Brazed Plate Heat Exchanger Freezing Detection
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Solution Overview
Problem
Brazed plate heat exchangers used as evaporators face challenges with freezing of water, leading to ice expansion and potential mechanical integrity issues, which can result in costly repairs and environmental hazards due to refrigerant leakage.
Innovation Solution
The implementation of a brazed plate heat exchanger with deformable wall portions in the cells, which are designed to absorb fluid volume expansion and provide early detection of freezing through sensor means, allowing for corrective actions to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heat exchanger plates are designed to withstand freezing without consequences, then the mechanical integrity is maintained, but the system cannot detect freezing conditions early enough to prevent damage
Solution Approach 1:
The patent introduces deformable wall portions and sensor means as preliminary detection mechanisms that activate before actual damage occurs. The deformable walls are designed to deform under freezing conditions, triggering sensors that alert operators before the ice expansion causes plate breaking or refrigerant leakage.
Solution Approach 2:
The patent uses deformable wall portions as intermediary elements between the freezing water and the rigid plate structure. These deformable walls absorb the initial expansion stress and trigger detection sensors, acting as a buffer that prevents direct transmission of freezing damage to the plate integrity while enabling early detection.
2Reliability
If deformable wall portions are added to absorb ice expansion, then freezing damage is prevented, but the device complexity increases
Solution Approach 1:
The patent applies deformable wall portions only in specific localized areas where ice expansion is most likely to cause damage, rather than making the entire plate structure deformable. This selective application maintains structural integrity where needed while providing flexibility where ice expansion occurs, thereby limiting the increase in overall device complexity.
Solution Approach 2:
The deformable wall portions function as flexible elements that can deform under freezing conditions. These thin, flexible walls are integrated into the plate structure and are designed to deform elastically to absorb ice expansion, providing protection without requiring a complete redesign of the entire heat exchanger structure.
3Difficulty of detecting and measuring
If sensor means are added to detect freezing, then early detection is enabled, but the manufacturing cost increases
Solution Approach 1:
The sensor means are integrated into the deformable wall portions such that the freezing condition itself triggers the detection mechanism. The deformation of the deformable walls under freezing conditions automatically activates the sensors, eliminating the need for separate active sensing systems and reducing manufacturing complexity and cost.
Solution Approach 2:
The patent employs visual indicators or color-changing elements as part of the detection system. When the deformable walls deform due to freezing, this physical change can be visually detected through color changes or other optical indicators, providing a simple, low-cost detection method that does not require complex electronic sensing systems.
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 solution effectively alerts operators to freezing conditions, enabling timely corrective actions to prevent damage and refrigerant leakage, thus reducing maintenance costs and ensuring operational safety.
Implementation Method 1
Each cell is separated by the first plate interspaces and/or the second plate interspaces through respective deformable wall portions. The deformable wall portions have a mechanical strength which is lower than the average mechanical strength of the metal sheets of the heat exchanger plates.
Implementation Method 2
at least one channel is provided between each cell and one of the side edges of the heat exchanger plates. Each channel puts in fluid connection the internal volume of the respective cell with the environment outside the heat exchanger.
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
A brazed plate heat exchanger (10) comprises a plurality of heat exchanger plates (12A, 12B, 12C) which are stacked onto one another. The heat exchanger plates (12A, 12B, 12C) are obtained by forming from respective metal sheets and are permanently joined to each other through brazing by means of a braze material, so as to form a plate package (30) provided with first plate interspaces (32) for a first fluid and second plate interspaces (34) for a second fluid. Each of the heat exchanger plates (12A, 12B, 12C) is provided with a plurality of portholes (P1, P2, P3, P4) and with one or more side edges (26, 28) which form the outer perimeter of the heat exchanger plates (12A, 12B, 12C). The brazed plate heat exchanger (10) comprises a plurality of cells (36) having a predefined internal volume (V). Each cell (36) is integral with a corresponding heat exchanger plate (12A, 12B, 12C) and is separated by the first plate interspaces (32) and/or the second plate interspaces (34) through respective deformable wall portions (38). The deformable wall portions (38) have a mechanical strength which is lower than the average mechanical strength of the metal sheets of the heat exchanger plates (12A, 12B, 12C). At least one channel (40) is provided between each cell (36) and one of the side edges (26, 28) of the heat exchanger plates (12A, 12B, 12C), each channel (40) putting in fluid connection the internal volume (V) of the respective cell (36) with the environment outside the brazed plate heat exchanger (10).