Extrusion ratio refers to the ratio between the cross-sectional area of the material before hot extrusion and the cross-sectional area after extrusion, generally in 8 to 50 times, while the cross-sectional area of the micro-channel aluminum tube is only about 4px2, extrusion ratio to reach more than 400 times, is more than 8 times the limit of aluminum extrusion process.

Micro-channel aluminum tube size accuracy is much higher than the “aluminum and aluminum alloy research to hot extrusion tube” national standards.

According to the national standard, the size deviation of typical varieties of width 16mm is ±0.3mm, while the width size deviation of micro-channel aluminum tube is ±0.03mm, and the high requirement even needs to be improved to ±0.01～±0.02mm.

A set of micro-channel heat exchanger has about 50 to 150 micro-channel aluminum tubes, as long as one airtightness defects (such as air holes, inclusions, etc.), the whole air conditioner will be scrapped, so the quality standard is measured in PPM (1 million pieces), and the measurement standard is 15 PPM or less.

The minimum limit wall thickness of micro-channel aluminum tube is only 0.13mm, if the purity of the cast bar material and hydrogen content cannot reach the requirement, as long as there is a very small pore or inclusions, it will make the thin wall of micro-channel aluminum tube leak, so it must use high purity refined bar with hydrogen content ≤ 0.09%.

Since the micro-channel aluminum tube has refrigerant medium inside and atmospheric corrosion outside, it is easy to produce leakage due to pitting corrosion, so a thin layer of zinc must be sprayed on its outer surface to protect the tube wall from corrosion.

There is no domestic manufacturer who can provide qualified zinc spraying equipment, and only a very few international manufacturers can provide it.

Due to the technical difficulty of micro-channel aluminum tube, there are many difficulties, how to use scientific and effective online flaw detection, surface quality and other inspection means in the production process, timely detection (marking) of defective products, the quality control of micro-channel aluminum tube is extremely critical.

Mainly including very low extrusion breakthrough force and very high dimensional accuracy and special molding capacity and has a very strong wear resistance hot extrusion die design, manufacturing technology; die wall wear resistance, heat resistance, the full application of super-lubrication technology; single multi-branch co-extrusion die multi-point temperature precision control technology.

Mainly including extruder die barrel constant temperature heating, equal speed extrusion technology; gradient heating technology of cast bar; porous micro ultra-thin wall balanced extrusion, thermal energy elimination and keep all links without product deformation factors and product defects technology; single multi-branch product winding and rewinding device and synchronization control technology, etc.

Mainly including the ability to select, modify, debug and combine various equipment according to the product production requirements; online zinc spraying and control technology; brazing roll coating online detection, defect marking and control feedback technology; product uncoiling, finishing, straightening and chipless cutting technology, etc.

The main performance is the ability to find the root cause of various problems in the production process in time and to find out the solution and the rapid response mechanism.

In 1989, the first international agreement to restrict the use of CFCs – the [Montreal Protocol] – was signed, thus accelerating the process of protecting ozone from chemical destruction. At that time, the preferred alternative was R22, which is now used in the majority of home and commercial air conditioners and other appliances today. But the massive consumption of R22 will bring another catastrophic damage to the earth – the greenhouse gas effect, so was also issued a ban: 65% in 2003, 35% in 2010, 10% in 2015, and a total ban in 2020 (later adjusted to 2030)! And has switched to R134a, R407C, R410a and other new environmentally friendly refrigeration, and first in the [automotive air conditioning system] to get mandatory use (EU regulations for 1996, China regulations for 2002). Now it is more common to use R410a with high pressure and high gas density, which can be used not only with smaller exhaust volume compressor, but also with smaller diameter pipeline and valve, so it becomes the best choice for home commercial refrigerant worldwide. The parallel flow micro-channel evaporator and condenser with high pressure resistance have become the best choice for home and commercial air conditioning systems.

Micro-channel heat exchangers (commonly known as parallel flow evaporators and condensers) were first researched by two professors at Stanford University in 1981, and began to be used in automotive air conditioning systems with the environmentally friendly refrigerant R134a as the refrigerant in 1996. At present, all automotive air conditioning systems in the world use this micro-channel heat exchanger.

The application of microchannel heat exchangers in domestic and commercial air conditioning systems is much later. First, the Japanese market was the fastest to shift to R410a, from the earliest use in small air conditioners of less than 2 hp, and gradually moved to large air conditioners, while taking measures to improve energy efficiency by expanding the heat exchange area of air conditioners to achieve high efficiency. The first choice for expanding the heat exchange area of air conditioners is undoubtedly the all-aluminum microchannel heat exchanger.

With the ban on the deadline is getting closer and closer, more and more well-known domestic and foreign air conditioning companies have begun to develop the use of all-aluminum micro-channel heat exchanger. The United States as early as nine years ago began to use all-aluminum microchannel heat exchanger on the home air conditioner, the U.S. air conditioning industry carrier “York” has 100% of the products on the use of all-aluminum microchannel heat exchanger; Japan and South Korea’s air conditioning production enterprises, such as Sharp, Samsung, etc. as early as a few years ago began the research of microchannel heat exchanger.

First, China’s air conditioning production became the world’s first many years ago, and in recent years has accounted for more than 70% of global annual air conditioning production, restrictions and bans on China is the first to bear the brunt.

Second, China’s national and commercial air conditioning market competition is extremely fierce, coupled with high copper prices so that enterprises can not afford, forcing companies to accelerate the “aluminum instead of copper” and the pace of application of new technologies, that is, to meet the environmental protection, efficiency, energy saving, but also to significantly reduce costs, and the same volume of aluminum price is only one twelfth of the price of copper, the application of parallel flow technology It is logical to become the main direction of cost reduction.

Third, the state has introduced a series of mandatory energy-saving policies, laws and regulations and industry standards. The air conditioner to achieve energy saving mainly three: one is the use of frequency control, but the frequency converter will increase the cost of many; two is in the copper tube heat exchanger refrigerant directly replaced with R410a refrigerant, but will lead to higher costs. Third, the use of parallel-flow micro-channel heat exchanger, both in line with environmental protection, effective energy saving, and can reduce costs by more than 50%. Therefore, the micro-channel has become the best choice and way out for home and commercial air conditioner replacement.

Microelectronics follow Moore’s Law rapid development, along with the increasing integration of transistors, high-speed electronic devices have reached 5 ~ 10MW/m2 thermal density, heat dissipation has become the main “bottleneck” of its development, micro-channel heat exchanger to replace the traditional heat transfer device has become an inevitable trend. Therefore, in embedded technology and high-performance computing depends on a high degree of aerospace, modern medical, chemical and biological engineering and many other fields, micro-channel heat exchanger will have a broad application prospects.

With the gradual maturity of microchannel heat exchanger technology, the automotive air conditioning industry and home air conditioning industry (such as the United States) has begun to produce related products. And happily, the current hot air water heater industry has also begun to enter the micro-channel field.

Energy saving.   Energy saving is an important indicator of today’s air conditioners. Conventional heat exchanger is difficult to manufacture high-grade products such as Ⅰ energy efficiency standards, micro-channel heat exchanger will be the best choice to solve the problem.

Outstanding heat transfer performance.   In home air conditioning, when the size of the flow channel is less than 3mm, the gas-liquid two-phase flow and phase change heat transfer law will be different from the conventional larger size, the smaller the channel, the more obvious this size effect. When the inner diameter of the tube is as small as 0.5~1mm, the convective heat transfer coefficient can be increased by 50%~100%. This enhanced heat transfer technology for air conditioning heat exchanger, appropriate changes to the heat exchanger structure, process and air side of the enhanced heat transfer measures, is expected to effectively enhance the heat transfer of air conditioning heat exchanger, improve its energy-saving level.

Promotion potential.   Microchannel heat exchanger technology in the field of air conditioning manufacturing and the potential to promote air water heaters, which can greatly enhance the competitiveness of products and sustainable development of enterprises.

Compared with conventional heat exchangers, microchannel heat exchangers not only small heat transfer coefficient, high heat transfer efficiency, can meet higher energy efficiency standards, and has excellent pressure resistance, can be CO2 for mass cooling, in line with environmental requirements, has attracted widespread attention of domestic and international academic and industrial circles. The key technology of microchannel heat exchanger – the production method of microchannel parallel flow tube has become mature in China, which makes it possible to use microchannel heat exchanger on a large scale.