Tube Sheet Brazing Assembly for Leak-Proof Heat Exchangers
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Solution Overview
Problem
Current methods for attaching tubes to tube sheets in shell and tube heat exchangers are prone to leakage and require difficult stainless steel welds, which are susceptible to failure.
Innovation Solution
A method involving the insertion of tubes through apertures in multiple tube sheets, followed by the injection of brazing material into a fill channel and heating to the melting point, allowing capillary action to form durable brazed joints between the tubes and tube sheets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical expansion and seal welding is used to attach tubes to tube sheets, then the joint is sealed to prevent leakage, but the welds are difficult to perform and prone to failure in service
Solution Approach 1:
The patent replaces the mechanical welding process with a brazing process that uses capillary action to draw molten brazing material into the joint between the tube and tube sheet. This substitution eliminates the difficulty of performing stainless steel welds while maintaining joint reliability, as the brazing material flows automatically into the joint space without requiring complex welding operations.
Solution Approach 2:
The patent changes the temperature parameter by heating the assembly to the melting point of the brazing material (approximately 2000°F to 2500°F). This temperature change causes the brazing material to melt and flow into the joint via capillary action, creating a reliable bond without the need for difficult welding operations. The parameter change from ambient to elevated temperature enables the brazing process to overcome the welding difficulty issue.
2Object-affected harmful factors
If stainless steel welds are used to join tubes and tube sheets, then the joint is sealed, but the welds are susceptible to failure and cross-contamination
Solution Approach 1:
The patent substitutes the welding process with a brazing process that uses capillary action to fill the joint with brazing material. This substitution creates a more reliable joint that is less susceptible to failure and cross-contamination, as the brazed joint provides a sealed connection without the vulnerabilities associated with stainless steel welds in bioprocessing applications.
Solution Approach 2:
The patent introduces brazing material as an intermediary substance that fills the joint between the tube and tube sheet. This brazing material acts as a mediator that creates a sealed, reliable connection, replacing the direct weld metal approach. The brazing material flows into the joint via capillary action and provides a sealed connection that prevents leakage and cross-contamination while being more resistant to failure than stainless steel welds.
3Strength
If brazing material is injected into the fill channel and heated to melting temperature, then durable brazed joints are formed, but the process requires precise temperature control and heating equipment
Solution Approach 1:
The patent replaces complex welding equipment with a heating system that simply raises the temperature to the brazing material's melting point. This substitution reduces device complexity while achieving strong joints, as the heating process is simpler than welding equipment but still provides durable brazed joints through capillary action.
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 method creates a robust and leak-proof joint that prevents cross-contamination in case of failure, addressing the issues of leakage and weld failure in traditional methods.
Implementation Method 1
heating to a melting point of the brazing material
Implementation Method 2
allowing capillary action to form durable brazed joints between the tubes and tube sheets
Data Source
AI summary
A method for heat exchanger construction includes inserting a plurality of tubes through corresponding apertures in a first tube sheet and inserting the plurality of tubes through corresponding apertures in a second tube sheet. Brazing material is injected into a fill channel in the first tube sheet and then the heat exchanger is heated to a melting temperature of the brazing material. The tube and shell heat exchanger has a plurality of tubes coupled within apertures in a first tube sheet and apertures in a second tube sheet. Brazing material inserted through a fill channel in the first tube sheet forms a brazed joint between the tubes and tube sheets.