The use of internally threaded copper tubing in refrigeration units and air conditioning systems dates back to the 1980s.
With the continuous improvement and advancement of female thread forming technology and the need for enhanced heat transfer in evaporators and condensers.
The general trend of copper tubes with internal threads is toward thin-walled, lightweight, fine diameter, and efficient heat transfer.
Research data to date has shown that the heat transfer effect of a high-performance female threaded tube is nearly four times better than that of a bare tube.
Therefore, whether it is used for condensing units, evaporator coil, or condenser coil, the higher thermal efficiency can be obtained.
Analysis of the Current Situation of Internal Thread Copper Pipe
Internally threaded copper tubes are widely used in air-cooled condensers and refrigeration evaporators as an efficient heat transfer element with high-efficiency aluminum or aluminum alloy fins.
The increasing demand for energy-efficient and compact air conditioning systems has led to the development of refrigeration equipment in the direction of smaller sizes.
This requires higher requirements for the performance of refrigeration compressors, as well as the use of highly efficient and compact condensers and evaporators.
At present, both refrigeration compressors and HVAC compressors have been developed in terms of performance for more than 30 years.
And the performance factor has been increased from 2.3 to 3.5.
It has become very difficult to significantly improve the performance of compressors again.
However, there is still great potential for enhanced heat transfer improvements in evaporators and condensers.
Therefore, the study of heat exchanger performance shifts to the study of internally threaded copper tubes.
Influenced by refrigerants, more efficient heat exchangers will also replace traditional heat exchangers.
With the increase of ozone layer protection and environmental requirements in the world, the use of CFC-type refrigerants has been restricted internationally.
This will force refrigeration plants to look for alternative refrigerants to R22 and R12.
Currently, neither R407C nor R410A or R290 or R417A are as good as R22 and R12 in terms of performance.
These unfavorable factors can reduce the performance of air conditioning heat transfer elements, so it is necessary to find better heat transfer elements to make up for this aspect.
The new copper tubes with internal threads are therefore widely used in refrigeration systems.
For more information about the structure of internal thread copper tubes, you can refer to what is internal thread copper tubes?
The Effect of New Refrigerants on Heat Transfer in Air Conditioning Heat Exchangers(HVAC Coil)
In recent years, international air conditioning manufacturers and copper tube manufacturers have done a lot of research work in the direction of new refrigerant applications and air conditioning miniaturization.
At present, the new products that replace R22 and R12 refrigerants are mainly R407C and R410A, which are both mixed refrigerants.
R407C is a non-azeotropic refrigerant consisting of R32/R125/R134a HFCs at 23/25/52/ by mass.
R410A is a near azeotropic refrigerant composed of two HFC work gases R32/R125 at 50/50/ by mass.
Studies have shown that R410A exhibits the behavior of a single refrigerant, with condensing characteristics close to R22 and evaporative properties not inferior to R22.
When R410A refrigerant is used in refrigeration systems, the evaporator and condenser copper tubes of the refrigeration system need to be replaced by trapezoidal or triangular copper tubes with internal threads.
By improving the structure of the refrigeration evaporator, it is possible to give full play to the performance of R410A refrigerant and even surpass R22 refrigerant.
However, the high condensing pressure of R410A refrigerant requires increasing the wall thickness of the heat transfer tube and reducing the diameter of the copper tube to improve the strength.
From the physical properties of R410A, the pressure loss of R410A during evaporation is much smaller than that of R22.
Based on this, it is very advantageous to reduce the diameter of the copper tube of the refrigeration evaporator and to reduce the increase of pressure loss caused by the diameter reduction.
As for R407C, due to its low evaporation and condensation, a thick boundary layer is generated in its liquid film during condensation, which is unfavorable for heat transfer.
Especially at low flow rates, the use of crossed copper tubes or M-shaped copper tubes can greatly improve the heat transfer efficiency of R407C refrigerant.
The Influence of the Internally Threaded Copper Tube to Enhance the Heat Transfer on the Evaporator and Condenser(Cooling Coil)
For the evaporator (evaporation process in the tube) the reasons for enhanced heat transfer are.
(1) increased evaporator unit heat transfer area.
(2) Increase in the number of gasification cores.
(3) an early transformation of the wavy flow pattern into a semi-annular and annular flow pattern, which increases the wetting surface
(4) Increases the turbulence of the liquid film (turbulence, disturbance).
For condensers (in-tube condensation process) the reasons for enhanced heat transfer are.
(1) Increased air-cooled condenser heat transfer area in the tube.
(2) It induces the condensate to leave the heat transfer surface and drain away under surface tension, reducing the thickness of the refrigerant liquid film between the top of the teeth and the grooves (this film is not conducive to heat transfer).
(3) It enhances the degree of turbulence of liquid refrigerant and enhances the mixing of gas-liquid two phases.
In summary, the research of internally threaded copper tubes has become a new trend and the development of new products is full of challenges.
Not only the research of copper tubes for evaporators and condensers of refrigeration systems is progressing, but also the breakthrough of solderless connection technology in the field of copper tube connection.
For more information on solderless lokring technology, you can refer to how to join copper pipes.
Miracle is willing to grow with you and work with you always.
For more information about geometric parameters of female copper tube structure, please refer to the influence of geometric parameters of the female threaded tubes on heat transfer performance.