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To establish a PCR detection method for Trichomonas foetus, the primers were designed and synthesized according to the 18S rRNA gene sequence of T. foetus published by GenBank. The positive recombinant plasmid pUCm-T-TF18S of T. foetus was used as the template, and the genomic DNA of Giardia felis, Coccidia +e-lis, feline parvovirus and cDNA of feline coronavirus were used as the control for PCR detection to analyze the specificity of this method. The positive T. foetus recombinant plasmid was serial to 8 different concentrations with a gap of 10 folds, and PCR was performed to analyze the sensitivity of this method. The pUCm-T-TF18S plasmids stored at -20 " for 3, 6, 9 and 12 months were detected by PCR to analyze the stability of the method. Twenty cat fecal samples were tested using this established PCR assay and compared with those of microscopic examination. The results showed that the recombinant plasmid pUCm-T- TF18S gave specific bands after PCR amplification. The sequencing results showed that the length of the product sequence was 1 264 bp, and the BLAST sequence comparison analysis showed 99.53% sequence identity, which is consistent with that of T. foetus from cats (GenBank registration number M81842.1). The PCR method for detection of T. foetus had no cross-reactivities with C. felis, G. felis, feline coronavirus and feline parvovirus;the minimum detectable template concentration is 4.52 X 105 copies/xl;The target band of T. foetus DNA can still be detected after being stored in the refrigerator at -20 " for 12 months. This method detected 16 positive samples of T. foetus nucleic acid from 20 cat fecal samples, which is more accurate and sensitive than the results from traditional microscopy (13 samples). It is suggested that the PCR method for the detection of T. foetus is highly specific, sensitive and stable, and can be used for clinical detection and epidemiological investigation of T. foetus.Copyright © 2022, National Institute of Parasitic Diseases. All rights reserved.
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Cold storage is expensive for smallholder farmers and seed processors in developing countries. Smallholder farmers continue to resort to traditional storage methods such as polypropylene (PP) bags for maize grain storage. They often dose the grains with chemicals to preserve them. However, hermetic bags have proven to provide superior protection to grains during storage without chemical treatment. With the advent of the COVID-19 virus which distorted many food systems across continents, stakeholders in the grain industry need to adopt better systems to reduce post-harvest food loss and improve food security. In this study, maize grain quality, nutritional content and viability were compared under three storage methods (PP bags with Phostoxin treatment, cold storage, and hermetic bag) over a storage period of four months. The results showed that the hermetic bag maintained the moisture content (MC) of the stored grains with 0.40% variations from the initial MC of 13% at the end of the storage period compared to 0.70% and 1.10% for grains stored under cold storage and in PP bags, respectively. Grain damage after the 4th month of storage in the hermetic bag had only increased by 0.40% from an initial 13.3% before storage compared to an increase of 6% for cold storage, which was attributed to unstable power during the storage period, and 4.30% for grains stored in the PP bag. Carbon dioxide concentration in the hermetic bag was maintained at about 11% throughout the storage period indicating low microbial activity. The hermetic bag technology was identified as the best option for quality preservation during storage of maize grain over the other methods, and its adoption by smallholder farmers in Ghana should be considered.
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To assess risk factors for COVID-19 transmission and address the closure of mass gathering events since March 2020, the UK Government ran the Events Research Programme (ERP), following which it reopened live events in sports, music, and culture in July 2021. We report the rapid post-occupancy evaluation of Indoor Air Quality (IAQ) and associated long-range airborne transmission risk conducted in the Environmental Study of the ERP. Ten large venues around the UK were monitored with CO2 sensors at a high spatial and temporal resolution during 90 events. An IAQ Index based on CO2 concentration was developed, and all monitored spaces were classified in bands from A to G based on their average and maximum CO2 concentrations from all events. High resolution monitoring and the IAQ Index depicted the overall state of ventilation at live events, and allowed identification of issues with ventilation effectiveness and distribution, and of spaces with poor ventilation and the settings in which long-range airborne transmission risk may be increased. In numerous settings, CO2 concentrations were found to follow patterns relating to event management and specific occupancy of spaces around the venues. Good ventilation was observed in 90% of spaces monitored for given occupancies. Practical applications: High-resolution monitoring of indoor CO2 concentrations is necessary to detect the spatial variation of indoor air quality (IAQ) in large mass gathering event venues. The paper summarises COVID-19 ventilation guidance for buildings and defines a methodology for measurement and rapid assessment of IAQ during occupancy at live events that can be implemented by venue managers. Comparisons of the CO2 concentrations measured during the events identified the spaces at high risk of long-range transmission of airborne pathogens. Building operators should be mindful of the ventilation strategies used relative to the total occupancy in different spaces and the occupant's activities.
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The case study learning methodology has been used for more than 20 years in teaching science and engineering. This methodology is known to be highly effective in promoting students' understanding of the concepts and improving their ability to make connections between the concepts. In 2020 and 2021, the limited access to laboratory equipment and facilities due to the COVID-19 pandemic encouraged instructors to implement alternative methods. One of the alternatives considered in the current institution is the use of case studies to enhance students' understanding of thermodynamics and fluid mechanics topics during the online and hybrid implementations of those courses. In this study, an industry-based air-conditioning (AC) unit is facilitated to prepare a case study to teach refrigeration cycles in the laboratory part of thermodynamics. All four components of the AC unit, which include a compressor, a condenser, an expansion valve, and an evaporator, are assembled on a single platform. In an actual application, the compressor and condenser are part of the outside unit while an evaporator and expansion valve would be located indoors. In the first phase of the case study, students analyze temperature and pressure data for the normal operation of the unit to understand the function of each component in the cycle. In addition, by using thermodynamics property tables, they determine enthalpy and entropy values at different stages of the process, generate a temperature versus entropy (T-s) diagram, and calculate the efficiency of the AC unit. In the second phase of the study, they are provided with temperature and pressure data collected for the cases corresponding to when there is a problem with the AC unit. They perform analysis of those cases. The examples of issues introduced include part of the condenser or evaporator coils being disabled or using a partially blocked air filter. The equipment used in the case study is modified by the manufacturer to simulate those issues. During data analysis, student teams are tasked with identifying the issue introduced by looking at the changes in temperature, pressure, and T-s diagram. This paper provides detailed information about the case study, data collection, and analysis. Copyright © 2022 by ASME.
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Research in ultra-low temperature refrigeration applications has intensified in recent years after the appearance of vaccines in response to the COVID-19 pandemic. There are few current technologies for this low-temperature range, with reduced energy performance and high global warming potential refrigerants. This work analyses the introduction of the ejector in two-stage cascade cycles for ultra-low temperature refrigeration. The proposal includes the assessment of the behaviour of the ejector while implementing it in a single stage or simultaneously in both stages. The study is carried out with refrigerants R-290 in the high-temperature stage and R-170 in the low-temperature stage since these are natural refrigerants with very low global warming potential. The results show that the ejector is a component that causes improvements in the cycle when placed in the high-temperature and low-temperature stages. On the other hand, changing evaporation and condensation temperatures, the evaporation temperature is more critical regarding cycle energy performance. With the results obtained, a cascade cycle with an ejector in both stages is proposed, obtaining a 21% higher coefficient of performance than the standard cascade cycle. Also, the cycle with the ejector in both stages causes an improvement of 13.6% compared to the previous generation's refrigerants (R-23 and R-507A) in the same cycle. The carbon footprint analysis shows that this cycle emits less than half of the equivalent CO2 than actual cycles for ultra-low temperatures, also with a new refrigerant like R-472A. © 2023 The Author(s)
ABSTRACT
In the present study, the operation performance of an ultralow-temperature cascade refrigeration freezer is experimentally researched. The natural refrigerants R290-R170 are adopted as high-temperature and low-temperature fluids. The experimental test is conducted in a type laboratory with a dry bulb temperature of 32.0 °C and a wet bulb temperature of 26.5 °C. Different state monitors are set to display the system operation performance, and several temperature monitors are arranged to study the pull-down performance and temperature variations in the freezer. Based on the established experimental rig, three freezing temperatures, including - 40 °C, - 80 °C, and - 86 °C, are measured and compared. The results show that it takes about 240 min for the freezer to be pulled down to - 80 °C. During the pull-down period, different monitors all experience rapid temperature drop, and the power consumption reduces from 1461.4 W to 997.5 W. Once the target temperature is achieved, the freezer comes into periodic start-stop operation. With the set temperature ranging from - 40 °C to - 86 °C, the inlet temperature of two compressors gradually decreases, while the discharge temperature has an increase trend. The cooling effect of the pre-cooled condenser reduces with the freezing temperature, while the long connection pipe has opposite variation profile. Moreover, it is observed that for different freezing temperatures, most of the space in the freezer can be cooled down to the target temperature. It is confirmed that the present ultralow-temperature freezer can be used for the storage and transportation of COVID-19 vaccines. However, it is also found that the cascade refrigeration system is not suitable for high freezing temperature, due to high power consumption and extensive start-stop switch of refrigeration system.
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Background/Objective: Messenger RNA (mRNA) vaccines have emerged as a promising treatment for the coronavirus disease-2019 (COVID-19) pandemic, but such a solution has its challenges. One such issue is the mRNA vaccine's molecular stability, which requires that it be kept under certain environmental conditions that restrict its global outreach in packages, such as disposable syringes, distributed worldwide using refrigeration. Designing an environmentally stable mRNA vaccine that can withstand shipment worldwide is a challenge, since a single slit or puncture can render the complete dose of the vaccine useless. If not kept under certain environmental conditions and left unmonitored, mRNA vaccines tend to degrade rapidly. To address this problem, agencies currently store mRNA vaccines under strict refrigeration, thus limiting their global reach. The objective was to develop a hybrid deep learning model that can efficiently predict mRNA vaccine degradation rate from RNA sequences, thus aiding researchers and scientists in designing and developing a more stable mRNA vaccine in the future Results: Research presented here discusses the capability of the in-house developed hybrid deep learning model. Conclusion(s): The model was developed with a performance of 0.2430 mean columnwise root-mean-squared error (MCRMSE) score on the test data.
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The economic prosperity plus technological growth of each & every county depend heavily on energy security, and the energy availability portrays the quality of life in that country. Solar energy is an alternative energy source for cooling systems where power is costly, unreliable, and unsustainable—the main options for electrically-powered refrigeration systems available for several years;are our gas and kerosene-driven refrigerators. The solar refrigeration system was a promising advancement in the early 1980s, creating an alternative to absorption technology to cater to the cold chain requirements in off-grid areas. The main objective of this research is to determine the feasibility of solar-powered refrigeration systems for rural dispensaries, sub-counties health centers, and health posts in Kenya;this is in line with the current COVID-19 pandemic, which demands that the vaccine be supplied to the local populace. This article provides essential recommendations on the solar-powered refrigeration system and highlights some critical parameters for the successful implementation of solar-powered refrigeration units into vaccination programs in the future, including;The supply chain of the vaccines in the country, the current state of the health system at sub-county hospitals, areas of improvements, and the recommendations
ABSTRACT
Research in ultra-low temperature refrigeration applications has intensified in recent years after the appearance of vaccines in response to the COVID-19 pandemic. There are few current technologies for this low-temperature range, with reduced energy performance and high global warming potential refrigerants. This work analyses the introduction of the ejector in two-stage cascade cycles for ultra-low temperature refrigeration. The proposal includes the assessment of the behaviour of the ejector while implementing it in a single stage or simultaneously in both stages. The study is carried out with refrigerants R-290 in the high-temperature stage and R-170 in the low-temperature stage since these are natural refrigerants with very low global warming potential. The results show that the ejector is a component that causes improvements in the cycle when placed in the high-temperature and low-temperature stages. On the other hand, given the change in evaporation and condensation temperatures, the evaporation temperature is more critical regarding cycle energy performance. With the results obtained, a cascade cycle with an ejector in both stages is proposed, obtaining a 21% higher coefficient of performance than the standard cascade cycle. Also, the cycle with the ejector in both stages causes an improvement of 13.6 % compared to the previous generation's refrigerants (R-23 and R-507A) in the same cycle. The carbon footprint analysis shows that this cycle emits less than half of the equivalent CO2 than actual cycles for ultra-low temperatures, also with a new refrigerant like R-472A.
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.
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With the urgent demand for ultralow-temperature refrigerators worldwide, the operation reliability and stability of the refrigeration system becomes greatly crucial. In this study, a -80 oC ultralow-temperature cascade refrigeration system (CRS) is developed. From aspects of global warming potential (GWP) and ozone depletion potential (ODP), the environmentally friendly refrigerants R290 and R170 are utilized in the high-temperature cycle and low-temperature cycle of CRS. The experimental measurement is conducted in a Type-laboratory with a dry bulb temperature of 25.0 °C and a wet bulb temperature of 20.2 °C. The pull-down and stable operation performance of the CRS freezer are experimentally investigated. Both the inlet and outlet temperature and pressure of two compressors are monitored, and the operation characteristic of the CRS is analyzed. With some temperature test points arranged in the freezer, the temperature drop and temperature fluctuation variation of air are assessed. The operation power consumption of the CRS is also measured during the whole process. It shows that the −80 °C temperature can be generated and realized by the developed ultralow-temperature freezer. © 2022 Elsevier Ltd
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Because of the impact that COVID-19 is having on conferences, please check the conference's website for the most up-to-date information. DECEMBER HARDI Annual Conference, Dec, 3-6, Houston, Contact Heating Air-conditioning & Refrigeration Distributors International at 888-253-2128, hardimail@hardinet.org or https://hardinet.org/events Buildings XV Conference, Dec, 5-8, Clearwater Beach, Fla, Contact ASHRAE at 800-527-4723, meetings@ashrae.org or www.ashrae.org/buildingsxv International Conference on Building Ventilation and Air Conditioning, Dec. 9-10, New York, N.Y. Contact organizers at https://tinyurl.com/ICBVAC22 2023 JANUARY ABMA Annual Meeting, Jan. 13-16, Carlsbad, Calif. Contact the American Council for an Energy-Efficient Economy at 202-507-4000 or www.aceee.org/2023-hot-water-forum IIAR Natural Refrigeration Conference & Heavy Equipment Expo, March 12-15, Long Beach, Calif.
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In response to the COVID-19 pandemic, some vaccines have been developed requiring ultralow-temperature refrigeration, and the number of these freezers has been increased worldwide. Ultralow-temperature refrigeration operates with a significant temperature lift and, hence, a massive decrease in energy performance. Therefore, cascade cycles based on two vapor compression single-stage cycles are traditionally used for these temperatures. This paper proposes the combination of six different cycles (single-stage with and without internal heat exchanger, vapor injection, liquid injection, and parallel compression with and without economizer) in two-stage cascades to analyze the operational and energy performance in ultralow-temperature freezers. All this leads to 42 different configurations in which the intermediate cascade temperature is optimized to maximize the coefficient of performance. Ultra-low global warming potential natural refrigerants such as R-290 (propane) and R-170 (ethane) for the cascade high- and low-temperature stage have been considered. From the thermodynamic analysis, it can be concluded that liquid and vapor injection cascade configurations are the most energy-efficient. More specifically, those containing a vapor injection in the low-temperature stage (0.89 coefficient of performance, 40 % higher than traditional configurations). Then, using an internal heat exchanger for such low temperatures is unnecessary in terms of energy performance. The optimum intermediate cascade temperature varies significantly among cycles, from -37 °C to 2 °C, substantially impacting energy performance. Parallel compression configuration improves energy performance over single-stage cycles, but not as much as multi-stage (between 20 % and 30 % lower coefficient of performance). For most of low-temperature cycles, the high-temperature stage can be based on a single-stage cycle while keeping the maximum coefficient of performance.
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Vaccines, currently used for prophylactic purposes, prevent more than three million deaths every year from diseases like diphtheria, pertussis, tetanus, poliomyelitis, measles and influenza. The general six stages of the development of a new vaccine are: i) Exploratory stage;ii) Pre-clinical stage;iii) Clinical development;iv) Regulatory review and approval;v) Manufacturing;vi) Quality control. Clinical development is a three/four-phase process. During Phase I, small groups of people receive the trial vaccine. In Phase II, the clinical study is expanded. In Phase III, the vaccine is given to thousands of people and tested for efficacy and safety. Many vaccines undergo Phase IV formal, ongoing studies after the vaccine is approved and licensed. Phase IV studies, also referred to as postmarketing surveillance studies (PMS). These processes are very similar to drug developments. However, there are several differences compared to drug development, namely: i) unlike drugs, which are given to patients, vaccines are received by healthy individuals, thus the safety margin should be very high;ii) as vaccines have to be stored under refrigeration, there are always logistical challenges during clinical trials;iii) Adjuvants are incorporated into vaccine formulations to modulate and improve the immune response (antigen/adjuvant formulation are important aspects of clinical development);iv) The immune response primarily measured during early stages of vaccine development (Phase I/II) should evaluate: Humoral/ cell-mediated/ cross-reactive antibodies or immune complexes/ immune landscape. A challenge in responding to pandemic diseases is that vaccines may not exist for them. For newly emerging threats without licensed vaccines, such as SARS, MERS, Marburg virus, Nipah virus, SARS CoV-2 and the like, the time required to develop and produce a safe, effective vaccine is unknown and would depend on the nature of the threat and the state of current vaccine research for that threat. In almost all cases, several months would be needed to respond with the first doses of vaccines. Unfortunately, six month later than WHO declared the public health emergency of international concern (27/01/2020) there are five important questions, essential for vaccine development that remain open for scientists, namely: 1) Why do people respond so differently to infection? 2)Has the virus developed any worrying mutations? 3)How well will a vaccine work? 4)Can we develop immunity and if so, how long does it last? 5)What is the origin of the virus? Until a safe, effective vaccine was ready, other public health and medical measures (social distancing, quarantine, and aspecific medications) would need to be employed to try to limit disease spread.
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This paper addresses the energy efficiency issue in household appliances, which has led to the establishment of policies at a global level in favor of setting minimum energy performance standards (MEPS), which guarantee end users are able to select more efficient equipment. The countries of the United States, Brazil, Mexico, Chile, and the Community of the European Union were taken as references to review their policies and implementation strategies, in order to be compared with the Colombian panorama (at the market, technical and political levels). This allows the establishment of common aspects and differences related to the determination of energy consumption, adjusted volume, and formalization of efficiency ranges, and in the specific case of domestic refrigeration. Managing to distinguish the most relevant aspects for the successful adoption of these policies in Colombia. It is evident that the implementation of these guidelines has a positive impact on the market of the countries and communities of reference. Similarly, the MEPS are shown as a mechanism to regulate energy consumption in the residential sector.
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Lately, vaccination has been a widespread action to fight the pandemic, requiring the vaccines to be sent out to various places at various distances while staying at optimal quality, usually using cooler boxes. However, today's cooler boxes use ice instead of having a continuous refrigeration system. Thus, this paper presents a vaccine refrigeration box design and fabrication that uses a modified thermoelectric system as the refrigeration system, a conventional and solar charging system as its charging system, and a Bluetooth temperature sensor. From the result of the experiment, the box maintained full functionality for 210 minutes after being charged using a solar charging system. In terms of fully charging the power source, the conventional charging system takes 4 hours and 8 hours using the solar charging system. © 2022 IEEE.
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In the modern conditions of the coronavirus pandemic, the issue of transportation of immunobiological drugs is particularly actual, since control measures in this direction provide for supply of vaccines to different states, that naturally involves duration of transportation and compliance with certain established temperature regime at all stages of logistics chain, violation of which results in loss of pharmaceutical properties by drugs. The analysis demonstrated that currently transportation of immunobiological drugs is carried out within the framework of cold chain approach, which establishes mandatory compliance with temperature range of storage and transportation. Thus, the most important issue is control of compliance with temperature regime, which requires appropriate technical equipment at all levels of cold chain, ensuring fixation of detected violations.
Subject(s)
Refrigeration , Vaccines , Drug Storage , TransportationABSTRACT
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.
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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).
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.