Heat Exchanger Guiding Plates for Condensate Drainage
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Solution Overview
Problem
Flat tubes in heat exchangers used in air conditioners tend to retain water droplets due to their cross-sectional shape, leading to reduced heat transfer performance, increased pressure drop, and prolonged defrosting times, which can cause damage and discomfort.
Innovation Solution
The implementation of guiding structures comprising inclined guiding plates above flat tubes to utilize capillary and gravitational forces for efficient drainage, preventing water re-attachment and ensuring water droplets fall off the tubes, thereby enhancing drainage and reducing defrosting duration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flat tubes are used as heat transfer tubes, then heat exchange performance is improved due to increased heat transfer area and decreased airflow resistance, but drainage performance deteriorates because water droplets tend to remain on the tube surfaces due to its cross-sectional shape
Solution Approach 1:
The flat tube surface is segmented by providing multiple guiding structures (protrusions) along the tube length. Each guiding structure creates separate drainage zones, preventing water droplets from coalescing and remaining on the surface. The segmentation divides the continuous flat surface into controlled drainage sections that actively guide water off the tube.
Solution Approach 2:
Guiding structures (protrusions) are introduced as intermediary elements between the flat tube surface and the external environment. These protrusions act as mediators that capture water droplets from the flat tube surface and facilitate their removal, solving the drainage problem without changing the fundamental flat tube design that provides good heat exchange performance.
2Ease of operation
If protrusions are formed to provide drainage path with fins, then condensate water drainage is improved, but water droplets re-attach to one end of the flat tube causing insufficient drainage
Solution Approach 1:
The guiding structures are designed with specific local geometric properties - protrusions with optimized height, width, and spacing that create favorable surface tension gradients. The local quality of these protrusions (their specific dimensions and arrangement) ensures that water droplets are captured and guided off the tube end without re-attachment, addressing the insufficient drainage problem.
Solution Approach 2:
The invention optimizes parameters of the guiding structures including protrusion height (5-20% of tube diameter), spacing between protrusions, and their position relative to tube ends. By changing these geometric parameters, the drainage efficiency is maximized while preventing water re-attachment that occurs with conventional protrusion designs.
3Device complexity
If protrusions are only at one side of the flat tube, then drainage path is provided, but water droplets don't fall down from the other side and tend to remain there
Solution Approach 1:
The guiding structures are positioned asymmetrically with different configurations at each end of the flat tube. One end has protrusions optimized for capturing water from the top surface, while the other end has protrusions configured for removing water from the bottom surface. This asymmetric arrangement ensures comprehensive water removal from both sides without requiring symmetric complexity.
Solution Approach 2:
The guiding structures extend into the space above and below the flat tube surface, utilizing the third dimension (vertical space) to create drainage paths. By positioning protrusions at different heights and locations in the vertical dimension, the invention enables water droplets to be guided off both ends of the tube effectively, solving the one-sided drainage limitation.
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 described solution effectively reduces water retention on flat tubes, improving heat exchanger performance by facilitating automatic drainage through capillary and gravitational forces, thus addressing issues of condensate retention and frost accumulation.
Implementation Method 1
utilize capillary and gravitational forces for efficient drainage
Implementation Method 2
utilize capillary and gravitational forces for efficient drainage
Data Source
Figure 1a~1d
Figure 2~3
AI summary
The invention relates to a heat exchanger (1), comprising a plurality of flat tubes (2) arranged in a first row in a main extension plane of the heat exchanger (1), the flat tubes (2) having a respective main extension plane and being configured to conduct a heat transfer medium, a plurality of plate fins (3) arranged in a second row in the main extension plane of the heat exchanger (1), where the second row extends in a direction transverse to the direction of the first row, and a plurality of guiding structures (4) for guiding condensed water (8) off the tubes (2), where each guiding structure (4) extends between two plate fins (3) along a corresponding tube (2), wherein each guiding structure (4) comprises at least a first guiding plate (5) with a first main extension plane and a second guiding plate (6) with a second main extension plane, where the first main extension plane is tilted with respect to the main extension plane of the flat tube (2) around a longitudinal axis of the flat tube (2) by a first tilt angle a1, and the second main extension plane is tilted with respect to the main extension plane of the flat tube (2) around the longitudinal axis of the flat tube (2) by a second tilt angle a2, with 0 degrees < al < a2 < 90 degrees, in order to provide a heat exchanger (1) with improved performance, in particular less problems with condensed water (8).