American Society Of Heating , Refrigerating And Air-Conditioning Engineers Research Articles

Operational Performance Characterization of a Heat Pump System Utilizing Recycled Water as Heat Sink and Heat Source in a Cool and Dry Climate

The wastewater leaving from homes and businesses contains abundant low-grade energy, which can be utilized through heat pump technology to heat and cool buildings. Although the energy in the wastewater has been successfully utilized to condition buildings in other countries, it is barely utilized in the United States, until recently. In 2013, the Denver Museum of Nature & Science at Denver, the United States implemented a unique heat pump system that utilizes recycled wastewater from a municipal water system to cool and heat its 13,000 m2 new addition. This recycled water heat pump (RWHP) system uses seven 105 kW (cooling capacity) modular water-to-water heat pumps (WWHPs). Each WWHP uses R-410A refrigerant, has two compressors, and can independently provide either 52 °C hot water (HW) or 7 °C chilled water (CHW) to the building. This paper presents performance characterization results of this RWHP system based on the measured data from December 2014 through August 2015. The annual energy consumption of the RWHP system was also calculated and compared with that of a baseline Heating, Ventilation, and Air Conditioning (HVAC) system which meets the minimum energy efficiencies that are allowed by American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 90.1-2013. The performance analysis results indicate that recycled water temperatures were favorable for effective operation of heat pumps. As a result, on an annual basis, the RWHP system avoided 50% of source energy consumption (resulting from reduction in natural gas consumption although electricity consumption was increased slightly), reduced CO2 emissions by 41%, and saved 34% in energy costs as compared with the baseline system.

An Investigation of Thermal Comfort and Adaptive Behaviors in Naturally Ventilated Residential Buildings in Tropical Climates: A Pilot Study

This article presents a pilot study of thermal comfort and adaptive behaviors of occupants who live in naturally ventilated dormitories at the campus of the National University of Singapore. A longitudinal survey and field measurement were conducted to measure thermal comfort, adaptive behaviors and indoor environment qualities. This study revealed that occupants living in naturally ventilated buildings in tropics were exposed to higher operative temperatures than what American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) comfort standards recommend for naturally conditioned spaces. However, they still felt that such conditions were acceptable. Two behavioral adjustments were found to have profound impacts on occupants’ acceptance of the imposed heat stresses: (1) increasing the indoor air velocity by turning on mechanical fans and opening the door/windows for cross ventilation, and (2) reducing clothing insulation by changing clothes and dressing in fewer clothes. Higher indoor air velocities were also associated with greater satisfaction with indoor air quality. The future study should develop a statistical model to correlate adaptive behaviors with temperature variations for tropical climates.

Visual Interactive Computer Package for Air Conditioning System Design: Case of the International Conference Centre, University of Ibadan, Nigeria

Air conditioning design has become an interesting aspect of human life with the aim of seeking environmental comfort for indoor spaces. Analytical work involves in the design of air-conditioning system is often time consuming and laborious. This work therefore aims at developing a visual interactive computer package for the design of air conditioning system using the international conference centre, University of Ibadan, Nigeria as a case study. Procedures for calculating heat gain through various building components were discussed in detail. Cooling load analysis was carried out using standard cooling load equations obtained from the American Society of Heating, Refrigeration and Air conditioning Engineers (ASHRAE) handbook. A computer program was developed using java programming language to compute the total cooling load in the building. The result from the computer program was obtained within a very short period of time when compared with that of the manual one. The cooling load of the building obtained was 3,194,414 btu/hr; a visual interactive computer package for the design of air conditioning system has been developed and tested positively; hence can be used to design air conditioning system for any building.

Environmental Approach for Energy Audits on Government Buildings: A Mexican Case for the Air Conditioning System

In the face of the climate change, energy consumption is one of the main issues to be solved. Energy audits are useful tools that may contribute to develop energy efficiency initiatives. The purpose of this paper is to provide insights into how energy audits, with a scope on air conditioning (AC) systems, contribute to develop energy efficiency options for a government building in the city of Hermosillo, Mexico. The methodology is based in the energy audit framework proposed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). Results show that, in a typical day of maximum consumption, AC represents 64% of the total electrical consumption, while office equipment accounted for 22%, and lighting 14%. Additionally, AC system has a yearly consumption of 54,419.40 kWh with an emission estimate of 24.92 tons of CO2-eq/year. Three approaches for energy efficiency proposals were addressed through AC systems: Improvement of the operation and consumption habits, maintenance and reconditioning of facilities, and replacement of AC units. While Mexico has international commitments through environmental treaties related to contribute to climate change mitigation, this study shows that, at least one government building still produces potential impacts that can be deterred by addressing structural and behavioral changes related to AC operation. Finally, this study may be used as reference for energy efficiency practitioners or decision-making authorities in the public administration field for developing better energy policies for government buildings.

Evaluation of thermal comfort and carbon dioxide levels during ventricular-assist-device implant.

Environmental measurements were performed in an operating theatre within a pediatric cardiac department, during a surgical operation involving the use of carbon dioxide for the implantation of a ventricular system (VAD). After some reports from the staff, who were complaining about low temperatures in the operating room, it was decided to check carbon dioxide levels, the conditions of thermal comfort and the presence of draughts. Microclimatic parameters and carbon dioxide concentration were performed with a microclimatic unit Delta OHM model HD 32.1. The carbon dioxide concentration values measured during the operation were below the levels at which the working environment was not comfortable, as expressed by both the ASHRAE (American Society of Heating, Refrigeration and Air Conditioning Engineers) and the ACGIH (American Conference of Government Industrial Hygienists) standards. PMV (Predicted Mean Vote) and PPD (Preticted Pencentage of Dissatisfied) values obtained indicate a thermal discomfort tendency to cold perception, perceived in particular by the anesthesiologist, circulating nurse and cardiovascular perfusionist. Airflow discomforts occurred at different stages of the operation. Acting on the air conditioning system, decreasing air velocity, while guaranteeing the minimum number of air recirculation prescribed by the regulations, appears to be the best prevention measure. Changing the mode of laminar air inlet above the cot may, however, affect the "wash" effect of the operating range. Otherwise, a "protective" measure could concern staff clothes, providing them with garments with better insulation, in order to protect the neck area, which is affected by the effects of draughts.

Field-test of the ASHRAE/CIBSE/USGBC performance measurement protocols: Part I intermediate level energy protocols

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)/Chartered Institution of Building Services Engineers (CIBSE)/U.S. Green Building Council (USGBC) performance measurement protocols provide a standardized set of protocols for measuring and comparing the operational performance of occupied commercial buildings. The ASHRAE performance measurement protocols has been developed at three levels of cost/accuracy, Basic (Indicative), Intermediate (Diagnostic), and Advanced (Investigative), for the following six performance categories: energy use, water use, thermal comfort, indoor air quality, lighting, and acoustics. This article presents the results of an effort to develop and apply a field test to evaluate the Intermediate level of the performance measurement protocols energy protocols in a case-study office building in Central Texas. The data collected include multi-year monthly whole-building electricity use, electric demand, and natural gas data for the total and major end uses of the case-study building, as well as coincident on-site weather data. The data collected were then analyzed to calculate the corresponding performance metrics based on the Intermediate level of the performance measurement protocols energy protocols and compared with the appropriate benchmarks. The problems and issues with implementing the performance measurement protocols Intermediate level energy protocols in a case-study building were noted throughout the entire research process. The evaluation revealed five issues, for each of which recommendations were developed to improve the current version of the performance measurement protocols. The results for the performance measurement protocols Basic level applications, including all six areas, were reported in Kim and Haberl (2012a). A companion article (Kim and Haberl 2017) presents the results of applying the performance measurement protocols Advanced level energy protocols.

Field-test of the ASHRAE/CIBSE/USGBC performance measurement protocols: Part II advanced level energy protocols

The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)/Chartered Institution of Building Services Engineers (CIBSE)/U.S. Green Building Council (USGBC) performance measurement protocols provide a standardized set of protocols for measuring and comparing the operational performance of occupied commercial buildings. The ASHRAE performance measurement protocols have been developed at three levels of cost/accuracy, Basic (Indicative), Intermediate (Diagnostic), and Advanced (Investigative), for the following six performance categories: energy use, water use, thermal comfort, indoor air quality, lighting, and acoustics. This article presents the results of an effort to develop and apply a field test to evaluate the Advanced level of the performance measurement energy protocols in a case-study office building in Central Texas. The data collected include multi-year sub-hourly whole-building electricity data for the total and major end uses, thermal data for chillers and condensers, and coincident on-site weather data, as well as monthly utility bills of the case-study building. The data collected were then analyzed to calculate the corresponding performance metrics based on the Advanced level of the performance measurement protocols energy protocols and compared with the appropriate benchmarks. The problems and issues with implementing the performance measurement protocols Advanced level energy protocols in a case-study building were noted throughout the entire research process. The evaluation revealed four issues, for each of which recommendations were developed to improve the current version of the performance measurement protocols. The results for the performance measurement protocols Basic level applications, including all six areas, were reported in Kim and Haberl (2012a). A companion paper (Kim and Haberl 2017) presents the results of applying the performance measurement protocols Intermediate level energy protocols.

Hydrocarbons as Refrigerants―A Review

Refrigerants used in air conditioning and refrigeration (AC&R) indusries have come full circle since the beginning of the industrialrevolution. With concern on issues relating to the environment such as the global warming and climate change issues, we should finda better alternative than to continue using these refrigerants that cause global warming and ozone depletion. AC&R industryplayers have blended in by introducing some new equipment and components that are specificallydesigned for hydrocarbon (HC) use. Mostnew refrigerators sold in Malaysia are already equipped with isobutane [a hydrocarbon designated as R-600a by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) standards]as refrigerants. Malaysia has ratifiedthe Montreal Protocol and targetted a 10% reduction in hydrochlorofluorocarbon(HCFC) consumption, beginning 2016 with the banning of 2.5 horsepower (hp) and below in air-conditioning (AC) equipment to be used. Instead,hydrofluorocarbon(HFC) R-410a was introduced as a replacement for HCFC- 22, whereas in other countries this HFC has been phased down. This article was initiated because of the difficultin findinga replacement for HCFC. Also, the possibilities of using HC as an alternative to replace HCFC insteadof using HFC as a transitional refrigerant in place of HCFC is reviewed in this article. The performance of HC is very similar to HCFC and flmmability issues could be easily overcome with the use of an effectivedesign. Their use could be facilitated with the adaptation of specific standards and properly enacted legislatio

A Fine-Tuned Metal-Organic Framework for Autonomous Indoor Moisture Control.

Conventional adsorbents, namely zeolites and silica gel, are often used to control humidity by adsorbing water; however, adsorbents capable of the dual functionality of humidification and dehumidification, offering the desired control of the moisture level at room temperature, have yet to be explored. Here we report Y-shp-MOF-5, a hybrid microporous highly connected rare-earth-based metal-organic framework (MOF), with dual functionality for moisture control within the recommended range of relative humidity (45%-65% RH) set by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). Y-shp-MOF-5 exhibits exceptional structural integrity, robustness, and unique humidity-control performance, as confirmed by the large number (thousand) of conducted water vapor adsorption-desorption cycles. The retained structural integrity and the mechanism of water sorption were corroborated using in situ single-crystal X-ray diffraction (SCXRD) studies. The resultant working water uptake of 0.45 g·g-1 is solely regulated by a simple adjustment of the relative humidity, positioning this hydrolytically stable MOF as a prospective adsorbent for humidity control in confined spaces, such as space shuttles, aircraft cabins, and air-conditioned buildings.

Adaptive thermal comfort in university classrooms in Malaysia and Japan

The range of students' classroom-based activities is generally restricted; therefore, individuals have limited options for adjusting themselves to the indoor thermal environment. This study investigated the comfort temperature and adaptive behaviour of university students in Malaysia and Japan. Classrooms in three universities (Universiti Teknologi Malaysia; Universiti Teknologi MARA, Malaysia; Kyushu University, Japan) were set to one of two conditions during the summer season: mechanical cooling (CL) mode, where AC was switched on for cooling purposes, and free-running (FR) mode, where AC was switched off. A total of 1428 responses were obtained. In Japan, 93.5% of the sample was male, while more even gender distributions were found in Malaysian samples. Additionally, clo values were generally higher amongst male respondents. In Japan, the mean comfort operative temperatures in FR mode was found to be 25.1 °C, while in Malaysia it was 25.6 °C. In CL mode, mean comfort operative temperatures were found to be 26.2 °C and 25.6 °C for Japan and Malaysia, respectively. Comfort temperatures in FR mode were compatible with Comité Européen de Normalisation (CEN) and American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) standards, while those in CL mode were mostly within Chartered Institute of Building Services Engineers (CIBSE) guidelines. While high proportions of students in both countries claimed that they did nothing to maintain their thermal comfort, the most common activity observed amongst Malaysian students was changing the AC temperature setting, due to the prevalence of CL in Malaysia.

Evaluation of Low-Cost Mitigation Measures Implemented to Improve Air Quality in Nursery and Primary Schools.

Indoor air pollution mitigation measures are highly important due to the associated health impacts, especially on children, a risk group that spends significant time indoors. Thus, the main goal of the work here reported was the evaluation of mitigation measures implemented in nursery and primary schools to improve air quality. Continuous measurements of CO2, CO, NO2, O3, CH2O, total volatile organic compounds (VOC), PM1, PM2.5, PM10, Total Suspended Particles (TSP) and radon, as well as temperature and relative humidity were performed in two campaigns, before and after the implementation of low-cost mitigation measures. Evaluation of those mitigation measures was performed through the comparison of the concentrations measured in both campaigns. Exceedances to the values set by the national legislation and World Health Organization (WHO) were found for PM2.5, PM10, CO2 and CH2O during both indoor air quality campaigns. Temperature and relative humidity values were also above the ranges recommended by American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE). In general, pollutant concentrations measured after the implementation of low-cost mitigation measures were significantly lower, mainly for CO2. However, mitigation measures were not always sufficient to decrease the pollutants’ concentrations till values considered safe to protect human health.

The 2015 New York City Legionnaires' Disease Outbreak: A Case Study on a History-Making Outbreak.

The 2015 New York City Legionnaires' Disease Outbreak: A Case Study on a History-Making Outbreak.

Modeling energy consumption in residential buildings: A bottom-up analysis based on occupant behavior pattern clustering and stochastic simulation

In residential buildings, occupant behavior and occupancy status have a significant impact on energy consumption variation. Although the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommends a uniform occupancy schedule for building energy assessment, occupant behavior patterns and schedules could be different for each building due to occupants’ lifestyles, preferences, occupations, and other differences. Existing occupant behavior models focus on analyzing occupants’ sociodemographic characteristics to predict their energy consumption with statistical approaches. This paper proposes to identify and classify occupants’ behavior with direct energy consumption outcomes and energy time use data through unsupervised clustering. Based on the American Time Use Survey (ATUS), the proposed approach integrates k-modes clustering and demographic-based probability neural networks and identifies 10 distinctive behavior patterns. With the results of the behavior classification and simulation, a bottom-up engineering model reveals that the proposed behavior model offers a more accurate and reliable prediction than the ASHRAE standard schedule. With qualified and sufficient time use data, the model is capable of automatically estimating energy consumption on even larger geographic scales.

Qualitative Study of Cumulative Corrosion Damage of Information Technology Equipment in a Data Center Utilizing Air-Side Economizer Operating in Recommended and Expanded ASHRAE Envelope

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.

Indoor Air Quality in Photocopy Centers, Nanoparticle Exposures at Photocopy Workstations, and the Need for Exposure Controls.

Photocopiers emit large amounts of nanoparticles (NP) and are a significant source of indoor air pollution. These emissions induce airway inflammation, irritation, and systemic oxidative stress in humans, lung injury and inflammation in animals, and cytotoxicity and epigenetic modifications in vitro. However, little is known regarding NP exposures at the workstation in the photocopy work environment, or the extent and use of emission controls. To survey the photocopy work environment with regards to emissions controls and to evaluate IAQ with emphasis on NP exposure at the operator's workstation. Work process, physical characteristics of the centers, and use of controls were recorded. Particle total number concentration (TNC), temperature, carbon dioxide, carbon monoxide, and percent relative humidity were measured during a random workday. Geometric mean (GM) TNC at workstations ranged between 1900 and 23000 particles cm-3, GSD 1.2-2.8, and maximum of 217000 particles cm-3. Fresh air ventilation was found to be less than American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) guidelines in 7 of 15 centers. Only one center used any type of emissions control. Elevated TNC at workstations was significantly correlated with number of copies (r = 0.72). While indoor/outdoor TNC ratios might be expected to be ≤1.0, the ratio here was >1.0 in 40% of centers visited, supporting the finding that copier emissions are a significant source of indoor air pollution. Number of copies per day was the most significant contributor to TNC. High NP concentrations at workstations were common and specific emission controls almost nonexistent. While 46% of copy centers had insufficient ventilation, high exposures were documented even for cases when ASHRAE ventilation guidelines per person were met or exceeded. We present various options to address IAQ in photocopy environment, including new clean photocopy technologies, engineering controls, and a comprehensive awareness campaign to improve the environmental health and safety, design, and operational conditions of these workplaces.

Relationship among environmental quality variables, housing variables, and residential needs: a secondary analysis of the relationship among indoor, outdoor, and personal air (RIOPA) concentrations database.

Retrospective descriptive secondary analyses of data from relationships of indoor, outdoor, and personal air (RIOPA) study homes (in Houston, Texas; Los Angeles County, California; and, Elizabeth, New Jersey May 1999-February 2001) were conducted. Data included air exchange rates, associations between indoor and outdoor temperature and humidity, and calculated apparent temperature and humidex. Analyses examined if study homes provided optimum thermal comfort for residents during both heating and cooling seasons when compared to current American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) Standards 62/62.1 and 55. Results suggested outdoor temperature, humidex, and apparent temperature during the cooling season potentially served as indicators of indoor personal exposure to parameters of thermal comfort. Outdoor temperatures, humidex, and apparent temperature during the cooling season had statistically significant predictive abilities in predicting indoor temperature. During the heating season, only humidex in Texas and combined data across study states were statistically significant, but with weaker to moderate predicative ability. The high degree of correlation between outdoor and indoor environmental variables provided support for the validity of epidemiologic studies of weather relying on temporal comparisons. Results indicated most RIOPA study residents experienced thermal comfort; however, many values indicated how several residents may have experienced some discomfort depending on clothing and indoor activities. With climate change, increases in temperature are expected, with more days of extreme heat and humidity and, potentially harsher, longer winters. Homes being built or modernized should be created with the appropriate guidelines to provide comfort for residents daily and in extreme weather events.

The effect of human-mattress interface's temperature on perceived thermal comfort

In recent years, methods that allow for an objective evaluation of perceived comfort, in terms of postural, physiological, cognitive and environmental comfort, have received a great deal of attention from researchers. This paper focuses on one of the factors that influences physiological comfort perception: the temperature difference between users and the objects with which they interact. The first aim is to create a measuring system that does not affect the perceived comfort during the temperatures' acquisition. The main aim is to evaluate how the temperature at the human-mattress interface can affect the level of perceived comfort. A foam mattress has been used for testing in order to take into account the entire back part of the human body. The temperature at the interface was registered by fourteen 100 Ohm Platinum RTDs (Resistance Temperature Detectors) placed on the mattress under the trunk, the shoulders, the buttocks, the legs, the thighs, the arms and the forearms of the test subject. 29 subjects participated in a comfort test in a humidity controlled environment. The test protocol involved: dress-code, anthropometric-based positioning on mattress, environment temperature measuring and an acclimatization time before the test. At the end of each test, each of the test subject's thermal sensations and the level of comfort perception were evaluated using the ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) scale. The data analyses concerned, in the first instance, correlations between the temperature at the interface and comfort levels of the different parts of the body. Then the same analyses were performed independently of the body parts being considered. The results demonstrated that there was no strong correlation among the studied variables and that the total increase of temperature at interface is associated with a reduction in comfort.

Energy use consequences of ventilating a net-zero energy house

A Net-Zero Energy Residential Test Facility (NZERTF) has been constructed at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland, to demonstrate that a home similar in size, aesthetics, and amenities to those in the surrounding communities can achieve net-zero energy use over the course of a year while meeting the average electricity and water use needs of a family of four in the United States. The facility incorporates renewable energy and energy efficient technologies, including an air-to-air heat pump system, a solar photovoltaic system, a solar thermal domestic hot water system, and a heat recovery ventilation system sized to meet American Society of Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) Standard 62.2-2010 ventilation requirements. The largest energy end use within the home was space conditioning, which included heat loss through the building envelope, ventilation air supplied by the heat recovery ventilator (HRV), and internal loads. While HRVs are often described as being able to save energy when compared to ventilating without heat recovery, there have been no studies using a full year of measured data that determine the thermal load and energy impacts of HRV-based ventilation on the central heating and cooling system. Over the course of a year, continuous operation of the HRV at the NZERTF resulted in an annual savings of 7% in heat pump energy use compared with the hypothetical case of ventilating without heat recovery. The heat pump electrical use varied from an increase of 5% in the cooling months to 36% savings in the heating months compared with ventilation without heat recovery. The increase in the cooling months occurred when the outdoor temperature was lower than the indoor temperature, during which the availability of an economizer mode would have been beneficial. Nevertheless, the fan energy required to operate the selected HRV at the NZERTF paid for itself in the heat pump energy saved compared with ventilation without heat recovery.

Instituting a filtration/pressurization system to reduce dust concentrations in a control room at a mineral processing plant.

The National Institute for Occupational Safety and Health has observed that many control rooms and operator compartments in the U.S. mining industry do not have filtration systems capable of maintaining low dust concentrations in these areas. In this study at a mineral processing plant, to reduce respirable dust concentrations in a control room that had no cleaning system for intake air, a filtration and pressurization system originally designed for enclosed cabs was modified and installed. This system was composed of two filtering units: one to filter outside air and one to filter and recirculate the air inside the control room. Eighty-seven percent of submicrometer particles were reduced by the system under static conditions. This means that greater than 87 percent of respirable dust particles should be reduced as the particle-size distribution of respirable dust particles is greater than that of submicrometer particles, and filtration systems usually are more efficient in capturing the larger particles. A positive pressure near 0.02 inches of water gauge was produced, which is an important component of an effective system and minimizes the entry of particles, such as dust, into the room. The intake airflow was around 118 cfm, greater than the airflow suggested by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) for acceptable indoor air quality. After one year, the loading of the filter caused the airflow to decrease to 80 cfm, which still produces acceptable indoor air quality. Due to the loading of the filters, the reduction efficiency for submicrometer particles under static conditions increased to 94 percent from 87 percent.

IBM z13: Energy efficiency, increased environmental range, and flexible data center characteristics

A maximum configuration IBM z13™ provides 45% more compute capacity per watt than its predecessor mainframe, the IBM zEnterprise® EC12 (zEC12). The z13 adds support of the American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) class A2 environment, with a maximum air-inlet temperature of 35 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">$^{\circ}\hbox{C}$</tex-math></inline-formula> , versus 32 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">$^{\circ}\hbox{C} $</tex-math></inline-formula> for the class A1, zEC12. It accomplishes this while maintaining a wide range of AC and higher voltage DC power capability, overhead and/or under-floor I/O cabling, raised or non-raised floor installation, and external air or direct water cooling, also with increased temperature. The z13 is discussed, in the context of the history of IBM z Systems™ energy efficiency and data center flexibility, with significant attention paid to the system's redesigned airflow and its customizable exhaust air direction capability. Using computational fluid dynamics modeling, this paper discusses the integration of the system into several data center environments. Also reviewed are the potential advantages of intermittently operating the data center at higher temperatures, including discussion of the cooling energy and hardware costs, economizers, and robustness improvements when faced with cooling infrastructure failures. Lastly, we describe the cooling innovations, designs, and protections that enable its wider temperature range capability.