The purpose of the article was to present information on heat recovery in ventilation systems and to highlight what has not been sufficiently researched in this regard. A lot of information can be ...found on methods and exchangers for heat recovery in centralized systems. Decentralized, façade systems for cyclical supply and exhaust air have not been sufficiently researched. It is known that these devices are sensitive to the influence of wind and temperature, hence heat recovery may be ineffective in their case. The literature describes the aspect of heat recovery depending on the location in climatic zones, depending on the number of degree days (HDD). Attention was also paid to the risk of freezing of heat recovery exchangers. The literature review also showed the lack of a universal method for assessing heat recovery exchangers and the method of their selection depending on the climate.
The recent pandemic due to SARS-CoV-2 has brought to light the need for strategies to mitigate contagion between human beings. Apart from hygiene measures and social distancing, air ventilation ...highly prevents airborne transmission within enclosed spaces. Among others, educational environments become critical in strategic planning to control the spread of pathogens and viruses amongst the population, mainly in cold conditions. In the event of a virus outbreak – such as COVID or influenza – many school classrooms still lack the means to guarantee secure and healthy environments.
The present review examines school contexts that implement air ventilation strategies to reduce the risk of contagion between students. The analysed articles present past experiences that use either natural or mechanical systems assessed through mathematical models, numerical models, or full-scale experiments. For naturally ventilated classrooms, the studies highlight the importance of the architectural design of educational spaces and propose strategies for aeration control such as CO2-based control and risk-infection control. When it comes to implementing mechanical ventilation in classrooms, different systems with different airflow patterns are assessed based on their ability to remove airborne pathogens considering parameters like the age of air and the generation of airflow streamlines. Moreover, studies report that programmed mechanical ventilation systems can reduce risk-infection during pandemic events.
In addition to providing a systematic picture of scientific studies in the field, the findings of this review can be a valuable reference for school administrators and policymakers to implement the best strategies in their classroom settings towards reducing infection risks.
•The integrated systems with radiant heating/cooling and ventilation are reviewed.•Thermal comfort and air quality of various integrated systems are discussed.•Design recommendations are given for ...selecting and designing the integrated systems with radiant heating/cooling and ventilation.
Radiant heating and cooling (RHC) systems typically work together with ventilation systems in order to take care of sensible loads, latent loads and pollutants. There are various combinations according to the location of radiant surfaces and air distribution principles. Even though there are extensive researches on radiant systems and ventilation systems individually, the design and performance of the integrated systems have not been discussed systematically. The objective of this paper is to summarize the integrated system configurations in the building environment from both scientific researches and practical applications, and to identify the system characteristics and suitable application area. The focus of this paper is on thermal comfort and indoor air quality and the critical design parameters that have impacts on these two aspects, such as location and amount of heat sources, contaminant source types, room geometry, and condensation risk. Design recommendation has been given at the end for selecting and designing the integrated systems, which is intended to be used by system designers, engineers, and architects.
What is bioturbation? Kristensen, Erik; Penha-Lopes, Gil; Delefosse, Matthieu ...
Marine ecology. Progress series (Halstenbek),
02/2012, Letnik:
446
Journal Article
Recenzirano
Odprti dostop
The term ‘bioturbation’ is frequently used to describe how living organisms affect the substratum in which they live. A closer look at the aquatic science literature reveals, however, an inconsistent ...usage of the term with increasing perplexity in recent years. Faunal disturbance has often been referred to as particle reworking, while water movement (if considered) is referred to as bioirrigation in many cases. For consistency, we therefore propose that, for contemporary aquatic scientific disciplines, faunal bioturbation in aquatic environments includesall transport processes carried out by animals that directly or indirectly affect sediment matrices. These processes include both particle reworking and burrow ventilation.With this definition, bioturbation acts as an ‘umbrella’ term that covers all transport processes and their physical effects on the substratum. Particle reworking occurs through burrow construction and maintenance, as well as ingestion and defecation, and causes biomixing of the substratum. Organic matter and microorganisms are thus displaced vertically and laterally within the sediment matrix. Particle reworking animals can be categorized as biodiffusors, upward conveyors, downward conveyors and regenerators depending on their behaviour, life style and feeding type. Burrow ventilation occurs when animals flush their open- or blind-ended burrows with overlying water for respiratory and feeding purposes, and it causes advective or diffusive bioirrigation ex change of solutes between the sediment pore water and the overlying water body. Many bioturbating species perform reworking and ventilation simultaneously. We also propose that the effects of bioturbation on other organisms and associated processes (e.g. microbial driven biogeochemical transformations) are considered within the conceptual framework of ecosystem engineering.
La Organización mundial de la Salud, ha señalado que 92% de la población mundial vive en lugares donde los niveles de calidad del aire se han reducido por debajo de los límites fijados, estimando que ...a nivel mundial aproximadamente 90% de las personas respiran aire contaminado y que la población de las ciudades pasa entre el 80 y el 90% de su tiempo en recintos cerrados, en un ambiente contaminado en mayor o menor grado; puesto que los niveles de contaminación pueden llegar a ser de 10 a 100 veces más elevados en espacios interiores respecto a los exteriores. La deficiencia en la calidad del aire interior puede dar origen a la manifestación de síntomas respiratorios relacionados como rinitis alérgica y asma, entre otras patologías y se estima que, a nivel global, millones de personas sufren de ambas enfermedades, reduciendo la calidad de vida de la población. Los ácaros constituyen los sensibilizantes respiratorios más extendidos en lugares de trabajo y están presentes en casi todos los hábitats, inclusive en el ambiente aéreo, movilizados por el viento o aerosoles, siendo la principal fuente de alérgenos interiores asociados a rinitis y asma. La presente revisión describe las características de los ácaros como fuente de contaminación ambiental y su posible utilidad como futuros bioindicadores de calidad del aire interior en sistemas de ventilación de edificios industriales con el fin de reducir la exposición y sensibilización de los trabajadores a sus alérgenos.
As the world continues to grapple with the reality of coronavirus disease, global research communities are racing to develop practical solutions to adjust to the new challenges. One such challenge is ...the control of indoor air quality in the COVID-19 era and beyond. Since COVID-19 became a global pandemic, the “super spread” of the virus has continued to amaze policymakers despite measures put in place by public health officials to sensitize the general public on the need for social distancing, personal hygiene, etc. In this work, we have reviewed the literature to demonstrate, by investigating the historical and present circumstances, that indoor spread of infectious diseases may be assisted by the conditions of the HVAC systems. While little consideration has been given to the possibility of indoor airborne transmission of the virus, the available reports have demonstrated that the virus, with average aerodynamic diameter up to 80–120 nm, is viable as aerosol in indoor atmosphere for more than 3 h, and its spread may be assisted by the HVAC systems. Having reviewed the vulnerability of the conventional ventilation systems, we recommend innovative air circulation concept supported by the use of UVGI in combination with nanoporous air filter to combat the spread of SARS-CoV-2 and other harmful microbes in enclosed spaces.
•Implementation of a model predictive control scheme for HVAC systems is presented.•The hardware/software solution is generalisable to most building management systems.•Cloud solutions can offer ...low-cost, scalable control in commercial buildings.•Economic MPC reduced energy usage by 1.7% compared to baseline control.•Building thermal performance strongly affects viability of MPC schemes.
Many businesses are looking for ways to improve the energy and carbon usage of their buildings, particularly through enhanced data collection and control schemes. In this context, this paper presents a case study of a food-retail building in the UK, detailing the design, installation and cost of a generalisable model predictive control (MPC) framework for its Heating, Ventilation and Air Conditioning (HVAC) system. The hardware/software solution to collect relevant data, as well as the formulation of the MPC scheme, is presented. By utilising cloud-based microservices, this approach can be applied to all modern building management systems with little upfront capital, and an ongoing monthly cost as low as $6.39/month. The MPC scheme calculates the optimal temperature setpoint required for each Air-Handling Unit (AHU) to minimise its overall cost or carbon usage, while ensuring thermal comfort of occupants. Its performance is then compared to the existing legacy controller using a simulation of the building’s thermal behaviour. When simulated across two months the MPC approach performed better and achieved the same thermal comfort for a lower overall cost. The economic optimisation resulted in an energy saving of 650 kWh, with an associated cost savings of $240 (an improvement of 1.7% compared to the baseline), while the carbon optimisation gave negligible CO2 savings due to the inability of the building to shift heating to low-carbon periods. Findings from this study indicate the potential for improving building performance via MPC strategies, however the level of impact will depend on specific building attributes.
The authors describe carbon system formulation and simulation characteristics of two new global coupled carbon–climate Earth System Models (ESM), ESM2M and ESM2G. These models demonstrate good ...climate fidelity as described in part I of this study while incorporating explicit and consistent carbon dynamics. The two models differ almost exclusively in the physical ocean component; ESM2M uses the Modular Ocean Model version 4.1 with vertical pressure layers, whereas ESM2G uses generalized ocean layer dynamics with a bulk mixed layer and interior isopycnal layers. On land, both ESMs include a revised land model to simulate competitive vegetation distributions and functioning, including carbon cycling among vegetation, soil, and atmosphere. In the ocean, both models include new biogeochemical algorithms including phytoplankton functional group dynamics with flexible stoichiometry. Preindustrial simulations are spun up to give stable, realistic carbon cycle means and variability. Significant differences in simulation characteristics of these two models are described. Because of differences in oceanic ventilation rates, ESM2M has a stronger biological carbon pump but weaker northward implied atmospheric CO₂ transport than ESM2G. The major advantages of ESM2G over ESM2M are improved representation of surface chlorophyll in the Atlantic and Indian Oceans and thermocline nutrients and oxygen in the North Pacific. Improved tree mortality parameters in ESM2G produced more realistic carbon accumulation in vegetation pools. The major advantages of ESM2M over ESM2G are reduced nutrient and oxygen biases in the southern and tropical oceans.
Indoor air pollution is one of the human health threat problems in the Gulf Cooperation Council (GCC) countries. In these countries, due to unfavorable meteorological conditions, such as elevated ...ambient temperature, high relative humidity, and natural events such as dust storms, people spend a substantial amount of their time in indoor environments. In addition, production of physical and biological aerosols from air conditioners, cooking activities, burning of Arabian incense, and overcrowding due to pilgrimage programs are common causes of low quality indoor air in this region. Thus, due to infiltration of outdoor sources as well as various indoor sources, people living in the GCC countries are highly exposed to indoor air pollutants. Inhalation of indoor air pollutants causes mortalities and morbidities attributed to cardiorespiratory, pulmonary, and lung cancer diseases. Hence, the aim of this review study is to provide a summary of the major findings of indoor air pollution studies in different microenvironments in six GCC countries. These include characterization of detected indoor air pollutants, exposure concentration levels, source identifications, sustainable building designs and ventilation systems, and the mitigation strategies. To do so, >130 relevant indoor air pollution studies across the GCC countries were critically reviewed. Particulate matters (PM10 and PM2.5), total volatile organic compounds (TVOCs), carbon dioxide (CO2), sulfur dioxide (SO2), nitrogen dioxide (NO2), and heavy metals were identified as the reported indoor air pollutants. Apart from them, indoor Radon and bioaerosols were studied only in specific GCC countries. Thus, future studies should also focus on the investigation of emerging indoor air pollutants, such as ultrafine and nanoparticles and their associated health effects. Furthermore, studies on the mitigation of indoor air pollution through the development of advanced air purification and ventilation systems could improve the indoor air quality (IAQ) in the GCC region.
•Infiltration and burning of Bakhour are the main sources of indoor air pollution.•Impacts of building ventilation systems on IAQ were reviewed.•There are limited health impact assessment studies attributed to IAQ in GCC.•IAQ mitigation studies are deficient in the GCC countries.
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