Research On The Uniform Distribution Of Flow In The Manifolds Of The Liquid Cooled Server Rack

With the rapid growth of data center industry scale,the energy consumption problem of data center is becoming increasingly prominent.Liquid cooling technology provides a new solution for the cooling of data center.In the practical application of cold plate liquid cooling technology in large-scale data center,the phenomenon of uneven distribution of cooling liquid among servers in a single cabinet is common.In order to prevent the over temperature and waste of energy consumption of individual servers in the cabinet,it is of great significance to carry out the research on the flow characteristics and optimal design of manifolds in the server rack.Based on the existing data center liquid cooling server frame pipeline system,the simplified physical model of manifolds is established.The flow resistance and distribution characteristics of manifolds under rated working conditions are studied by CFD software.The influence of structural parameters(diameter of manifolds,branch diameter and branch length)on resistance and distribution characteristics of manifolds is analyzed,through the local transformation of the manifolds,can effectively improve the fluid distribution performance goal.The influence of the diameter ratio of manifolds on the flow distribution of manifolds is discussed by numerical simulation and theoretical calculation.The results show that the performance of the manifolds can be improved effectively by selecting the ratio of diameter Kbest=0.6～0.8.The flow resistance and distribution characteristics of manifolds under variable conditions(opening,closing and fluctuating)are studied.The results show that under variable conditions,the manifolds always follows the distribution law:the closer the branch pipe is to the inlet,the greater the flow rate,and the flow rate of the branch pipe decreases monotonously with the increase of the distance between the branch pipe and the inlet.Under the same flow rate,the greater the increasing speed of flow,the worse the uniformity of flow distribution.With the decrease of inlet flow,the flow distribution in parallel pipeline tends to be uniform,but when the inlet flow is close to 0,the uniformity of flow distribution in parallel pipeline deteriorates sharply.The flow rate of each branch pipe fluctuates with the fluctuation of inlet flow rate,and the flow distribution uniformity of the manifolds also changes periodically.The smaller the fluctuation period is,the more severe the fluctuation of flow distribution uniformity is.On this basis,the pressure distribution model in the manifolds is constructed,and the optimization design method of fluid uniform distribution under certain working conditions is put forward with the objective of optimal uniform distribution.The numerical simulation of the optimized model is carried out by using CFD software.The results show that the structure obtained by this method has better flow distribution performance than the initial structure.The influence of static pressure conversion coefficient,local loss coefficient and friction coefficient of the model is studied.The results show that the value of static pressure conversion coefficient has a great influence on the calculation results.Local loss has little effect on the results.The friction coefficient has a great influence on the accuracy of the method.When the static pressure conversion coefficient is calculated accurately,fitting the friction coefficient expression can improve the accuracy of the method,and the flow distribution performance of the calculated structure is better.The results show that the flow distribution performance of the optimized structure is better than that of the original structure near the rated condition of 0.085kg/s,and the fluid distribution performance gradually deteriorates with the increase of inlet flow.When the fluctuation amplitude is small,the fluid distribution performance of the optimized structure is obviously better than that of the initial structure.With the increase of the fluctuation amplitude,the distribution performance of the optimized structure begins to deteriorate near the peak and trough of the inlet flow,and the maximum nonuniformity also increases.When the fluctuation period is large,the distribution performance of the initial structure is similar to that of the optimized structure.The distribution performance of the optimized structure deteriorates gradually with the decrease of the fluctuation period.