The combination and optimal design of the thread geometric parameters of the female copper pipe should take into account the geometry, heat transfer efficiency, and processability of the three factors.
In this way, the heat transfer performance of the female threaded pipe can be fully improved.
In addition to the outer diameter “D”, inner diameter “d”and thread shape, the design elements such as bottom wall thickness “Tw”, thread height “Hf”, thread number “n”, helix angle “β”, top angle “α” and bottom width “W” of the thread groove should be considered.
Design Factors of Internal Thread Copper Tube
➣ Internal Thread Copper Pipe Thread Bottom Wall Thickness Tw
With the in-depth research, the current trend is to reduce the wall thickness of the bottom of the internal thread.
Typically, Miracle internally threaded copper tubing has a bottom thickness of 0.25-0.3mm.
This is the best choice based on internally threaded copper tubing characteristics, as a smaller wall thickness will result in better heat dissipation.
All materials have a critical value, and so does the female threaded copper pipe.
The wall thickness of the copper tube should not be reduced too much, because this will lead to a reduction in the stability of the copper tube.
➣ Thread Height of Internal Thread Copper Pipe Hf
Another parameter that affects the thermal performance of internally threaded copper tubes is the height of the internal threads.
In the design of internally threaded copper tubes, the height of the internal threads is usually increased appropriately to obtain a larger internal surface area.
Like the wall thickness of internally threaded copper tubes, the parameter of the height of the internal thread cannot be increased arbitrarily.
According to research, it is reasonable to control the height of the internal thread between 0.1 and 0.25 mm.
At the same time, it can also get optimistic internal surface area and heat dissipation performance.
➣ Internal Thread Copper Pipe Thread Helix Angle β
To obtain a larger heat transfer coefficient in the same length of pipe, a larger internal surface area is required.
This evolved another concept – the helix angle of internally threaded copper pipes.
The helix angle of internally threaded copper pipes has the following advantages:
✓ Creates a secondary flow of refrigerant in the pipe.
✓ The intensity of the refrigerant turbulence inside the evaporator and condenser copper tubes is increased.
Therefore, the helix angle of the female copper tube is also an important parameter in designing the female thread structure.
But, the spiral angle is not the larger the better, but there is a reasonable range.
At present, the helix angle of the inner thread tube is usually in the range of 10°~25°.
In this range, the spiral angle of the evaporation tube is smaller and better, and the spiral angle of the condensation tube is larger and better.
In addition, the spiral angle and the outer diameter of the copper tube have a mutually constraining relationship.
When the diameter of the copper pipe is small, the flow resistance of the refrigerant is large, then the thread angle should take a small value.
When the diameter is larger, the flow resistance of the refrigerant is smaller, then the thread angle should take a large value.
Related Links: Refrigeration Coil.
➣ Top Angle of Internal Thread Copper Pipe α
The top angle of the female copper tube is positively related to the heat transfer efficiency of the female copper tube.
Therefore, it is also necessary to study the angle of the top angle of the internally threaded copper pipes.
Different angles will have different effects on the internally threaded copper pipes.
If the top angle of the thread is too small, the anti-expansion strength of the top angle of the threaded copper tube is too small.
The deformation generated by the thread height after expansion will cause the heat dissipation performance to be reduced.
Therefore, under the premise of the thread anti-expansion strength, the thread top angle of the female threaded pipe should be as small as possible, currently generally between 40°and 60°.
➣ Number of Threaded Strips of Internal Thread Copper Pipeｎ
Increasing the density of the internal threads increases the number of vaporization cores.
When this type of copper tube is used in evaporators it can greatly improve the performance of the refrigeration equipment.
But, if the density of threads is increased too much, the thread pitch will be too small, which will weaken the strength of the fluid being stirred inside the tube.
Therefore, the number of threads should be controlled within a certain range.
At present, the number of threaded copper tubes is generally between 50 and 70.
Among them, when the female threaded copper tube is used to make a cooling coil, the number of teeth is generally between 50 and 60.
When the female threaded tube is used to make a refrigeration condenser, the number of teeth is generally between 60 and 70.
In addition, reference should be made to the copper tube diameter, when the tube diameter is small, take the small value.
When the diameter of the tube is larger, take the larger value.
➣ Thread Groove Width of Internal Thread Copper Pipe Ｗ
The large size of the bottom of the groove is good for heat transfer.
However, the width of the bottom of the groove is again limited by the height of the internal thread.
This is due to the need for tube expansion during the processing of evaporator and condenser copper tubes.
Therefore, under the premise of ensuring the strength of the anti-expansion tube, the width of the bottom of the groove should be increased appropriately.
➣ Liquid Storage Area of Internal Thread Copper Pipe
For air-cooled condenser copper tubes, increasing the reservoir area can significantly increase the condensation heat transfer effect.
At present, the liquid storage area is increasing, and the increase of the liquid storage area can be achieved by increasing the thread height.
The above are the main parameters of the geometric parameters of copper tubes with internal threads, which directly affect the performance and application environment of copper tubes with internal threads.