Data centers are mission critical facilities that typically contain thousands of data processing equipment, such as servers, switches, and routers. In recent years, there has been a boom in data center usage, leading their energy consumption to grow by about 10% a year continuously. The heat generated in these data centers must be removed so as to prevent high temperatures from degrading their reliability, which would cost additional energy. Therefore, precise and reliable thermal management of the data center environment is critical. This paper focuses on recent advancements in data center modeling and energy optimization. A number of currently available and developmental thermal management technology in data centers are broadly reviewed. Computational fluid dynamics (CFD) for raised-floor data centers, experimental measurements, containment systems, economizer cooling, hybrid cooling, and device level cooling are all thoroughly reviewed. The paper concludes with a summary and presents areas of potential future research, which are based on the holistic integration of workload prediction and allocation, and thermal management using smart control systems.

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An information technology (IT) container needs to be supplied with cold air to cool IT equipment housed in it. The type of cooling system to be used depends on many factors including geographical location of the modular data center. Data centers located in regions where the climate is cold benefit from use of air-side economization (ASE) and those located in hot and dry climate benefit from use of direct and/or indirect evaporative cooling (DIEC) systems. In terms of energy saving, ASE, direct evaporative cooling (DEC) system, and indirect evaporative (IEC) systems are better than compressor based cooling systems such as computer room air conditioning (CRAC) units and air handling units (AHU). In this study, an existing DIEC unit which can also be operated in ASE mode is modeled in a computational fluid dynamics (CFD) tool. The cooling unit is intended to be used for supplying cold air to a containerized data center with specified volume flow rate, dry-bulb temperature and relative humidity. The CFD model is compared with published data of the cooling unit to see how well the CFD model represents the actual system and few design improvement ideas are tested by modifying the CFD model and running simulations. Results show that supplying air horizontally or as a downdraft to an IT container has negligible effect on the overall system. Results also show that orientation of dampers and placement of blanking panels inside the mixing chamber could affect the lifespan of air filters.

Deployment of airside economizers (ASEs) in data centers is rapidly gaining acceptance to reduce cost of cooling energy by reducing hours of operation of computer room air conditioning (CRAC) units. Airside economization has associated risk of introducing gaseous and particulate contamination into data centers, thus degrading the reliability of information technology (IT) equipment. The challenge is to determine reliability degradation of IT equipment if operated in environmental conditions outside American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) recommended envelope with contamination severity levels higher than G1. This paper is a first attempt at addressing this challenge by studying the cumulative corrosion damage to IT equipment operated in an experimental modular data center (MDC) located in an industrial area with measured level of air contaminants in ISA severity level G2. This study serves several purposes including: correlating IT equipment reliability to levels of airborne corrosive contaminants and studying degree of reliability degradation when IT equipment is operated outside ASHRAE recommended envelope at a location with high levels of contaminants. Reliability degradation of servers exposed to outside air via an airside economizer was determined qualitatively by examining corrosion of components in these servers and comparing the results to corrosion of components in other similar servers that were stored in a space where airside economization was not used. In the 4 years of the modular data center's servers' operation, none of the servers failed. This observation highlights an opportunity to significantly save data center cooling energy by allowing IT equipment to operate outside the currently recommended and allowable ASHRAE envelopes and outside the ISA severity level G1.

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