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  1. Free, publicly-accessible full text available March 1, 2023
  2. Most of the thermal management technologies concentrate on managing airflow to achieve the desired server inlet temperature (supply air operating set point) and not to manage/improve the amount of cool air (CFM) that each computer rack (i.e. IT servers) should receive in order to remove the produced heat. However, airflow is equally important for quantifying adequate cooling to IT equipment, but it is more challenging to obtain a uniform airflow distribution at the inlet of computer racks. Therefore, as a potential option for improving airflow distribution is to eliminate the sources of non-uniformities such as maldistribution of under-floor plenum pressuremore »field caused by vortices. Numerous researchers focus on the adverse effects of under-floor blockages. This study focused to numerically investigate the positive impact of selectively placed obstructions (on-purpose air-directors); referred as partitions; Quantitative and qualitative analysis of underfloor plenum pressure field, perforated tiles airflow rate and racks inlet temperature with and without partitions using two Computational Fluid Dynamics (CFD) models, which were built using Future Facilities 6SigmaRoom CFD tool. First, a simple data center model was used to quantify the partitions benefits for two different systems; Hot Aisle Containment (HAC) compared to an open configuration. Second, the investigation was expanded using a physics-based experimentally validated CFD model of medium size data center (more complicated data center geometry) to compare different types of proposed partitions. Both models results showed that partition type I (partitions height of $\frac{2}{3}$ of plenum depth measured from the subfloor) eliminates the presence of vortices in the under-floor plenum and hence, more uniform pressure differential across the perforated tiles that drives more uniform airflow rates. In addition, the influence of proposed partitions on the rack inlet temperature was reported through a comparison between open versus hot aisle containment. The results showed that the partitions have a minor effect on the rack inlet temperature for the hot aisle containment system. However, the partitions significantly improve the tiles flowrate. On the other hand, for the open system, the presence of partitions has improved the tiles airflow rate, rack inlet temperature and hence eliminate the hot spots formation at computer rack inlet« less
  3. The constant increase in data center computational and processing requirements has led to increases in the IT equipment power demand and cooling challenges of highdensity (HD) data centers. As a solution to this, the hybrid and liquid systems are widely used as part of HD data centers thermal management solutions. This study presents an experimental based investigation and analysis of the transient thermal performance of a stand-alone server cabinet. The total heat load of the cabinet is controllable remotely and a rear door heat exchanger is attached with controllable water flow rate. The cooling performances of two different failure scenariosmore »are investigated. One is in the water chiller and another is in the water pump for the Rear Door Heat eXchanger (RDHX). In addition, the study reports the impact of each scenario on the IT equipment thermal response and on the cabinet outlet temperature using a mobile temperature and velocity mesh (MTVM) experimental tool. Furthermore, this study also addresses and characterizes the heat exchanger cooling performance during both scenarios.« less
  4. During the lifespan of a data center, power outages and blower cooling failures are common occurrences. Given that data centers have a vital role in modern life, it is especially important to understand these failures and their effects. A previous study [16] showed that cold aisle containment might have a negative impact on IT equipment uptime during a blower failure. This new study further analyzed the impact of containment on IT equipment uptime during a CRAH blower failure. It also compared the IT equipment performance both with and without a pressure relief mechanism implemented in the containment system. The resultsmore »show that the effect of implementing pressure relief in containment solution on the IT equipment performance and response could vary and depend on the server's airflow, generation and hence types of servers deployed in cold aisle enclosure. The results also showed that when compared to the discrete sensors, the IPMI inlet temperature sensors underestimate the Ride Through Time (RTT) by 32%. This means that the RTT calculations based on the IPMI inlet sensors may be inaccurate due to variations in the sensor readings; as they exist today; in these servers. as discussed in a previous study [26]. Additionally, it was shown that all Dell PowerEdge 2950 servers have a similar IPMI inlet temperature reading, regardless of mounting location. As external system resistance increases during cooling failure, the servers exhibit internal recirculation through their weaker power supply fans, which is reflected in the high IPMI inlet temperature readings. For this server specifically, a pressure relief mechanism reduces the external resistance, thereby eliminating internal recirculation and resulting in lower IPMI inlet temperature readings. This in turn translates to a lower RTT. However, pressure relief showed conflicting results where the discrete sensors showed an increase in inlet temperature when pressure relief was introduced, thereby reducing the RTT. The CPU temperatures conformed with the discrete sensor data, indicating that containment helped increase the RTT of the servers during failure.« less