Expanded Heat Transfer Pipe Geometry for Low Pressure Loss
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Solution Overview
Problem
Heat exchangers with metal heat transfer pipes face issues of reduced condensation/evaporation performance due to crushed tall projections during expansion, leading to decreased adhesion with fins and increased pressure loss, which affects the efficiency of refrigeration cycle devices.
Innovation Solution
The heat transfer pipe design features tall and short projections with specific geometric configurations, where the height difference between them is maintained to optimize surface area and adhesion, and the pipe-expanding method is adjusted to prevent deformation of short projections, ensuring efficient heat transfer without increasing pressure loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the heat transfer pipe is expanded by the mechanical pipe-expanding method, then the adhesion between the heat transfer pipe and fins is improved, but the tall projections are crushed and the condensation/evaporation heat transfer performance is reduced
Solution Approach 1:
The invention creates different types of projections with different heights on the inner surface of the heat transfer pipe. The first projections (tall projections) have a height of 0.03mm to 0.06mm to provide adhesion with fins, while the second projections (short projections) have a height of 0.01mm to 0.03mm to prevent crushing during expansion. This local differentiation of projection heights resolves the contradiction between needing tall projections for adhesion and preventing their crushing during the expansion process.
2Strength
If the plate thickness at the bottom of grooves is increased to prevent deformation, then the strength of the heat transfer pipe is improved, but the pressure loss in the pipe increases
Solution Approach 1:
The invention optimizes the plate thickness parameter at the bottom of grooves to be within the range of 0.01mm to 0.03mm. This parameter change maintains sufficient strength to prevent deformation during expansion while keeping the groove depth adequate to maintain low pressure loss. By precisely controlling this parameter, the contradiction between strength and pressure loss is resolved.
3Area of stationary object
If the width of the tip portion of first projections is increased, then the adhesion area with fins is improved, but the pressure loss in the pipe increases
Solution Approach 1:
The invention creates a local quality difference in the width of the first projections, making the tip portion width (0.02mm to 0.04mm) larger than the base portion width (0.01mm to 0.02mm). This local expansion at the tip portion maximizes the adhesion area with fins where it is most needed, while maintaining a narrower base portion to minimize the impact on pressure loss in the pipe.
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 enhances condensation/evaporation heat transfer performance while maintaining low pressure loss, resulting in a high-efficiency heat exchanger with improved adhesion to fins, reducing energy consumption and allowing for size reduction.
Implementation Method 1
a pipe-expanding ball is pushed into the pipe to expand the heat transfer pipe from the inside so that the heat transfer pipe comes into close contact with the fins and is bonded to the fins
Implementation Method 2
The refrigerant that flows through the heat transfer pipe undergoes a phase change (condensation or evaporation) as a result of heat exchange with air or the like outside the heat transfer pipe
Implementation Method 3
The refrigerant that flows through the heat transfer pipe undergoes a phase change (condensation or evaporation) as a result of heat exchange with air or the like outside the heat transfer pipe
Implementation Method 4
The refrigerant that flows through the heat transfer pipe undergoes a phase change (condensation or evaporation) as a result of heat exchange with air or the like outside the heat transfer pipe
Implementation Method 5
utilizing a fluid agitation effect provided by the groove portions or an effect of holding a liquid film between the groove portions provided by capillary action of the groove portions
Data Source
Figure 1(a)~1(b)
Figure 2(a)~2(b)
Figure 3~4
AI summary
A heat exchanger includes fins that are arranged in a direction orthogonal to a direction in which air flows and a heat transfer pipe 20 that extends through the fins and that is bonded and fixed to the fins when the heat transfer pipe 20 is radially expanded by a pipe-expanding method. Tall projections 22A and short projections 22B are provided on an inner surface of the heat transfer pipe 20. The tall projections 22A are arranged in a circumferential direction and extend in an axial direction of the heat transfer pipe 20. The short projections 22B are arranged between the tall projections 22A and extend in the axial direction. A height of the tall projections 22A is greater than or equal to a height of the short projections 22B after the expansion of the heat transfer pipe 20. Opposing side surfaces of the tall and short projections 22A and 22B after the expansion of the heat transfer pipe 20 are so inclined that when extensions are drawn from the side surfaces, the extensions cross each other in an inner region of the heat transfer pipe 20.