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NaokiAizawa MemberA SHRAE ABSTRACT In recent times, server power utilization in data centers has increased considerably. A liquid immersion cooling system and conventional air-cooling system for low-load Hard Disk Drive (HDD) storage are used together at a data center that includes a high load server. In our previous study, we proposed the zoned server room based on heat densities and confirmed the possibility of an annual power usage effectiveness (PUE) of less than 1.04 for our proposed cooling system. In this study, we change the configuration of the cooling system using general purpose element equipment based on the results of our experiment and last fiscal year’s annual energy consumption simulation. We measure the power consumption and PUE, and confirmed the stable operation of this cooling system in the zoned server room, achieving an annual average PUE of approximately 1.02. 摘要 近些年，数据中心的服务器用电功率大幅提升。液体浸入式冷却系统和用于低负载硬盘驱动器（HDD）存储的传统空气冷却系统在拥有高负载服务器的数据中心中经常一起使用。在之前的研究中，我们提出了基于热密度进行分区的服务器机房并证实了我们建议的制冷系统年PUE值低于1.04的可能性。在本研究中，我们根据实验结果和上一财年的年度能耗模拟，使用通用的元件设备改变制冷系统的配置。我们测量功耗和PUE值并确保该制冷系统在分区服务器机房中稳定运行，最终实现了年度PUE平均值约为1.02。 INTRODUCTION In order to drastically reduce the power for cooling information and communication technology(ICT) equipment such as servers, research is ongoing for the development ofcooling elements and cooling systems for Internet data centers (IDCs) (Ministry of the Environment, 2016). In particular, the objective of the current project is to realize a power usage effectiveness (PUE=total power of the IDC÷power of ICT equipment) of less than 1.02. 介绍 为了大幅降低冷却ICT（信息和通信技术）设备（如服务器）的功率，我们正在展开研究以开发用于互联网数据中心（IDCs）的制冷单元和制冷系统（日本环境省，2016年）。特别是，当前项目的目标是实现PUE值低于1.02（PUE = IDC的总功率÷ICT设备的功率）。 In recent times, server power utilization in IDCs has considerably increased, owing to high-power computer infrastructure and high-end GPU computing. For IDCs with high-load servers, a liquid immersion cooling system and a conventional air-cooling system for low-load hard disk drive storage are used together; however, in doing so, energy efficiency is not considered. Though energy conservation through the use of outside air and natural energyh as progressed for the latest large-scale IDCs (over 1000 racks), leading to a PUE of around 1.1 (Aizawa et al.2013–2015). The better energy conservation approaches and energy-saving technologies that are compatible with small-and medium-scale server rooms (less than several 100 racks) are desired. It should be noted that improving energy efficiency in small-to-medium-scale data centers is more difficultthan in the case of large-scale IDCs, owing to the difficulty in installing such cooling systems as well as the associated high costs or low suitability of particular energy conservation systems at such centers. Considering this, our proposed system is suitable for both small- to medium-as well as large-scale server rooms. Inparticular, we intend to develop a cooling system that leads to the reduction in power consumption using general-purpose auxiliary peripherals (e.g.,pumps and fans) to nearly zero. 近年来，归功于高功率计算机基础设施和高端GPU计算，IDC中服务器的电功率大大增加。对于具有高负载服务器的IDC，液体浸入式冷却系统和传统的用于低负载硬盘驱动器存储的空气冷却系统会一起使用；然而，这样做并没有考虑到能源效率。尽管通过使用室外空气和自然能源的节能措施已经在最新的大型IDC（超过1000个机架）中取得进展并促使PUE值低至约1.1（Aizawa等，2013-2015年），但我们还需要更好的能与中小型服务器机房（少于100个机架）兼容的节能方法和节能技术。应该指出的是，由于这种制冷系统的安装难度以及相关的高成本和低适用性，提高中小型数据中心的系统能效要比大型IDC更难。考虑到这一点，我们建议的系统应能适用于小型到中型以及大型服务器机房。我们特地打算开发一种制冷系统，该系统通过使用通用的外围辅助设备（例如泵和风机）将其能耗降低到几乎为零。 In a previous study (Aizawa 2018), we proposed a server room with zones based on heat densities (high, medium, or low) and a cooling system that utilized outside air. In our previous study, cooling water was provided by a cooling tower, and the amount of time for which the cooling tower is employed increases with increasing temperature conditions of server as much as possible. We constructed a physical large-scale cooling system using cooling devices such as general-purpose chillers, cooling towers, pumps, and fans; based on our experimental results and energy simulations, we confirmed that the proposed approach leads to an annual average PUE of less than 1.04. 在之前的一项研究（Aizawa，2018）中，我们构建了一个服务器机房，其中有基于热密度（高、中或低）进行的分区和利用室外空气的制冷系统。在我们先前的研究中，冷却水由冷却塔提供并且冷却塔的使用时间随着服务器设定的温度条件增高而增加。我们使用通用的冷水机组、冷却塔、泵和风机等制冷设备构建了大型物理制冷系统；基于我们的实验结果和能耗模拟，我们证实了该方法下的平均PUE可以低至1.04。 In this study, however, we change the configuration of the previously proposed cooling system based onthe results of our experiment and last fiscal year’s annual energy consumption simulation. In particular, we changed the cooling tower and piping from an open-type to closed-type system, removed some heat exchangers and heat storage tank, and included a chiller. The chiller is used as infrequently as possible, being used only in the cases when sufficient cooling cannot be maintained owing to high wet-bulb temperature of the outside air. In addition, we measured the power consumption and PUE of the modified cooling system under variable flow control and variable fan speed control. Based on the experimental results and annual energy simulation, we confirmed the stability of this modified cooling system in the zoned server room, achieving an annual average PUE of approximately 1.02. 然而，在本研究中，我们根据实验结果和上一财年的年度能耗模拟改变了之前提出的制冷系统的配置，特别是将冷却塔的供回水管道从开式改为闭式并拆除了部分换热器和蓄冷罐，同时增加了一台冷水机组。冷水机组的使用频率越低越好，只有在室外空气的湿球温度较高导致无法维持足够的制冷量时才使用冷水机组。此外，我们还对改进后的制冷系统在变流量及风机变速下的功耗和PUE进行了测试。根据实验和年度能源模拟的结果，我们证实了这种改进后的制冷系统在热密度分区的服务器机房中的稳定性并实现了低至约1.02的年平均PUE。 Figure 1 shows an overview of the zoned server room and proposed cooling system. The server room can be zoned according to the heat load densities as high, medium, and low. When a server room with mixed heat load densities is cooled, the cooling efficiency reduces because the cooling is dictated by the high heat load density. In particular, theheat load density is said to be high, medium, or low if it is 16kW (54.6kBtu/h) or more, 9–16kW (30.7–54.6kBtu/h), or 8kW (27.3kBtu/h) or less per rack, respectively; in the case of a high heat load density, air cooling is not effective, whereas in the case of low heat load density, liquid immersion is not. For example, hard disk storage has a low heat load and can only be air-cooled. In this project, a low PUE was realized by using different types of cooling approaches for different heat load densities: liquid immersion cooling by natural convection of are frigerant in a liquid tank for high heat loads (Matsuoka et al. 2018) (Matsuoka et al. 2017), drop coolant for medium heat loads (Matsuda et al. 2017), and air cooling for racks with low heat load (Impress 2017). 图1展示了热密度分区的服务器机房和我们提出的制冷系统的简要情况。服务器机房可根据热负荷密度分为高，中，低。当为多种热负荷密度的服务器机房制冷时，系统制冷效率会降低，因为制冷系统（形式、容量等）是由高热负荷密度来决定的。如果热负荷密度分别为16 kW（54.6 kBtu/h）或更高，9-16 kW（30.7-54.6 kBtu/h），8 kW（27.3 kBtu/h）或以下时，则称其热负荷密度等级分别为高，中或低；在高热负荷密度的情况下，空气冷却是无效的，而在低热负荷密度的情况下，液浸式冷却是无效的。例如，硬盘存储器具有较低热负荷并且只能进行空气冷却。在本项目中，针对不同的热负荷密度，采用不同类型的冷却方式，实现了较低的PUE值：液浸式冷却，即通过液体槽中的制冷剂的自然对流进行液体浸没式冷却以消除高热负荷（Matsuoka等人，2018年）（Matsuoka等人，2017年），用于中等热负荷密度时可减少冷却剂（Matsuda等人2017）的量，处理低热负荷密度的机架时采取空气冷却（Impress 2017）方式。 Figure 1 Schematic diagram of the proposed server room and cooling system. 图1：热密度分区服务器机房和建议的制冷系统示意图 To achieve an annual PUE of 1.02 or less, which is the primary objective of this study, it is necessary to reduce the power of the cooling system by more than half from that of the system with an annual PUE of 1.04 that was presented in the previous study. Thus, we study the countermeasures and configuration of the cooling system using annual energy simulation. We set the upper limit for the temperature of the cooling water to 40°C (104°F) to ensure stable operation of the ICT equipment based on the individual experiments in the previous study at each load. 为了达到本研究的主要目标，即年PUE为1.02或更低，有必要将制冷系统的功率比上一研究中提出的年PUE为1.04的系统功率降低一半以上。因此，我们采用年度能耗模拟的方法研究了制冷系统的对策和配置。为保证ICT设备在各种负荷下的稳定运行，我们在前期研究的基础上，将冷水温度上限设定为40℃(104°F)。 Figure 2 shows the outline of the cooling system proposed in our previous study before the above mentioned changes were implemented. In particular, the previous cooling system was composed of an open-type cooling tower, heat storage tank, primary pump, heat exchanger, and secondary pump; in addition, the cooling tower and each load were connected via heat exchangers. The secondary pump and heat exchangers were included to adjust the temperature and flow rate at each load; however, the ratio of the energy consumed by the secondary pump to the total power of the cooling system was high. Furthermore, the temperature exchange efficiency in the heat exchanger was around 0.6. Although our approach involved storing the cooled water produced at night in a heat storage tank for use during the summer day peak temperature, the difference between the outside air wet-bulb temperature during the day and night during the summer peak in Japan was small, and therefore, a sufficient cooling water temperature could not be obtained. Compared with an IDC that circulates air in the server room, the proposed system can reduce the power of heat sources as well as that of the fan used to circulate indoor air. 图2展示了我们之前研究中提出的（在上述改变实施之前）制冷系统架构。先前的制冷系统由开式冷却塔、蓄冷罐、一次泵、换热器、二次泵组成。此外，冷却塔通过换热器处理各类负荷，采用二次泵和二次换热器调节各负荷的温度和流量；然而，二次泵的能耗占制冷系统总能耗的比值很高。此外，换热器的换热效率约为0.6。虽然我们的方法是将夜间生产的冷水储存在蓄冷罐中以便在夏季白天的高温期间使用，但在日本夏季高温时期，室外空气湿球温度的昼夜差异很小，因此此举不能获得足够低的冷却水温度。同那些在IDC的服务器机房中进行空气循环冷却相比，此系统不仅可以降低室内空气循环风机的功率，还可以降低冷源的功率。 Figure 2 Outline of the cooling system before changes were made. 图2：配置更改前的制冷系统图 Table 1 lists the comparative conditions of the annual energy simulation and annual PUE results. The annual PUE values for different cooling water set temperatures with the open-type and closed-type cooling tower (including the presence or absence of the cooling tower heat exchanger), chiller, primary pumps, secondary pumps, and heat exchangers, were compared. For outside air conditions, the 2010 standard weather data (Tokyo) was used. For equipment characteristics, we used the experimental results from the previous study, new equipment basic characteristics as well as manufacturer specification values for new equipment. The electric power consumption and coefficient of performance (COP) of the chiller were measured during the winter and summer peaks. As can be seen from Table1, the annual PUE is around 1.02 in Cases 2, 3a, and 3b for the closed-type cooling tower (without the cooling tower heat exchanger), with the primary pumps (capacity division) and secondary pumps, but without the heat exchangers. 表1列出了年度能耗模拟结果与年度PUE设定条件的对比情况，比较了开式和闭式冷却塔(包括有无冷却塔换热器)以及冷水机组、一次泵、二次泵、二次换热器等在不同的冷水设定温度下的年PUE值。对于室外气象条件，我们使用了东京地区的2010年标准天气数据。至于设备性能，我们沿用了之前研究的试验结果数据、新设备的基本性能采用了制造商提供的规格值。我们对冷水机组冬、夏两季的功耗和性能系数(COP)进行了测试。由表1可以看出，工况2、3a、3b的年PUE在1.02左右（采用闭式冷却塔（不带冷却塔换热器）、一次泵(分组配置)和二次泵，无二次换热器） Table 1 Comparative conditions of the annual energy simulation and annual PUE. 表1：年度能耗模拟结果及年度PUE的设定条件对比 Figure3 shows the graphical representation of the cooling system power consumption, which is listed in Table 1. In Case1, the powe consumed by the chiller and secondary pump is larger than in other cases. The reason for the large amount of electric power consumed by the chiller is the longer operation time because of the effect of temperature loss in the heat exchanger. In Case 3b wherein the cooling water set temperature was 35.2°C (95.4°F) (with a margin to upper limit temperature for stable operation of the IC Tequipment), the annual PUE was 1.023, suggesting the feasibility of our objective. In particular, the primary changes to the configuration of the cooling system are as follows: 1) The open-type cooling tower was changed to the closed-type one (with removing the cooling tower heat exchanger), 2) The secondary pump and heat exchanger were removed, and the capacity division in the primary pump was changed, 3) The heat storage tank was changed to a chiller during the peak summer time. 图3展示了表1中所描述的各类型制冷系统年度耗电情况。在案例1中，冷水主机和二次泵的电力消耗大于其他案例。由于受冷却塔换热器的温度损失的影响，冷水主机运行时间较长是冷机消耗大量电能的原因。在案例3b中，冷却水设定温度为35.2℃（95.4°F） (确保ICT设备稳定运行的上限温度值)，年PUE值为1.023，这证明了我们目标的可行性。我们特地对制冷系统的配置做出如下主要改变：1)开式冷却塔改为闭式的(同时取消冷却塔换热器)；2)取消了二次泵和对应的换热器，改为分组配置的一次泵进行流量分配；3)在夏季负荷高峰期，使用冷水主机代替蓄冷罐。 Figure 3 Electrical power consumption of the cooling system (Table 1). 图3：制冷系统年度耗电量（表1） EXPERIMENTAL PROCEDURES Figure 4 shows the system diagram of the cooling system after the configuration changes specified above were made. In Figure 4, the measurement points such as temperature, flow rate, and electrical power consumption, among others, are shown. In addition, the PUE calculation process is depicted on the right side of the figure. The cooling system consists of the closed-type cooling tower (with a fan and pump), primary pumps, and chiller; it allows indirect outside air cooling (free cooling). In this cooling system, the cooling water produced by the cooling tower is supplied to each load; the ICT equipment is cooled by exchanging heat with the heat medium (refrigerant or air) at heat exchangers of each load after the headers. Temperature and flow rate as well as other properties were measured around the headers of each load and at the inlet and outlet of the equipment, and the operation state of the cooling system was confirmed. Electrical power consumption was measured using a power meter on the power panel; furthermore, the PUE is calculated based on the power consumption of the cooling tower fans and pumps, primary pump, and chiller. In the measurement and calculation of PUE, a stable average value for 10 min during operation was used. Moreover, power for lighting and loss is not included in the PUE calculation. In our experiment, to simulate heat loads for the cooling system, pipe insertion-type electric heaters were added to the downstream of the return header. The thermal load was set at around 16, 15, and 8 kW (54.6, 51.2, 27.3 kBtu/h) for high, medium, and low loads, totaling around 39 kW (133kBtu/h). 图4为按上述配置更改后的制冷系统图。在图4中，展示了诸如温度、流速和电功率等测量点。另外，PUE计算过程如图中右侧所示。制冷系统由闭式冷却塔(带风机和泵)、一次泵和冷水机组组成且此系统可以运行间接自然冷却模式。在该制冷系统中，冷却塔产生的冷却水供应给各负载；通过设置在分集水器后的与每个负载所对应的热交换器处与热介质（制冷剂或空气）进行热交换来冷却ICT设备。在每个负载的主管周围以及设备的进出口处对温度、流速和其他数据进行监测以此确认制冷系统的运行状态，使用电源面板上的电表来测量耗电情况；此外，还根据冷却塔风机和泵、一次泵及冷水机组的功耗计算了PUE值。在PUE测量和计算中，我们使用的是稳定运行10min内的平均值。另外，PUE计算中不包括照明功率和损耗功率。在我们的试验中，为了模拟制冷系统的热负载，在分集水器的下游增加了管道插入式电加热器。高、中、低负载的负荷分别为16kW、15kW、8kW(54.6、51.2、27.3kBtu/h)左右，总负荷约为39kW（133kBtu/h）。 Figure 4 System diagram of the cooling system. 图4：制冷系统图（配置更改后） Figure 5 shows the installation conditions of the cooling tower and chiller on the roof of the building where the experiment was conducted. The pump unit of the experimental apparatus was installed below the rooftop and the headers supplied cooling water to each load. We installed two cooling towers and two chillers, because, as future work, we plan to examine the influence of two driving in summer. 图5展示了进行试验的建筑物屋面上的冷却塔和冷水主机的安装条件。试验装置的水泵单元安装在屋面下层，集水器为每个负载提供冷水。我们安装了两台冷却塔和两台冷水主机，因为在未来工作中，我们计划对夏季两组设备全开的工况进行检测。 Figure 5 Installation conditions for the cooling system. 图5：制冷系统实际安装条件 RESULTS AND DISCUSSION Experiments were performed to characterize the auxiliary machines and measure the power consumption and PUE as well as the operation status of the system. Furthermore, the annual PUE was calculated based on the experimental results. 结果和讨论 我们对辅助设备的特性进行了实验研究并测量了系统的功耗、PUE和运行状态。在此基础上，根据实验结果计算了年度平均PUE值。 Basic characteristics of the equipment. As the operating characteristics of the pump, electrical power consumption and differential pressure with varying flow rates of the cooling water were experimentally measured. Figure 6 shows the measurement results for power consumption and differential pressure of the primary pump (small pump) with different flow rates of cooling water. Figure 7 shows the relationship between the inverter frequency and power consumption of the fan as well as spraying water pump in the cooling tower. Figure 8 shows the relationship between the inverter frequency of the cooling tower fan and spraying water pump and the approach (i.e., cooling water outlet temperature−outside air wet-bulb temperature) as the operating characteristics of the cooling tower, when the outside air wet-bulb temperature is around 8 °C (46.4 °F). The results were, the approach was around 4 °C (7.2 °F) in the rated frequency of the cooling tower fan, the approach was around 4 °C to 6 °C (7.2°F to 10.8 °F) when the cooling tower fan inverter frequency was 30 Hz to 50 Hz, the approach was around 4 °C (7.2 °F) when the water spray pump inverter frequency was 30 Hz to 50 Hz, and when the water spray pump inverter frequency was 20 Hz, the approach increased to around 16 °C (28.8 °F). 设备的基本特性。根据水泵的工作特性，对水泵的耗电量和冷却水流量变化时的压差进行了实验测量。图6显示了不同冷却水流量下的一次泵(小型泵)的能耗和压差测量结果。图7展示了冷却塔风机和喷水泵的变频器频率与能耗之间关系。图8展示了在室外空气湿球温度在8℃左右（46.4℉）的工况下，冷却塔风机及喷淋水泵的变频频率与冷却塔出水温度逼近度（即，冷却塔出水温度与室外空气湿球温度接近的程度）的关系并以此作为冷却塔的运行特性。结果显示：当冷却塔风机运行频率为额定功率（50Hz）时，逼近度约为4℃（7.2℉）；当风机频率为30Hz到50Hz时，逼近度约为4℃-6（7.2℉-10.8℉）；当喷淋水泵频率为30Hz到50Hz时，逼近度接近4℃；当喷淋水泵频率为20Hz时，逼近度升高到约16℃（28.8℉）。 Figure 6 Power consumption and differential pressure of the primary pump (small pump). 图6：一次泵（小型泵）的能耗与其压差的关系 Figure 7 Inverter frequency and power consumption of the fan and spraying water pump in the cooling tower. 图7：冷却塔风机/喷淋水泵的变频器频率与其能耗的关系 Figure 8 Inverter frequency and approach (cooling water outlet temperature − outside air wet-bulb temperature) of the cooling tower. 图8：冷却塔风机/喷淋水泵的运行频率与冷却塔出水温度逼近度的关系 Operation status of the cooling system. Figure 9 shows the transition of the driving situation when the outside air wet-bulb temperature was 17–18°C (62.6–64.4°F). At the time 18:00 in Figure 9, the return cooling water temperature was around 37°C (98.6°F) and power consumption of the cooling system was 1.2 kW (4.1kBtu/h) (PUE=1.031) with the cooling tower fan frequency, cooling tower spray pump frequency, and primary pump (small pump) frequency set at 50 Hz, 30 Hz, and 23 Hz, respectively. Then, the cooling tower fan frequency was set at 15 Hz, cooling tower pump frequency was set at 25 Hz, and small pump frequency was raised such that the inlet water temperature of 35°C (95°F) at the cooling tower is achieved. After 19:00, the small pump frequency was further increased to 35 Hz; consequently, the inlet water temperature at the cooling tower was almost stable at about 36°C (96.8°F). At that time, the cooling system power consumption was around 0.52 kW (1.8kBtu/h) (PUE=1.013). The approach increased as the cooling tower fan and spraying pump were throttled; in addition, the flow rate of the small pump was increased to handle the same heat load, but the electrical power consumption of the cooling system decreased owing to power consumption characteristics of the element equipment. Even when the return water temperature target is the same, the cooling system’s electrical power consumption could be lowered by selecting an operating method based on the electrical power characteristics of the element equipment. The final inlet water temperature target of 40°C (104°F) indicated the upper limit temperature of the return water for stable operation of the ICT equipment. Then, when the small pump frequency was lowered to 25 Hz, the inlet water temperature at the cooling tower stabilized at around 40°C (104°F). The stable cooling operation was confirmed based on the transition of the cooling water temperature, when the cooling system power consumption was around 0.42 kW (1.4kBtu/h) (PUE=1.011). 制冷系统的运行状态。图9显示了系统在室外空气湿球温度为17-18°C（62.6-64.4°F）时的运行状态的变化。在图9中的18:00时，冷却水回水温度约为37°C（98.6°F），制冷系统的耗功率为1.2 kW（4.1kBtu / h）（PUE = 1.031），冷塔风机频率，喷淋泵频率和一次泵（小型泵）频率分别设置为50 Hz，30 Hz和23 Hz。随后，冷却塔风机频率降低至15Hz，喷淋泵频率降低至25Hz同时提高一次泵（小型）频率，使得冷却塔处的入口水温变为35°C（95°F）。19:00后，小型泵频率进一步增加至35 Hz，冷却塔的进水温度基本稳定在约36°C（96.8°F），此时制冷系统的功耗约为0.52千瓦（1.8kBtu / h）（PUE = 1.013）。由于冷却塔风机和喷水泵的降速节流，逼近度（即，冷却塔出水温度与室外空气湿球温度接近的程度）有所增加；此外，在相同的负荷下，增加了小型泵的流量，但由于元件设备的能耗特性，制冷系统的整体能耗反而降低。即使当回水温度的目标值相同，也可以基于元件设备的能耗特性合理选择运行策略从而降低制冷系统的能耗。最终，冷塔入口的目标温度（即回水温度）设定为40°C（104°F），这是可以保证ICT设备稳定运行的回水上限温度。然后，当小型泵频率降至25 Hz时，冷却塔的入口水温可以稳定在40°C（104°F）左右。最后，以冷却水温度变化为标志的制冷系统运行趋于稳定，此时制冷系统能耗功率约为0.42kW（1.4kBtu / h）（PUE = 1.011）。
Figure 9 Transition of the driving situation when the outside air wet-bulb temperature was 17–18°C (62.6–64.4°F). 图9：当室外空气湿球温度为17-18℃（62.6-64.4℉）时的系统运行状态曲线 PUE of the cooling system. Figure 10 shows the outside air wet-bulb temperature and PUE trend for the cooling system after the configuration change. The horizontal axis in the figure represents the outside air wet-bulb temperature. In particular, the subfigure on the top shows the annual occurrence frequency (hour of occurrence) of each wet-bulb temperature in the standard meteorological data (Tokyo), while the one below shows the PUE against the outside air wet-bulb temperature. The dashed line in the subfigure below shows the case when the annual PUE is 1.02 in the energy simulation for the cooling system after the configuration change. When the outside air wet-bulb temperature is around 20°C (68°F) WB or less, the PUE is low, approximately 1.01, and when the outside air wet-bulb temperature is higher than 20°C (68°F) WB, the PUE increases; this is due to the increase in cooling system power consumption because of the cooling tower, primary pump, and chiller. 制冷系统的PUE。图10显示了配置变化后制冷系统的室外空气湿球温度和PUE的变化趋势。图中的横轴表示室外空气湿球温度。特别是，上部的子图显示了标准气象数据（东京）中每个湿球温度的年发生频率（小时数），而下图则显示了跟随室外空气湿球温度变化的PUE变化情况。下图中的虚线是配置更改后制冷系统的年度平均PUE为1.02的具体变化曲线。当室外空气湿球温度约为20°C（68°F）WB或更低时，PUE很低，约为1.01，当室外空气湿球温度高于20°C（68°F）时WB，PUE增加；这是由于冷却塔，一次泵和冷水主机的运行导致的制冷系统能耗增加。
Figure 10 Outside air wet-bulb temperature and PUE for the modified cooling system. 图10：室外空气湿球温度和改进后的制冷系统PUE值的变化曲线 The experimental result when the outside air wet-bulb temperature was 17°C (62.6°F) WB is also shown in Figure 9; the energy simulation values were in agreement with our experimental results. When the outside air wet-bulb temperature is around 8°C (46.4°F) WB, the estimated value includes assumed countermeasures against electrical power reduction in the experimental results owing to the equipment characteristics in the cooling system after the configuration change. Furthermore, when theoutside air wet-bulb temperature is around 27°C (80.6°F) WB, the estimated value is considered to be the manufacturer specification value of the chiller and the electrical power consumption of the cooling tower and primary pump based on the experimental equipment characteristics. Based on these results, the feasibility of obtaining an annual PUE of less than 1.02 forthe modified cooling system can be confirmed. 当室外空气湿球温度为17°C（62.6°F）WB时的实验结果已在图9中展示，能耗模拟值与我们的试验结果一致。当室外空气湿球温度在约8℃（46.4°F）WB时，测定值考虑了假想对策来针对由于配置改变之后制冷系统的设备特性带来的功率降低。另外，当室外空气湿球温度在27°C（80.6°F）WB左右时，基于试验设备的特点，测量值可以认为是冷水机组的出厂规格值及冷却塔和一次泵的能耗值。基于这些结果，我们可以确认改进后的制冷系统获得年PUE值小于1.02的可行性。 CONCLUSION In our study, the configuration of a previously proposed cooling system that utilized outside air for a zoned server room based on heat density was modified to improve its PUE based on the annual energy simulation results. 结论 在我们的研究中，基于年度能耗模拟结果，我们对之前提出的利用室外空气的制冷系统（服务于按热密度进行分区的服务器机房）的配置进行了调整以提高其PUE。 An experiment was conducted using a real-scale modified cooling system after the configuration change and simulated load devices, including a real server machine and cooling auxiliary devices. Then, the annual average PUE was estimated. Our results not only confirmed stable operation of the cooling system, but also the feasibility of an annual average PUE of approximately 1.02. Our future work will involve confirming the estimated PUE through actual measurements during the summer season. 在配置改变后，采用实际规模的改进型制冷系统，同时模拟负载设备（包括一台真实的服务器设备和制冷辅助设备）进行了实验，然后估算年平均PUE。我们的研究结果不仅证实了制冷系统可以稳定运行，而且验证了年平均PUE低达1.02的可行性。在未来的工作中，我们将会在夏季通过实际的测量来确认预估的PUE值。 ACKNOWLEDGMENTS This study was supported by the development and demonstration projects for CO2 emission reduction of the Ministry of the Environment in Japan. Liquid immersion- and refrigerant sprinkle-type ICT equipment cooling elements were developed by Osaka University, EEC Research Institute, and Fujitsu Limited. We give sincere thanks to the members of these institutions for their helpful comments. In particular, we would like to thank Mr. Matsuoka and Mr. Matsuda of Osaka University and EEC Research Institute; Mr. Fujimaki, Mr. Yamamoto, and Mr. Kubo of Fujitsu Limited; and Mr. Shibata, Mr. Ikeda, and Mr. Murataof Takasago Thermal Engineering Co., Ltd. for the fruitful discussions. 致谢 本研究得到了日本环境省的二氧化碳减排发展示范项目的资助和支持。液体浸入式和制冷剂喷洒式ICT设备冷却原件由大阪大学、ECC（欧洲经济共同体）研究所和富士通有限公司共同开发。对此我们表示衷心的感谢，感谢这些机构的成员提供的有帮助的意见。此外，我们特别要感谢大阪大学的松冈先生和松田先生；ECC研究所的藤崎先生、山本先生；富士通公司的久保先生以及高雄热力工程有限公司的柴田先生、池田先生、村田先生同我们进行的富有成效的讨论。 REFERENCES 参考文献 Ministry of the Environment. 2016. The development and demonstration projects for CO2 emission reduction of the Ministry of the Environment in Japan. Tokyo: Ministry of the Environment of Japan. (http://www.env./press/102545.html) Aizawa, N., Shibata, K., Ikeda, M., Matsuoka, M. et al. 2013–2015. Development of air conditioning system for data center toward radical low-carbon (1st – 3rd). Tokyo: The Society of Heating, Air-conditioning and Sanitary Engineers of Japan. Aizawa, N. 2018. Cooling System with Low PUE Cooling Power for Server Rooms. ASHRAE Wiinter Conference 2018, ConferencePaper. Matsuoka, M., Matsuda, K., and Kubo, H. 2017. Liquid immersion cooling technology with natural convection in data center. IEEE 6th International Conference on Cloud Networking. Plague: IEEE. Matsuoka, M., Matsuda, K., and Kubo, H. 2018. Effective Cooling of Server Boards in Data Centers by Liquid Immersion Based on Natural Convection Demonstrating PUE below 1.04. ASHRAE Wiinter Conference 2018, Conference Paper. Matsuda, K., Matsuoka, M., and Miyake, Y. 2018. Proposal of Cooling System for High Performance Computing by Drip-Feeding Cooling. ASHRAE Wiinter Conference 2018, Conference Paper. Impress. 2017. Demonstration project of next-generation data center supporting IoT societystarts. http://sgforum./article/3634?page=0%2C0 Copyright of ASHRAE Transactions is the property of ASHRAE and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. 《ASHRAE Transactions》的版权归ASHRAE所有，未经版权所有者的明确书面许可，任何人不得将其内容复制或通过电子邮件的形式发送至网站或论坛。但是，用户可以打印，下载或通过电子邮件发送文章供个人使用。 翻译：
陈亮宇 广东优世联合控股集团股份有限公司-暖通运维工程师 DKV(DeepKnowledge Volunteer)计划成员 校对：
李建利 广东优世联合控股集团股份有限公司-数据中心高级运维经理 DKV(DeepKnowledge Volunteer)计划精英成员 Uptime Institute认证AOS专家 |
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