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1. COLD-AISLE CONTAINMENT IN DATA CENTRES
the smart concept for optimal energy use
www.knuerr.com
Application Report
Cold-Aisle Containment in Data Centres
The smart concept for optimal energy use
Cooling requirements in data centres are continually rising, causing conventional climate control systems to be
overloaded.
Switching to a water cooled systems is an option, but structurally and financially this is not always possible.
Cold-Aisle Containment (CoolFlex) is another option. This option consistently separates cold and warm areas
without requiring structurally changes to the data centre.
Over several weeks the efficiency of CoolFlex was tested and proved. The test was conducted using fan heaters to
simulate the heat load generated by servers.
The result: At a thermal load of ca. 14kW per rack, the required temperature of 23°C in the cold aisle was
reached. During further tests, several computer room air conditioning units (CRAC) were switched off to
simulate an emergency. During these tests the cold aisle temperature of 23°C was only marginally
exceeded.
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2. COLD-AISLE CONTAINMENT IN DATA CENTRES
the smart concept for optimal energy use
www.knuerr.com
Description of application:
Test conditions
The raised floor provided greater energy efficiency by directing cool air through perforated plates in the cold aisle
and by sealing the cable entry in to the racks. Knürr isolated the cold and hot zones within the server racks using
infill panels. All 4 cold aisles were then enclosed using cold aisle containment.
The 342 KW heat capacity was simulated via fan heaters (38 x 9kW = 342 kW). 288 kW heat capacity was
simulated within aisle 2. Aisle 1, 3 and 4 were not in use and therefore produced no heat. The remaining 54 kW
were distributed throughout the room, simulating the heat capacity in the network and free standing racks.
To minimise the loss of circulation and pressure caused by the raised floor, Knürr used special “grate catch”
instead of perforated raised floor plates. All holes for cables through the floor were sealed to prevent hot air
shortcuts.
The CRAC units used were designed to use 250 kW in their energy-efficient, normal mode and 500 kW at high
power mode. The capacity of the fans is proportional to the third power of the circulatory. Therefore it is more
energy-efficient to run all CRAC units at lower speed, instead of using less CRAC units at their maximal speed. By
consistently isolating cold and warm air, the nominal capacity of the CRAC units is increased, therefore the same
number of CRAC units can run at a high power mode, without reducing redundancy.
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3. COLD-AISLE CONTAINMENT IN DATA CENTRES
the smart concept for optimal energy use
www.knuerr.com
Test areas
Test 1: Energy-efficiency in normal mode
6 CRAC units in normal mode (speed ca. 30%)
Pressure test with a rising thermal load
Results during full load(ca. 288 kW in aisle + 54 kW)
Temperature of cold aisle: 23,0 °C
Temperature of warm aisle: 37,0 °C
Test 2: Emergency (Breakdown of 2 CACUs)
3 CRAC units in emergency mode (speed ca. 80%)
Results during full load(ca. 288 kW in aisle + 54 kW
Temperature of cold aisle: 23,1 °C
Temperature of warm aisle: 42,9 °C
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4. COLD-AISLE CONTAINMENT IN DATA CENTRES
the smart concept for optimal energy use
www.knuerr.com
Test 3: Extreme emergency (Breakdown of 4 CACUs)
2 CRAC units in emergency mode (speed 100%)
Results during full load(ca. 288 kW in aisle + 54 kW)
Temperature of cold aisle: 23,5 °C
Temperature of warm aisle: 47,0 °C
With only 2 CRAC units the temperature in the cold aisle did not exceed the required 24°C.
After a time the fan heaters simulating server heat load failed due to a fail safe switch.
Results and Conclusions
To discover the maximum capacity of cold aisle containment by increasing the heat capacity in the data centre.
- Load per Rack 3.6kW (Face: 3.5 m² = ca. 1‘000 W/m²) = possible!
- Load per Rack 7.6kW (Face: 3.5 m² = ca. 2‘000 W/m²) = possible!
- Load per Rack 10.8kW (Face: 3.5 m² = ca. 3‘000 W/m²) = possible!
- Load per Rack 14.4kW (Face: 3.5 m² = ca. 4‘000 W/m²) = possible!
The cold aisle containment could possibly discharge a higher heat load however the fan heater fail safe thermostat
caused at collapsed after 4'000W/m². Also the test equipment was not calibrated for higher heat load. Therefore
we could not demonstrate the limits of the cold aisle containment.
Note: It is important to note that during this pilot project, fan heaters were used to demonstrate the cooling
capacity. Fan heaters can only simulate the heat generated by servers, as they have a lower flow volume across
the server. We are positive, that in a real situation, 10 to 12 KW per rack should be possible (various other experts
do not differentiate between the use of fan heater and real servers)
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5. COLD-AISLE CONTAINMENT IN DATA CENTRES
the smart concept for optimal energy use
www.knuerr.com
Pictures of test site
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6. COLD-AISLE CONTAINMENT IN DATA CENTRES
the smart concept for optimal energy use
www.knuerr.com
Services provided
Using trained personnel, Knürr is able to provide the following services:
Consulting, calculation, and simulation of a solution.
Simple installation into existing racks (dependent of make of rack).
Integration and installation without the need for down time.
• Data Centres Thermal Assessment
- Review of thermal demands and air flow within the data centre
- Thermal imaging of the computer centre, several aisles and/or racks
- Proposal of cost effective measures
- Complete report, with achievable improvements
• “Cold Aisle Containment” implementation of the solution
- Site visit (inclusive demarcation of project specific items, especially competitor racks)
- Creation of project plan
- Detailed pricing offer
Knürr AG
Mariakirchener Straße 38
94424 Arnstorf
Telefon +49 (0) 87 23-27-0
Telefax +49 (0) 87 23-27-154
E-Mail: info@knuerr.com
www.knuerr.com
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