Double-Walled Dry Heat Exchanger Coil Leak Detection
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Solution Overview
Problem
Existing dry transformer cooling systems are costly and complex, with chambered headers restricting efficient circuit design and requiring multiple leak detectors, which can lead to water contamination and system failure in marine environments.
Innovation Solution
A non-evaporative heat exchanger coil design featuring straight inner tubes connected by return bends outside the air flow, with outer tubes capturing leaks and directing them to a drip pan for detection, eliminating the need for chambered headers and allowing continued operation despite leaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chambered headers with separate chambers for inner and outer tubes are used, then leak detection capability is provided, but device complexity and material cost increase
Solution Approach 1:
The patent merges the leak detection function into the existing header structure by utilizing the space between inner and outer tubes. Instead of creating separate chambered headers, the design allows leaked fluid to travel through the annular space to a detection point, combining structural support and leak detection in a single integrated header assembly.
Solution Approach 2:
The header serves multiple functions: it provides structural support for both inner and outer tubes, acts as a flow distribution manifold, and incorporates leak detection capability through the annular space between tubes. This multi-functionality eliminates the need for separate chambered structures while maintaining all necessary capabilities.
2Reliability
If chambered headers are used to capture leaks, then leak detection is enabled, but manufacturing cost and construction complexity increase
Solution Approach 1:
The leak capture function is merged with the header structure by using the annular space between inner and outer tubes as the leak collection path. This eliminates the need for separate capture chambers, reducing manufacturing steps and material requirements while maintaining effective leak capture capability.
3Reliability
If chambered headers with separate tube terminations are used, then leak isolation is provided, but coil circuiting flexibility is restricted
Solution Approach 1:
The coil is segmented into multiple circuits with independent flow paths. The header design allows flexible configuration of these segments, enabling various circuiting patterns (series, parallel, or combinations) while maintaining leak isolation capability through the annular space between tubes that directs leaked fluid to detection points regardless of circuit configuration.
4Reliability
If double-walled tubes are used throughout the entire coil including return bends, then leak detection is provided, but material cost and construction complexity increase
Solution Approach 1:
The double-walled construction is applied locally only where heat exchange is required (straight tube sections), while return bends use single-walled construction. This localized approach maintains leak detection capability in the critical heat exchange zones while reducing overall material cost and construction complexity in non-critical sections where heat exchange is not needed.
Solution Approach 2:
The outer tube is extracted or omitted from the return bend sections where it is not needed for heat exchange. This reduces material usage and simplifies construction in areas where the protective and detection functions are less critical, while maintaining double-walled construction in the heat exchange zones where it provides maximum benefit.
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 design provides a cost-effective, flexible cooling solution that prevents water contamination and allows marine transformers to operate safely until repairs can be made, reducing downtime and maintenance costs.
Implementation Method 1
air used for cooling a transformer is passed over a series of coils through which water is circulated
Implementation Method 2
Air is passed only over the tubes... Cooling fluid is circulated through the inner tubes
Implementation Method 3
the inner surfaces of the outer tubes are dimpled, grooved, ribbed, or otherwise patterned to create both contact points and voids between the inner and outer tubes
Implementation Method 4
Leaks occurring in the straight inner tubes are captured by the outer tubes and the leaking fluid will flow in the space between the inner and outer tubes, drip or flow out the end of the outer tube, outside of the air flow path, to be captured in a drip pan or leak detector box
Data Source
Figure 1A
Figure 1B
Figure 2A~2B
AI summary
A dry heat exchanger coil having a plurality of straight inner tubes connected by a plurality of return bends. The return bends are located outside of the air flow passing over the coil. The inner tubes are situated within a corresponding outer or "safety" tube. The outer tubes do not contain and are not connected to return bends, but the ends of the outer tubes are located outside of the air flow path. Leaks in the inner tubes are captured by the outer tubes and the leaking fluid will flow in the space between the inner and outer tubes, flow out the end of the outer tube, to be captured in a drip pan at the bottom of the coil housing. Leaks occurring in the return bends will also be captured in drip pan.