Molten Salt Heat Exchanger Helical Baffles U-Tubes
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Solution Overview
Problem
Current heat exchangers in Molten Salt Steam Generators for Concentrated Solar Power plants face inefficiencies in thermal gradient flexibility, pressure drop, internal leakage, fouling, and reliability, with existing designs not adequately addressing these issues.
Innovation Solution
A heat exchanger design featuring parallel U-bent tubes connected via a 180° bend, with an internal and external cylindrical shell forming an annular flow path and utilizing continuous helical baffles to enhance heat transfer and reduce pressure drop, along with a thicker tube sheet to manage pressure differences and prevent leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional shell and tube heat exchanger design is used, then structural simplicity is maintained, but thermal efficiency and heat transfer coefficient are insufficient
Solution Approach 1:
The heat exchanger is divided into multiple passes with separate inlet and outlet manifolds, allowing independent optimization of each pass for heat transfer efficiency while maintaining manageable structural complexity through modular design
Solution Approach 2:
Spherical end caps are used instead of conventional flat or dished ends, providing uniform stress distribution and optimal fluid distribution across the tube bundle, enhancing both thermal efficiency and structural integrity without significantly increasing complexity
2Productivity
If straight tube design is used, then manufacturing ease is maintained, but pressure drop is high and heat transfer is insufficient
Solution Approach 1:
The tubes are bent into U-shapes with optimized curvature radii, extending the heat transfer surface area within the same footprint and improving heat transfer coefficient while maintaining manufacturability through standard tube bending processes
Solution Approach 2:
The tube arrangement transitions from a single-plane configuration to a three-dimensional U-tube bundle configuration, utilizing vertical and horizontal spaces more efficiently to increase heat transfer area without proportionally increasing device volume
3Reliability
If thin tube sheet is used, then device complexity is reduced, but internal leakage and reliability are increased
Solution Approach 1:
The tube sheet is designed with variable thickness, being thickest at the center where tubes are most densely packed and experiencing highest stress, gradually thinning toward the edges, providing enhanced leakage prevention where needed while minimizing overall material usage and complexity
4Productivity
If conventional baffle design is used, then device complexity is maintained, but fouling and pressure drop are increased
Solution Approach 1:
The shell is equipped with preliminary filtering screens or strainers at the inlet, preventing particulate matter from entering the heat transfer zones and causing fouling before it can accumulate on tube surfaces or in baffle areas
Solution Approach 2:
Continuous helical baffles are used instead of discrete segmental baffles, creating a smooth continuous flow path that eliminates dead zones and stagnation areas where fouling would accumulate, maintaining consistent heat transfer efficiency throughout operation
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 achieves improved thermal efficiency, reduced internal leakage, enhanced heat transfer coefficients, easier drainage, and increased reliability, while maintaining a competitive cost and long lifetime.
Implementation Method 1
an annular space between an internal cylindrical shell (3) and an external cylindrical shell (4) allowing a hot thermal fluid (second fluid) to flow in a helical path through the annular space and heat the process fluid (first fluid) flowing in the tubes
Implementation Method 2
continuous helical baffles to enhance heat transfer and reduce pressure drop
Implementation Method 3
The ends of each tube 21 are connected to water boxes or plenums 29 through holes provided in separating plates called 'tube sheets' 27. The tubes 21 may be straight, as depicted in FIG. 2, or bent in 'U' (U-tubes)
Implementation Method 4
said intershell space enclosing the baffles, each said connection being made of a tube sheet which is designed to withstand the difference between the second fluid low pressure inside said intershell space and the first fluid high pressure inside the respective bonnet
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A heat exchanger (1), wherein the bundle of parallel U-bent tubes (2) is connected via a connection to a first end, where a first hemispherical bonnet (16) distributes the first fluid to the tubes (2) of the first straight section (9), and to a second end, where a second hemispherical bonnet (16) collects the first fluid from the tubes (2) of the second straight section (10), each said connection being made of a tube sheet (11, 12) which is designed to withstand the difference between the second fluid low pressure inside the intershell space (5) and the first fluid high pressure inside the respective bonnet (16), wherein the tube sheet comprises a circular plate (12) having a central circular orifice and wherein the tube sheet further comprises a hemispherical shell (11) located over said orifice and tightly connected to said circular plate (12), so as to make a physical separation between the first fluid and the second fluid.