Numerical Simulation And Optimization Of The Air Distribution In High Heat Density Data Center

Data center is a kind of special building which is specially used to store IT equipment and realize centralized processing of data information.With the rapid development of IT technology,the scale and capacity of data center are constantly expanding,along with the rapid growth of energy consumption and heat density.The increasing demand for heat dissipation puts forward higher requirements for the design of air conditioning system.At present,the air conditioning system of data center in China generally has the problems of high energy consumption and poor air distribution.The unreasonable air distribution causes local hot spots and excessive cooling,the former will pose a threat to the stable operation of IT equipment,while the latter will cause a waste of cooling capacity and increase the energy consumption of air conditioning.The energy consumption of the air conditioning system accounts for about 40% of the total energy consumption of the data center,with great potential for energy saving.In order to reduce the energy consumption of the air conditioning system,improve the thermal environment of the data center and improve the operational stability of IT equipment,this paper is devoted to the numerical simulation and optimization of the air distribution in the data center.The work mainly includes the following aspects:1)Study on overall air distribution in the data center.The CFD model of a typical computer room in a data center in Nanjing was established by means of CFD simulation.Based on the analysis of the air distribution problems in floor plenum,cold aisle and hot aisle,the results show that there are problems such as uneven floor plenum pressure,uneven temperature and air supply in cold aisle,uneven exhaust temperature and flow field disorder in hot aisle.At the same time,the thermal environment of the computer room was measured,and the accuracy and reliability of the numerical simulation were verified.2)Study on local air distribution of the rack.One single rack was taken as the research object.The CFD model was partly improved.The characteristics of the airflow in the cold aisle were specifically analyzed.The upper of the rack is cold and the lower is hot,and then the cause of the temperature gradient in the vertical direction of rack was expounded.Aiming at the mismatch of perforated floor air supply,imbalance of perforated floor air supply,and gap at the bottom of the rack,the influence of local air distribution on the rack was simulated quantitatively.The influence of the above three factors on the temperature distribution at the rack outlet was illustrated by the temperature nephogram,the streamline diagram and the box chart,which provides theoretical guidance for the local air supply optimization and accurate air supply of the rack.3)Optimization of air distribution in the data center.Three optimization schemes were put forward: the trapezoidal plenum chamber,variable opening rate of perforated floor and deflector of perforated floor.Through CFD simulation,it is pointed out that the trapezoidal plenum chamber can reduce the pressure gradient and eliminate the vortex,and the influence of the geometric parameters of the trapezoidal plenum chamber on the optimization effect was explored.Through trial and error design,an optimization scheme of variable opening rate of perforated floor was put forward and the uniformity of air supply is greatly improved after optimization.The influence of the deflector on the flow field was described.The vertical temperature distribution of the rack with different air supply angles was analyzed,then the best air supply angle was chosen as 45°~60°.The local hot spot temperature decreases 6.5 ?,and the distribution of rack outlet temperature becomes more uniform.4)Study on transient thermal environment of the data center.The server transient heat transfer model including heat capacity and convection heat transfer coefficient was established,and the simulation results were compared with the experimental data in the literature to verify the accuracy and reliability of the model.Using the transient model,the simulation research of variable power transient and air conditioning failure transient was carried out.The change rule of the average temperature of the hot channel with time under different working conditions was obtained.The influence of the rack power density on the transient response was expounded.And the transient temperature field in each working condition was analyzed,so that the countermeasures were put forward according to different situations.Transient simulation provides a theoretical reference for predicting temperature change of data center and realizing feedforward control of air conditioning system.