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1.
International Journal of Air-Conditioning and Refrigeration ; 29(1), 2021.
Article in English | ProQuest Central | ID: covidwho-2138153

ABSTRACT

Air curtains are installed to reduce heat loss due to drafts intruding into the indoor through the open doorways, and play the role of separating two climatic zones and different environmental zones. It is also used to protect the workplace from impurities or to reduce the spread of cigarette smoke in restaurants. Recently, aircraft to provide the individual air barrier by the vertical blowing air curtains have installed a physical barrier in the breathing zone between adjacent seats to protect passengers from COVID-19. The main factors affecting the sealing performance (SP) of the air curtain are the difference of temperature and pressure between indoor and outdoor, and are used to make the proper jet flow an air barrier with the high airtightness. Until now, various types of air curtains are manufactured and sold. Air curtains with the improved SP do not only have a discharge port but also a suction port. This study was conducted to evaluate the SP of the horizontal blowing air curtain according to the discharge pressure, and to select the minimized volume flow rate required for creating the proper zone separation. The volume flow rate of outdoor air intruding into the indoor through the doorways is used to evaluate the SP of the air curtain, and is calculated using the SVE4 proposed by Murakami in this study.

2.
International Journal of Air-Conditioning and Refrigeration ; 28(2), 2020.
Article in English | ProQuest Central | ID: covidwho-2138152

ABSTRACT

Recent concerns raised by the World Health Organization over the Coronavirus raised a worldwide reaction. Governments are racing to contain and stop the Coronavirus from reaching an epidemic/pandemic status. This research presents a way in tracking such a virus or any contagious germ capable of transferring through air specifically where such a transfer can be assisted by a mechanical room ventilation system. Tracking the spread of such a virus is a complicated process, as they can exist in a variety of forms, shapes, sizes, and can change with time. However, a beginning has to be made at some point. Assumptions had to be made based on published scientific data, and standards. The tracking of airborne viruses was carried out on the following assumption (for illustrative purposes);one person with one sneeze in a period of 600 s. The presence of viruses was tracked with curves plotted indicating how long it could take to remove the sneezed viruses from the mechanically ventilated room space. Results gave an indication of what time span is required to remove airborne viruses. Thus, we propose the following: (a) utilizing CFD software as a possible tool in optimizing a mechanical ventilation system in removing contagious viruses. This will track the dispersion of viruses and their removal. The numerical solution revealed that with one typical adult human sneeze, it can take approximately 640 s to reduce an average sneeze of 20,000 droplets to a fifth;(b) upscaling the status of human comfort to a “must have” with regards to the 50% relative humidity, and the use of Ultraviolet germicidal irradiation (UVGI) air disinfection in an epidemic/pandemic condition. A recommendation can be presented to the local authorities of jurisdiction in enforcing the above proposals partially/fully as seen fit as “prevention is better than cure”. This will preclude the spread of highly infectious viruses in mechanically ventilated buildings.

3.
ASHRAE Transactions ; 127:43-52, 2021.
Article in English | ProQuest Central | ID: covidwho-1980951

ABSTRACT

This study investigated the impacts of the COVID-19 pandemic on the electricity consumption of a university dormitory building in the southern US. The historical electricity consumption data of this university dormitory building and weather data of an on-campus weather station, which were collected from January 1st, 2017 to July 31st, 2020, were used for analysis. Four inverse data-driven prediction models, i.e, Artificial Neural Network, Long Short-Term Memory Recurrent Neural Network, eXtreme Gradient Boosting, and Light Gradient Boosting Machine, were exploited to account for the influence of the weather conditions. The results suggested that the total electricity consumption of the objective building decreased by nearly 41% (about 276,000 kWh (942 MMBtu)) compared with the prediction value during the campus shutdown due to the COVID-19. Besides, the daily load ratio (DTR) varied significantly as well. In general, the DTR decreased gradually from 80% to nearly 40% in the second half of March 2020, maintained on a relatively stable level between 30% to 60% in April, May, and June 2020, and then slowly recovered to 80% of the normal capacity in July 2020.

4.
ASHRAE Transactions ; 127:100-107, 2021.
Article in English | ProQuest Central | ID: covidwho-1980720

ABSTRACT

As the coronavirus pandemic has brought about global economic recession and reduction in greenhouse gas emissions, energy efficient building retrofitting has become a comprehensive solution to increase the employment rate and reduce the energy consumption of buildings. This situation requires more energy-efficient integrated generation systems. In this study, an integrated generation system is proposedfor building integrated photovoltaic, thermoelectric generator, and phase change material as an enhanced generation system for buildings. In the proposed system, the phase change material absorbs solar radiation as latent heat within the melting temperature, increasing the photovoltaic conversion efficiency. Additionally, the thermoelectric generator harvests additional electricity as the temperature difference is maintained during the phase change. The total generated energy of the proposed system highly depends on the melting temperature and thickness of the phase change material. Therefore, the appropriate melting temperature and thickness design conditions of the phase change material were derived with the following simulations based on transient energy balance equations in 12 daily profiles. As a result, the optimal melting temperature increased by 5.4°F (3.6°C) and 1.9°F (1.04°C) with an insolation increase of 317 Btu/ft2 (1000 Wh/m2) and a 1.8°F (1°C) increase in ambient temperature, respectively. In addition, the optimal thickness increased by 0.04 in (2.5 mm) with an insolation increase of 317 Btu/ft2 (1000 Wh/m2).

5.
ASHRAE Transactions ; 127:246-253, 2021.
Article in English | ProQuest Central | ID: covidwho-1980710

ABSTRACT

The purpose of a ventilation system for indoor spaces is to create a safe environment for the occupants by diluting the concentration levels of hazardous contaminants and to minimize the risk of infection due to spread of airborne pathogens. The effectiveness of ventilation system depends on several inter related factors including the supply airflow rate, number and locations of supply diffusers, and number and locations of return grilles. With the help of Computational Fluid Dynamics (CFD) analyses, this study systematically evaluates the impact of three different HVAC configurations on the airflow patterns, distribution of contaminant, and the risk of infection in a small office space with two cubicles. The HVAC configuration with a single supply and a single return can create adverse airflow patterns which can promote spread of contaminants and increase the risk of infection farther from the source. When an additional supply diffuser is introduced with the same single return, the zone of high risk of infection remained in the vicinity of the source. However, the overall risk of infection in the space remained the same. Addition of another return created aerodynamic containment zones in the space which provided easy path for the contaminated air to leave the space and reduced the overall risk of infection. Since the location of an infected individual is not known a priori, the aerodynamic containment with distributed supply and distributed return can be the best strategy for reducing the probability of infection in indoor spaces. These studies demonstrate that CFD analyses can help in identifying the potential risk of high infection due to poor airflow distribution into a space and can provide valuable insights for developing appropriate mitigation strategies to create safe indoor environment.

6.
ASHRAE Transactions ; 127:53-61, 2021.
Article in English | ProQuest Central | ID: covidwho-1980697

ABSTRACT

As stay-at-home orders, temporary school closures, and other preventative measures have been implemented across the nation to slow the spread of COVID- 19, typical pre-COVID-19 routines have been significantly changed as people are advised to avoid social engagements and limit travel. With this shiftin behavior, people are working from home and children are learning remotely. This has resulted in a shiftin use of household appliances, HVAC, and other energy-consuming devices during typical working hours to support the work and school functions that usually occur outside of the home. Submetered energy usage data has been reviewed for several hundred residential buildings, including pre-COVID-19 and post-COVID-19 time periods, to assess the impact of this shifton residential building energy consumption for both HVAC and non-HVAC loads. Non-HVAC end use energy consumption, particularly during typical working hours, increased compared to pre-COVID periods. In addition, daily energy consumption increased when compared to identical months and homes in pre-COVID scenarios. Weather-normalized HVAC consumption trends were also found to have increased. The results of these findings indicate the importance of considering previous assumptions for HVAC use, internal loads, and other end uses, how they may change moving forward, and the need to further study these trends.

7.
ASHRAE Transactions ; 127:174-184, 2021.
Article in English | ProQuest Central | ID: covidwho-1980303

ABSTRACT

Thirty years of evidence supports the efficacy of ultra-clean air in preventing surgical site infection (SSI). Ultraclean is defined as fewer than 10 Colony Forming Units (CFUs) per cubic meter or <10CFU/m3 (35ft3) However, achieving and maintaining ultraclean conditions in the contemporary operating room has proven challenging. For decades, Laminar Air Flow (LAF) systems were recommended for use in rooms where infection sensitive joint arthroplasty procedures are performed. But, a growing body of evidence has called the efficacy of LAF in prevention of these infections into question. As a result, CD C no longer recommends use of LAF for joint arthroplasty. The WHO has gone a step further issuing a conditional recommendation against its use in these procedures. At the same time, demand for total hip and knee arthroplasties are expected to grow exponentially over the next decade and for reasons that are unclear rates of prosthetic joint infection (PJI) are on the rise. Taken together, these factors suggest that the time has come to rethink management of airborne contamination and ventilation technology in the operating room. Temperature-controlled Air Flow (TcAF) is a novel ventilation technology that has been proven to maintain ultra-clean conditions throughout the entire operating room. TcAF uses continuous HEPA filtration and combines a robust central unidirectional down-flow driven by gravity from a temperature gradient together with mixing ventilation in the periphery of the room. While TcAF has been scientifically validated to maintain ultra-clean conditions of <10CFU/m3(35ft3) throughout the entire operating room, the impact of TcAF on prevention of surgical site infection was unknown. The aim of this study was to evaluate the efficacy of TcAF on prosthetic joint infection (PJI). A retrospective case control study was performed with 1,000 consecutive cases of primary total joint arthroplasty before and 1,000 consecutive cases after the installation of an ultra-clean TcAF system. TcAF was associated with a statistically significant reduction in surgical site infection. With reduction in surgical site infection proving to be ever more challenging and demand for infection sensitive procedures rising, more rigorous attention to airborne contamination may represent a new pathway to improvement. While not the focus of this paper, the advent of Covid-19 should bring into greater focus the risk of airborne transmission andfurther incentiviņe mitigation.

8.
ASHRAE Transactions ; 127:254-262, 2021.
Article in English | ProQuest Central | ID: covidwho-1980287

ABSTRACT

Airborne diseases are a current concern. Infections can spread through the air even when a disease may not be characterized as "airborne" in medical terms. Some installed HVAC systems can spread infectious agents to those who are not currently infected. Cross contamination through leakage in energy recovery ventilation (ERV) devices can provide a pathway for infection. Energy recovery devices are currently required in many new buildings codes and standards. They are often installed in retrofit projects in older buildings in order to save energy. The risk from cross-contamination can be estimated using the Wells-Riley infection model. Energy recovery ventilation device applications can be designed, specified, and installed to effectively eliminate the risk of cross contamination in new systems using current technology so this is an avoidable risk.. A framework for evaluating currently installed ERV systems is providedfor facilities managers and HVAC systems operators to identify and minimize cross contamination infection risk.

9.
ASHRAE Transactions ; 128:472-479, 2022.
Article in English | ProQuest Central | ID: covidwho-1970765

ABSTRACT

Increasing demands for sustainable design solutions have fostered a myriad of certification systems (GxN and Danish Building Research Institute, 2018). Sustainability certification systems quantify designs based on predefined criteria and are gaining momentum due to market demand. The DGNB assessment methodology is widely used in the Danish building industry today (Green Building Council Denmark, 2021). An aim of the current Danish climate strategy is to reduce greenhouse gases by 70% from 1990 levels by 2030. As part of this strategy, the Danish Government introduced the voluntary sustainability class (VSC) in May 2020 to be included in Danish Building Regulations by 2023. The VSC will be optional until 2023, and after 2023 it will become a mandatory part of the Danish Building Regulations (Bolig og Planstyrelsen, 2021). The VSC could serve as a central element in the transition of the building industry towards sustainable buildings and urban designs. The present study adopts a multi-level perspective (MLP), which is a transition framework. The VSC is an example of how a macro-level change, such as the green transition brought about by climate change, can aid in the transition to increased sustainability in a socio-technical system (Geels, 2002). Semi-structured interviews with experts from the construction industry were conducted to shed light on the potential,possibilities and challenges associated with the new regulation;however, the present study did not consider whether amending the Danish Building Regulations could increase the sustainability of buildingprojects. The results showed that certain factors, such as knowledge and prior experience of regulatory changes, could lessen the impact of any future change in regulations. In relation to the effect of the voluntary sustainability programme, the present study showed that the programme is most likely to target companies with a lower level of ambition regarding sustainable initiatives.

10.
ASHRAE Transactions ; 128:393-401, 2022.
Article in English | ProQuest Central | ID: covidwho-1970685

ABSTRACT

During the COVID-19 pandemic, building owners and operators sought to protect their occupants by following ASHRAE and CDC guidance for HVAC and water system risk mitigation. This paper presents the results of building readiness assessments conducted for 95 commercial office buildings across the United States. In these assessments, the authors evaluated buildings for initial alignment with ASHRAE Epidemic Task Force (ETF) guidance and recommended action where additional risk mitigation measures were warranted. The engineering assessments focused on outdoor air ventilation rates, filtration efficiency levels, flushing spaces during unoccupied periods, and Eegonella water management practices. Primary challenges to implementing ETF guidance included resistance to operational changes with potential adverse energy impacts, concerns regarding existing system limitations, and in a limited number of cases, ventilation system design constraints. The assessments showed that most of the office buildings could modify their HVAC and water system operatingpractices to minimize the spread of harmful pathogens without major upgrades to equipment or significant increases in energy use. Almost all subject buildings had the capacity to meet or exceed minimum ventilation rates, upgrade to at least MERV-13 filters, implement appropriate flushing periods to achieve target clean air changes, and manage their water systems to minimize Legionella risk.

11.
ASHRAE Transactions ; 128:348-356, 2022.
Article in English | ProQuest Central | ID: covidwho-1970600

ABSTRACT

Indoor air quality is increasingly recognized as a serious health hazard in many international environments. During the recent pandemic, this concern was amplified as Covid-19-related mortality closely correlated with poor air quality. Even a comparatively small decline in the Air Quality Index (AQI) can be linked to a sharp mortality increase. Worsening air quality levels are compounded by distinct air-quality issues in different geographical areas. In the face of this serious and wide-ranging threat, the common solution-introducing a high MERV-rated filter-comes up short, as these filters create back pressure that often exceeds the capacity of the HVAC systems in which they are installed. High-backpressure filters also use more energy and require frequent filter changes, making them more expensive to maintain and bad for the environment. This paper describes a new form of electrostatic filtration that is ideal for international markets since it has a uniform performance, low back pressure, is energy efficient, and can be tuned to perform at a range of filtration levels depending on demand. Developed at the University of Washington, the technology features porous electrodes that collect and hold, a large capacity of particles regardless of their size and physical properties. This paper will describe the technology, prototype testing, including a 6-month pilot installation, and will detail how the technology can be used to achieve on-demand MERV 15 filtration levels in systems that require continuous low back pressure and reduced energy consumption.

12.
ASHRAE Transactions ; 128:340-347, 2022.
Article in English | ProQuest Central | ID: covidwho-1970581

ABSTRACT

The wavelength band of200-280 nm of UV-C radiation generated by the Ultraviolet Germicidal Irradiation (UVGI) system can destroy the reproduction ability of microorganisms. Severalfactors related to UVfixtures, HVAC layout, and the resulting airflow flow patterns can affect the performance of upper-room UVGI applications. With the help of Computational Fluid Dynamics (CFD) analyses, this study systematically evaluates the impact of UV-C intensities on the effectiveness of an upper room UVGI system. It shows that the addition of even a small amount of UV-C energy in the upper region of space can significantly reduce the probability of infection as predicted by the Wells-Riley model. Increasing the UV-C output shows a further reduction in the infection probability, although with a diminishing impact. A further investigation is necessary to evaluate the effect of airflow patterns on the performance of UVGI systems. These studies demonstrate that CFD analyses can help optimize the performance of UVGI systems to minimize the probability of infection in indoor spaces.

13.
ASHRAE Transactions ; 128:480-486, 2022.
Article in English | ProQuest Central | ID: covidwho-1970422

ABSTRACT

This paper discusses aerosol risk in typical dental suite spaces: private rooms, and open spaces. It also considers the risk to physically separated occupants within the same suite. Risks are compared, using a standard environmental aerosol risk (SEAR) methodology, to show the higher and lower mitigation values of the various options. When a source of infectious aerosols in present, the highest aerosol exposure risk occurs for the workers sharing the immediate space with the source. There is also risk present for occupants in other moms. Source controls, if it can be effectively accomplished, is the most beneficial strategy for all parties. It reduces risk for the workers in the room with the source. And, having removed the aerosols, it reduces risk for all occupants outside the room. Treatment very near the source, with a local HEPA filter device, can also effectively reduce the risk both locally and for occupants outside the room. Closed doors can also be effective. If patients can be seen in private rooms with normally closed doors, risk for occupants in other areas is significantly reduced, since the aerosols will be more contained. If a known infectious source is present, use of an airlock or anteroom (two doors), and negative pressure can virtually eliminate risk for other areas.

14.
ASHRAE Transactions ; 128:323-330, 2022.
Article in English | ProQuest Central | ID: covidwho-1970403

ABSTRACT

Urban-scale energy simulation relies on the understanding of occupants' presence in buildings and consequently in cities. Therefore, occupancy profiles (i.e., the relative number of occupants in a specific hour of the day) are usually used in the energy simulation on the city level. However, available occupancy standard profiles are incapable of considering the dynamic nature of occupancy schedules and any changes that occurred due to contextual changes (such as the dramatic increase in remote working last year). Therefore, the need for a scalable method to generate dynamic occupancy profiles for buildings is crucial. Moreover, the targeted method should allow for tracking the changes that occur in occupancy profiles due to external disruption such as pandemics. In this context, this study aims at using the emerging mobile positioning data to generate context-specific data-driven occupancy profiles for commercial and institutional buildings in New York City. The generated profiles were then compared versus ASHRAE standard profiles for each building category. Then, the occupancy profiles were clustered for each building category, using K-means clustering algorithm. Finally, the effect of COVID-19 pandemic on the peak points and shape of occupancy profiles was investigated. The results showed a significant difference between the data-driven and ASHRAE standard profiles. Additionally, a considerable variation in the shape and peak hours of the generated occupancy profile clusters was detected for some building categories. These results can be used to improve the accuracy of the urban-scale simulation models. Furthermore, they can provide a more precise evaluation of the occupant's schedules and consequently the urban scale energy consumption before field implementation of the operational strategies.

15.
ASHRAE Transactions ; 128:505-512, 2022.
Article in English | ProQuest Central | ID: covidwho-1970210

ABSTRACT

Hygienic design of the Air Handling Unit (AHU), the custom-designed industrial HVAC system used in hospitals, laboratories, and similar sterile areas to supply clean, filtered, and conditioned air, has become more prevalent during the covid-19 pandemic. Improper maintenance of the air handling system can carry germs or viruses at any stage. This study concentrates explicitly on Air Handling Units used in hospitals, which should maintain higher quality standards than conventional air handling systems to reduce all kinds of dirt, debris, mold, and bacteria from the system. Throughout the paper, the critical parameters and control points of the air handling units for hospitals are analyzed from a hygienic viewpoint, and the existing hygienic design standards are explained through an implemented case study.

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