Primary Heat Exchanger with Stratified Buffer for Condensing Boilers
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Solution Overview
Problem
Existing primary heat exchangers in condensing boilers face inefficiencies due to direct flow of heated supply water into the cold return system when the bypass valve is open, which affects condensation rates and requires complex external designs or large water volumes.
Innovation Solution
Integration of a stratified storage tank within the primary heat exchanger, allowing for temperature stratification and buffering, ensuring continuous cold water supply for condensation and reducing system size by eliminating the need for external lines and increasing water volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bypass valve is used to ensure minimal circulation, then the circulating heat transfer medium volume flow is sufficient to avoid local heat accumulation, but heated supply water flows directly into the cold system return and raises the return temperature, reducing condensation rate
Solution Approach 1:
The heat exchanger is divided into multiple heating sections (first, second, and third heating sections) with different water flow paths. The bypass valve is specifically positioned to affect only the third heating section, allowing segmented control of where bypass water enters the system, thereby minimizing its impact on overall condensation while maintaining safe operation.
Solution Approach 2:
The bypass valve is positioned to introduce heated water at a specific location (third heating section) rather than at the beginning of the heat exchanger. This preliminary positioning ensures that the heated water joins the flow after cold water has already been utilized in the first and second heating sections, preserving condensation conditions in those sections while still providing the safety function.
2Loss of energy
If external stratified storage tank is used to further cool exhaust gases, then additional condensation is achieved, but the design becomes very complex with additional exhaust gas lines and fresh air lines
Solution Approach 1:
The stratified storage tank function is merged directly into the heat exchanger structure. The heat exchanger itself is designed with multiple heating sections that create natural stratification zones, eliminating the need for a separate external stratified storage tank while achieving the same condensation enhancement effect.
Solution Approach 2:
The heat exchanger is designed to serve multiple functions simultaneously: it acts as the primary heat exchange surface, creates stratified flow zones for enhanced condensation, and provides the bypass water introduction point. This multi-functionality eliminates the need for separate dedicated components for each function, reducing overall system complexity.
3Device complexity
If water reservoir is integrated in the heat exchanger housing, then compact design is achieved, but the water volume becomes large which affects system efficiency
Solution Approach 1:
Instead of providing water storage throughout the entire heat exchanger housing, the invention introduces heated water at a specific local position (the third heating section). This localized intervention provides the necessary buffer volume effect only where needed, maintaining compact design while minimizing the quantity of water that needs to be managed.
Solution Approach 2:
The system uses dynamic flow control through the bypass valve to create a moving buffer effect. Rather than relying on a large static water reservoir, the continuously circulating water with controlled bypass injection creates a dynamic thermal buffer that achieves the same efficiency benefits with much smaller water volume.
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 maintains condensation efficiency and compact design by providing a buffer volume for cold water, preventing reduced condensation rates and allowing for controlled operation based on temperature thresholds, ensuring reliable heat transfer.
Implementation Method 1
the stratified storage tank separates cold and warm water
Implementation Method 2
the hot gas giving off its remaining heat to the stratified storage tank
Implementation Method 3
condensing boilers with condensation of the exhaust gas to increase efficiency
Data Source
Figure 1
AI summary
The invention relates to a condensing boiler comprising a burner 1 and a primary heat exchanger 2 for transferring heat from the exhaust gas of the burner 1 to a heat transfer medium. A bypass 17 protects the condensing boiler from overpressure in the event of a blockage in the heating circuit. The temperature increase in the heat exchanger, and the associated decrease in the condensation rate, is prevented by the inclusion of a stratified storage tank 12 within the primary heat exchanger 2. This allows the heat exchanger to continue to be supplied with cold return heat transfer medium for a certain period of time before the burner 1 is switched off.