Double Cavity Evaporator Tubes for Refrigerant Boiling
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Solution Overview
Problem
Existing heat transfer tubes for evaporators in air conditioning and refrigeration systems fail to significantly enhance boiling heat transfer coefficient and are heavy due to inefficient nucleation sites and material usage.
Innovation Solution
A heat transfer tube design featuring outer fins with a double cavity structure, including fin top platforms with lateral fins that form a double cavity structure, enhancing vapor bubble growth and nucleation sites while reducing material and weight by minimizing fin height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional outer fin structures with channels or cavities are used to form nucleation sites, then boiling heat transfer is enhanced, but the heat transfer tube becomes heavy and wastes raw material
Solution Approach 1:
The invention changes the geometric parameters of the fin structure by introducing lateral fins that extend from the outer fin walls into the channel chambers, creating a double cavity structure. This modifies the cavity volume and shape parameters to optimize nucleation site effectiveness while reducing the overall fin height and material usage, thereby reducing weight while maintaining enhanced boiling heat transfer performance.
Solution Approach 2:
The invention segments the single channel chamber into two separate cavities by introducing lateral fins that divide the channel chamber along its length. This segmentation creates multiple nucleation sites within what would otherwise be a single large cavity, improving boiling heat transfer efficiency while allowing the outer fin height to be reduced, thus decreasing material consumption and weight.
2Productivity
If fin height is increased to enhance heat transfer surface area, then boiling heat transfer performance improves, but the tube weight and material usage increase
Solution Approach 1:
The invention transitions from a two-dimensional fin surface area enhancement approach to a three-dimensional double cavity structure by extending lateral fins into the channel chamber depth. This dimensional change creates additional heat transfer surfaces within the existing fin height, providing enhanced boiling heat transfer performance without increasing the overall fin height and material consumption.
Solution Approach 2:
The lateral fins are nested within the channel chambers, extending from the outer fin walls into the cavity space. This nesting arrangement creates additional heat transfer surfaces and nucleation sites within the existing structural envelope, enhancing heat transfer performance without requiring additional material or increasing the overall tube dimensions.
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 double cavity structure improves boiling heat transfer coefficient and boiling heat transfer performance while reducing the tube's weight by enlarging the liquid micro layer area under vapor bubbles and maintaining nucleation sites, thus enhancing overall heat transfer efficiency.
Implementation Method 1
the boiling of a liquid requires the existence of nucleation sites for evaporating... Cavities formed from grooves and cracks in the heating surface most probably become nucleation sites for evaporating
Implementation Method 2
evaporation of liquid micro layers between the wall and the bottoms of the vapor bubbles plays an important role and even a dominant role in the growing process of the vapor bubbles
Implementation Method 3
it has a much small thermal resistance... the liquid micro layer below the vapor bubble has a thickness of the order of magnitude of about 1 micrometer
Implementation Method 4
as it is difficult for a portion of steam retained by the cavities to be completely expelled by a liquid flowing towards the cavities due to the action of surface tension of the liquid
Data Source
AI summary
Heat transfer tubes for evaporators in air conditioning and refrigeration systems, each tube including: a tube body (1); outer fins (2) extending on an outer wall surface of the tube body (1) and having outer fin walls opposite to the outer fin walls of the adjacent outer fins; channels (6) located between the adjacent fins (2) so as to constitute channel chambers; fin top platforms (3) on respective tops of the outer fins (2), the fin top platforms (3) including fin top edges (3a) extending from both sides of the fin top platforms (3) so that the channel chambers form a cavity structure as a whole; channel chamber openings constituted by gaps between the adjacent fin top edges (3a) of the fin top platforms (3) of the outer fins; and lateral fins (4) arranged on portions or substantially middle portions of the outer fin walls of the outer fins (2) in a height direction of the outer fins (2) and at intervals in an spreading direction of the outer fins (2), so that the cavity structure is formed into a double cavity structure.