Experimental and Computational Studies on the Role of Confinement Systems in Data Center Thermal Managemen

Data centers are centralized facilities housing information technology (IT) equipment that provide compute, storage, telecommunication or a combination of these functions. Based on data center standards, the reliability of IT equipment can only be guaranteed if they operate in the correct environment (temperature, humidity, etc). A large number of factors determine whether sufficient cooling is provided under a wide range of operating conditions. Typical data centers utilize central site chilled water and different types of forced air convective cooling. The design of cooling systems for data centers significantly impacts the overall energy efficiency. Because of the rapid growth in the number of data centers combined with the high density heat dissipation of IT and telecommunications equipment, energy efficient thermal management of data centers has become a key research focus in the electronics packaging community.;In this dissertation, data center thermal management is addressed at three levels: 1) For individual IT equipment, the air flow and thermal characteristics were analyzed experimentally and the data utilized to develop compact models for larger-scale computational simulations. A semi-empirical methodology was employed to quantify the thermal mass of the internal components, which is necessary to capture the transient thermal behavior.;2) At the cabinet level, a detailed experimental/computational study of a hybrid, fully-enclosed server cabinet was performed. A comprehensive validation procedure for the Computational Fluid Dynamics (CFD) model of the hybrid cooled enclosed cabinet is presented. Experimentally obtained data are used to validate the results from computational modeling. Two cases with different air flow rates are compared. Due to relatively high pressure inside the cabinet, it is possible that air leakage from the cabinet may be responsible for the discrepancy between the model and experimental results. A sensitivity study was applied to the validated model to investigate the effect leakage had on the cabinet's performance. Also, the thermal performance of a hybrid, rear door heat exchanger is investigated experimentally. Localized hybrid air-water cooling is one approach to more effectively control the cooling when there is wide variation in the amount of dissipation in neighboring racks. The cooling performance of the rear door heat exchanger in three failure scenarios was investigated: water chiller failure, water pump failure, and air blower failure. Each scenario was designed to diminish one part of the overall system. The impact on the IT equipment and the cabinet outlet temperatures were assessed. For the air blower failure study, there was a significant reduction in the air flow to the IT equipment. The impact of reduced air flow on different parts of the cabinet, as well as the cooling performance of the heat exchanger, was characterized during both failure and recovery.;3) Finally, room level studies were conducted on a unique research data center facility. The room level study elucidated the particular behavior of airflow in the cold aisle when row-based cooling is utilized; specifically, the change in the location of the airflow source. Correlations are derived to predict the ability of air conditioning units to maintain set points at different air flows. In addition, comparisons between Cold Aisle Containment (CAC) and Hot Aisle Containment (HAC) indicate that there is a slight advantage of the latter in terms of ambient room temperature, failure scenarios and heat exchanger efficiency, although CAC systems can be easier to install. The impact of air flow leakage was also addressed. Leakage can introduce different flow and temperature conditions at server inlets depending on whether CAC or HAC is being used.