数据机房用分离式热管散热器运行特性分析

信息化水平的不断提高直接带来了数据中心耗电量的急剧增加。数据机房不同于一般的公共建筑,考虑到隔热、隔湿及洁净度的要求,即使在冬季也需供冷降温。而在满足散热需求的前提下,最大限度利用自然冷源则是降低空调能耗的最有效方法。但目前自然冷源的利用中常出现受环境影响大、节能效率低等问题,热管式散热器能将室内外空气完全隔绝,具有启动温差小、体积小、安装灵活等优点,在机房节能中有很大的应用潜力。以节能和良好的环境适应性为目标,对数据机房应用分离式热管的被动式散热方式进行了理论分析。以本学科工程领域现有技术为基础,理论分析了应用分离式热管的意义及优势,定义了分离式热管蒸发段及冷凝段的换热效率,建立了数据机房应用分离式热管散热系统的理论分析模型,以某名义排热量为30 kW的管翅式换热器为例,研究换热效率随风量的变化关系,得出分离式热管散热下可运行的最高允许室外温度、全年运行时间、功耗及全年节电量等关键参数。以某一30 kW冷负荷数据机房为模型进行CFD软件模拟,获得了采用分离式热管散热器的机房内部温度场分布,并与普通空调进行了比较。针对室外温度下降所引起的室内侧送风温度过低问题,提出减小室外侧风量的具体改进措施。利用理论模型设计分离式热管换热系统蒸发段和冷凝段,提出可根据热负荷及实际机房灵活配置,建设成本低,有效适应机房现有散热系统的方法。主要结论如下:(1)分离式热管散热器应用于数据机房散热,换热效率随着风量增加而减小,分离式热管散热器应用于数据机房散热,换热效率随着风量增加而减小,但可利用室外冷源的温度升高,可利用室外冷源的时间也随之增加,可根据换热器及所在地区设计最佳风量。(2)分离式热管散热下风量较大时,机柜进风温度比普通空调散热更为均匀,机房内热环境更好,可减少机房内局部热点。(3)若风量不变,分离式热管散热器蒸发段送风温度随室外温度降低,并有可能低于机房送风的标准温度。可通过减小室外侧风量使室内蒸发段出风温度满足数据机房送风温度,同时散热器的能效也可进一步提高。

Working Characteristic of Separate Heat Pipe in Data Center

The improvement of information technology has also brought a sharp increase in the power consumption of data center. The data center is different from the general public buildings because the constant temperature and humidity of the data center should be maintained, therefore the air conditioning system must operate continuously throughout the year. To meet the demand of controlling temperature and energy conservation, the most effective way is to make full use of the outdoor cold source. However, at present, the utilization of outdoor cold sources is often affected by environment, and the efficiency is low. The separate heat pipe can completely isolate the indoor and outdoor air. It has several advantages such as little starting temperature difference, small volume and flexible installation. It has great potential for energy conservation in data center so the separate heat pipe for data center is studied theoretically for high reliability and environmental adaptability. Based on the existing technology of engineering, the significance and advantages of separate heat pipe were analyzed. The heat transfer efficiency of the evaporating section and condensing section of the separated heat pipe was defined. The analytical model of the separate heat pipe was established. A fin heat exchanger with nominal heat rejection of 30kW was taken as an example. Then the relationship between the heat transfer efficiency and the air flow was studied to obtain the highest permission outdoor temperature and run time through out the year. The numerical research was carried out based on a 30kW cooling load data center. The temperature field of the data center with separate heat pipe was obtained and the result was compared with ordinary air conditioning. To solve the declination of indoor air supply temperature caused by the declined outdoor ambient temperature, the solution to reduce outdoor air supply was proposed. It was found that the separate heat pipe system is energy -saving and suitable for high heat density buildings such as data center and base station. The main conclusions are as follows:(1) When the separate heat pipe was used in data center, heat transfer efficiency decreased with the increase of air supply volume. Meanwhile, the maximum permission outdoor temperature and the time available for outdoor cooling source increased. According to the heat exchanger and climatic conditions, the optimum air flow could be designed. (2) When the large indoor air flow of the separate heat pipe was utilized, the air inlet temperature of the cabinet is more uniform than that with the ordinary air conditioner because of the larger supply air volume, while the data center temperature environment is better. The hot spots can be reduced as well. (3) When the air supply volume is constant, the air temperature of the indoor evaporating section of the separate heat pipe will decrease with the outdoor temperature, and it may be lower than the standard cabinet supply air temperature in data center. By reducing the outdoor air volume, the air temperature in the evaporating section meets the air supply temperature of the data room, and the energy efficiency of the radiator can be further improved.