Jimil M. Shah 1 Mechanical and Aerospace Engineering Department, University of Texas at Arlington, Arlington, TX 76019 e-mail: jimil.shah@mavs.uta.edu Roshan Anand Mechanical and Aerospace Engineering Department, University of Texas at Arlington, Arlington, TX 76019 Prabjit Singh IBM Corporation, 2455 South Road, Poughkeepsie, NY 12601 Satyam Saini Mechanical and Aerospace Engineering Department, University of Texas at Arlington, Arlington, TX 76019 Rawhan Cyriac Mechanical and Aerospace Engineering Department, University of Texas at Arlington, Arlington, TX 76019 Dereje Agonafer Mechanical and Aerospace Engineering Department, University of Texas at Arlington, Arlington, TX 76019 Mike Kaler Mestex, a Division of Mestek, Inc., 4830 Transport Drive, Dallas, TX 75247 Development of a Precise and Cost-Effective Technique to Measure Deliquescent Relative Humidity of Particulate Contaminants and Determination of the Operating Relative Humidity of a Data Center Utilizing Airside Economization A remarkable amount of energy in data centers is consumed in eliminating the heat gen- erated by the information technology (IT) equipment to maintain and ensure safe operat- ing conditions and optimum performance. The installation of airside economizers (ASEs), while very energy efficient, bears the risk of particulate contamination in data centers, hence, deteriorating the reliability of IT equipment. When relative humidity (RH) in data centers exceeds the deliquescent relative humidity (DRH) of salts or accumulated partic- ulate matter, it absorbs moisture, becomes wet, and subsequently leads to electrical short-circuiting because of degraded surface insulation resistance (SIR) between the closely spaced features on printed circuit boards (PCBs). Another concern with this type of failure is the absence of evidence that hinders the process of evaluation and rectifica- tion. Therefore, it is imperative to develop a practical test method to determine the DRH value of the accumulated particulate matter found on PCBs. This research is a first attempt 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 inter- digitated comb coupon. To validate this methodology, the DRH of pure salts like MgCl 2 , NH 4 NO 3 , and NaCl is determined, and their results are then compared with their pub- lished values. This methodology was therefore implemented to help lay a modus operandi of establishing the limiting value or an effective relative humidity envelope to be main- tained at a real-world data center facility situated in Dallas industrial area for its contin- uous and reliable operation. [DOI: 10.1115/1.4047469] 1 Introduction An airside economizer (ASE) is defined by ASHRAE (Ameri- can Society of Heating, Refrigeration and Air-Conditioning Engi- neers) as an arrangement of a duct, a damper, and an automatic control system that works in conjunction with the cooling sys- tems, under favorable climatic conditions, to supply outside free cold air, thus, eliminating or reducing the requirement for mechanical cooling [1]. In particular, ASHRAE guidelines have an expanded “recommended” and “allowable” temperature and humidity zones allowing up to 35–45  C inlet temperature for short periods of time thus making airside economization extremely useful. This efficient cooling method draws in outside air from the ambient and is then filtered using MERV (minimum efficiency rating value) 11 or MERV 13 filters to eliminate partic- ulate contaminants before being introduced into the cold aisle of a data center. The amount of enthalpy in the air is acceptable and no auxiliary conditioning is required if the outside air is both suffi- ciently cool and dry. This mode of cooling operation is generally termed as free cooling [2]. The utilization of ASEs results in a sig- nificant reduction in energy consumption of a data center in asso- ciation with the cooling infrastructure. The risk that comes with the use of ASEs is that the temperature and humidity levels must be within specified ranges and more importantly is the entry of particulate and gaseous contaminants that should be within the allowable cleanliness standards. The physical environment surrounding the information technol- ogy (IT) equipment is mainly defined by temperature, relative humidity, and gaseous and particulate contaminants [3–8]. These factors can have adverse effects on IT equipment and can cause its failure in two ways: first type of failure is caused by corrosion of silver termination in surface mount components leading to elec- trical open circuits. This type of failure mode occurs mainly in geographical areas with high levels of sulfur bearing gaseous con- taminants [9]. Manufacturers have improved their hardware to tackle this failure mode. The second type of failure is caused by a few mechanisms that result in electrical short circuits: (i) in 2006, the European Union’s restriction on hazardous substances (RoHS) 1 Corresponding author. Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received October 16, 2019; final manuscript received May 31, 2020; published online June 23, 2020. Assoc. Editor: Saket Karajgikar. 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