A, condenser processing technology analysis
1, the main composition of condenser
The air-cooled condenser of household air conditioner is mainly made of U-shaped tube (copper tube) and aluminum alloy fin by welding.
Copper tube beam splitter and internal thread tube, copper tube generally adopts φ9.52x0.35 (smooth tube), φ9.52x0.4 1 (threaded tube), φ7x0.35 (smooth tube) and φ7x0.4 1 (threaded tube).
Aluminum alloy fins are generally flat, corrugated and punched, and the thickness is generally 0. 1 15 (bare aluminum) and 0. 105 (hydrophilic aluminum). The condenser is generally composed of 1-2 rows of fins, and the spacing between each row of fins is generally1.5-2.0 mm. At present, the commonly used fins are treated by coating hydrophilic films on their surfaces.
2. Processing of main parts of condenser
Processing of (1) long U-shaped tube (shaped like English letter U)
When processing long U-shaped pipes, automatic coil feeding is generally adopted. The automatic card-issuing pipe bender pulls the copper pipe from the tray frame, straightens it, cuts it into copper pipes with fixed size, bends it into U-shaped pipes (also called card-issuing pipes), and then automatically discharges it to become qualified products.
Problems needing attention in processing long u-shaped pipes;
Due to the thin wall of copper tube (0.35mm for smooth tube and 0.4 1mm for threaded tube), the tube is easy to lose its stability during processing, which makes the inner side of the tube wall wrinkle, resulting in stress concentration, and it is in a high pressure state when working, and it is easy to break and leak at the wrinkled place.
Therefore, when bending a pipe, it is necessary to insert a finger-shaped mandrel head or a universal mandrel head at the bend of the pipe for support. When there are many folds inside the bend of the pipe, it is necessary to insert some mandrel heads at the bend; When the outside of the pipe elbow is broken, it is necessary to take out the mandrel head from the elbow. This is repeated many times until the copper tube is bent and the shaft head is adjusted to meet the requirements.
(2) Processing of fins
At present, the processing of fins is mainly carried out on the automatic production line of high-speed punching machine, using the progressive die of air-conditioning fins, and the punching speed of the punching machine can reach more than 320 times per minute. After spreading, oiling and initial feeding, the aluminum anchor enters a punching machine for stamping and forming, and after being cut into a fixed length, it is stacked by a material suction device, and finally becomes the required fin. The production line generally adopts PLC programmable controller to set the punching speed and the number of holes of fins.
There are six specifications of aluminum foil thickness: 0.105,0.115,0.13,0.15,0.20,0.25mm, of which 0./kloc-0.
The technological process of fin stamping is as follows:
Primary drawing → secondary drawing → primary flanging and punching → secondary flanging → cutting.
The secondary stretching of aluminum foil with fin progressive die produces plastic deformation, which can greatly reduce the cracks caused by aluminum foil flanging and avoid the pipe breakage defect during pipe expansion.
According to the design requirements of the condenser, fins with different flanging heights can be punched by adjusting the die adjusting disc, and the flanging height of the condenser is generally1.5-0.21mm. Fins with different shapes can be punched by replacing the corresponding working parts on the upper and lower die holders. Because of the good heat transfer effect of slotted fins, they gradually occupy a dominant position.
3. Fastening method of copper tube and fin
Mechanical tube expanding method is widely used because of its simple processing, stable quality and high efficiency. There are two kinds of tube expander: vertical and horizontal. At present, vertical tube expander is widely used in tube expander of copper-based tube condenser.
4. Assembly process of finned tube condenser
Wear a long U-tube → expand the tube → degrease and dry → set a small U-shaped copper elbow → automatic welding → repair welding → condenser bending and forming → leak detection → shaping → inspection → stacking for later use.
(1) Long U-tube threading: On the insertion table, correct the U-tube positioning frame, put the end plate in place according to the design requirements, then put the fin with the middle hole turned over on the table, and insert the processed long U-tube into the fin hole from front to back. Care should be taken to avoid damaging fins or cutting hands.
(2) Tube expansion: generally completed on a vertical tube expander. Before expanding the tube, the stroke of the expansion rod of the tube expander and the position of the clamping door to prevent the tube expanding from being unstable should be adjusted, and the U-shaped bracket should be installed on the bottom die base according to the arrangement and quantity of the condensing tube groups. Put the finned tube group with sleeve on the U-shaped bracket of the expander, and start the expander after positioning and fixing it with the clamp door on the equipment. The head of the telescopic rod is introduced into the copper tube from top to bottom under the pressure of the hydraulic cylinder to expand the tube, thus realizing the processes of primary tube expansion, secondary flaring and tertiary flanging.
After tube expansion, it is required that the shortening of the effective dimension of the laminated height should not be greater than 65438±0mm, and the bending degree of the heat exchange tube should not be greater than 2 mm ... The fins are in close contact with the heat exchange tube, and no looseness is allowed, and there is no serious turnover phenomenon.
(3) Degreasing and drying: Because a large amount of grease will remain in the stamping process of bent U-shaped tubes and fins, it needs to be removed. Degreasing and drying furnace of heat exchanger is the equipment for removing residual volatile oil during condenser processing, which is mainly composed of conveying device and drying furnace. The workpiece runs continuously and horizontally on the production line and enters the drying furnace for drying and degreasing.
(4) Small U-shaped copper elbow suit: insert the small U-shaped copper elbow with welding ring into the workpiece hole according to the drawing requirements.
(5) Automatic welding: According to the welding process of condenser production line, gas automatic welding machine is used for welding, and anti-oxidation flux is used to protect the welding surface. Through visual inspection, the incomplete elbow circumferential seam is repaired manually on the automatic welding machine.
(6) Bending and forming of condenser: (If it is a linear condenser, this process is not needed) Bend the condenser into an L shape with an integral condenser bender according to the drawing requirements, and reduce the overall size of the outdoor unit of the splitter on the premise of ensuring sufficient heat exchange area.
(7) Leak detection: seal the nozzle of the condenser with quick connector, first fill nitrogen to detect large leakage, then vacuum, then fill R22 gas (halogen detection) or helium gas (helium detection) into the condenser, and use halogen leak detector or helium leak detector to detect leakage. If there is leakage, it should be repaired if it is a solder joint leakage, and it should be scrapped if it is a pipe group leakage. Repeat the above leak detection steps until they are qualified.
(8) Shaping: Straighten the flattened heat sink with a fin comb or other tools.
(9) Inspection: ① There is no serious chip damage or chip falling off, and there is no water drop on the surface of heat sink and copper tube; (2) The number of overlapping fins at the condenser end shall not exceed 3, the number of burnt fins shall not exceed 4, and the number of loose fins shall not exceed 3; (3) There should be no obvious wrinkles in the bent part of condenser elbow and long U-tube, and there should be no obvious cracks in the flanging of condenser fin hole; (4) The average fin spacing of the condenser shall not exceed 2% of the specified fin spacing within the fin length of 100; ⑤ Check the residual water in the tube according to the determination method specified in the standard, and the residual water in the tube shall not exceed 120mg /m2.
(10) Stacking for standby: seal the nozzle of qualified condenser with rubber cap or rubber plug, carefully stack it on the designated cushion frame, or pack it and transfer it to the warehouse, or transfer it to the air conditioning assembly line for assembly.
Second, the evaporator processing technology analysis
1, processing characteristics of evaporator
Evaporators also need to process long U-shaped tubes and fins as required, and then fasten them together in a certain way. The difference is that the indoor unit is getting smaller and smaller, and the size of the indoor unit is mainly affected by the size of the evaporator. In order to reduce the size of evaporator on the basis of ensuring heat transfer performance, multi-connected evaporator is widely used in indoor units at present.
2. Assembly process of finned tube evaporator
Wear a long U-tube → expand the tube → degrease and dry → set a small U-shaped copper elbow → automatic welding → repair welding → evaporator cutting and bending forming → leak detection → shaping → inspection → stacking for later use.
As can be seen from the above, the assembly process of evaporator is basically the same as that of condenser, the only difference is that the cutting and bending forming of evaporator replaces the bending forming of condenser.
Evaporator cutting and bending forming: on the evaporator cutting and bending forming machine, the air cylinder is used to drive the blade to cut the fin at the special-shaped gap in the middle of the pre-punched fin, and then it is bent to the required angle.
Third, the calculation in the key process
Whether it is a condenser or an evaporator, the key calculation is how to determine the length of the long U-shaped tube, which is mainly determined by the shrinkage rate of the expanded tube. In the process of tube expanding, copper tube will undergo a shortening process, which involves many factors, such as material, tube expanding speed, lubrication and so on. At present, there is no accurate formula, and most of them are determined by experience. The shrinkage rate is generally 1.037— 1.04. (Length before expansion: length after expansion)
For example, if the length of the unfolded U-shaped tube is 586 mm, where the height from the cup mouth to the end plate is 13 mm and the height of the U-shaped bracket is 15 mm, then the length of the long U-shaped tube to be bent is: (the shrinkage rate is 1.037).
(586+13) ×1.037+15 = 636 mm.
That is, it is necessary to bend a 636mm long U-shaped pipe on the pipe bender.
In a word, a good product needs not only a good design, but also an economical and reasonable processing technology. The processing technology of condenser and evaporator is constantly summarized and improved in production practice. For more process principles of the expander, please refer to.