Spreading of SARS-CoV-2 via Heating, Ventilation, and Air Conditioning Systems—An Overview of Energy Perspective and Potential Solutions

2020 ◽  
Vol 143 (8) ◽  
Author(s):  
Ahmad K. Sleiti ◽  
Samer F. Ahmed ◽  
Saud A. Ghani
Keyword(s):  
Air Conditioning ◽  
High Performance ◽  
Public Perception ◽  
High Efficiency ◽  
Uv Light ◽  
Experimental Studies ◽  
High Energy ◽  
Penalty Cost ◽  
Energy Penalty ◽  
Air Conditioning Systems

Abstract The role of heating, ventilation, and air conditioning systems (HVAC) in spreading SARS-CoV-2 is a complex topic and has not been studied thoroughly. There are some existing strategies and technologies for health and high performance buildings; however, applications to other types of buildings come at large energy penalty: cost; design, regulations and standards changes, and varied public perception. In the present work, different factors and strategies are reviewed and discussed and suggested mitigations and solutions are provided including the required air flowrates with the presence of infectors with and without mask and disinfection techniques including ultraviolet (UV) light. Experimental and numerical research in open literature suggests that the airborne transmission of SARS-CoV-2 is sufficiently likely. However, in situ detailed experimental studies are still needed to understand the different scenarios of the virus spread. Displacement ventilation, underfloor air distribution, chilled beams, radiant ceiling panels, and laminar flow systems have varied effectiveness. High-efficiency particulate arrestance (HEPA) filters and UV light can clean viruses but at high energy cost. Suggested solutions to reduce the infection probability include recommended levels of ventilation and a combination of virus sampling technologies including cyclones, liquid impinger, filters, electrostatic precipitators, and water-based condensation.

A Study on the Performance of Drinking Fountain Using CO2 Heat Pump under Different System Pressures

2010 ◽  
Vol 44-47 ◽  
pp. 2433-2437 ◽  
Author(s):  
Yu Lieh Wu ◽  
Yu Dai Shiue ◽  
Kuo Hsiang Chien ◽  
Chiu Li Wang
Keyword(s):  
Carbon Dioxide ◽  
Heat Source ◽  
Heat Pump ◽  
Air Conditioning ◽  
High Performance ◽  
High Efficiency ◽  
Electric Heating ◽  
Alternative Refrigerant ◽  
Saving Effect ◽  
Natural Refrigerant

To avoid continuous damage of ozone layer and deterioration of global warming, many countries have devoted to the development and application of natural refrigerant. Although CO2, an alternative refrigerant in the area of air conditioning is not the best all-temperature refrigerant, it has the lowest operating risk as compared to hydrocarbon (HCs) and ammonia.Traditional drinking fountain provides heat source through secondary energy source - electric heating; however, the heating effect is limited. Since heat pump has a high performance, this study used a carbon dioxide heat pump, which has energy-saving effect and high efficiency, to provide heat source to drinking fountains. It further assembled the drinking fountain system with carbon dioxide heat pump and analyzed its performance.

Design for Sustainable Data Center Energy Use and Eco-Footprint

2010 ◽  
Author(s):  
Milton Meckler
Keyword(s):  
Data Center ◽  
Air Conditioning ◽  
Fossil Fuels ◽  
Energy Use ◽  
Data Centers ◽  
Ghg Emissions ◽  
High Energy ◽  
Operational Reliability ◽  
Energy Utilization ◽  
Air Conditioning Systems

What does remain a growing concern for many users of Data Centers is their continuing availability following the explosive growth of internet services in recent years, The recent maximizing of Data Center IT virtualization investments has resulted in improving the consolidation of prior (under utilized) server and cabling resources resulting in higher overall facility utilization and IT capacity. It has also resulted in excessive levels of equipment heat release, e.g. high energy (i.e. blade type) servers and telecommunication equipment, that challenge central and distributed air conditioning systems delivering air via raised floor or overhead to rack mounted servers arranged in alternate facing cold and hot isles (in some cases reaching 30 kW/rack or 300 W/ft2) and returning via end of isle or separated room CRAC units, which are often found to fight each other, contributing to excessive energy use. Under those circumstances, hybrid, indirect liquid cooling facilities are often required to augment above referenced air conditioning systems in order to prevent overheating and degradation of mission critical IT equipment to maintain rack mounted subject rack mounted server equipment to continue to operate available within ASHRAE TC 9.9 prescribed task psychometric limits and IT manufacturers specifications, beyond which their operational reliability cannot be assured. Recent interest in new web-based software and secure cloud computing is expected to further accelerate the growth of Data Centers which according to a recent study, the estimated number of U.S. Data Centers in 2006 consumed approximately 61 billion kWh of electricity. Computer servers and supporting power infrastructure for the Internet are estimated to represent 1.5% of all electricity generated which along with aggregated IT and communications, including PC’s in current use have also been estimated to emit 2% of global carbon emissions. Therefore the projected eco-footprint of Data Centers into the future has now become a matter of growing concern. Accordingly our paper will focus on how best to improve the energy utilization of fossil fuels that are used to power Data Centers, the energy efficiency of related auxiliary cooling and power infrastructures, so as to reduce their eco-footprint and GHG emissions to sustainable levels as soon as possible. To this end, we plan to demonstrate significant comparative savings in annual energy use and reduction in associated annual GHG emissions by employing a on-site cogeneration system (in lieu of current reliance on remote electric power generation systems), introducing use of energy efficient outside air (OSA) desiccant assisted pre-conditioners to maintain either Class1, Class 2 and NEBS indoor air dew-points, as needed, when operated with modified existing (sensible only cooling and distributed air conditioning and chiller systems) thereby eliminating need for CRAC integral unit humidity controls while achieving a estimated 60 to 80% (virtualized) reduction in the number servers within a existing (hypothetical post-consolidation) 3.5 MW demand Data Center located in southeastern (and/or southern) U.S., coastal Puerto Rico, or Brazil characterized by three (3) representative microclimates ranging from moderate to high seasonal outside air (OSA) coincident design humidity and temperature.

scholarly journals Experimental studies of energy efficiency of heat pump equipment for hot water supply and air conditioning systems in apartment buildings

2021 ◽  
Vol 937 (4) ◽  
pp. 042037
Author(s):  
Gregory Vasilyev ◽  
Victor Gornov ◽  
Marina Kolesova ◽  
Vitaliy Leskov ◽  
Victoria Silaeva ◽  
...  
Keyword(s):  
Water Supply ◽  
Heat Pump ◽  
Air Conditioning ◽  
Energy Savings ◽  
Experimental Studies ◽  
Hot Water ◽  
Apartment Buildings ◽  
Pump Equipment ◽  
Hot Water Supply ◽  
Air Conditioning Systems

Abstract Experimental studies of this article are aimed at solving the problem of reforming the housing and communal services of Russia through rational integration of non-traditional energy sources and secondary energy resources into the energy balance of buildings and structures. An important component of the work was the creation and development of industrial production of reliable competitive heat pump systems of a new generation, cogenerating heat energy and cold in an autonomous mode and providing energy savings of at least 50% due to the combined use of low-potential thermal energy of the soil, the atmospheric air and the exhaust air of ventilation systems for hot water supply and air conditioning systems of apartment buildings.

scholarly journals Recent Advances in Synthesis and Properties of Nitrated-Pyrazoles Based Energetic Compounds

Molecules ◽  
2020 ◽  
Vol 25 (15) ◽  
pp. 3475 ◽  
Author(s):  
Shijie Zhang ◽  
Zhenguo Gao ◽  
Di Lan ◽  
Qian Jia ◽  
Ning Liu ◽  
...  
Keyword(s):  
Energetic Materials ◽  
High Performance ◽  
High Efficiency ◽  
Low Cost ◽  
Rapid Development ◽  
Development Trend ◽  
High Heat ◽  
High Energy ◽  
Heat Of Formation ◽  
Energetic Compounds

Nitrated-pyrazole-based energetic compounds have attracted wide publicity in the field of energetic materials (EMs) due to their high heat of formation, high density, tailored thermal stability, and detonation performance. Many nitrated-pyrazole-based energetic compounds have been developed to meet the increasing demands of high power, low sensitivity, and eco-friendly environment, and they have good applications in explosives, propellants, and pyrotechnics. Continuous and growing efforts have been committed to promote the rapid development of nitrated-pyrazole-based EMs in the last decade, especially through large amounts of Chinese research. Some of the ultimate aims of nitrated-pyrazole-based materials are to develop potential candidates of castable explosives, explore novel insensitive high energy materials, search for low cost synthesis strategies, high efficiency, and green environmental protection, and further widen the applications of EMs. This review article aims to present the recent processes in the synthesis and physical and explosive performances of the nitrated-pyrazole-based Ems, including monopyrazoles with nitro, bispyrazoles with nitro, nitropyrazolo[4,3-c]pyrazoles, and their derivatives, and to comb the development trend of these compounds. This review intends to prompt fresh concepts for designing prominent high-performance nitropyrazole-based EMs.

Numerical Analysis and Parametric Study of a Thermoelectric-Based Radiant Ceiling Panel for Building Cooling Applications

2020 ◽  
Author(s):  
Mohadeseh Seyednezhad ◽  
Hamidreza Najafi
Keyword(s):  
Solid State ◽  
Parametric Study ◽  
Air Conditioning ◽  
High Energy ◽  
Radiant Cooling ◽  
Ceiling Temperature ◽  
Te Modules ◽  
Building Cooling ◽  
Air Conditioning Systems ◽  
Solid State Cooling

Abstract Buildings are known as one of the foremost energy consumer sectors in the world with a share of nearly 40% and hence the design and development of clean and energy efficient building energy systems is an important step towards a sustainable future. Cooling and air conditioning systems, as an essential component for occupants’ comfort, are among the largest energy end-users in buildings. Additionally, most air conditioning systems rely on using refrigerants that are harmful for the environment with considerable potential for ozone depletion and global warming. Solid-state cooling technologies that do not require refrigerant are therefore of interest to eliminate these environmental concerns. Thermoelectric (TE) modules, as a solid-state cooling technology, when supplied by DC electricity, produce a temperature gradient through the Peltier effect that can be used for cooling purposes. Due to the attractive characteristics that TE technology offers, mainly high controllability, lack of refrigerant and large moving parts, quiet operation, promising efficiency and requiring minimum maintenance required, TE-based systems are becoming an emerging technology for building cooling applications. TE-based cooling technologies have been developed and tested through integrated and non-integrated systems in the building envelope. In the present paper, the design of a TE-based radiant cooling ceiling panel is investigated through numerical modeling and parametric study. The system can be incorporated in the ceiling and will maintain a reduced ceiling temperature to provide cooling through radiation and convection for the occupants. COMSOL Multiphysics is used for modeling and simulation purposes and the performance of the system under various configurations is assessed. The effect of number and placement of TE modules for a given size of ceiling panel are investigated using several simulations in COMSOL to achieve a desired and uniform surface temperature in the minimum amount of time. The impact of incorporating various amounts of phase change material (PCM) in the ceiling panel is also assessed. PCM allows the ceiling panel to maintain the desired temperature for an extended amount of time, but it also increases the time that it takes for the panel to reach the desired temperature. Transient thermal simulations are performed for both start up and shut down scenarios and the amount of time that it takes for the ceiling temperature to cool down to the desired level (on-mode) or heat up (off-mode) to the temperature at which it has to turn back on again are calculated for various system configurations. The results from this study can be used for optimal design of TE-based radiant cooling ceiling panels to achieve high energy efficiency and low operating cost while maintaining occupants’ comfort in the buildings.

Thermodynamic Analysis of a Liquid Desiccant Cooling System Under Mediterranean Climatic Conditions

2012 ◽  
Author(s):  
I. P. Koronaki ◽  
R. I. Christodoulaki ◽  
V. D. Papaefthimiou ◽  
E. D. Rogdakis
Keyword(s):  
Air Conditioning ◽  
Cooling System ◽  
Peak Load ◽  
Climatic Conditions ◽  
Liquid Desiccant ◽  
Step Method ◽  
Mass Rate ◽  
Energy Penalty ◽  
Condensed Water ◽  
Air Conditioning Systems

Liquid desiccant air conditioning systems have recently been attracting attention, owing to their merits in handling the latent heat. Desiccant systems avoid not only the energy penalty caused by overcooling and reheating, but also the bacteria generation caused by condensed water. They can also significantly reduce the electricity peak load caused by conventional compression type air conditioning systems, especially in hot and humid regions. Desiccant systems are thus more energy efficient, healthy and environmentally friendly than conventional mechanical cooling. This paper presents the results from a theoretical study of a liquid desiccant system that provides air conditioning to a typical office building. A coupled heat and mass transfer analytical model was developed, based on the Runge-Kutta fixed step method, to predict the performance of the device under Mediterranean conditions. A parametric analysis was implemented to investigate the effects of ambient temperature and humidity ratio on the dehumidification mass rate, the load coverage and the thermal COP of the system. Simulation results showed that under hot and humid weather, the COP reaches its maximum value, 1.075. However, as the weather becomes more humid, the latent load coverage of the system is decreased and as it becomes hotter, the sensible load coverage of the system is decreased. The maximum latent load coverage, 91.8%, happened at 40°C, 0.011kgw/kgdα. Results can be useful for researchers and engineers.

scholarly journals Effects of air-conditioning systems in the public areas of hospitals: A scoping review

2021 ◽  
Vol 149 ◽  
Author(s):  
Han Ting Wu ◽  
Qiu Shuang Li ◽  
Rong Chen Dai ◽  
Shan Liu ◽  
Li Wu ◽  
...  
Keyword(s):  
Scoping Review ◽  
Air Conditioning ◽  
Microbial Contamination ◽  
High Efficiency ◽  
Cross Sectional ◽  
The Public ◽  
Public Areas ◽  
Almost All ◽  
Air Conditioning Systems ◽  
The Impact

Abstract Almost all hospitals are equipped with air-conditioning systems to provide a comfortable environment for patients and staff. However, the accumulation of dust and moisture within these systems increases the risk of transmission of microbes and have on occasion been associated with outbreaks of infection. Nevertheless, the impact of air-conditioning on the transmission of microorganisms leading to infection remains largely uncertain. We conducted a scoping review to screen systematically the evidence for such an association in the face of the coronavirus disease 2019 epidemic. PubMed, Embase and Web of Science databases were explored for relevant studies addressing microbial contamination of the air, their transmission and association with infectious diseases. The review process yielded 21 publications, 17 of which were cross-sectional studies, three were cohort studies and one case−control study. Our analysis showed that, compared with naturally ventilated areas, microbial loads were significantly lower in air-conditioned areas, but the incidence of infections increased if not properly managed. The use of high-efficiency particulate air (HEPA) filtration not only decreased transmission of airborne bioaerosols and various microorganisms, but also reduced the risk of infections. By contrast, contaminated air-conditioning systems in hospital rooms were associated with a higher risk of patient infection. Cleaning and maintenance of such systems to recommended standards should be performed regularly and where appropriate, the installation of HEPA filters can effectively mitigate microbial contamination in the public areas of hospitals.

scholarly journals Chelate Coordination Compounds as a New Class of High-Energy Materials: The Case of Nitro-Bis(Acetylacetonato) Complexes

Molecules ◽  
2021 ◽  
Vol 26 (18) ◽  
pp. 5438
Author(s):  
Danijela S. Kretić ◽  
Ivana S. Veljković ◽  
Aleksandra B. Đunović ◽  
Dušan Ž. Veljković
Keyword(s):  
Electrostatic Potential ◽  
High Performance ◽  
Density Functional ◽  
High Efficiency ◽  
High Energy ◽  
Molecular Surface ◽  
Energy Materials ◽  
Dissociation Energies ◽  
Central Regions ◽  
And Performance

The existence of areas of strongly positive electrostatic potential in the central regions of the molecular surface of high-energy molecules is a strong indicator that these compounds are very sensitive towards detonation. Development of high-energy compounds with reduced sensitivity towards detonation and high efficiency is hard to achieve since the energetic molecules with high performance are usually very sensitive. Here we used Density Functional Theory (DFT) calculations to study a series of bis(acetylacetonato) and nitro-bis(acetylacetonato) complexes and to elucidate their potential application as energy compounds with moderate sensitivities. We calculated electrostatic potential maps for these molecules and analyzed values of positive potential in the central portions of molecular surfaces in the context of their sensitivity towards detonation. Results of the analysis of the electrostatic potential demonstrated that nitro-bis(acetylacetonato) complexes of Cu and Zn have similar values of electrostatic potential in the central regions (25.25 and 25.06 kcal/mol, respectively) as conventional explosives like TNT (23.76 kcal/mol). Results of analysis of electrostatic potentials and bond dissociation energies for the C-NO2 bond indicate that nitro-bis(acetylacetonato) complexes could be used as potential energetic compounds with satisfactory sensitivity and performance.

Aromatic Polyurea for High Temperature High Energy Density Capacitors

2008 ◽  
Vol 1134 ◽  
Author(s):  
Yong Wang ◽  
Xin Zhou ◽  
Minren Lin ◽  
Sheng-Guo David Lu ◽  
Jun-Hong Lin ◽  
...  
Keyword(s):  
High Temperature ◽  
Energy Density ◽  
High Performance ◽  
High Efficiency ◽  
Breakdown Strength ◽  
Dielectric Material ◽  
Weibull Model ◽  
High Energy ◽  
High Energy Density ◽  
Low Dissipation

AbstractWe investigate aromatic polyureas which can be fabricated in the form of thin films through CVD. It was found that the polymer possesses a flat dielectric response (k∼ 4.2 and loss <1%)) to more than 200°C. The frequency-independent dielectric properties in the investigated frequency range(1kHz∼1MHz), low conductance, low dissipation factor (∼0.005), high breakdown strength (>800MV/m), high energy density (>12J/cm3) and high efficiency suggest this polymer can be a good candidate material for high temperature energy storage capacitors. Breakdown strength was analyzed with Weibull model over a broad temperature range (25°C ∼180°C). Experimental results indicate that aromatic polyurea is more like a nonpolar linear dielectric material because of its highly cross-linked structures. The experiment results further show that this polymer maintains its high performance even at high temperatures.

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