Figure 1
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Figure 3~4
AI summary
This exchanger comprises a pair of primary tube bundles (5a, 5b) surrounding a gas or oil burner (4a, 4b), and a secondary tube bundle (6) on which condensation of water vapor takes place. contained in the burnt gases escaping from the primary bundles, these three bundles (5a, 5b, 6) being mounted parallel side by side inside an envelope (10) impermeable to gases, and communicating with each other, means being provided for circulating water to be heated, between the tubes constituting the secondary bundle (6) and the tubes constituting the primary bundles (5a, 5b); the envelope (10) is subdivided at the level of the secondary beam (6) by a partition (7-70) which extends both inside and outside this beam (6), the arrangement being such that only a circumferential sector of the latter is capable of being licked and traversed by the hot gases issuing from one of the two primary beams (5a), its remaining sector being capable of being licked and traversed only by the hot gases from the other primary beam (5b). High efficiency domestic or industrial heating installation in a small footprint.