ORCID Identifier(s)

0000-0003-2297-7413

Graduation Semester and Year

2018

Language

English

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering

Department

Mechanical and Aerospace Engineering

First Advisor

Dereje Agonafer

Abstract

The Datacom facility which comprises rooms or closets used for communication, computers/servers or electronic equipment requires cooling unit which consumes 31% (23% HVAC cooling + 8% HVAC fans) of overall energy. The ASHRAE TC9.9 subcommittee, on Mission Critical Facilities, Data Centers, Technology Spaces, and Electronic Equipment, has suited the data center’s executives by permitting brief period outings of the environmental conditions outside the prescribed temperature-humidity range, into passable extents A1-A3. To comprehend the expanding server densities and the required cooling vitality costs, data center operators are falling back on cost cutting measures. For instance, they are not firmly controlling the temperature and humidity levels as per ASHRAE recommended envelope and as a rule turning to airside economizers with the related danger of bringing particulate and gaseous contaminants into their data centers. This dissertation is a first attempt at addressing this challenge by characterizing contamination found in a real-world data center to expand ASHRAE envelope. In situ studies of contaminants found in data centers using air-side economization and corresponding ASHRAE Envelope Expansion in Airside Economization is the main objective of this PhD Dissertation. This study serves several purposes: 1.) Cumulative corrosion damage study for the correlation of equipment reliability to levels of airborne corrosive contaminants and the study of the degree of reliability degradation, when the equipment is operated, outside the recommended range, in the allowable temperature-humidity range in geographies with high levels of gaseous and particulate contamination. 2.) Experimental description of information technology equipment reliability exposed to a data center using airside economizer operating in recommended and allowable ASHRAE envelopes in an ANSI/ISA classified G2 environment to estimate the end of the life of the components and to determine the free air cooling hours for the site. The study took place at the modular data center which uses air-side economizer located at Dallas Industrial area which falls under ISA 71.04-2013 severity level G2. 3.) The servers were removed, and qualitative study of cumulative corrosion damage was carried out. The particulate contaminants were collected from different locations of a server and material characterization was performed using Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometer (EDS) and Fourier Transform Infrared Spectroscopy (FTIR). The analysis from these results helps to explain the impact of the contaminants on IT equipment reliability. 4.) To develop a precise and cost-effective technique to measure deliquescent relative humidity of particulate contaminants found in a data center utilizing airside economization. To develop an experimental technique to measure the DRH of dust particles by logging the leakage current versus %RH for the particulate matter dispensed on an interdigitated comb coupon. To validate this methodology, the DRH of pure salts like MgCl2, NH4NO3 and NaCl is determined and their results are then compared with their published values. This methodology can therefore be implemented to help lay a modus operandi of establishing the limiting value or an effective relative humidity envelope to be maintained at a real-world data center facility for its continuous and reliable operation at its respective location. 5.) The interdigitated comb coupon is lodged with a dust solution in the form of slurry taken from various servers in an actual modular Data Center. The results obtained, and the methodology used in this study can pioneer in standardizing the limiting %RH values for various operating conditions in real world Data Centers, and 6.) This dissertation also examines the flow path of contaminants in high density data centers to determine the most vulnerable location using the computational techniques. Full submersion of servers in dielectric oils offers an opportunity for significant cooling energy savings and increased power densities for data centers. The enhanced thermal properties of oil can lead to considerable savings in both the upfront and operating costs over traditional air cooling methods. Despite recent findings showing the improved cooling efficiency and cost savings of cooling fluids, this technique is still not widely adopted. Many uncertainties and concerns persist regarding the non-thermal aspects of a single-phase immersion cooled data center. This study serves multiple purposes: 1.) To measure the thermal performance of a single-phase immersion cooled server at extreme temperatures for prolonged time. Thermal overstress experiment was performed on a fully immersed server and its cooling system components. This work explores the performance of a server and other components like pump including flow rate drop, starting trouble and other potential issues under extreme climatic conditions. 2.) The dissertation presents impact of form factor on a maximum junction temperature and thermal resistance at the server level. This work is to provide an insight to increase the rack density by reducing form factor of an existing server. The heat sink is a critical part for cooling effectiveness at server level. This work is to provide an efficient range of operation for heat sink with numerical and computational modelling of a third-generation open compute server for immersion cooling application. A parametric study is conducted, and the thermal efficiency has been optimized for mineral oil and EC 100. 3.) This research reviews the changes in physical and chemical properties of information technology (IT) equipment and compatibility of materials like polyvinyl chloride (PVC), printed circuit board (PCB) and switching devices with mineral oil and EC 100 to characterize the interconnect reliability of materials. For the first time, material compatibility is being tested. Accelerated thermal degradation testing of printed circuit board, passive components and optical fibers for single phase immersion cooling systems is a significant part of this study. The study proposes a testing methodology which can be adopted by all for evaluating the reliability of electronic packages and components when immersed in a dielectric fluid. The study indicates the effect of mineral oil and EC 100 on IT equipment reliability and reliability enhancements for immersion cooled data centers and, 4.) This dissertation also includes Cup Burner Experiment as per ISO 14520/NFPA 2001 standard to determine the minimum design concentration of fire extinguishing agent for the class B hazard of heavy mineral oil and the class C hazard of electronic equipment as a part of the safety concerns for oil cooled data centers.

Keywords

Gaseous contaminants, Harsh environment, Immersion cooling, Reliability, Electronic packaging, Synthetic fluids, Particulate contaminants

Disciplines

Aerospace Engineering | Engineering | Mechanical Engineering

Comments

Degree granted by The University of Texas at Arlington

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