Dual Heat Exchanger Control for Low-NOx Heat Generators
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Solution Overview
Problem
Conventional heat generator efficiency improvement methods are limited by conservative sizing, which reduces efficiency under varying operating conditions and increases nitrogen oxide emissions, as they often rely on single heat exchangers and custom designs.
Innovation Solution
A method and apparatus utilizing dual heat exchangers for fluid and combustion air heat exchange, with regulation of flue gas flow rates based on fluid temperature, optimizing heat transfer and reducing nitrogen oxide concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conservative sizing is used for heat exchangers, then reliability is improved by avoiding overheating and damage, but heat recovery efficiency deteriorates under varying operating conditions
Solution Approach 1:
The patent implements dynamic control of the heat exchanger system by regulating flue gas flow rate based on real-time temperature measurements of the fluid. This allows the system to adapt to varying operating conditions, maximizing heat recovery efficiency while preventing overheating through active feedback control rather than static conservative sizing
Solution Approach 2:
The system changes the operational parameters of the heat exchanger by adjusting flue gas flow rate as a function of fluid temperature. This dynamic parameter adjustment enables the heat exchanger to operate efficiently across a range of conditions without requiring oversized conservative design, resolving the contradiction between reliability and efficiency
2Productivity
If preheating combustion air is performed using flue gases, then combustion efficiency is improved, but nitrogen oxide concentration increases
Solution Approach 1:
The system dynamically regulates flue gas flow rate to the heat exchanger based on fluid temperature feedback. This prevents excessive preheating of combustion air that would lead to high nitrogen oxide formation, while still maintaining efficient heat recovery. The dynamic control allows optimization of both combustion efficiency and emissions
Solution Approach 2:
The patent implements a feedback control mechanism where flue gas flow rate is regulated as a function of the temperature of the fluid delivered from the heat exchanger. This feedback loop prevents over-preheating of combustion air, thereby controlling nitrogen oxide concentration while maintaining combustion efficiency
3Device complexity
If single heat exchanger configuration is used, then device complexity is reduced, but adaptability to varying operating conditions deteriorates
Solution Approach 1:
Rather than using multiple static heat exchangers, the patent employs a single heat exchanger with dynamic flue gas flow rate regulation. This dynamic approach provides adaptability to varying operating conditions without increasing device complexity, as the flexibility is achieved through control rather than through multiple components
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
Enhances heat generator efficiency across varying conditions while maintaining low nitrogen oxide emissions, achieving higher thermal energy recovery and reduced pollutant emissions.
Implementation Method 1
a first heat exchange, through first heat exchanger means, between at least a first fraction (or the total flow rate) of said fluid and the combustion air to be delivered to the heat generator so as to cool said fluid and heat said combustion air
Implementation Method 2
a second heat exchange, through second heat exchanger means, between this fraction (or the total flow rate) of fluid (cooled by said first heat exchanger means) and the flue gases produced by the heat generator so as to heat the fluid to be delivered to the heat generator and so as to cool said flue gases
Implementation Method 3
the method and the apparatus according to the invention allow recovery of part of the latent evaporation heat contained in the gases, through their condensation, thus also reducing the concentration of nitrogen oxides present in the same gases
Data Source
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AI summary
The present invention relates to a method and to an apparatus for improving the efficiency of a heat generator destined to heat a feed fluid such as water. The method according to the invention provides for the performance of a first heat exchange between at least a first flow rate of feed fluid and a flow rate of combustion air so as to heat the combustion air and cool the first flow rate of fluid from a first to a second temperature. The method also provides for the performance of a second heat exchange between the feed fluid at said second temperature and at least part of the flue gases produced by the heat generator so as to cool said flue gases and heat the feed fluid from said second to a third temperature. The method also provides for regulation of the flow rate of flue gases subjected to the second heat exchange as a function of the temperature reached by the fluid following the same second heat exchange.