Research On Long-term Reliability Of The Pipeline In A Kind Of Liquid Cooling System Of Large-scale Server

With the rapid development of Internet and information industry in China,as the core equipment of information processing in the industry,servers are also showing a strong development trend both in the market and in the performance.However,as the performance of servers,especially the large-scale servers,continues to improve,a kind of efficient cooling system has to be applied to deal with the severe problem of heat dissipation.In various cooling system,indirect liquid cooling system is the mainstream development direction of the industry at present.But it must be ensured that the liquid cooling system,especially the pipelines in the system,is safe and reliable.In this thesis,the reliability of the pipelines in a kind of liquid cooling system of large-scale server under long-time running is studied.The main failure factors and their failure theories of the pipelines of general liquid cooling system are firstly analyzed from the two aspects of microbial propagation and vibration.Then,the reliability of the object in this thesis is analyzed in detail,which is based on its specific structural characteristic and operating condition.The main contents of this thesis are as follows:(1)For the microbial propagation problem of the pipelines in general liquid cooling system,the mechanisms of the main bacteria causing microbial corrosion and microbial slime are analyzed respectively.And combined with the environmental characteristics of the liquid cooling system,the main factors affecting growth and reproduction of these bacteria are analyzed.(2)For the microbial propagation problem of the pipelines in the liquid cooling system studied in this thesis,the quality of the cooling liquid in the liquid cooling system is firstly analyzed to judge the growth status and breeding trends of different microorganisms in the system pipelines,and to infer the severity of microbial corrosion and the growth status of microbial slime in the pipelines.Then,according to the analysis results,comparison experiments were conducted to further verify the growth status of microbial slime in the system.(3)For the vibration problem of the pipelines in general liquid cooling system,the common mechanisms of pipeline vibration are analyzed.The vibration failure of pipeline is further more analyzed from the viewpoint of fatigue failure and resonance.(4)For the vibration problem of the pipelines in the liquid cooling system studied in this thesis,the structural characteristic and operating condition of the system is firstly analyzed.And it’s judged that the main factor of pipeline vibration in this system is the fluid pressure pulsation in pipeline,and the main severe vibration areas are the inlet pipelines and the outlet pipelines of the motherboard cooling modules.On this basis,the finite element analysis software ANSYS Workbench is used to analyze and calculate the vibration,to find out the positions of the pipelines which have the largest stresses under the vibration.And then they were regarded as the key positions of the system pipelines failure.(5)Under the 99.9% survival rate,the endurance fatigue limits of the key positions of the system are calculated.And the calculation results are firstly modified according to the average stress under a suitable correction model,and then are divided by a safety factor.Finally,the calculation results are compared with the results of the finite element analysis,to determine the safety issues of the system pipelines vibration.