Flexible Header Heat Exchanger for Supercritical CO2
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Solution Overview
Problem
Conventional heat exchangers face challenges in efficiently managing thermal expansion and stress within high-temperature, high-pressure fluid systems, particularly in supercritical carbon dioxide power cycles, where temperature gradients and pressure differences lead to structural integrity issues and reduced efficiency.
Innovation Solution
A heat exchanger design featuring small-diameter, closely spaced tubes with a flexible header and baffles to prevent bypass flow, allowing for effective heat transfer and mitigating thermal stresses through a counter-flow arrangement and flexible header configuration, which reduces thermal and mechanical stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid header is used to maintain structural stability, then structural integrity is improved, but thermal stress and mechanical stress increase due to thermal expansion
Solution Approach 1:
The header is designed with dynamic flexibility to adapt to thermal expansion conditions. The header can flex and deform elastically in response to temperature changes, allowing the structure to accommodate thermal growth without generating excessive stresses. This dynamic behavior resolves the contradiction by maintaining structural integrity while reducing thermal stress through controlled flexibility.
Solution Approach 2:
The material properties or geometric parameters of the header are optimized to balance rigidity and flexibility. By adjusting parameters such as thickness, material modulus, or cross-sectional geometry, the header achieves an optimal state where it maintains sufficient structural strength while possessing enough flexibility to accommodate thermal expansion without excessive stress accumulation.
2Ease of manufacture
If tubes are spaced farther apart to reduce manufacturing complexity, then ease of manufacture is improved, but heat transfer efficiency decreases
Solution Approach 1:
Instead of using a single large header, the design employs multiple smaller headers or tube bundles arranged in a modular configuration. This allows the system to achieve high heat transfer efficiency through increased surface area and closer effective tube spacing, while each individual header unit remains simple to manufacture. The modular approach copies the basic header-tube assembly multiple times to achieve the desired overall performance.
3Stress or pressure
If the header is made more flexible to accommodate thermal expansion, then thermal stress is reduced, but structural integrity may be compromised
Solution Approach 1:
The header incorporates flexible elements or thin-walled structures that can deform elastically under thermal load. These flexible portions are strategically designed to accommodate thermal expansion while maintaining sufficient structural strength through appropriate material selection, wall thickness optimization, and geometric design. The flexible shell approach allows stress reduction without compromising overall structural integrity.
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
Enhances heat transfer efficiency and structural integrity by allowing for flexible thermal expansion, reducing stress and maintaining high efficiency in supercritical carbon dioxide power cycles, thereby improving energy recovery and system performance.
Implementation Method 1
heating, via a heat exchanger, the source fluid via transfer of heat from the exhaust fluid
Data Source
AI summary
A heat exchanger includes a shell housing a plurality of tubes and defining an exhaust fluid flow path within a first volume enclosed by the shell. The outer surfaces of the plurality of tubes are in fluid communication with the exhaust fluid flow path. The heat exchanger includes a cap attached to a first end of the shell and defining a second volume. A header is configured to separate the first volume from the second volume, flex with thermal expansion, and define tube inlet and outlet positions. The tube inlets and outlets are in fluid communication with a source fluid flow path, and each tube is substantially U-shaped and defines a flow path of the source fluid within the exhaust fluid flow path. The heat exchanger includes at least one longitudinal flow baffle within the shell configured to reduce an amount of exhaust fluid that may bypass the tubes.