2013-02-07 15:24:19 - Data Centre environments have come a long way over the years, as technology has moved on so has the need for data centre cooling, whilst at the same time reducing energy consumption to minimise environmental impact.

With millions of pounds worth of sophisticated IT equipment at stake and a risk way beyond financial calculation in terms of business continuity, data centres are probably the most critical air cooled environments in the commercial world. Indeed the air cooling systems specified for such applications are often extremely sensitive and advanced, with additional cooling capacity built into the system to minimise the risk of equipment overheating.

Adding to the challenges of meeting such a prescriptive criteria of temperature and atmospheric conditions is the fact that data centres are a notoriously difficult environment to control. There is no question of opening a window or leaving the door ajar to let cool air circulate as one might expect to do in an

office. What’s more, the equipment itself generates heat and, as hardware becomes more advanced, the level of power that it consumes – and, therefore, the level of heat it generates – is increasing. For example, traditional servers consume approximately 1 - 2 kW of power per rack whilst contemporary Blade servers can have a cooling demand of up to 40kW per rack. As a result, the level of heat being produced by the facility itself can fluctuate significantly and like-for-like replacement of old servers with newer equipment may result in a disproportionate increase in temperature. Given that the temperature in an average data centre can rise from 15°C to 30°C within just twenty minutes when the air conditioning system fails’.

It’s worth noting too that it’s not just the cost of replacing expensive IT hardware that’s at stake here: the risk of data loss also makes it imperative that the hardware infrastructure is never allowed to overheat. With risks that can amount to millions of pounds within hours of a small rise in temperature.

No data centre would be built without proper attention being paid to the cooling system and the systems in these environments are often state-of-the-art, extremely efficient and specified with extra capacity built in. This means that they are not only able to cope well with sudden rises in temperature but also that they are able to adjust to the addition of new equipment to the data centre which will, inevitably, impact on the level of heat produced.

Thanks to its constant and relevant research in technology for this application, CAREL offers high efficiency solutions through optimised and integrated control systems, capable of bringing significant energy savings and consequently reducing environmental impact to data centres.

One of the solutions is the new evaporative cooling system called optiMist. The new optiMist works both as an evaporative cooler and a humidifier, as a single solution inside the AHU you have two functions. In particular, the evaporative cooling reduces the air-conditioning system load guaranteeing an effective energy saving and consequently the reduction of carbon dioxide emissions.

The optiMist is installed in the humidification compartment and in the exhaust air flow (upstream of the heat exchanger) on air handling units. It receives two separate signals, one relating to humidification (winter) and one to evaporative cooling (summer), producing a flow of atomised water inside the AHU.

The optiMist (summer/winter) features a water inlet circuit, a volumetric pump and two solenoid valves to distribute pressurised water at 16 bars. The electrical panel includes the power circuit, a programmable electronic controller and an inverter.

It receives the control signal from a remote control unit or directly from the temperature or humidity probes. The electronic controller calculates the flow-rate of atomised water required to meet the evaporative cooling or humidity demand, and signals the required pump speed to the inverter. This ensures linear modulation of water atomisation, avoiding waste.

Specifically, evaporative cooling occurs due to the spontaneous evaporation of the water droplets produced: the change in phase from liquid to vapour subtracts energy from the air, which is consequently cooled. Evaporation of 100 kg/h of water absorbs 69 kW of heat from the air. The exhaust air can be substantially cooled without restrictions in terms of humidity level, as it is discharged by the AHU. This cooling capacity can be exploited to cool the fresh inlet air, via a heat exchanger, with efficiency - depending on the heat recovery unit - that easily exceeds 50%. This means the size, capacity and power consumption of the cooling coil and chiller can be reduced.

Special care has been paid to hygiene when designing the optiMist, to ensure effective Legionella prevention.

For further information contact CAREL on 0208 391 3540 or visit their website www.careluk.co.uk