Condenser for condensing boiler with double return
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Solution Overview
Problem
Double-return condensing boilers face issues with overheating and scaling in the condenser when the low-temperature water return is absent, such as in summer, leading to potential damage and reduced heat exchanger performance.
Innovation Solution
A condensing boiler design that utilizes natural convection between the high-temperature water return and the condenser tubes, with strategically positioned inlet and outlet openings, allows for continuous water circulation and prevents overheating by ensuring a temperature gradient, even without low-temperature water return, thereby maintaining efficient heat exchange and preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a permanent bypass is inserted between the low temperature water return circuit and the high temperature water return circuit upstream of the connection with the condenser, then the risk of overheating in the condenser is reduced, but the condensation is limited and the performance of the heat exchanger is diminished
Solution Approach 1:
The system uses natural convection currents generated by temperature differences to automatically circulate water through the condenser tubes, eliminating the need for external control mechanisms. The cooler water from the high temperature return naturally rises and enters the condenser, while heated water descends back to the lower water box, creating a self-sustaining circulation loop that protects against overheating without requiring active control
Solution Approach 2:
The invention introduces an intermediary circulation path through the condenser tubes that allows heat transfer from the flue gases to the water in the absence of low temperature return flow. This intermediary mechanism enables the system to maintain condenser functionality and prevent overheating by creating an alternative heat dissipation route that does not compromise the primary heat exchange performance
2Productivity
If a valve is used instead of a bypass to control water flow, then the condensation performance can be optimized, but the cost of the heat exchanger is significantly increased due to automation requirements
Solution Approach 1:
The system eliminates the need for expensive automated valves or manual intervention by utilizing natural convection currents. The temperature difference between the cooler water from the high temperature return and the heated water in the condenser tubes creates automatic circulation, making the system self-regulating and cost-effective while maintaining optimal condensation performance
Solution Approach 2:
The invention replaces the mechanical control system (valves, actuators, control electronics) with a passive thermal convection system. Instead of using mechanical means to control water flow and optimize condensation, the system relies on natural buoyancy-driven circulation caused by temperature differences, significantly reducing complexity and cost while maintaining efficiency
3Temperature
If the low temperature water return is absent, such as in summer when the heating circuit is stopped, then the water temperature in the condenser stagnates, but the flue gases can be hot enough to boil the water causing overheating and potential damage
Solution Approach 1:
The invention converts the harmful effect of hot flue gases that would otherwise cause overheating into a beneficial heat transfer mechanism. By directing the flue gases through the condenser tubes during periods when low temperature return is absent, the system utilizes the temperature difference to drive natural convection circulation, transforming a potential damage source into an active heat exchange process that prevents stagnation and overheating
Solution Approach 2:
The system proactively establishes a circulation path through the condenser that prevents water stagnation before overheating can occur. The natural convection current is continuously maintained by the temperature difference between the incoming cooler water and the heated water in the tubes, ensuring that water is always in motion and heat is continuously dissipated, preventing the conditions that lead to boiling and damage
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 enhances the boiler's efficiency by maintaining heat exchange and preventing condenser damage, achieving a 3% gain in overall efficiency and ensuring the condenser operates optimally even without low-temperature water return, while being cost-effective and passive.
Implementation Method 1
create natural convection of the water in the tubes heated with the flue gases, towards the upper ends of the tubes so as to open into the water box. superior
Implementation Method 2
perform a heat exchange between a heat transfer fluid which will be referred to generically in this document as 'water'... and the fumes produced by the combustion
Implementation Method 3
the low temperature water return RBT is used in the second part to continue the heat exchange and condense the water vapor contained in the flue gases
Data Source
AI summary
The condensing boiler includes at least one low-temperature water return (LTWR), at least one high-temperature water return (HTWR), and a heat exchange device (100) comprising • a heat exchanger (1), and • a condenser (4) comprising a lower water box (8), an upper water box (12), and tubes (6) for circulating water, each tube (6) comprising - a lower end opening into the lower water box (8), said lower water box (8) being fluidly connected to the low-temperature water return (LTWR), and - an upper end opening into the upper water box (12), said upper water box (12) having an inlet opening (9) fluidly connected to the high-temperature water return (HTWR) and an outlet opening (14) fluidly connected to a water inlet (2) of the heat exchanger (1) of the boiler.