Radiating Tube Recuperator with Radially Offset Return Section
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Solution Overview
Problem
Existing heat recuperators for radiant tube burners face challenges in improving thermal performance, increasing flue gas recirculation to reduce nitrogen oxide emissions, achieving uniform temperature, limiting pressure drops, ensuring reliable cold ignition, and reducing manufacturing costs.
Innovation Solution
A heat recuperator design featuring a counter-current heat exchanger with parallel exchanger tubes and a radially offset return section, allowing for direct and indirect heat exchange between combustion air and flue gases, optimized to reduce pressure drops and enhance thermal efficiency, using all-welded stainless steel construction and a bypass system for cold air short-circuiting during ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the heat exchanger occupies a larger portion of the connecting pipe cross section, then heat transfer efficiency improves, but pressure drops increase
Solution Approach 1:
The heat exchanger is divided into multiple separate tubes rather than a single large structure, allowing the combustion air flow to be segmented into multiple streams. This segmentation reduces the pressure drop across each individual tube while collectively providing sufficient heat transfer surface area, thus resolving the contradiction between heat transfer efficiency and pressure drops.
Solution Approach 2:
The invention transitions from a two-dimensional cross-sectional occupancy approach to a three-dimensional arrangement where multiple tubes are distributed throughout the connecting pipe volume. This spatial distribution optimizes both heat transfer surface area and flow path characteristics, reducing pressure drops while maintaining effective heat exchange.
2Object-generated harmful factors
If flue gas recirculation is increased to reduce nitrogen oxide emissions, then emission levels decrease, but combustion temperature uniformity becomes harder to control
Solution Approach 1:
The heat exchanger tubes are strategically positioned and sized to create localized heat exchange zones within the connecting pipe. This allows different regions to have different heat transfer characteristics, enabling precise control over the temperature profile of the preheated combustion air while maintaining high flue gas recirculation rates for emission reduction.
3Use of energy by moving object
If a more complex heat exchanger design is used to improve thermal performance, then heat transfer efficiency increases, but manufacturing cost increases
Solution Approach 1:
The invention uses multiple simple, standardized tubes instead of a single complex heat exchanger structure. These simple tubes are easier and cheaper to manufacture using conventional processes, while collectively providing the required thermal performance through their combined surface area and counter-current flow arrangement.
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 design improves heat transfer efficiency, increases flue gas recirculation, reduces nitrogen oxide emissions, ensures reliable ignition, and lowers manufacturing costs by optimizing tube geometry and material usage, resulting in improved thermal performance and operational reliability.
Implementation Method 1
an outbound section for directing the air that is to be preheated toward a ferrule positioned at the end of the recuperator at the flue gas inlet end, and a return section opening toward a line supplying the burner with air
Implementation Method 2
the flue gases exchanging heat with the air across the exchanger tubes, the two fluids having parallel flows in opposite directions
Implementation Method 3
the ferrule defining a path for reversing the direction of flow of the combustion air and directing it toward the return section
Implementation Method 4
the assembly being designed so that part of the flue gases is entrained by and mixed with the combustion air so as to reduce the level of nitrogen oxides in the products of combustion
Implementation Method 5
to make the cold ignition of the burner more reliable
Data Source
AI summary
The invention relates to a heat recuperator (R) for a radiating tube burner having a burner pipe and an exhaust pipe (1), the recuperator being placed at the outlet of the exhaust pipe (1) and including a heat exchanger (E) that comprises: an outgoing section (5) for directing the air to be preheated to a ferrule (6), placed on the end of the recuperator, from the fume intake side, and a return section (7) opening towards a pipe (8) for supplying air from the burner, the assembly being provided such that part of the fumes are led through, and mix with, the combustion air; the heat exchanger (E) occupies only part of the cross-section of the exhaust pipe (1), the other part (1a) of the cross-section remaining free for the fumes; the combustion air is heated by the fumes in the outgoing section (5) and in the return section (7), being radially shifted outside the outgoing section (5) and immersed in the fumes.