Continuous cooling solutions for high-density data centers

As the power consumption of data center units continues to increase, the heat generated by the equipment room is getting higher and higher. In this case, once the power supply fails, although the server can continue to operate by the ups system, the refrigeration equipment stops running. As a result, the temperature of the equipment room rises rapidly, which will still cause the server to overheat and stop running. Therefore, the current trend of high-density equipment rooms requires the design of an uninterrupted refrigeration system to ensure that the cooling system or part of the refrigeration system can continue to operate in the event of a power failure, maintaining the ambient temperature of the equipment room for a period of time to avoid excessive temperature rise. Thereby protecting the safe operation of the server equipment, waiting for the power system to recover or the standby power generation system to be put into use. Based on relevant standards and practices, this paper discusses the design of refrigeration systems in high-density computer rooms.

Room temperature when the cooling system is stopped

When the cooling system is stopped, the temperature rise of the equipment room varies depending on the installed density of the data center room. In the traditional computer room, because the power consumption of a single cabinet is small, after the refrigeration system is stopped, it still has a long period of time to maintain normal operation of the equipment. For example, in a single cabinet 1.2KW machine room, after 10 minutes of cooling system shutdown, the temperature will rise by 10.5 ° C, the administrator can have time to enable the standby generator or shut down the server equipment.

However, with the increase in the installed capacity of the computer room, the temperature rise has become very rapid. According to Intel's experimental analysis, a single-cabinet data center with a power consumption of about 9 kW, once the cooling system stops running, the temperature is from 22 ° C. It takes only 18 seconds to rise 40°C and 35 seconds to rise to 57°C. Once it exceeds 32 ° C, the computer equipment will malfunction, the temperature will continue to rise, and the computer equipment will stop running or even be damaged. Therefore, for a high-density computer room, it is necessary to configure an uninterrupted refrigeration system.

The refrigeration system is divided into three grades of ABC, and the grade A is an uninterrupted refrigeration system. The uninterrupted refrigeration system needs to be equipped with UPS for the fan of the precision air conditioner and the secondary pump, and the cold storage tank is added; the grade B is the continuous refrigeration system: the continuous refrigeration system It is necessary to configure the UPS for the fan and secondary pump of the precision air conditioner, but does not increase the cold storage tank; the C-class is an interruptible refrigeration system, that is, the refrigeration system is not equipped with any UPS equipment, and the cooling system is stopped in the event of a power failure. UPTIME grades the refrigeration system and provides several solutions.

Several Solutions for Continuous Cooling in High Density Computer Rooms

For high-density computer rooms, what measures should be taken to maintain the operation of the refrigeration system or part of the operation during the intermittent power failure? The UPTIME organization and related vendors have proposed several solutions.

The first type is to configure the UPS system for the entire refrigeration system. For the chilled water type precision air conditioner, the chiller unit, the cooling tower, the secondary pump and the precision air conditioner are all equipped with a UPS system. This approach maintains the operation of the entire refrigeration system, but for high-power chillers and cooling towers, the cost of all UPS systems is very high, so it is rarely used today.

Second, in a system using a chilled water type precision air conditioner, a UPS is installed for a fan of a precision air conditioner and a secondary pump of chilled water, and a cold storage tank is added to the chilled water circulation system to reserve chilled water. . When the power interruption is not restored, or the chiller is temporarily unable to start due to the power interruption, the cold source is provided by the cold storage tank and the water pump, and the air conditioner in the equipment room is maintained by the fan of the precision air conditioner, thereby maintaining the temperature of the equipment room or for a period of time. Prevent the room from heating up quickly, waiting for power to recover or the chiller to return to normal operation.

Both the first and second methods have met the criteria for Class A uninterrupted cooling.

Third, in a system using a chilled water type precision air conditioner, a UPS is provided for a fan of a precision air conditioner and a secondary pump of a chilled water, but a cold storage tank is not disposed in the chilled water circulation system. When the power interruption is not restored, or the chiller is temporarily unable to start due to power interruption, the fan of the precision air conditioner can still maintain the air circulation in the equipment room, and use the remaining chilled water in the pipeline to cool the equipment room. In this way, the room temperature can be slowed down, but the effect is not as significant as the first two.

Fourth, for systems using direct evaporative precision air conditioning, neither the cold storage system nor the residual cooling of the pipeline can be utilized. However, it is still possible to configure the UPS for the fan of the precision air conditioner, in order to maintain the air circulation of the data center in the event of a failure, and also to slow down the temperature of the equipment room.

The third and fourth methods have met the criteria for Class B continuous refrigeration.

Choice of Continuous Cooling Solutions for High Density Computer Rooms

So, how do you choose the builder or design unit for the above several continuous cooling solutions? In this regard, the author suggests that the builder and the design unit can choose a suitable continuous cooling solution from the above solutions based on the heat density of the data center and the importance of the data center, and the configuration of the backup system such as the diesel engine. For example, in a machine room with a power consumption of less than 1.2 kW in a single cabinet, it is expected that the temperature rises to 32 ° C for more than 10 minutes, and the diesel engine system can be used to provide backup power. As the power consumption of a single cabinet is increased, a UPS solution for a fan of a precision air conditioner can be used to provide air circulation, and the heat absorption capability of the environment can be utilized to slow down the temperature rise rate.

However, for a high-density computer room with a power consumption of 6kW or more for a single cabinet (according to ASHRAE's forecast, the server single cabinet will be above 12KW in 2010), a chilled water type precision air conditioning system is required. UPTlME's Class A uninterrupted cooling scheme is selected to provide UPS to the chilled water circulation system and set a certain volume of cold storage tank to maintain the cooling during the power outage or during the restart of the chiller after the power failure, waiting for the complete recovery of the refrigeration system.

In short, in the face of the development trend of high-density computer rooms, the configuration of continuous cooling facilities to maintain equipment operation during power outages and chiller restarts to protect equipment safety has become an important issue that builders and design units must consider. · At present all parties are actively exploring and implementing. At the same time, with the continuous planning and construction of high-density computer rooms, more solutions are expected to meet the needs of continuous cooling of high-density computer rooms.