Simulation And Experimental Study Of Water Cooling Based On High Heat Flux Data Center

With the development of the Internet,the data center,as a hardware facility supporting the Internet industry,has been unprecedentedly prosperous.The global data center market is getting increasingly larger.Due to land cost and other reasons,the construction of data centers has a prevailing trend towards large-scale and high-density,which will bring serious heat dissipation problems.High-power electronic devices intensive data centers consume a lot of power,how to solve the heat dissipation problems,improve the heat dissipation efficiency of the data center,reduce the heat dissipation energy consumption of the data center and lower the PUE value are the key factors to data center cooling research.Due to the constant indoor ambient temperature of the data center and the fact that the outside air temperature is lower than the indoor ambient temperature for majority of a year in different climate zones across the country,the concept of free cooling is proposed by scholars,which refer to that the outdoor cold source is utilized to replace the traditional mechanical way of cooling when the outdoor air temperature is relatively low.Under the premise of meeting the indoor ambient temperature in data center,eliminating the local hot spots and strengthen the mixing of hot and cold airflow,and improving the utilization of the natural cold source as much as possible,are the main directions of data center cooling research.In order to eliminate hot spots,this paper is based on solving the heat problem from the server level.The most commonly used blade server model was established.The finned heat sink for cooling the server chip has an optimized fin height,fin thickness and number of teeth.Under the condition that the consumed power of the chip was 50W,the air flow velocity was 9m/s,the chip with optimized finned heat sink structure has decreased in temperature from 40.9℃to 39.2℃。The temperature of water-cooled chip is 30.1℃,which is better than 38.1℃,which was under the condition of 13m/s air flow velocity.And if the air flow velocity and the water flow velocity remain unchanged,the more input power of the chip has,the larger temperature difference between air-cooled chip and water-cooled chip get.The server temperature distribution cross section is analyzed,and it is concluded that if the chip is cooled by water,and the low-heat-flow-density heating elements,like memory strip,are cooled by air,such mixing cooling method has obvious advantages at optimizing the temperature filed unevenness of server chip.The heat dissipation model of water-cooled channel-type heat sink is established and analyzed.Results show that the temperature of the chip is linearly proportional to the heat flux density and the water flow rate of the heat sink and the inlet water temperature of the heat sink are the main parameters affecting the temperature of the chip.As the water flow increases,the total thermal resistance of the heat sink decreases,but the decreasing trend is slower and slower,and the temperature of the chip shows the same decreasing trend.When the flow rate is constant,the temperature of the chip decreases as the temperature of the inlet water decreases,and the rate of change remains unchanged.Under the condition that the inlet water temperature is 20℃,the heat flux density is between 34 and 90 W/cm~2,and the water flow rate varies from 0.3 L/min to 0.6 L/min,the temperatures of the chip was between 30℃to 55℃.When the heat flux density is 68 W/cm2,the water flow rate is 0.6L/min,and the inlet temperature varies from 20℃to 30℃,the chip temperature changes at the range from 40.8℃to 50.8℃.Moreover,the pressure drop of the water in the heat sink increases as the flow rate increases.The physical model of the mixing cooling server is established,taking advantage of such mixing cooing method,the results,according to this model shows that under the ambient air temperature 20℃,the server chip with a input power as high as 2160kw has a temperature peak at 29.6℃,the section temperature staying even.The experiment was carried out using a water-cooled air-cooled/mixed cooling data center experimental system.The effect of flow and inlet water temperature on chip temperature and thermal resistance presents the same trend with the simulation.Experimental analysis shows that the contact thermal resistance between the chip and the water-cooled heat sink and the total thermal resistance of the heat sink have a great influence on the heat dissipation effect.Under the condition that the heat flux density was between 44 to 50.8 W/cm~2,the inlet water temperature was 19℃,and the water flow rate ranged from 0.4 L/min to 0.43L/min,the temperature of the chip varies from 50.7℃to58.7℃.Under the condition that the inlet water temperature is between 21.2℃to 25℃,the input power of the chip decreases to 50%,and the water flow rate is 0.444 L/min,the temperature of chip was between 40.4℃to 53.8℃.The higher the IT load,the lower the PUE.During the test,the highest IT load with the traditional chiller cooling unit and the cooling tower is 50%and 60%,the lowest PUE value is 2.25 and 1.56 respectively.Therefore,the water-cooling heat dissipation has a good heat dissipation effect in the heat dissipation of the high heat flux device,and is more convenient to utilize the natural cold source.The cooling mode integrating with water-cooling and air-cooling has a good prospect in the application of the high heat flux data center,and is a practical and viable cooling solution.