Why do many factories use elliptical flat tubes
Source：
h3652.cn Release date： 2025-06-16
Information summary：Elliptical flat tube is a type of pipe with an elliptical or rectangular cross-section, widely used in factory production due to its unique structural design, performance advantages, and process adaptability. The core reasons for factories using elliptical flat tubes are analyzed from multiple dimensions as follows:
1、 Heat transfer efficiency and advantages of fluid mechanics
1. Strengthen heat
Elliptical flat tube is a type of pipe with an elliptical or rectangular cross-section, widely used in factory production due to its unique structural design, performance advantages, and process adaptability. The core reasons for factories using elliptical flat tubes are analyzed from multiple dimensions as follows:
1、 Heat transfer efficiency and advantages of fluid mechanics
1. Strengthen heat transfer performance
Structural principle: The flat cross-section of the elliptical flat tube increases the contact area with fluids (air, water, refrigerant, etc.). Compared with the commonly used 10mm round tube and 5mm × 15mm elliptical flat tube, the latter can increase the surface area by 20% -30%, and the heat transfer efficiency is significantly improved under the same length.
Application scenarios:
Air conditioner heat exchanger: After using elliptical flat tubes for the evaporator/condenser of household air conditioners, the heat transfer can be increased by 15% -20%. For example, a certain brand of air conditioner uses a φ 7mm × 16mm aluminum flat tube, which increases the energy efficiency ratio (COP) by 0.3-0.5.
Car radiator: The engine cooling water tank uses elliptical flat tubes, which increase the turbulence level when air flows (vortices are generated at the edges of the flat tubes), resulting in a 10% -15% higher heat dissipation efficiency than circular tubes, and can reduce the volume of the radiator.
2. Reduce fluid resistance
Aerodynamic advantages: The streamlined cross-section of the elliptical flat tube (with the long axis parallel to the fluid direction) can reduce wind resistance. For example, when air flows through a circular tube at a speed of 5m/s, the resistance coefficient is about 1.2, while when flowing through an elliptical flat tube with a length to length ratio of 3:1, the resistance coefficient can be reduced to 0.8, which is suitable for scenarios sensitive to wind noise and energy consumption (such as household electric fans and ventilation ducts).
2、 Space utilization and lightweight design
1. Compact layout suitable for narrow spaces
Advantages of flat structure: Elliptical flat tubes can be arranged in parallel to form flat bundles, occupying less space. For example, the thickness of the refrigerator condenser can be reduced from 80mm to 50mm by using flat tubes, saving 25% of installation space and making it easy to integrate into ultra-thin household appliances.
Application in the automotive field: The cooling plate for new energy vehicle batteries uses 0.5mm × 10mm ultra-thin aluminum flat tubes, which can be embedded in the gaps between battery modules to achieve millimeter level space utilization while ensuring coolant flow (for example, after using flat tubes for a certain vehicle model's cooling plate, the temperature difference between the batteries is controlled within ± 2 ℃).
2. Lightweight and material saving
Under the same strength, the weight is lighter: the cross-sectional moment of inertia (resistance to bending) of elliptical flat tubes is better than that of circular tubes. Taking 6063 aluminum alloy as an example, the bending strength of a 10mm × 20mm flat tube (with a wall thickness of 1mm) is similar to that of a φ 16mm round tube (with a wall thickness of 1mm), but the weight is reduced by 15% -20%, making it suitable for lightweight demand scenarios such as aerospace and rail transit (such as reducing the weight of flat tubes for high-speed rail air conditioning heat exchangers by 30%).
Improved material utilization: Flat tubes can be processed in one go through extrusion molding, reducing cutting waste. For example, the waste rate for producing 1 meter diameter 12mm round pipes is about 8%, while the waste rate for 10mm × 20mm flat pipes is only 3%, which is particularly suitable for processing high priced metals such as aluminum and copper.
3、 Process adaptability and production efficiency
1. Easy to integrate and connect
Welding and assembly advantages: The flat surface of the elliptical flat tube is easy to weld (such as brazing, laser welding), and can form a large area of contact with the fins and bottom plate. The welding strength is high and the sealing is good. For example, in air conditioning heat exchangers, flat tubes and fins are connected through tube expansion technology, which reduces the contact thermal resistance by 40% compared to circular tubes, and significantly reduces the risk of fluoride leakage.
Convenience of bending forming: Flat pipes have good flexibility in the long axis direction and can be processed into complex curves (such as U-shaped and S-shaped) through CNC bending machines, while round pipes are prone to elliptical deformation during bending. A certain car oil cooler uses flat tubes bent into a spiral shape, achieving a heat transfer area of 12 square meters in a 0.5m 3 space, which is 50% higher than the circular tube scheme.
2. High efficiency of large-scale production
Advantages of extrusion molding: Elliptical flat tubes can be continuously produced through mold extrusion, with a speed of 5-10 meters/minute, suitable for large-scale manufacturing. For example, a certain aluminum profile factory produces 50 tons of flat tubes per day, which is 1.5 times the production capacity of round tubes of the same specification, and the dimensional tolerance is controlled within ± 0.1mm.
Automated processing compatibility: The regular cross-section of flat tubes is easy for automated equipment to grasp, transport, and process. For example, on a heat exchanger production line, flat tubes can be automatically loaded, punched, and finned by robots, reducing the production cycle time to 15 seconds per piece, which is three times more efficient than manual assembly of round tubes.
4、 Targeted demands for specific industries
1. Household appliances and refrigeration industry
Energy efficiency and volume balance: Refrigerators, air conditioners and other equipment pursue "small volume, high cooling capacity", and the heat transfer advantage of elliptical flat tubes can reduce the size of heat exchangers. For example, a certain brand of 1.5-horsepower air conditioner uses a 7mm × 16mm aluminum flat tube, which reduces the volume of the external unit by 10% while maintaining the same cooling capacity.
Noise reduction requirement: The streamlined design of the flat tube reduces air flow noise. Tests have shown that the outdoor unit noise of air conditioners using flat tubes is 2-3 decibels lower than that of circular tube solutions, which meets the household appliance noise reduction standards (such as the national standard requiring outdoor unit noise to be ≤ 55 decibels).
2. In the field of automobiles and new energy
Optimization of thermal management system: The cooling system for electric vehicle batteries and motors adopts flat tubes, which can achieve temperature control. For example, the battery cooling plate of Tesla Model 3 uses 0.3mm × 8mm ultra-thin flat tubes, and when the coolant flow rate is 0.5m/s, the battery temperature fluctuation is ≤ 1 ℃, ensuring the stability of the battery life.
Vibration resistance and fatigue resistance: The cross-sectional structure of elliptical flat tubes has a more uniform stress distribution in vibration environments. A test conducted by a certain automobile manufacturer shows that the fatigue life of flat tube radiators in 50Hz vibration testing (simulating road conditions) reaches 1 million times, which is 50% higher than that of circular tubes, reducing the risk of oil and liquid leakage.
5、 Comprehensive advantages of cost and environmental protection
Material cost reduction: Taking aluminum flat tubes as an example to replace copper tubes, the amount of aluminum used is reduced by 30% under the same heat exchange area, and the price of aluminum is about one-third of that of copper. The cost of a single air conditioner heat exchanger can be reduced by 20-30 yuan.
Environmental protection and recycling advantages: The flat tube structure is simple, and the material purity is higher when disassembled and recycled. For example, the recycling rate of aluminum flat tube radiators in scrapped cars is 95%, while the recycling rate of round tubes is about 80% due to their complex structure, which meets the EU ELV environmental standards (waste recycling rate ≥ 95%).
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