Cooling system

Abstract

This invention provides a cooling system that can improve cooling performance by increasing heat exchange efficiency without increasing the circulating water volume in the cooling tower and heat exchanger. [Solution] The system includes a cooling tower 2 having a fan 21 for cooling the cooling water, a heat exchanger 4 that performs heat exchange between the cooling water and the coolant, and a cooling device 5 that performs heat exchange between the coolant and the gas in the server room of the data center DC. The cooling tower has a spray nozzle below the fan that extends horizontally from the upper end of the rotating shaft and sprays cooling water toward the packing material positioned below. The spray nozzle is equipped with auxiliary blades that receive the airflow generated by the fan on an inclined main body to promote the rotation of the rotating shaft.

Description

Technical Field

[0006] , , , , , ,

[0001] The present invention relates to a cooling system including a cooling tower and a heat exchanger.

Background Art

[0002] Due to the leap of AI technology and the like, the heat density of the racks in data centers where computer servers are installed has been significantly increasing. Also, with concerns about global abnormal weather, temperatures in various parts of Japan have exceeded past weather data, and the energy required for cooling has been increasing.

[0003] Especially in data centers that require cooling throughout the year, in many cases, a cooling system using outside air by free cooling as disclosed in Patent Documents 1 and 2 is adopted to reduce cooling energy. However, due to temperature rises and losses during heat exchange, the cooling performance cannot be fully exerted.

[0004] ] The cooling systems of Patent Documents 1 and 2 are cooling devices mainly using free cooling that combines a cooling tower and a heat exchanger. If the free cooling period can be extended, the operation of the chiller device can be suppressed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, due to factors such as the increasing thermal density of racks and the effects of extreme heat, the period during which free cooling can be applied has decreased, making it difficult to achieve energy-saving effects. As a result, there is a growing demand for more efficient cooling systems. For example, increasing the circulation flow rate of the cooling system and enlarging the heat exchanger improves cooling performance, but this increases the energy required for transport, making it difficult to achieve energy-saving effects.

[0007] Therefore, the present invention aims to provide a cooling system that can improve cooling performance by increasing heat exchange efficiency without increasing the amount of circulating water between the cooling tower and the heat exchanger. [Means for solving the problem]

[0008] To achieve the above objective, the cooling system of the present invention comprises a cooling tower having a fan for cooling cooling water, a heat exchanger for exchanging heat between the cooling water and a coolant, and a cooling device for exchanging heat between the coolant and a gas in the space to be cooled, wherein the cooling tower has a spray nozzle below the fan for spraying the cooling water toward a packing material that extends horizontally from the upper end of the rotating shaft and is positioned below, and the spray nozzle is provided with auxiliary blades that receive the airflow generated by the fan with an inclined main body to promote the rotation of the rotating shaft.

[0009] Here, the main body can be configured to be inclined upward from the upper surface of the watering nozzle. Furthermore, the mounting angle of the main body is preferably 5°.

[0010] Furthermore, the edge of the auxiliary blade opposite to the rotation axis can be configured to be raised upwards.

[0011] The cooling device may be configured to have two heat transfer sections that perform heat exchange between the cooling liquid and the gas, and at least one of the two heat transfer sections may be configured to switch between the cooling liquid and chiller water. [Effects of the Invention]

[0012] In the cooling system of the present invention configured in this way, auxiliary blades are provided below the fan of the cooling tower to receive the airflow generated by the fan with an inclined main body, with respect to the cooling water spray nozzle that rotates around a rotation axis.

[0013] In round-type cooling towers, the water spray nozzles rotate due to the water flow. Therefore, when the flow rate is reduced below the rated flow rate to improve cooling performance, the rotational force of the water spray nozzles may decrease.

[0014] In contrast, if auxiliary blades are provided that promote the rotation of the rotating shaft with airflow generated by a fan, the heat exchange efficiency can be increased without increasing the amount of circulating water between the cooling tower and the heat exchanger, thereby improving cooling performance. [Brief explanation of the drawing]

[0015] [Figure 1] This is an explanatory diagram showing an overview of the cooling system of this embodiment. [Figure 2] This is an explanatory diagram showing the outline of a cooling tower. [Figure 3] This diagram illustrates the configuration of auxiliary fins, where (a) is a perspective view showing the basic shape, and (b) is an explanatory diagram showing a modified example. [Figure 4] This is an explanatory diagram showing the overview of the cooling system. [Figure 5] This is an explanatory diagram showing the structure of the heat transfer section of a cooling device. [Figure 6] This is an explanatory diagram illustrating a cooling system used during free cooling. [Figure 7] This is an explanatory diagram illustrating a cooling system used when a chiller is in operation. [Figure 8] This is an illustrative diagram illustrating the overview of a cooling system applied to a data center equipped with air-cooled and liquid-cooled servers. [Figure 9] This is an explanatory diagram illustrating the outline of a verification experiment applying the cooling system of this embodiment. [Figure 10]It is a graph showing the relationship between the secondary-side water temperature and the blown-out temperature confirmed by experiments. [Figure 11] It is a graph showing the relationship between the primary-side water temperature and the wet-bulb temperature confirmed by experiments. [Figure 12] It is a graph showing the relationship between the wet-bulb temperature and the blown-out temperature. [Figure 13] It is an explanatory diagram showing the calculation result of the annual free-cooling period according to the comparative example. [Figure 14] It is an explanatory diagram showing the calculation result of the annual free-cooling period by the cooling system of the present embodiment. [Figure 15] It is an explanatory diagram showing the operation result of the cooling system of the present embodiment by the number of occurrences of the annual wet-bulb temperature and the PUE value.

Embodiment for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing an overview of the cooling system 1 of the present embodiment.

[0017] The cooling system 1 of the present embodiment cools the spaces of buildings including room applications that require cooling throughout the year, such as data centers DC and manufacturing factories, and buildings with a high cooling demand ratio, such as offices and commercial facilities, as the cooling target spaces.

[0018] From the perspective of energy conservation, it is desirable for the cooling system 1 of the present embodiment to have a configuration that can extend the applicable period of free cooling as long as possible and suppress the operation of the chiller device. In particular, for the data center DC, it is required to reduce the PUE (Power Usage Effectiveness).

[0019] In the cooling system 1 of the present embodiment, an open-type cooling tower 2 that focuses on the wet-bulb temperature lower than the dry-bulb temperature and can bring the temperature of the cooling water close to the wet-bulb temperature is applied. Furthermore, by combining the cooling tower 2, a highly efficient heat exchanger 4, and a cooling device 5, the extension of the free-cooling period is achieved.

[0020] The cooling system 1 of this embodiment includes a cooling tower 2 having a fan 21 for drawing in outside air to cool the cooling water, a heat exchanger 4 that performs heat exchange between the cooling water and the coolant, and a cooling device 5 that performs heat exchange between the coolant and the gas in the space to be cooled.

[0021] Cooling loads are generated in the space to be cooled, including through-flow load, solar radiation load, body heat generation, internal heat generation, and ventilation. In particular, in the server room of the data center DC exemplified in this embodiment, servers such as the air-cooled server S1 are installed in racks, and heat is generated by the operation of the servers.

[0022] In the cooling system 1 of this embodiment, air (gas) whose temperature has risen due to a cooling load such as the operation of the air-cooled server S1 is cooled by heat exchange with a coolant flowing through a cooling device 5 installed in the same server room.

[0023] The coolant, whose temperature has risen through heat exchange with the air in the space to be cooled, such as the server room, is sent outside by the circulation pump 11 and exchanges heat with the cooling water in the cooling tower 2 via a heat exchanger 4 for isolation. The cooling water, whose temperature has risen through this heat exchange, is then sent to the cooling tower 2, which is installed on the roof of the data center (DC).

[0024] The cooling water, cooled by the cooling tower 2 (described later) which is capable of high-efficiency heat exchange, is then sent again by the circulation pump 11 to the heat exchanger 4 for isolation, and used to lower the temperature of the coolant in the cooling device 5.

[0025] Figure 2 is an explanatory diagram showing an overview of the cooling tower 2. This cooling tower 2 is a so-called round-type, open-circular cooling tower. Inside the cylindrical casing 27, a fan 21, which is rotated by a motor 211, is located at the top.

[0026] Below the fan 21, multiple pipes extending horizontally from the upper end of the rotating shaft 22 are provided as water spray nozzles 23 (see Figure 3). The rotating shaft 22 is formed in a cylindrical shape, and the cooling water sent in from the inlet 25 located at the bottom of the cooling tower 2 rises inside the rotating shaft 22, and rotation occurs due to the reaction force when the water is blown out from the water spray nozzles 23.

[0027] As the rotation axis 22 rotates, the watering nozzles 23 also rotate around the rotation axis 22. The watering nozzles 23 are arranged in four, for example, a cross shape in plan view, and multiple watering holes are drilled on the underside at intervals along the longitudinal direction.

[0028] The cooling water that rises along the rotating shaft 22 flows into the sprinkler nozzle 23, which is a pipe connected to it, and as it flows through the inside of the sprinkler nozzle 23, it is dripped out from the sprinkler holes. The sprinkler holes are drilled at equal intervals from the rotating shaft 22 side to the inner wall of the casing 27.

[0029] As the watering nozzle 23 rotates instead of remaining in one place, the cooling water is evenly sprayed into the cylindrical interior of the casing 27 located below the watering nozzle 23.

[0030] A filler material 24 is placed in the space below the water spray nozzle 23. The filler material 24 is a material that is filled into the cavity of the casing 27 in order to increase the contact rate by increasing the contact time between the cooling water and the air, thereby improving the cooling efficiency of the cooling water.

[0031] The filler material 24 is structured in such a way that water sprayed from the watering nozzle 23 flows easily in a film-like manner, and a uniform air passage (see dashed arrow in Figure 2) is formed, allowing air to be drawn in from below the casing 27 and rise. For example, a resin honeycomb can be used as the filler material 24.

[0032] In other words, in the cooling tower 2, outside air (air) drawn in from below the casing 27 by the rotation of the fan 21 causes the cooling water sprayed from the spray nozzle 23 to exchange heat with the packing material 24 in the area where it is placed. For this reason, the lower the outside temperature, the more efficiently the cooling water can be cooled.

[0033] Cooling water, sprayed from the spray nozzles 23 and having exchanged heat with the outside air as it passes through the packing material 24, is received in the lower water tank 28 and discharged from the outlet 26. The cooling water discharged from the cooling tower 2 is sent towards the heat exchanger 4 for isolation.

[0034] The cooling tower 2 incorporated into the cooling system 1 of this embodiment has been improved to enable efficient heat exchange at the wet-bulb temperature. The cooling tower 2 has been designed to increase the contact surface area with the packing material 24 in order to achieve the ability to bring the cooling water temperature closer to the wet-bulb temperature. However, when using standard products, it is difficult to modify the packing material 24.

[0035] On the other hand, it is possible to select a cooling tower 2 in which the rated circulation flow rate is approximately 3 to 5 times higher, thereby increasing the contact surface area of ​​the packing material 24 with respect to the flow rate. Therefore, in the cooling system 1 of this embodiment, a cooling tower 2 is selected in which the rated circulation flow rate is greater than the actual flow rate.

[0036] As described above, the round-type cooling tower 2 has a structure in which the water spray nozzle 23 rotates due to the flow of cooling water. Therefore, when it is rotated at a flow rate far less than the rated flow rate, the water spray nozzle 23 tends to lose rotational force.

[0037] If the water spray nozzle 23 stops rotating, the cooling water will be sprayed unevenly and will not be able to make sufficient contact with the packing material 24, resulting in a decrease in the cooling effect. Therefore, in this embodiment, the cooling tower 2 is equipped with auxiliary blades 3 on the water spray nozzle 23 to compensate for the decrease in rotational force.

[0038] In other words, the watering nozzle 23 is equipped with auxiliary blades 3 that receive the airflow generated by the fan 21 and promote the rotation of the rotating shaft 22. Figure 3 is a diagram illustrating the configuration of the auxiliary blades 3, and Figure 3(a) shows the basic shape.

[0039] The auxiliary blade 3 is a plate-shaped member attached to the upper side of the watering nozzle 23. Lightweight and rigid plate materials such as aluminum plates or resin plates can be used for the auxiliary blade 3. The auxiliary blade 3 can be attached to the middle of the watering nozzle 23 in the longitudinal direction or around the tip opposite the rotation axis 22.

[0040] The auxiliary blade 3 illustrated in Figure 3(a) has a main body 31 formed to have a blade shape similar to that of a rectangular propeller fan in plan view. The auxiliary blade 3 is mounted at an angle to the watering nozzle 23, and the inclined plate-shaped main body 31 receives the airflow, supplementing the force that rotates the watering nozzle 23.

[0041] Therefore, it is preferable to mount the auxiliary blade 3 so that its lower end is positioned above the axis of the watering nozzle 23, thereby creating a structure that allows the watering nozzle 23 to easily obtain rotational force. For example, by setting the mounting angle θ of the auxiliary blade 3 to 5° relative to the horizontal, and aligning the lower end of the main body 31 with the axis of the watering nozzle 23, a structure is created that allows the watering nozzle 23 to easily obtain rotational force.

[0042] The auxiliary blade 3 can supplement the rotational force of the rotating shaft 22 even if it is only attached to one of the four watering nozzles 23. Alternatively, the auxiliary blade 3 can be attached to multiple watering nozzles 23.

[0043] As shown in Figure 2, the airflow formed by the rotation of the fan 21 is an upward airflow directed from the bottom to the top of the cooling tower 2. Therefore, when the wind is received over almost the entire lower surface of the main body 31, which is inclined upward from the water spray nozzle 23 at the mounting angle θ, a force is generated that pushes the water spray nozzle 23 in the rotational direction (see arrow in Figure 3(a)).

[0044] Figure 3(b) is an explanatory diagram showing a modified example of the auxiliary blade 3A. The auxiliary blade 3A has the same shape and mounting angle θ as the main body 31 in Figure 3(a), but a raised portion 32 is provided on the edge opposite the rotation axis 22, which is raised upwards. By providing a raised portion 32 that is triangular or trapezoidal in side view, like an airplane wing, the rotation efficiency can be further increased.

[0045] By providing the auxiliary blades 3 and 3A on the watering nozzle 23 in this manner, the watering nozzle 23 can be rotated even when the airflow of the fan 21 is low. Furthermore, even when the flow rate of the cooling water is less than the rated flow rate of the cooling tower 2, and it is difficult to rotate the watering nozzle 23 with only the flow rate of the cooling water rising up the rotating shaft 22, the auxiliary blades 3 and 3A make it possible to rotate the watering nozzle 23.

[0046] If the water spray nozzle 23 can rotate to ensure even contact between the packing material 24 and the water, the cooling performance of the cooling tower 2 can be improved. Furthermore, if the flow rate of the cooling water is low and the descent speed of the cooling water sprayed from the water spray nozzle 23 is low, the contact rate between the cooling water and the outside air (air) on the packing material 24 increases, thereby improving the cooling performance.

[0047] The heat exchanger 4, installed outside the server room for isolation purposes, acts as a liquid / liquid heat exchanger between the cooling water of the cooling tower 2 and the coolant of the cooling device 5. The heat exchanger 4 is designed to accommodate small volumes of cooling water, and it is preferable to use a two-pass heat exchanger to improve the heat exchange efficiency. Here, a two-pass design refers to a specification where the heat exchange path in the heat transfer section is lengthened by having the heat exchanger 4 reciprocate through its interior.

[0048] While large heat exchangers tend to have a larger heat transfer surface area and thus better heat exchange efficiency, the increased pitch between plates leads to a higher required flow rate and thus increased transport energy. The two-pass heat exchanger 4 of this embodiment is highly efficient and can handle small water volumes, resulting in a compact shape that reduces transport energy and improves flexibility in facility planning.

[0049] Next, we will describe the cooling device 5, which is installed in the server room and functions as a liquid / air heat exchanger. Figure 4 is an explanatory diagram showing an overview of the cooling device 5. Figure 5 is an explanatory diagram showing the structure of the heat transfer section of the cooling device 5.

[0050] As shown in Figure 4, the cooling device 5 takes in air at, for example, around 38°C, cools it to around 23°C through heat exchange, and blows it out. Meanwhile, the coolant used for heat exchange with the air enters the cooling device 5 at around 22°C and is discharged from the outlet at around 27°C.

[0051] In this way, the cooling device 5 cools the air by transferring heat from the high-temperature air to the coolant side, resulting in heat exchange. To increase the heat exchange efficiency, the device structure was designed to use a small amount of water and have low pressure loss. Note that if the heat exchange efficiency increases, the outlet temperature on the coolant side will rise.

[0052] In the cooling device 5, as a way to efficiently transfer heat from the cooling liquid to the air, it is preferable to have a heat transfer section structure in which fins provided in the gas flow path are in close contact with the liquid flow path. In other words, if a fine air layer is formed at the connection between the outer shell of the liquid flow path and the fins, it will cause a decrease in heat transfer performance, so it is preferable to manufacture the heat transfer section using a joining means that allows the fins to be in close contact with the outer shell.

[0053] Furthermore, it is preferable that the heat transfer section of the cooling device 5 be formed such that the cross-sectional area of ​​the flow path through which the gas passes is larger than the cross-sectional area of ​​the flow path through which the liquid passes, as shown in Figure 5. For example, the cross-sectional area of ​​the liquid flow path is not circular like a pipe, but rather an oval flow path (flat type) as shown in Figure 5.

[0054] By making the flow channel cross-section flat, the outer shell has more flat surfaces, increasing the heat transfer area in contact with the fins, and making it easier for the heat (cold) of the coolant to dissipate to the fins. For example, by creating a structure in which the lower and upper ends of aluminum fins are in close contact with the plate-shaped upper and lower surfaces of the flat liquid flow channel, a highly efficient heat transfer section can be created.

[0055] For example, compared to a typical heat transfer section in which fins are attached to a cylindrical tube, the temperature efficiency of the typical heat transfer section is 20% to 70%, while the heat transfer section of cooling device 5, which combines plates and fins, achieved a temperature efficiency of 40% to 96.5%, as confirmed by actual measurements.

[0056] Furthermore, if we consider the gas-side cross-sectional area of ​​a typical heat transfer section (fins + cylindrical) to be 100%, the heat transfer section of the cooling device 5 in this embodiment (Figure 5) can reduce the gas-side cross-sectional area to 50% to 70%, thus reducing the area and volume of the heat transfer section and enabling space saving. As a result, flexibility in facility planning is improved.

[0057] The cooling device 5 can cool without using a chiller as long as the wet-bulb temperature is 20°C or lower. Figure 6 is an explanatory diagram illustrating the cooling device 5 during free cooling. This cooling device 5 has a configuration in which two heat transfer sections of two-pass specifications are stacked in two stages. By connecting the outlet of the lower heat transfer section of the two-pass specification to the inlet of the upper heat transfer section, it is also possible to create a four-pass cooling device 5.

[0058] As shown in Figure 6, when the wet-bulb temperature (WB) is 20°C or lower and the cooling water temperature is 23°C or lower, the cooling device 5 can perform free cooling. Therefore, not only the heat transfer section located in the upper section, but also the heat transfer section in the lower section, which also functions as a chiller, is supplied with coolant through free cooling to cool the air.

[0059] Under conditions where the wet-bulb temperature (WB) is 20°C or lower and the cooling water temperature is 23°C or lower, for example, air at 38.3°C can be cooled to 24°C by the cooling device 5.

[0060] On the other hand, Figure 7 is an explanatory diagram illustrating the cooling system 5 when using a chiller. In the range of 20°C to 27°C, where the wet-bulb temperature (WB) is high (cooling water is below 28.8°C), chiller water is supplied to the chiller portion of the heat transfer section, which is designed in two stages: one for free cooling and the other for chiller use. The heat transfer section that also functions as a chiller may be the upper stage or both stages.

[0061] By operating in this manner, under conditions where the wet-bulb temperature (WB) is below 27°C and the cooling water temperature is below 28.8°C, the cooling device 5 can cool the 38.3°C air to 24°C. Using the cooling device 5 configured in this way, the chiller load can be reduced to approximately 40.8% or less of the total load at its maximum during the summer, thereby achieving energy savings.

[0062] Figure 8 is an illustrative diagram illustrating the overview of cooling system 1A applied to a data center (DC) equipped with an air-cooled server S1 and a liquid-cooled server S2. Due to the rapid advancements in AI technology, data centers are increasingly adopting high-performance, heat-generating servers equipped with GPUs (Graphics Processing Units). As the thermal density of the server racks increases, air cooling alone becomes insufficient, making the introduction of a liquid cooling system essential. Here, servers cooled by an air-cooled system are referred to as air-cooled servers S1, and servers cooled by a liquid-cooled system are referred to as liquid-cooled servers S2.

[0063] However, even when a liquid cooling system is adopted because the air cooling system alone is insufficient for heat treatment, it is not possible to treat all the heat with liquid cooling alone. Approximately 20% of the heat will still require air cooling. Therefore, even in a server room equipped with a liquid-cooled server S2, it is necessary to install an air cooling device 5.

[0064] Therefore, a cooling system 1A will be constructed that enables hybrid cooling using air and liquid cooling, by sharing the cooling tower 2 with the heat exchanger 4 outside the server room, as shown in Figure 8.

[0065] This cooling system 1A has the same configuration as the cooling system 1 described above, but it is equipped with a chiller device 12 that can supply chiller water. When the chiller device 12 is operated during high temperatures in summer to generate chiller water at a lower temperature, it can be supplied directly to the liquid-cooled server S2. In addition, chiller water can also be supplied to the cooling device 5 for the air-cooled server S1 and the cooling device 5 for the liquid-cooled server S2.

[0066] Next, we will describe the results of an experiment that confirmed the effectiveness of the cooling system 1 of this embodiment. Figure 9 is an explanatory diagram showing an overview of a confirmation experiment using an air cooling system equivalent to the cooling system 1 of this embodiment.

[0067] Here, for the cooling water that travels between the cooling tower 2 and the heat exchanger 4 installed on the rooftop, the side heading towards the heat exchanger 4 will be called the primary forward path, and the side returning to the cooling tower 2 will be called the primary return path. Similarly, for the coolant that travels between the heat exchanger 4 and the cooling device 5, the side heading towards the cooling device 5 will be called the secondary forward path, and the side returning to the heat exchanger 4 will be called the secondary return path.

[0068] Figure 10 is a graph showing the relationship between secondary water temperature and outlet temperature, as confirmed by experiment. Here, secondary water temperature refers to the temperature of the coolant measured in the secondary supply and return paths, with the supply temperature towards the cooling device 5 being lower than the return temperature when it returns to the heat exchanger 4.

[0069] When examining the relationship between the secondary water temperature of this coolant and the outlet temperature of the cooling device 5, it can be seen that the relationship between the supply water temperature to the cooling device 5 and the outlet temperature is within 1.0°C, indicating extremely high thermal efficiency (see the dashed line in Figure 10).

[0070] On the other hand, Figure 11 is a graph showing the relationship between primary water temperature and wet-bulb temperature as confirmed by experiment. Here, primary water temperature refers to the temperature of the cooling water measured in the primary supply and return paths, with the supply temperature towards the heat exchanger 4 being lower than the return temperature when the water returns to the cooling tower 2.

[0071] When examining the relationship between the primary water temperature of this cooling water and the wet-bulb temperature of the ambient air, the approach (temperature difference between the wet-bulb temperature and the cooling water) is 1.5°C to 2.5°C, indicating excellent thermal efficiency (see the dashed line in Figure 11).

[0072] Generally, the approach temperature of a cooling tower is said to be 5°C, and a difference of 3°C is considered the limit. However, in the cooling tower 2 equipped with the auxiliary vanes 3 used in the cooling system 1 of this embodiment, it can be seen that efficient heat exchange is taking place.

[0073] Figure 12 is a graph showing the relationship between wet-bulb temperature and discharge temperature. By showing the relationship between the outdoor wet-bulb temperature where cooling tower 2 is installed and the discharge temperature of cooling device 5 located in the server room, we can evaluate the air cooling system shown in Figure 9.

[0074] Figure 12 shows that in order to keep the outlet temperature of the cooling device 5 below 24°C, the wet-bulb temperature of the outside air must be below 21°C. Therefore, we evaluate this air cooling system by applying these results to the annual wet-bulb temperature and showing the number of days on which the outlet temperature of the cooling device 5 remains below 24°C.

[0075] First, Figure 13 shows the estimated annual free cooling period for the comparative example. In the comparative example, the approach temperature difference was 7°C, resulting in a free cooling period of 224 days. In contrast, Figure 14 is an explanatory diagram showing the estimated annual free cooling period for this air-cooling system.

[0076] As can be seen by comparing Figure 13 and Figure 14, by applying this air cooling system, the number of free cooling days for obtaining 24°C air per year is 224 days in a conventional system with an approach temperature difference of 7°C, but by applying the cooling system 1 of this embodiment, it becomes 279 days, thus shortening the annual operating days of the chiller device.

[0077] Based on the above results, in order to further reduce energy consumption, the fan 21 of the cooling tower 2 was reduced in airflow so that the outlet temperature of the cooling device 5 would be 24°C, on days when the outdoor wet-bulb temperature was lower than 21°C. Figure 15 is an explanatory diagram showing the operating results of this air-cooling system in terms of the number of times the wet-bulb temperature occurs per year and the PUE value.

[0078] As can be seen in Figure 15, when the wet-bulb temperature is in the range of 21°C to 19°C, the fan 21 can be operated at a frequency of 50Hz, and when it is in the range of 18°C ​​to 15°C, it can be operated at 20Hz, making it possible to set the outlet temperature of the cooling device 5 to 24°C.

[0079] Furthermore, when the wet-bulb temperature was between 14°C and 5°C, the outlet temperature of the cooling device 5 could be controlled by intermittently operating the fan 21 at a frequency of 20Hz at a rate of 40-60%. When the wet-bulb temperature was 4°C or lower, it was confirmed that further energy savings were possible by reducing the circulation flow rate of the cooling water from 30 L / min to 25 L / min by intermittently operating it at a rate of 40%.

[0080] Based on these factors, when we calculated the annual PUE value, an energy metric for data centers (DCs), we obtained a PUE value of 1.21, which is significantly lower than the typical design value of 1.4 for data centers.

[0081] Next, the operation of the cooling system 1 of this embodiment will be described. In this configuration, the cooling system 1 is provided below the fan 21 of the cooling tower 2, with an auxiliary blade 3 that receives the airflow generated by the fan 21 on an inclined main body 31 for the spray nozzle 23 of cooling water that rotates around a rotation axis 22.

[0082] In round-type cooling towers, the water spray nozzles rotate due to the water flow. Therefore, when the flow rate is reduced below the rated flow rate to improve cooling performance, the rotational force of the water spray nozzles may decrease.

[0083] In contrast, if auxiliary blades 3 are provided to promote the rotation of the rotating shaft 22 with the airflow generated by the fan 21, the cooling performance can be improved without significantly modifying the standard cooling tower.

[0084] The cooling system 1 of this embodiment focuses on the wet-bulb temperature, which is lower than the dry-bulb temperature, and efficiently performs heat exchange at the wet-bulb temperature. This system cools target spaces such as data centers and manufacturing plants, which include rooms that require cooling throughout the year, as well as offices and commercial facilities, which have a high proportion of cooling demand.

[0085] Furthermore, with the cooling system 1 of this embodiment (see the air cooling system in Figure 9), for example, if the temperature of the hot aisle (a passage for releasing hot air waste heat from electronic equipment) in the server room is 34°C, the temperature of the cold aisle (a passage for cold air to cool electronic equipment) can be reduced to 24.0°C if the wet-bulb temperature of the outside air is 21°C or lower, and cooling can be performed.

[0086] While embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and any design modifications that do not depart from the spirit of the present invention are included in the present invention.

[0087] For example, in the above embodiment, the space to be cooled was described using a server room in a data center (DC) as an example, but the present invention is not limited to this, and the cooling system 1 can be applied to other air conditioning facilities as well. [Explanation of Symbols]

[0088] 1.1A: Cooling system 2: Cooling tower 21: Fan 22: Rotation axis 23: Watering nozzle 24: Filling material 3,3A: Auxiliary blades 31: Main body 32: Startup Department 4: Heat exchanger 5: Cooling device 12: Chiller device θ: Mounting angle

Claims

1. A cooling tower having a fan to cool the cooling water, A heat exchanger that performs heat exchange between the cooling water and the coolant, The system includes a cooling device that performs heat exchange between the cooling liquid and the gas in the space to be cooled. The cooling tower has a spray nozzle below the fan that sprays the cooling water toward a packing material that extends horizontally from the upper end of the rotating shaft and is positioned below it. A cooling system characterized in that the water spray nozzle is provided with auxiliary blades that receive the airflow generated by the fan with an inclined main body to promote the rotation of the rotating shaft.

2. The cooling system according to claim 1, characterized in that the main body is inclined upward from the upper surface side of the water spray nozzle.

3. The cooling system according to claim 2, characterized in that the mounting angle of the main body is 5°.

4. The cooling system according to any one of claims 1 to 3, characterized in that the edge of the auxiliary blade opposite to the rotation axis is raised upward.

5. The cooling device comprises a two-stage heat transfer section for performing heat exchange between the cooling liquid and the gas, and at least one of the two heat transfer sections is capable of switching between the cooling liquid and chiller water, as described in any one of claims 1 to 3.

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