Premix burner internal flue shield
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Solution Overview
Problem
HVAC systems with low NOx burners face high temperature stresses and safety risks due to extreme heat, with existing insulation solutions either relocating heat issues or using environmentally damaging materials.
Innovation Solution
A flue shield is introduced within the combustion chamber, creating an air gap between its inner and outer surfaces and extending through holes to direct combustion into heat exchanger inlets, effectively dissipating heat and reducing surface temperatures without using hazardous materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If insulation is added within the burner to lower surface temperatures, then surface temperature is reduced, but heat is redirected to different locations creating stresses in other areas
Solution Approach 1:
A flue shield is introduced as an intermediary component between the combustion chamber and the heat exchanger. The flue shield has an inner surface facing the combustion and an outer surface facing the heat exchanger, creating an air gap that acts as a thermal buffer. This intermediary structure dissipates heat gradually through the air gap rather than directly transferring it, preventing both surface overheating and heat redirection to problematic areas.
Solution Approach 2:
The flue shield extends into the heat exchanger through holes in the combustion chamber, adding a spatial dimension to heat management. By projecting extensions into the heat exchanger inlet, the shield creates a three-dimensional heat dissipation structure that distributes thermal energy across multiple zones rather than concentrating it in single locations.
2Temperature
If insulation is used to reduce high temperatures, then temperature control is improved, but environmentally damaging materials are required
Solution Approach 1:
The flue shield serves as a passive thermal intermediary that relies on natural convection and radiation through the air gap rather than requiring insulating materials. This eliminates the need for environmentally damaging insulation materials while still achieving effective temperature control in the combustion chamber and heat exchanger.
Solution Approach 2:
The invention replaces the mechanical/chemical insulation system with a structural air gap system. Instead of using insulating materials to trap heat, the design uses the natural thermal resistance of an air space created by the flue shield geometry, substituting material-based insulation with geometry-based thermal management.
3Productivity
If high temperatures are maintained for efficient combustion, then combustion efficiency is improved, but stresses on burner and heat exchanger components increase
Solution Approach 1:
The flue shield divides the thermal environment into distinct zones: a high-temperature combustion zone within the shield, a moderate-temperature air gap zone, and a lower-temperature heat exchanger zone. This segmentation allows efficient combustion to occur where needed while protecting components in other zones from excessive thermal stress.
Solution Approach 2:
The flue shield creates a thermal gradient across multiple spatial dimensions, with temperature decreasing from the inner surface near the combustion to the outer surface near the heat exchanger. This dimensional temperature distribution enables high combustion efficiency while progressively reducing thermal loads on downstream 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
The flue shield efficiently lowers combustion chamber and heat exchanger tube temperatures by 15-20%, maintaining efficiency and safety while eliminating the need for harmful insulations.
Implementation Method 1
the flue shield operable to fit within the combustion chamber and surround the combustion of the mixture and create an air gap between an inner surface of the combustion chamber and an outer surface of the flue shield
Implementation Method 2
the flue shield comprising a second plurality of holes; and one or more heat exchanger inlets, each of the heat exchanger inlets operable to receive the combustion of the mixture through the first and second plurality of holes
Data Source
AI summary
A flue shield is described for use within HVAC systems and inside of a combustion chamber. The flue shield can be installed around the burner and within the combustion chamber to help dissipate heat that builds up as a result of the combustion of gas and air. Extensions from the flue shield extend through holes in the combustion chamber and into tubes of a heat exchanger. An air gap is created between the flue shield and the inner surfaces of the combustion chamber and heat exchanger tubes. Installation of a flue shield provides better efficiency than insulation solutions, reduces stresses on the heat exchanger, and provides safety benefits.