Inverse-L Fired Heat Exchanger Tubes for Steam Bubble Control
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Solution Overview
Problem
The formation of steam bubbles on the surface of the circular tube sheet in fired heat exchangers impedes heat exchange, and increasing the number of tubes for combustion gas flow to enhance efficiency is not feasible due to operational constraints.
Innovation Solution
The design features tubes for combustion gas flow that are inverse 'L' shaped with embossed ribs, holes at varying heights on the combustion chamber side wall, and a conical or cylindrical combustion chamber with a narrowing shape, along with a water distributor and drain tubes for efficient water distribution and condensate management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of tubes for combustion gas flow is increased to improve heat exchange efficiency, then heat transfer intensity increases, but the cross-sectional area of the heater increases which is not convenient for operating properties
Solution Approach 1:
The patent changes the geometric parameters of existing tubes by adding embossed ribs to create turbulence promoters, and by configuring inverse L-shape geometry. This modifies the flow characteristics and heat transfer coefficients without changing the number of tubes or overall heater dimensions, thus improving heat exchange efficiency while maintaining compact size.
Solution Approach 2:
The patent introduces a new spatial dimension by adding embossed ribs that protrude from the tube surfaces into the combustion gas flow path. This three-dimensional feature creates turbulence and extends the effective heat transfer surface area without increasing the planar cross-sectional area of the heater.
2Productivity
If steam bubbles form on the tube sheet surface due to high temperature, then heat exchange is impeded, but increasing tube number is not feasible
Solution Approach 1:
The embossed ribs on the tubes create mechanical turbulence in the combustion gas flow, which prevents steam bubbles from stabilizing on the tube sheet surface. The disturbed flow pattern continuously disrupts bubble formation and promotes better contact between combustion gases and heat exchange surfaces.
Solution Approach 2:
The patent utilizes the hydraulic characteristics of combustion gas flow by designing inverse L-shaped tubes with embossed ribs that optimize gas distribution and velocity profiles. This pneumatic design ensures high-velocity gas flow patterns that prevent steam bubble accumulation on horizontal surfaces.
3Productivity
If tubes are arranged to improve heat exchange, then heat transfer intensity increases, but device complexity increases
Solution Approach 1:
The patent segments the tube structure by adding embossed ribs that divide the tube surface into multiple zones, creating localized turbulence regions. This segmentation of the flow path enhances heat transfer without requiring multiple separate tube components, thus improving heat exchange intensity while maintaining relatively simple device structure.
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 heat exchange intensity by promoting turbulence and uniform water distribution, improving the overall heat transfer efficiency while maintaining operational convenience.
Implementation Method 1
The tubes for combustion gas flow are conveniently close in shape to the inverse letter 'L', with its shorter arm connected to the combustion chamber and having embossed ribs
Implementation Method 2
a fired heat exchanger, designed mainly for heating hot domestic or drinking water
Implementation Method 3
The combustion chamber side wall is either cylindrical or conical, with a narrowing upwards or downwards
Implementation Method 4
The combustion chamber bonnet is conveniently provided with at least one drain tube to discharge condensate from the combustion chamber and is inclined towards that drain tube
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The fired heat exchanger, having an outer shell (1), water inlet pipe (4) at the bottom and water outlet pipe (3) at the top part, with a combustion chamber (7) enclosed at the bottom with a bonnet (8) with a burner hole (9), connected with tubes (10) for combustion gas flow, through a flue duct (12), to the stack, whereby the tubes (10) for combustion gas flow are arranged in the water tank (14) around the combustion chamber (7) side wall and are connected with the flue duct (12) to the stack with the tube sheet (13) of the water tank (14), according to the invention, is characterised in that the tubes (10) for combustion gas flow are connected to the combustion chamber (7) through holes (11) made in the upper part of the combustion chamber (7) side wall. The tubes (10) for combustion gas flow are conveniently close in shape to an inverse letter "L", with its shorter arm connected to the combustion chamber (7) and having embossed ribs (15).