Plate Heat Exchanger Bypass Passages for Freeze Prevention
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Solution Overview
Problem
In plate heat exchangers, fluid stagnation occurs near inlets and outlets, leading to rapid temperature drops and potential freezing, which damages the heat exchanger, and existing solutions either reduce heat transfer area or fail to effectively direct fluid flow.
Innovation Solution
A plate heat exchanger design with bypass passages that allow fluid to flow from inlet peripheral areas to heat-exchanging passages, reducing stagnation without decreasing the heat transfer area, by connecting upstream-side bypass passages to heat-exchanging passages with a gradually reducing cross-sectional area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sealed portions are provided near inlet and outlet to prevent fluid stagnation, then fluid stagnation is avoided, but heat transfer area is reduced
Solution Approach 1:
The passage is divided into multiple flow paths: a main flow path from inlet to outlet, and multiple bypass passages that branch off and reconnect. This segmentation allows fluid to take different routes, ensuring complete coverage of the heat transfer area while preventing stagnation in any single region.
Solution Approach 2:
Bypass passages are arranged in multiple layers stacked in the vertical direction, utilizing the third dimension to create additional flow paths without reducing the planar heat transfer area. This multi-layer bypass structure enables fluid to reach areas that would otherwise be stagnant while maintaining full heat exchange surface utilization.
2Ease of operation
If waves extend parallel to one another at regular intervals, then flow direction is controlled, but fluid velocity is reduced and stagnation occurs before reaching outer edges
Solution Approach 1:
The bypass passages have asymmetric cross-sectional areas that gradually change along the flow direction. The cross-sectional area is larger near the inlet side and gradually decreases toward the outlet side, creating a pressure gradient that maintains fluid velocity while controlling flow direction through the bypass passages.
Solution Approach 2:
The cross-sectional area parameter of the bypass passages is varied along the flow direction, transitioning from larger to smaller areas. This parameter change creates a pressure differential that drives fluid through the bypass passages at appropriate velocities, preventing both stagnation and excessive speed.
3Ease of operation
If radial waves are provided, then flow paths are created, but no passages force fluid toward outer edges opposite inlet/outlet, resulting in stagnation
Solution Approach 1:
Different regions of the heat transfer plate have different structures: the central region has the main inlet and outlet, while the peripheral regions have bypass passages that specifically target areas prone to stagnation. Each local region is optimized with appropriate bypass passage configurations to ensure fluid reaches all necessary areas.
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
Prevents fluid stagnation, maintains effective heat transfer, and reduces the risk of freezing, enhancing the heat exchanger's performance and reliability.
Implementation Method 1
the upstream-side bypass passage allowing some of the first fluid having flowed therein from the inlet to flow from the long-side-peripheral portion into the heat-exchanging passage
Implementation Method 2
a heat-exchanging passage formed between the inlet and the outlet and in which the first fluid and the second fluid that flows through the second passage adjacent to the first passage exchange heat therebetween
Data Source
AI summary
A plate heat exchanger includes a plurality of rectangular plates each having, at four corners thereof, inlets and outlets and others for a first fluid and a second fluid. The plates are stacked such that first passages each defined by adjacent two of the plates and through which the first fluid flows and second passages each defined by adjacent two of the plates and through which the second fluid flows are provided alternately. The first passage includes a bypass passage extending from an inlet peripheral portion, which is an area around the inlet, along the outlet for the second fluid up to a long-side-peripheral portion of the plate that is nearer to the second outlet. The bypass passage allows some of the first fluid having flowed therein from the inlet to flow from the long-side-peripheral portion into a heat-exchanging passage.