External Ambient Air Research Articles

High Temperature Ternary Chloride Molten Salt Pump

A ternary chloride (MgCl2-NaCl-KCl) molten salt pump has been developed to operate up to 720°C. The design is the result of a thermal, structural and material study of critical components. The vertical overhung pump incorporates first of a kind salt-wetted hydrodynamic bearings. Several bearing material pairings were tested which include: colmonoy grades, stellite grades, and a novel NiWC-based alloy (i.e. HybrimetTM NiWC3b) used as a High Velocity Oxygen Fuel (HVOF) coating. The coating withstands the corrosion effects of the molten salt, and is also used to protect a 316L stainless steel pump reservoir. The pump bowl assembly components are made of Inconel 625. A Nitrogen flushed carbon ring seal is used to keep salt vapors from interacting with external ambient air. Preliminary testing shows a promising pump design for use in the Concentrating Solar Power Gen 3 systems and sets the ground for further development of the HybrimetTM NiWC3b as a competitive alternative to available superalloys.

Effectiveness of novel artificial seabird nest modules for reducing ambient temperature transfer in a warming climate

AbstractArtificial habitat for cavity nesting birds can provide excellent opportunities for research and conservation efforts but may expose species to the negative impacts of warming ambient temperatures with climate change. Artificial nest boxes have been successfully used to monitor the breeding activity of the Cassin's auklet (Ptychoramphus aleuticus), a small burrow‐nesting seabird, on Southeast Farallon Island (SEFI) since 1971. Mean monthly ambient air temperatures on SEFI during the summer months have increased at an annual rate of roughly 0.03°C from 1971 to 2022, along with an increase in the number of extreme heat days and average maximum temperature, confirming a warming trend at this seabird colony. Given a projected increase in global temperature, we assessed the effectiveness of traditional wooden nest boxes vs. newer ceramic modules at buffering external ambient air temperatures in normal and extreme heat days across a gradient of microclimates on SEFI. Results from fitting linear mixed effects models indicated that, on average, internal temperatures of wooden and ceramic nests (of comparable size and shape) exhibited similar rates of deviation from ambient air temperature of approximately 0.15°C, even during extreme heat events. Ceramic modules did keep nest chambers cooler by approximately 1.2°C than wooden boxes during extreme events at the warmer, drier southern location of the island. Our results can help guide future efforts to design artificial nests that can effectively provide habitat for seabirds as ambient temperatures increase.

Energy use for tulip cultivation in a subtropical zone

Tulip growth involves a warm–cold–warm cycle and this work addresses the possibility of carrying out the final warm step of this cycle during the winter months of a subtropical country where electric power has a low price — Paraguay. This is a result of an abundance of renewable energy resources mainly due to the presence of two large hydroelectric power plants. This final cultivation step requires temperatures between 16 °C and 20 °C during a period of about five months. Historic climate data suggest that the city of Encarnación is suitable for tulip cultivation in Paraguay. However, because of temperature fluctuations, air conditioning may occasionally be necessary for cooling or heating. Using a transient model, we simulate the thermal conditions of the nursery to find the energy needed for air conditioning. Good thermal insulation and injection of external ambient air to control the nursery’s temperature whenever possible reduce the use of electrical energy.

Effects of a solar heating system on the microclimate of an agricultural greenhouse. Application on zucchini (Cucurbita pepo)

Agricultural production has made records thanks to new heating systems that are more economical and less costly, able to cope with the temperature drops of the microclimate of agricultural greenhouses while promoting the profitability of products in terms of quality, quantity and duration of growth. This work focuses on studying experimentally the effect of a solar heating system (SHS) on the microclimate of an agricultural greenhouse. This heating system is a combination of a copper tube placed between the double roof glazing and a sensible heat storage system. This installation is based on the daily thermal conversion of solar energy and its storage for night restitution. This experimentation also includes a second control greenhouse (GC) without any heating system that allows comparison at different stages of crops growth under the agricultural greenhouses. The results of this experiment during the cold season are reflected in a temperature gain on the experimental greenhouse (GE) by 4 °C compared to the GC and 6 °C compared to external ambient air. In addition, the relative humidity recorded for the GE was in the range [70%; 74%] against [78%; 96%] in the GC. However, the relative humidity of ambient air was between [90%; 99.9%]. For the efficiency of the SHS reached out 73%. As for the cultivation under the GE equipped with a SHS, the zucchini plants developed the fruit 16 days earlier than the zucchini plants grown under the GC.

Numerical investigation of photothermal performance of glazed window integrated with airflow channel and phase change material

ABSTRACT Double-glazed window coupled with phase change material (PCM) improves the thermal inertia and heat storage capacity, but the inefficient utilization of latent heat stored in PCM restricts the application in cold regions in winter. To surmount the deficiencies, a PCM ventilation window (PCMVW) with an airflow channel installed outside is proposed, in which the external ambient air enters the room after being heated by the PCM layer to realize the adequate utilization and recovery of the energy stored in the PCM. A two-dimensional model was established to investigate the photothermal performance of PCMVW in winter. Then, the effects of airflow rate and PCM melting point on the photothermal performance of PCMVW are analyzed. The results show that the thermal performance of the structure achieves significant enhancement with the airflow channel installed, which saves 521 kJ/d of energy, and the temperature fluctuation is 0.68 times that of the traditional PCMW. Meanwhile, the airflow improves the dynamic transmittance of the window at certain times. Remarkable enhancement of the thermal performance and optical performance of the PCMVW is achieved by adjusting the air mass flow rate and PCM melting point, which provides solutions for the application of PCMVW in cold regions.

Air pollution and health prevention: A document of reflection.

Ambient air quality, pollution and its implication on health is a topic of enormous importance that is normally dealt with by major specialists in their particular areas of interest. In general, it is not discussed from multidisciplinary approaches or with a language that can reach everyone. For this reason, the Health Sciences Foundation, from its prevention area, has formulated a series of questions to people with very varied competences in the area of ambient air quality in order to obtain a global panorama of the problem and its elements of measurement and control. The answers have been produced by specialists in each subject and have been subjected to a general discussion that has allowed conclusions to be reached on each point. The subject was divided into three main blocks: external ambient air, internal ambient air, mainly in the work-place, and hospital ambient air and the consequences of its poor control. Along with the definitions of each area and the indicators of good and bad quality, some necessary solutions have been pointed out. We have tried to know the current legislation on this problem and the competences of the different administrations on it. Despite its enormous importance, ambient air quality and health is not usually a topic of frequent presence in the general media and we have asked about the causes of this. Finally, the paper addresses a series of reflections from the perspective of ethics and very particularly in the light of the events that the present pandemic raises. This work aims to provide objective data and opinions that will enable non-specialists in the field to gain a better understanding of this worrying reality.

Developing an insulation box with automatic temperature control for PM2.5 measurements in cold regions

Low-cost PM2.5 sensors are now used worldwide to assess air pollution. However, their operation is generally challenging in severely cold regions like Siberia, Alaska, the Arctic, and Antarctica. We made an insulation box with automatic internal temperature control developed for a low-cost PM2.5 sensor to maintain a warm operational environment with four light-bulb heaters when the air temperature inside of the insulation box falls slightly below 5 °C under the current preset temperature setting. We confirmed the performance of the temperature controller with four light-bulb heaters in a −25 °C cold temperature room. In addition, we found that the insulation box must be attached to a small electric fan to forcibly ventilate the box to accurately reflect the external ambient air conditions into the insulating box. Our observations with the data from our low-cost PM2.5 sensor fitted with the insulation box were validated against the Sapporo National Ambient Air Monitoring Station (NAAMS) data in Sapporo, Japan, showing good correspondence with the hourly station-measured data. Then, we installed our PM2.5 measurement system on the roof of the International Arctic Research Center (IARC), University of Alaska Fairbanks, Alaska, USA, in June 2019. The sensor sufficiently captured two instances of significant increases in PM2.5 mass concentrations during the Alaskan wildfires in the summer of 2019. Our developed insulation box for low-cost PM2.5 sensors, called “the portable PM2.5 measurement system for cold regions”, will help assess air quality in many cold regions in future studies.

Mathematical Modeling of Rough Rice Dehydration with Dehumidified Air in a Fluidized Bed Drying System

Highlights <list list-type=bullet><list-item> Verma and Modified Henderson models were best fit for fluidized bed rice drying with and without dehumidification. </list-item><list-item> Coefficient of determination for Verma et al. and Modified Henderson and Pabis models ranged from 0.9760 to 0.9996. </list-item><list-item> The moisture diffusivity increased with the increase in air temperature and with air dehumidification. </list-item><list-item> Activation energy under dehumidification conditions was lower than under non-dehumidification conditions. </list-item></list> Abstract. There are numerous well-developed empirical models for rice drying, but none have been fitted to check their relevance with ambient air dehumidification of rough rice and fluidized bed drying systems. Consequently, the goals of this research were (1) to determine the best-fit model or models for rough rice dehydration in a fluidized bed dryer system using ambient air or dehumidified air, and (2) to assess the effective moisture diffusivity and the activation energy of rough rice drying. Nine mathematical models were selected and fitted to the experimental data of rough rice fluidized bed drying at 40°C, 45°C, and 50°C using ambient air or partially dehumidified air. Ambient air dehumidification was introduced as a novel technology to partially dehumidify humid ambient air to maintain the drying process running mainly in damp conditions. Nonlinear regression analysis instituted that Verma et al. model and Modified Henderson and Pabis model were the two best models for describing fluidized bed drying characteristics of rough rice with and without dehumidification conditions. The goodness of fit was determined using coefficient of determination (R2), root mean square error (RMSE), and reduced chi-square (χ2), with values for the two best models ranging from 0.9760 to 0.9996, 0.0000 to 0.0022, and 0.0040 to 0.0180, respectively. Verma et al. model was the best fit of 66.67% of the studied cases. Modified Henderson and Pabis model was the best fit for 33.33% of the studied cases. The results revealed that the evaluated adequate moisture diffusivity increased with the drying air temperature and ambient air dehumidification. It varied from 2.19x10-9 to 2.44x10-9 m2/s with R2 higher than 0.9556. The activation energy under the dehumidification conditions (13.720 kJ/mol) was lower than the activation energy under the non-dehumidification conditions (19.756 kJ/mol). Pre-exponential factor values were 4.908 x 10-7 and 4.940 x 10-6 with and without dehumidification, respectively. Future grain drying research can utilize the modeling results about the fluidization drying technique and external ambient air dehumidification.

Onsite production of medical air: is purity a problem?

Introduction: Medical air (MA) is widely used in hospitals, often manufactured onsite by compressing external ambient air and supplied through a local network piping system. Onsite production gives rise to a risk of impurities that are governed by the same pharmacopoeia purity standards applicable to commercially produced MA. The question to be addressed in this paper is how to assess if a lack of purity poses a medical problem? Methods: The MA produced onsite at a major Canadian hospital was monitored for carbon dioxide (CO2) and other impurity gases at high frequency (one per minute) over a two-month period. Results: The average CO2 concentration was 255 ppm. The United States Pharmacopeia (USP) threshold of 500 ppm was exceeded during 1% of the total study period, and the average while exceeding the threshold was 526 ppm. The maximum concentration was 634 ppm. Discussion and conclusion: To our knowledge, there is only one study that evaluated the effects suffered by respiratory patients of elevated nitric oxide in MA; thus, it is not clear what are the medical bases for the thresholds stated in the USP. To perform a Quality Risk Assessment, the threshold and the time above threshold should be considered in determining the frequency of sampling and analysis, and operating methods required to ensure the quality of MA entering the pipeline meets the clinical, regulatory, and patient safety standards. In conclusion, because the USP does not provide impurity thresholds for specific patients nor time above thresholds, there is a need for the medical community to determine these quantities before it can be known if the purity of MA is a problem.

Onsite production of medical air: is purity a problem?

IntroductionMedical air (MA) is widely used in hospitals, often manufactured onsite by compressing external ambient air and supplied through a local network piping system. Onsite production gives rise to a risk of impurities that are governed by the same pharmacopoeia purity standards applicable to commercially produced MA. The question to be addressed in this paper is how to assess if a lack of purity poses a medical problem?MethodsThe MA produced onsite at a major Canadian hospital was monitored for carbon dioxide (CO2) and other impurity gases at high frequency (one per minute) over a two-month period.ResultsThe average CO2 concentration was 255 ppm. The United States Pharmacopeia (USP) threshold of 500 ppm was exceeded during 1% of the total study period, and the average while exceeding the threshold was 526 ppm. The maximum concentration was 634 ppm.Discussion and conclusionTo our knowledge, there is only one study that evaluated the effects suffered by respiratory patients of elevated nitric oxide in MA; thus, it is not clear what are the medical bases for the thresholds stated in the USP. To perform a Quality Risk Assessment, the threshold and the time above threshold should be considered in determining the frequency of sampling and analysis, and operating methods required to ensure the quality of MA entering the pipeline meets the clinical, regulatory, and patient safety standards. In conclusion, because the USP does not provide impurity thresholds for specific patients nor time above thresholds, there is a need for the medical community to determine these quantities before it can be known if the purity of MA is a problem.

Modelagem computacional aplicada ao estudo de um trocador de calor solo-ar com diferentes configurações geométricas

&lt;div&gt;&lt;p class="SPabstract"&gt;Com o intuito de diminuir o consumo de energia elétrica utilizam-se fontes de energias renováveis, desta forma, é possível aproveitar a radiação solar que atinge a superfície do solo como energia térmica através do uso de trocadores de calor solo-ar (TCSA) em ambientes construídos. Os TCSA são dispositivos onde o ar ambiente externo é resfriado ou aquecido ao circular dentro de dutos horizontalmente enterrados nas camadas superficiais do solo. Esta troca acontece pela inércia térmica do solo, de modo que no verão o ar que circula pelo TCSA sai com temperatura mais baixa que o ar externo; enquanto no inverno o ar externo ganha calor ao circular pelo TCSA, saindo com temperatura mais elevada. Sendo assim, este trabalho tem como objetivo simular numericamente o comportamento térmico e fluidodinâmico de um TCSA, mantendo constante sua área de troca térmica, permitindo a avaliação da influência da configuração geométrica da instalação no potencial térmico do TCSA. Através de um modelo computacional tridimensional, verificado e validado, desenvolvido no software FLUENT (baseado no Método dos Volumes Finitos), obteve-se os resultados numéricos que indicaram uma pequena diminuição no potencial térmico do TCSA em relação à considerável redução da porção de solo necessária para sua instalação, evidenciando a importância e a aplicabilidade da modelagem computacional neste tipo de problema de engenharia.&lt;/p&gt;&lt;/div&gt;

An intrinsically safe facility for forefront research and training on nuclear technologies — General description of the system

In the framework of research on generation-IV reactors, it is very important to have infrastructures specifically dedicated to the study of fundamental parameters in dynamics and kinetics of future fast-neutron reactors. Among various options pursued by international groups, Italy focused on lead-cooled reactors, which guarantee minimal neutron slowdown and capture and efficient cooling. In this paper it is described the design of a the low-power prototype generator, LEADS, that could be used within research facilities such as the National Laboratory of Legnaro of the INFN. The LEADS has a high safety standard in order to be used as a training facility, but it has also a good flexibility so as to allow a wide range of measurements and experiments. A high safety standard is achieved by limiting the reactor power to less than few hundred kW and the neutron multiplication factor keff to less than 0.95 (a limiting value for spent fuel pool), by using a pure-uranium fuel (no plutonium) and by using solid lead as a diffuser. The proposed core is therefore intrinsically subcritical and has to be driven by an external neutron source generated by a proton beam impinging in a target. Preliminary simulations, performed with the MCNPX code indicated, for a 0.75mA continuous proton beam current at 70MeV proton energy, a reactor power of about 190kW when using a beryllium converter. The enriched-uranium fuel elements are immersed in a solid-lead matrix and contained within a steel vessel. The system is cooled by helium gas, which is transparent to neutrons and does not undergo activation. The gas is pumped by a compressor through specific holes at the entrance of the active volume with a temperature which varies according to the operating conditions and a pressure of about 1.1MPa. The hot gas coming out of the vessel is cooled by an external helium-water heat exchanger. The beryllium converter is cooled by its dedicated helium gas cooling system. After shutdown, the decay is completely dissipated by conduction through the lead reflector and steel vessel, and then evacuated by irradiation from the vessel surface to the external ambient air.

A new computational modeling to predict the behavior of Earth-Air Heat Exchangers

The use of renewable energy sources to improve the thermal conditions of built environments and hence decreasing the consumption of conventional energy is an important aspect to design a sustainable building. Within this context, it is possible to harness the solar energy that reaches the Earth's surface and is stored by the soil as thermal energy. To do so, the Earth-Air Heat Exchanger (EAHE) device can be employed, consisting of a buried duct through which the external ambient air is insufflated. The flowing air exchanges heat with surround soil, and leaves the device with a milder temperature compared to its input temperature. The main goal of this work was to present a new computational modeling to predict the thermal behavior of EAHE. This new numerical model has the advantage of needing a lower computational effort, allowing the study about the influence of operational and constructive parameters, as well as, the application of geometric optimization methods in EAHE. A case study was developed where influence of the installation depth in the thermal potential of an EAHE was investigated. The results are in agreement with those found in literature; however they were obtained with a reduction in processing time of almost 45%.

Heat transfer and energy consumption in the freezing of guava pulp in large containers

Abstract The heat transfer process, including the convective transfer coefficients (h), freezing times and power consumption, was evaluated during the air blast freezing of 600 kg of guava pulp. Three packaging configurations were tested: plastic boxes (34 L), buckets (20 L) and metal drums (200 L). The air velocity inside the freezer tunnel was measured at several points, and sensors were installed to monitor the temperature. The heat infiltration from external ambient air was also verified. Correlations of the Nusselt number versus the Reynolds and Prandtl numbers were used to estimate the convective heat transfer coefficients according to the configuration of the systems. The coefficients were applied to freezing-time prediction models. The h values and consequent freezing time prediction were found to be more precise for the packaging in the bucket configuration. For the drum configuration, the correlation that considered the turbulence factor effects was found to be satisfactory. In the box configuration, the correlation produced good results only for the boxes located in the central area of the stack. The results indicate that the correlations may be applicable to the analysis and the differences explained by airflow and the difficulty of maintaining constant heat flow on the surfaces.

Thermal chimney equipped audio speaker cabinet

A thermally conductive chimney tube extends through a loudspeaker cabinet that encloses a volume of air heated by a speaker driver. The open ends of the chimney are outside the cabinet. A column of air within the chimney is in contact with the external ambient air, but sealed off from the enclosed volume of air. As the speaker driver heats the enclosed volume of air, the material of the chimney transfers the heat to the column of air, which rises and carries the heat away into the external ambient air, cooling the inside of the loudspeaker cabinet and thus cooling the speaker driver.

Are lichens active under snow in continental Antarctica?

Photosynthetic activity, detected as chlorophyll a fluorescence, was measured for lichens under undisturbed snow in continental Antarctica using fibre optics. The fibre optics had been buried by winter snowfall after being put in place the previous year under snow-free conditions. The fibre optics were fixed in place using specially designed holding devices so that the fibre ends were in close proximity to selected lichens. Several temperature and PPFD (photosynthetic photon flux density) sensors were also installed in or close to the lichens. By attaching a chlorophyll a fluorometer to the previously placed fibre optics it proved possible to measure in vivo potential photosynthetic activity of continental Antarctic lichens under undisturbed snow. The snow cover proved to be a very good insulator for the mosses and lichens but, in contrast to the situation reported for the maritime Antarctic, it retained the severe cold of the winter and prevented early warming. Therefore, the lichens and mosses under snow were kept inactive at subzero temperatures for a prolonged time, even though the external ambient air temperatures would have allowed metabolic activity. The results suggest that the major activity period of the lichens was at the time of final disappearance of the snow and lasted about 10-14 days. The activation of lichens under snow by high air humidity appeared to be very variable and species specific. Xanthoria mawsonii was activated at temperatures below -10 degrees C through absorption of water from high air humidity. Physcia dubia showed some activation at temperatures around -5 degrees C but only became fully activated at thallus temperatures of 0 degrees C through liquid water. Candelariella flava stayed inactive until thallus temperatures close to zero indicated that liquid water had become available. Although the snow cover represented the major water supply for the lichens, lichens only became active for a brief time at or close to the time the snow disappeared. The snow did not provide a protected environment, as reported for alpine habitats, but appeared to limit lichen activity. This provides at least one explanation for the observed negative effect of extended snow cover on lichen growth.

Stochastic modelling of temperatures affecting the in situ performance of a solar-assisted heat pump: The univariate approach

Univariate stochastic modelling, using Box-Jenkins methods, is carried out for three air temperatures which can influence the performance of a solar-assisted heat pump system. In this system, external ambient air (the low grade source) is pre-heated by the conventional tiled roof of an occupied domestic residence. The air then crosses the evaporator of an electrically driven split heat pump which is situated in the roof space. Autocorrelation coefficients are presented for time series of the following dry-bulb temperatures: the external air, the residence internal (lounge) air, and the air in the roofspace after pre-heating but prior to crossing the heat pump evaporator. Hourly data relating to a two-week period in the heating season was utilised, providing a 336-h dataset. Univariate models fitted to the first 300 observations were validated by forecasting ahead for the remaining 36 h in steps of 1 h. Comparison of forecasted and measured values showed good agreement, except for a 4-h period in which the intensity of solar radiation exceeded that which prevailed during the modelled period. It is concluded that the Box-Jenkins approach can be used to develop univariate mathematical models which adequately describe building and climate thermal behaviour, and that the importance of solar radiation in this respect should not be overlooked.