Rise in heat density data center (TTDL) has a major impact computer technology for years. Density increased focus also makes cooling the heat load capacity higher than difficult.
 In recent years, the design cooling system traditionally has been proven no match to remove heat concentrated in the load (to the 20KW/Rack).

This problem has led to structural changes in the cooling data centers. The appearance of a new cooling structure is designed for higher heat density increased performance of TTDL. This article will mention the outstanding performance of the structure to cool the structure in comparison with two other universal cooling.

Figure 1: air-conditioning machine room Figure 2: The equipment on the roof

A prominent structure is used to cool TTDL since appeared mainframe server system is moving air through the speakers from the floor machine room Air Conditioning (CRAH). In this method, the CRAH are arranged around the perimeter of the room and distribute cold air from the floor through a hole or floor pads lead directly triep cold air into the room (Figure 1.) The density lower, (1 to 5 kW / rack) the cooling provided to the sensor IT despite the air in the room was mixed.
Layout design eliminates air in the hot and cold air supply more relevant, it also brings the benefits of energy efficiency. The first is to reduce the fan energy needed to move the air.
A distribution system similar to air fresheners used to TTDL system central air conditioning (CAHU) (Figure 2). These systems are used more widely, more focus on the cooling device with air distribution similar structure in the form of floor CRAH author or to the duct above.
When the capacity of a rack more than 5 kW limit, the distribution of air and heat rejection becomes a difficult challenge for the two systems and CRAH CAHU. Biggest drawback of this structure is the ability to transport air to length. The distance between the cooling equipment and parts heat load hinders the elimination of waste heat from the IT equipment that is not mixed with the air supply source. This separation has led the design of air distribution becomes very complex and unsolvable.
Figure 3: Cooling the goods. Cooling the structure found, as described, using a device that does not waste gas by using tubes or any hot or cold gas chamber which

A further difficulty is the demand of air traffic IT equipment also increased with energy density. Because the system uses CAHU CRAH and ventilation to transport air (hot air up and feedback in a specific design), a significant amount of fan capacity to be mobilized huge pressure on ventilator and overcome the power distribution system in the air. Also, to win the mixed effects of the flow of air circulation to more than the air flow requirements of the IT equipment, rather than adjust the energy consumed by fans.

To overcome the limitations of the air distribution and cooling systems and CRAH CAHU, cooling the goods began appearing in many designs TTDL (Figure 3). In order to solve the problem separate from the cooling equipment and heat load, the design was found by placing the air conditioning in the middle rows Rack. Design combination of hot and cold blocks, heat due to IT equipment to be removed as waste in the heat range.
Besides overcoming the limitations of the elimination of hot air and supply air cooling, the design also brings in the benefits of energy efficiency. The primary benefit is to reduce fan capacity needed to move the air. The aggregated load of the heat makes the air distribution path and remove heat much shorter. This result is a shift of the air distribution system from the data center to supply cold air cooling. Take away heat from the heat before it blocks the opportunity to mix the air around the office for the rest of the room with a large air supply. That way, the length of the system
Figure 4: Power consumption variable speed fan. Note: Save energy and gas flow variations can not be evaluated by all the cooling system as found. This feature is specific to systems integration algorithm variable speed control.

Distributed by air in just a few feet (variable according to the number of equipment racks and air conditioning).
In most application process and structure CAHU CRAH, maintaining a fixed speed fan to distribute the pressure necessary for uniform airflow distribution through the holes wind is very necessary. In designing the closed design found, the static pressure required to decrease significantly, with more force against the cooling section. No need to ask about the pressure of a fixed layout design as found for variable air flow rate of the fan speed with heat load requirements. This feature increases energy efficiency through work load and increase sales to lower the load as in Figure 4.
To eliminate the blending of hot and cold airflow has created interest in energy from the temperature warmer air back to the cooler. Some advantages of the air is warm:
• The cooling capacity per unit has to lower the overall cooling. Return air temperature warmer supply gap to higher temperatures at the ceiling and cold conductor system around, so heat was taken away more heat.
• Effective keep hot air as higher temperatures increase the likelihood for warm (no need to compensate for cooling air to blending).

    * Limit or not to condense the steam, to reduce the formation of moisture needs.

Several configurations according to the layout found on the market, using different layout of the cooling device and found several methods to remove more heat. While the method of cooling by this arrangement is for the highest energy efficiency, the benefits of energy is indeed a structural arrangement found on the air distribution system such as system and CRAH CAHU . The comparison in the next section will illustrate the ability to save energy by cooling the structure found.
The comparative performance of the structure TTDL cooling.
Comparing the three structures to cool the refrigeration system of the state space mission information technology. The key is to compare the power consumption by cooling parts against consumption by information technology equipment. Comparison is trying to understand and calculate all power consumption through heat exchange process. (Rack technical information waste heat into the outside environment).

System of units calculated according to the metric system, from the formula above, bringing the rate of cooling capacity of the capacity of IT equipment. Accordingly, the value of the result is more energy efficiency of the cooling structure is higher.
Basis compared
The structures considered include the structure of computer room air (CRAH), central air conditioning (CAHU) and the air conditioning services (IRAH). Analysis below focuses only on the cooling requirements for setting up IT equipment that does not consider moisture control space (as wet or dry throat).
A point to note is that structures and equipment use CRAH CAHU rate is lower than the thermal devices IRAH and consume more energy to maintain the moisture requirements of space.
Basically, the transmitter in accordance with a tradition that became the standard of the three methods yield distribution and air conditioning in each particular structure.
Heat by the actual IT equipment and lighting system in model form in TTDL analysis is 0.75 MW. Cooled water source for IT equipment, lighting and air conditioning equipment powered by compressed gas cooling, using compression technology provided by the cyclones inverter. Equipment cooling provides cooling water temperature is fixed 450F (70oC) for all three structures to be considered. Heat emitted by the cooling equipment will be removed by the cooling tower.

Table 1: Binh stop hourly Table 2: Performance with cooling water temperature

Temperature of the water from the cooling tower can last in the humid heat set temperature of the surrounding environment to low temperature flow leaving the tower is 550F (130C). Temperature outside the tower is determined on the curve showing the operation of the cooling tower with 100% flow at temperature 100F (-120C). The combination of the inverter compressor and the low temperature condensation create effective cooling needed in the process of improving the cooling device is low.
But in reality, condensing water systems can turn natural flow of water condensation similar to the operation of a cooling device, but in this analysis, the flow of condensed water will be kept unchanged for increased level of efficiency of cooling equipment. Accordingly, the working cycle of cooling fans in the cooling tower was also adjusted to adapt to the requirements of the cooling device set by the cooling structure is considered.
Table 2 model building activities of the cooling device according to the concentration kWh consumption and load kWh. Cooling chosen with special high load levels and improve their effectiveness low. This is an intentional choice to avoid the purpose expands the effect of flow between multiple cooling structure. Choose the less efficient flow of air conditioning (cooling equipment, pumps and cooling tower) will increase the total energy consumed by the fan cooling device increases. The ratio of energy to cool the condensing temperature greater than 850F (290C) will be extrapolated. Problems occur when using this method is very limited by operating time beyond this temperature up only 3% of the time.
Denmark circulated cold water will lose 40 feet (12 meters) of the column to allow for pressure equipment and piping and cooling equipment is calculated on the total loss of air conditioning for each structure cooling . The rate of flow of cooling water will be located at the value required by a specific structure cooling.
Air conditioning in the (IRAH)
An alternative method and structure to cool today's popular devices for the delivery of IT equipment air conditioning in the middle of the rack containing IT equipment. The air conditioning equipment is designed with special control algorithms to maximize the stability of the environment temperature. Particularly, the air conditioning is usually small, so solving the problem of space in IT equipment cabinets. Moreover, the air conditioning set between rows will minimize the mixing of the air flow from the air conditioning will be easy from access to IT equipment over.
Table 3: power consumption of the cooling infrastructure
* The specifications of IRAH:

* 2900 cfm (1369 L / s) the discharge by
* Cooling identify: 25.2 kWh in DB and 67.70F WB 95oF (35oC and 20oC DB WB)
* The rate of heat identification is: 1.0
* The water: September 17 gpm at 25 ft of column pressure (1.13 L / s) at the column pressure 8m
Air temperature outside the tower radiators 76.4oF (19.7oC) (from formula 2)
* Energy Fan: 1 kWh
* CW pump power: 0.34 kW (formula 2)
Download TTDL used in the analysis of energy at 0.75 MW will need equipment IRAH 30, plus June 30 KW fan power and pump water February 10 kW with IT equipment and lighting at 750 kW. The formula will enable students to power the cooling equipment at 791 kW.
Air conditioning computer room (Computer Room Air Handler - CRAH)
Currently, the usual experimental target to reduce initial investment costs for cooling solutions based on large cooling equipment, feasibility and commercialization in the market.
A device is considered more of a fan models CRAH arranged inside the air distribution lines. The fan was placed in the bottom part of the equipment CRAH with a few or no change in the exit on the floating floor ventilation. The result is an impact on the system fan with the three resonant impact on the fans still another. Impact is a function of air flow area, exit area, speed and length redirection. The impact of the system exit is not usually pay attention to and often lead to the products were installed bring the number of gas flow is less than expected.
Model theory CRAH below the cooling capacity was 102 kWh compared to 750 kWh for the load capacity of IT equipment and lighting load combination. In this case, the full capacity without load balance will need equipment CRAH 7.3 per specifications mentioned below. IT equipment is considered necessary to 8 devices CRAH with a number in excess of immediate supply is 1.09 times the basic load.
CRAH eight devices mentioned above will be combined plus the fan power is 88 kW and pump capacity of 11.2 kW cooling and IT equipment and lighting at 750 kW. This formula shows that the total cooling load is 893 kW at the rate of heat are aware 0.95.
CAHU
Most applications use air conditioning center will have air-conditioning equipment is designed and built for the specific project. The diversity of design practice and the selection makes them difficult to show the performance data of the equipment in all phases. Values used in this document is used for the purpose of comparison and are trusted to reflect the value is not true. However, some changes can be foreseen.
Can see that impact the system output, a factor contributing significantly to the loss of fan CRAH not referred to above in the example below CAHU. That may be understood as the physical geometry of the air conditioning equipment required for operation better thanks to the layout and operation of our fans. However, in many cases, unfortunately, the benefits derived from reducing or eliminating effects system fan exit is often offset by the increase in pressure loss: a system of pipes , seats fold your song and diffusion. Assume that data center load is 0.75 MW will require a number of four devices with CAHU specifications below, without any downloading any balance. With these models built CAHU equipment required, the number of backup devices can be controlled carefully for achieving the safety factor.
CAHU four models mentioned above will add to the capacity of each fan plus capacity of 83.2 kW and a cooling water pump 11.2 kW again as above mentioned for the 750 kW cooling load technology information and download lighting. This scenario brings the total cooling load is 888 kW at the rate of heat are aware 0.95.
Conclusion
Annual electricity costs of three cooling architecture is IRAH, CRAH, & CAHU turn is estimated 139,572 USD, 201,878 USD and 197,211 USD (the price 0.10USD/kWh). Of course, electric power save will vary depending on the performance of cooling devices, the price of accessories, download the information technology and lighting equipment. Cooling works sequentially as compared to the above two options for reducing to two thirds of electricity to the fan by the cooling equipment consumption, along with increased savings through infrastructure cooling unified comprehensive.
Despite the cooling in a fairly large advantage in cost of operation, it is still not perfect architecture for all applications. Obviously, the number of data centers is much larger number of data centers built a new and very capable of cooling the structure, including all the structures mentioned above, will be confused with together and will be deployed in the same data center. When TTDL development and increased density, a hybrid approach to cooling the concentrated heat density can be the result obvious. However, the space center new data (whether to expand or build entirely new) should also always appreciate the cooling in order to achieve energy efficiency and capabilities can best estimate whenever can.
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John Bean Jr. Is director of Innovation for the solution to cool in APC Rack.
** Kevin Dunlap is director of The Center's product solution cooling modules / high density in APC