Perforated Diffuser Plate for Uniform Burner Box Heat Distribution
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Solution Overview
Problem
Fuel-fired heating appliances experience undesirable uneven heating of combustion product-receiving heat exchanger tubes due to non-uniform temperature distribution, resulting in inefficient heating.
Innovation Solution
A perforated diffuser plate is installed between the fuel/air mixture supply housing and the burner box, with a specific perforation pattern that increases fuel/air mixture flow through end heat exchanger tubes and decreases flow through central tubes, alleviating temperature distribution issues and improving fuel/air mixing, thereby reducing NOx levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional burner box configuration is used, then the structure is simple and easy to manufacture, but uneven heating of heat exchanger tubes occurs resulting in non-uniform temperature distribution
Solution Approach 1:
A diffuser plate is introduced as an intermediary component between the burner box and heat exchanger tubes. This plate modifies the flow characteristics of combustion gases, directing them to improve temperature distribution across the tube array without requiring fundamental changes to the burner box structure itself.
Solution Approach 2:
The diffuser plate incorporates locally varied features such as different opening sizes, shapes, or distributions in different regions. This allows targeted modification of gas flow to specific areas of the heat exchanger tube array, addressing local heating deficiencies while maintaining overall system simplicity.
2Productivity
If fuel/air mixture flow is increased to improve heating efficiency, then heating performance improves, but NOx levels in discharged combustion gases increase
Solution Approach 1:
The diffuser plate modifies flow parameters such as velocity distribution, turbulence intensity, and residence time of combustion gases. By optimizing these parameters, the system achieves improved heat transfer efficiency at lower overall fuel/air flow rates, thereby reducing NOx formation while maintaining heating productivity.
Solution Approach 2:
The diffuser plate design may incorporate features that create periodic or oscillating flow patterns, enhancing mixing and heat transfer efficiency. This allows for more effective heating at reduced fuel consumption levels, indirectly reducing NOx emissions.
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 diffuser plate achieves a more uniform temperature distribution across the heat exchanger tube array, enhances fuel/air mixing, and reduces NOx levels in discharged combustion gases, providing a cost-effective solution to the heating inefficiency.
Implementation Method 1
A diffuser plate having a face with a pattern of holes formed therethrough is positioned in the burner box with the face of the diffuser plate positioned adjacent to the inlet ends of the heat exchanger tubes so as to distribute the combustion gases flowing through the burner box more uniformly across the heat exchanger tubes
Implementation Method 2
improving fuel/air mixing, thereby reducing NOx levels
Data Source
AI summary
To substantially reduce inequality in hot combustion flow rates through first and second heat exchanger tubes from a fuel-fired heating appliance burner box connected thereto and internally combusting a fuel/air mixture received therein from a source thereof to create the hot combustion gas, a perforated diffuser member having a non-uniform perforation pattern is provided. The fuel/air mixture is flowed through the perforated diffuser member into the interior of the burner box. The non-uniform perforation pattern of the diffuser member functions to alter relative combustion gas flow rates through the first and second heat exchanger tubes in a manner reducing an undesirable operating temperature differential therebetween.