Analysis And Research On The Quality Of Hydraulic Expansion Of Air Conditioning Heat Exchanger

The reliability and service life of the sealing structure are very important In the hydraulic expansion process.When designing the sealing structure,rubber seal is good at sealing performance,but frequent insertion and pulling out of copper tube in hydraulic expansion process will cause wear failure of rubber seal,and the service life of sealing structure is shorter.Frequently replacement of seal will reduce the expansion efficiency.The main research content of this thesis is the hydraulic expansion quality of air-conditioning heat exchangers.The expansion quality is mainly reflected in three aspects:the pull-out force of different parts of the copper tube（front,middle and close to the elbow backend）,the contact state between different parts of copper tube and fin,and the axial shrinkage of the copper tube.The main research contents of this thesis are as follows:（1）Designing a new sealing structure which is more wear-resistant solves the problem of wear and failure of rubber seals and improves the service life of the sealing structure;（2）Research the effect of expansion process parameters（expansion pressure and pressure maintain）on the pull-out strength of different parts of the copper tube;（3）Research the contact state between different parts of the copper tube and the fin by the expansion process parameters;（4）Research the influence of expansion parameters on the axial shrinkage of copper tube;（5）Analyze the possible causes of poor expansion quality,and optimize the expansion process for the places with poor expansion quality.The results of the research show that:（1）Through the burst test,it is found that hard seal which can meet the sealing requirements of the hydraulic expansion of the air conditioner heat exchangerv has a good sealing performance,and is relatively wear-resistant,which solves the problem of frequent replacement of rubber seals due to wear;（2）With the increase of expansion pressure,the pull-out force of each part of the copper tube increases.Under the expansion pressure of 11MPa,there is little difference in the pull-out force of each part of the copper tube.When the expansion pressure is 12MPa,the pull-out force in the middle part of the copper tube is the largest.When the expansion pressure is 13MPa and 14MPa,the maximum pull-out force appears at the front of the copper tube,and the minimum pull-out force appears at the back end of copper tube;When the expansion pressure is 11MPa and the pressure maintain is 4S and 6s,there is little difference in the pull-out force of each part of the copper tube.When the pressure maintain is 8s,10s and 12s,the maximum pull-out force appears in the middle part of the copper tube;（3）With the increase of expansion pressure,the gap thickness of the front and middle parts of the copper tube is reduce.The gap thickness of the front and middle parts of the copper tube fluctuates greatly under the expansion pressure of 11MPa.The gap thickness in the middle of the copper tube is smaller than that in the front of the copper tube under the expansion pressure of 12MPa.At 13MPa and 14MPa,the gap thickness between the front and middle of the copper tube has little difference;In each expansion pressure,the backend of the copper tube gap thickness value is larger,the closer to the elbow part of the gap thickness value is greater.When the expansion pressure is 11MPa and the pressure maintain is 4S and 6s,the gap thickness at the front of the copper tube is the smallest.When the pressure maintain is 8s,10s and 12s,the gap thickness in the middle part of the copper tube is less than both ends;（4）When the expansion pressure is in the range of11MPa-14MPa,the axial shrinkage of copper pipe increases with the increase of expansion pressure.In the pressure maintain 4-12s（expansion pressure is11MPa）,the axial shrinkage of copper tube increases first and then decreases with the increase of pressure maintain.When the pressure maintain is 10s,the axial shrinkage of copper tube is the largest;（5）The simulation results show that the expansion quality can be improved by reducing the yield strength near the back end of the copper tube（near the elbow）:When the yield strength of the back end of the copper tube decreases from 152MPa to 100MPa,the maximum gap thickness value decreases from 117.2×10^-3mm to 16.7×10^-3mm.