Evaporative Cooling in Data Centers

The concept of evaporative cooling is a very primitive technique which has been passed on ancestrally. The principle of this technique is very simple; it uses water to cool the inflowing air. Generally in a refrigeration cycle, the exchange of heat occurs at the evaporator. The working fluid absorbs heat at the evaporator and changes its state from liquid to vapor and then releases the heat absorbed when it comes in contact with refrigerant like ammonia to change its state from vapor to liquid in the condenser. Here generally the working fluid comes in contact with refrigerant which has a very low melting point.

To decipher this thermodynamic cycle in a more simplistic sense, evaporative cooling is very much similar to the air coolers used in modern days where a fan blows air through layers of wet sheets and the air temperature is reduced due to the heat transfer between water and air. Water absorbs the heat in the air and vaporizes and cooled air is the end product.

Data centers generate a large amount of heat, since they work round the clock. Since conventional air conditioning systems increase the power consumed by data centers on a whole. To cut down costs companies look at alternative cooling systems which reduce the overall expenses incurred in maintaining an efficient cooling system.

Evaporative cooling is a widely employed cost reduction cooling system across data centers that provide an economical as well as thermally stable temperature control system.

Though evaporative cooling has been commercially used in homes and offices for sometime now, their implementation across data centers was very recent. Considering the large amount of heat generated evaporative coolers provide a reliable and economical alternative source of supplementary cooling systems to the pre-installed air conditioning systems.

The thermal analysis of evaporative coolers reveals that they have a higher efficiency in pure engineering terms, but the major drawback of the system is the effect of cooling cannot be up scaled that easily. For providing an efficient cooling system it is necessary for a plant engineer to decide the tonnage of air conditioning required. But in case of evaporative coolers the tonnage of cooling cannot be accurately predicted as it involves a number of variables. In case of evaporative coolers the temperature of the ambient air at inlet plays a major role in deciding the overall cooling effect. Incase the ambient air is at a high temperature, the overall cooling is significantly low.

This unpredictable factor in the system, where it cannot provide a continuous pre-calculated cooling effect has confined evaporative coolers to just being subsidiary cooling systems. Besides this the system also extensively depends on water. The water used in these systems must be at the freezing point or well below the ambient temperature to achieve efficient cooling. This raises the need for a cooling system to maintain the water for the evaporative coolers below the ambient temperature which significantly increases the cost in maintaining the data centers in all.

With data centers eating into the majority of IT expenses, it has forced them to abandon evaporative cooling systems as a prospective solution and concentrate on greener and efficient systems.

Threshold environment conditions in a data center

Environmental factors influence the operation of data centers to great extent. Industrial design primarily concentrates on human safety and equipment ergonomics. Ergonomics is a science in itself which defines the structured guidelines for setting up safe operating layout for the human machine interface. The color codes for instance followed in factories and industries are self explanatory of the precautions that the employees must take while operating them.

Since it’s not possible to describe the hazards of operating certain machine equipments, this necessitates the need for developing a safe and systematic approach to provide safe working atmosphere.

Providing a sustainable environment to operate not only increases the efficiency of hardware components but also gives the employees a self satisfaction, since safety is their primary goal at work.

Thermal factors such as temperature, humidity, pressure play a significant role in the design of data centers. Though their optimal conditions vary depending on the size of the plants and equipments, their influence on environment factors describe the very essentials of the threshold limits for environmental standards. Monitoring them plays a critical role in maintaining a unified safe operating environment. There are software’s that constantly monitor the threshold limits and by installing electronic sensors factors like temperature and humidity can be easily controlled.

Recommended Computer Room Humidity

Relative humidity (RH) is defined as the amount of moisture in the air at a given temperature in relation to the maximum amount of moisture the air can hold at the same temperature. In a data center, maintaining ambient relative humidity levels between 45% and 55% is recommended for optimal performance and reliability.

When relative humidity levels are too high, water condensation can occur which results in hardware corrosion and early system and component failure. If the relative humidity is too low, computer equipment becomes susceptible to electrostatic discharge (ESD) which can cause damage to sensitive components. When monitoring the relative humidity in the data center, it is recommended early warning alerts at 40% and 60% relative humidity, with critical alerts at 30% and 70% relative humidity. It is important to remember that the relative humidity is directly related to the current temperature, so monitoring temperature and humidity together is critical. As the value of IT equipment increases, the risk and associated costs can increase exponentially.

Environmental and Energy thresholds are both incredibly important factors in the smooth operation of any data center. Operating data centers above the set threshold limits can not only damage the hardware but increase the maintenance costs and overall expenses incurred.

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