High Air Humidity Research Articles

Lavender and Black Pine Waste as Additives Enhancing Selected Mechanical and Hygrothermal Properties of Cement Mortars

The paper presents the mechanical and hygrothermal properties of cement mortars containing bio-powders made from lavender waste and black pine wood. The wastes were mechanically ground with a hammer mill to a fraction not exceeding 0.5 mm and then dried in air-dry conditions. The influence of bio-additives in amounts of 1.5% and 2.5% of the overall mortar volume was tested. The aim of the paper was to determine the impact of bio-additives on the mechanical and hygrothermal properties of the tested cement mortars. This publication included tests of compressive and flexural strength, elastic modulus, water absorption, absorption due to capillary rise, sorption and desorption properties, thermal properties, microstructural tests using mercury intrusion porosimetry and SEM, and EDS. The main conclusions of the research indicate that mortars with both 1.5% and 2.5% bio-powders are characterized by strong bactericidal properties, lower sorption properties at high air humidity, lower thermal conductivity, reduced compressive strength by 22–27%, no significant effect on the flexural strength, and significant reduction in capillary action of mortars both with short-term and long-term water exposure.

Cooperative lattice theory for CO2 adsorption in diamine-appended metal-organic framework at humid direct air capture conditions.

The effect of humidity on the cooperative adsorption of CO2 from the air on amine-appended metal-organic frameworks is studied both experimentally and theoretically. Breakthrough experiments show that, at low relative humidities, there is an anomalous induction effect, where the kinetics at short times are slower than kinetics at long times. The induction effect gradually vanishes as relative humidity is increased, corresponding to an increase in CO2 adsorption rate. A new theory is proposed based on the lattice kinetic theory (LKT), which explains these experimental results. LKT can accurately represent the measured data over the full range of humidities by postulating that the presence of adsorbed water shifts the equilibrium clusters from cooperatively bound chains to non-cooperatively bound CO2. A consequence of this transition is that CO2 exhibits step adsorption isotherm in dry air and a standard Langmuir adsorption isotherm in high humidity air.

Unraveling the regional environmental ecology dominated baijiu fermentation microbial community succession and associated unique flavor.

Chinese baijiu as one of the famous distilled liquor in which fermented in open environments, with various microorganisms (i.e., bacteria, fungi, and yeast) involved in their brewing process, and created corresponding unique flavor. However, the sources of environmentally enriched microbial communities associated with liquor fermentation are still being characterized yet. Given the dependence of microbial growth and reproduction on environmental ecology, it is important to understand the correlation between baijiu fermentation microbial community and surrounding environmental ecology (i.e., temperature, humidity, wind, and precipitation). This study systematically overviewed the sources of microorganisms in the Jiang-flavor-Baijiu fermentation system. The results showed that microorganisms in baijiu brewing (i.e., mold, lactic acid bacteria, and yeast) mainly originated from surrounding environmental matrices, including the air (i.e., Yeast, Streptomyces and Bacillus), soil (i.e., Xanthomonas, Methanococcus and Comamonas) and water (i.e., Flavobacterium, Acinetobacter, and Pseudomonas) via atmospheric transport, raw material transfer and surface runoff. In addition, the unique baijiu fermentation microbial community diversity depends on local geology and meteorological conditions, highlighting that the structural stability and diversity of the microorganisms in the Baijiu brewing process dominated by local environmental ecology. We also explored the regional environmental conditions on the microbial community and found that the unique Jiang-flavor-Baijiu fermentation microbial community diversity depends on local geology and meteorological conditions. The Jiang-flavor-Baijiu workshop is located in the basin of the middle-and low latitude mountainous areas, with sufficient solar irradiation and rainfall, high air humidity, and low wind speed that favor the growth and propagation of Baijiu fermentation microorganisms. Therefore, the obtained conclusions provide new insights unraveling the key factor controlling the unique flavor of Chinese Baijiu, where protecting the ecology of baijiu brewing-regions is fundamental for maintaining the long-term quality of baijiu.

Thermal Performance of Becool-Roof Coating in Reducing Heat Gain on Fisherman’s Settlement of Gorontalo City

Abstract Tanjung Kramat in Gorontalo, Indonesia is a village fostered by the department of Architecture, Universitas Negeri Gorontalo. The village is home to around two hundred families whose majority job is fishing. The people suffer from the uncomfortable condition of tropical coastal environment due to the high air temperature, humidity, and wind speed. Not to mention people in Gorontalo prefer to cover their upper structure using metal zincalume roof since they are more affordable. The highly thermal conductivity roof accounts for excessive heat gain to the house. Through a CSR program by Becool, the villagers received Cool Roof Coating to reduce heating and mitigate global warming. Before and after painting measurements of roof surface temperatures, radiant temperatures, and ground air temperatures are conducted. After the application of the coating, the analysis shows a positive result as the roof surface temperature is reduced by about 20ºC, followed by an improvement in ground air temperature by an average of 0.8ºC. The cool roof coating has succeeded in improving the neighborhood of Tanjung Kramat village.

Mould Risk in Technical Room in Four Underground Water Reservoirs

Abstract This conference article analyses the indoor climate of a technical room in four underground water reservoirs. This indoor climate with minimal input energy is specific by high relative humidity and low air temperature, as shown in the experimental measurement. The unsteady 2D numerical simulation of the detail section (partly sub-terrain peripheral wall and floor) in software Calculation Area 4.0e calculates fluctuation of internal surface temperature and relative humidity. Finally, the empirical predictive Finnish VVT model predicts the seasonal mould risk on the internal surface of the peripheral wall.

Insight into the mechanisms and in-plane reaction heterogeneity of the dynamic response of proton exchange membrane fuel cells

The voltage undershoot is one of the main dynamic problems of proton exchange membrane fuel cells (PEMFCs) under dynamic loadings. However, its mechanisms remain poorly understood due to its complex and coupled influencing factors. Besides, PEMFCs with a large active area are more prone to local dynamic failures for their pronounced in-plane (I-P) heterogeneity, while few studies have focused on the I-P heterogeneity of the dynamic response of large-area fuel cells. In this work, the mechanisms and the I-P heterogeneity of the voltage undershoot of a 320 cm2 PEMFC are thoroughly studied based on an in-situ monitoring method and a voltage loss decoupling method. Results show that the voltage overshoot is primarily driven by the ohmic loss (OL) overshoot and the concentration polarization (CP) overshoot. Results also prove that the OL overshoot is mainly caused by the instantaneous water shortage in the proton exchange membrane (PEM) which depends on the initial water content in the PEM. Besides, the CP overshoot is due to the instantaneous reactant shortage at the catalyst, and it is much sensitive to the change in the oxygen diffusion coefficient of the ionomer caused by the change in its water content. Meanwhile, both OL overshoot and CP overshoot demonstrate significant I-P heterogeneities under poor dynamic operating conditions, especially in cases of high load step and low inlet air humidity. Finally, the influences of operating conditions on the voltage undershoot and its I-P heterogeneity are discussed, and suggestions for improving the dynamic performance of PEMFCs are proposed.

Performance study of the rapid heating drying system based on the reverse Brayton air cycle for agricultural application

Air temperature and humidity control are important for crop storage. Current drying methods in agriculture include solar heating and air source heat pumps, whereas solar heating may lead to poor quality of the dried product and air source heat pumps may not reach the desired temperature when the environment is harsh. In this paper, a rapid heating and drying system based on reverse Brayton air circulation is proposed to obtain high temperature and low humidity air quickly by adjusting the pressure ratio to achieve an adjustable crop drying process. An improved rapid heating and drying system with a water cooler is also proposed to increase the drying efficiency of the system. The results show that the total dehumidification rate of the improved system can reach 11.51 g/s, which is 1.48 g/s higher than that of the rapid heating and drying system without a water cooler, and the dehumidification energy efficiency of the improved system can reach 1.26 kg/(kW.h), which is 0.11 kg/(kW.h) higher than that of the rapid heating and drying system without a water-cooling device.

The Moderating Effects of Urban Design on Willingness to Walk in a Tropical City

Walkability and the willingness to walk (WTW) are enhanced with supportive urban design in temperate climate cities. Walking in a tropical city is challenged by the physiological stresses brought on by high air temperature, intense sunlight and humidity but it remains unknown to what extent urban design compensates for these stressors in walking behaviour. In this study, the relative impacts of the walking environment and microclimate on WTW and on walking distance were measured in a field study in Singapore. Participants executed a planned walk and reported assessments of 10 environmental factors, as well as WTW, at assigned locations. Restoration in WTW was observed at certain points on the itinerary across participants, while total voluntary walked distance equalled that of an indoor, air-conditioned walk at the same location. All environmental design variables showed a positive relationship with WTW, but not with objectively measured temperature and humidity. Urban design has a significant impact on willingness to walk in a tropical city.

The Moderating Effects of Urban Design on Willingness to Walk in a Tropical City

Walkability and the willingness to walk (WTW) are enhanced with supportive urban design in temperate climate cities. Walking in a tropical city is challenged by the physiological stresses brought on by high air temperature, intense sunlight and humidity but it remains unknown to what extent urban design compensates for these stressors in walking behaviour. In this study, the relative impacts of the walking environment and microclimate on WTW and on walking distance were measured in a field study in Singapore. Participants executed a planned walk and reported assessments of 10 environmental factors, as well as WTW, at assigned locations. Restoration in WTW was observed at certain points on the itinerary across participants, while total voluntary walked distance equalled that of an indoor, air-conditioned walk at the same location. All environmental design variables showed a positive relationship with WTW, but not with objectively measured temperature and humidity. Urban design has a significant impact on willingness to walk in a tropical city.

Construction and Preparation of the Novel ADN/CL-20 Cocrystal via Directional Hydrogen Bonding Design for Turning Hygroscopicity.

Ammonium dinitramide (ADN), as a novel and environmentally friendly oxidizer, has strong hygroscopicity when exposed to high-humidity air, which seriously hinders its application in solid propellants. Modification of oxidizers by cocrystallization is an effective strategy to improve the hygroscopicity of energetic components. In this paper, the theoretical simulation of ADN/CL-20 cocrystals was developed via a directional hydrogen bonding design to establish a cocrystal with improved hygroscopicity. Intermolecular interaction analyses reveal that hydrogen bonds and van der Waals interactions synergistically lead to the formation of cocrystals. The ADN/CL-20 cocrystal was prepared experimentally by the spray drying self-assembly technique, and the corresponding thermal analysis and sensitivity properties were conducted to illustrate the thermal stability and high safety. Furthermore, the critical relative humidity (CRH) measurement was carried out to evaluate the hygroscopicity of the cocrystal, exhibiting a certain degree of antihygroscopic effect with a CRH of 65%. The hydrogen bonds formed between ADN and CL-20 saturate the ammonium ions of ADN, further preventing ADN from absorbing water molecules in the air. The ADN/CL-20 cocrystal has high specific impulse characteristics (Isp: 272.6 s). Accordingly, this work clearly demonstrates that the ADN/CL-20 cocrystal is expected to be used in a solid propellant to make up for the deficiency of the ADN oxidizer.

Temporal and spatial distribution of PM2.5 in the Xinjiang region based on AOD fusion data and the GTWR model

ABSTRACT By integrating MODIS aerosol optical depth data and combining it with ground-based PM2.5 measurements and meteorological data, a geographically and temporally weighted regression (GTWR) model was used to estimate the spatiotemporal distribution of PM2.5 in Xinjiang in 2022. Findings include the following: (1) The GTWR model effectively represents PM2.5 distributions, with a correlation coefficient of 0.92, surpassing the geographically weighted regression model by 5.7% and the land use regression model by 9.5%. (2) Monthly PM2.5 levels in Xinjiang exhibit a pattern of initial decline followed by an increase. Elevated coal-fired heating in February and high air humidity in July contribute to higher atmospheric particulate concentrations. The peak monthly average concentration reaches 79.05 µg m−3 in February, and the lowest concentration drops to 33.86 µg m−3 in July. (3) Influenced by dust-prone conditions and atmospheric diffusion in the Taklimakan Desert region, PM2.5 levels in Xinjiang show a notable southwest-to-northeast gradient.

Kinetic and cracking analysis of paddy rice drying using refrigeration-assisted air dehumidification system

The presence of high relative air humidity in regions characterized by a humid climate results in a slow drying process and the rehydration of paddy. To address this issue, the utilization of a liquefied petroleum gas refrigeration system for the purpose of dehumidifying the ambient air has been shown to reduce drying time and enhance the quality of the final product. In the present investigation, the impact of ambient air dehumidification on the quality and moisture reduction of the Hashemi rice variety was examined. The drying of paddy was modeled and optimized using the Response Surface Method, taking into consideration three key factors: temperature (40, 45, and 50 °C), air velocity (1.7, 2.2, and 2.7 m/s), and relative air humidity (70, 80, and 90 %) as the variables in the conducted experiments. The findings of this study revealed that under dehumidification conditions, samples with a moisture content of 6 % exhibited the lowest cracking rate of 2 %. Moreover, the use of liquefied petroleum gas resulted in a 13 % reduction in cracking and drying times, ranging from 22.3 % to 68.9 %, depending on the experimental conditions. Irrespective of whether dehumidification was employed or not, the temperature was identified as the most influential parameter, impacting the experimental responses by 73.29 % and 73.09 % for the non-dehumidified and dehumidified conditions, respectively. Under optimal conditions, a cracking rate of 2 % was attained during dehumidification at a temperature of 40 °C, a relative air humidity of 80 %, and an air velocity of 1.7 m/s, yielding a desirability index of 0.958. The Response Surface Method, when applied in the dehumidification case, displayed an excellent fit between the experimental and predicted data for both the moisture content (R2 = 0.99) and the cracking index (R2 = 0.98). These results demonstrate the efficacy of the refrigeration system that employs liquefied petroleum gas inefficiently drying paddy in humid regions, rendering it applicable in industrial settings.

Effect of storage conditions on lignocellulose biofuels properties

This article examines the effects of different storage conditions on selected physicochemical properties of three types of agro-biomass pellets: sunflower husks, wheat straw and hemp hurds, and wood pellets. The tests were carried out in a climatic chamber, which allows simulation of real storage conditions, i.e. conditions with high air humidity and variable (±) ambient air temperatures. The results showed higher degradability of agro-biomass pellets compared to woody biomass. The pellets degraded to a less extent at varying ± temperatures than at high humidity (90% RH). After complete moisture saturation, durability decreases for agro-pellets by an average of 9%, while after freezing and defreezing for sunflower husk pellets and woody pellets durability decreases by 2%, and for hemp hurd pellets by 11%. In contrast, strength-by-dropping index for agro-pellets decreased by 20% after being in the environment (30 °C and 90%RH) and 15% under varying temperature conditions. No change in the energy parameters of all pellets in the dry matter was noted. On the other hand, an increase in the moisture content of pellets when they are stored under different environmental conditions results in a decrease in calorific value.

Research and Application of New Anti-Condensation System of High-Voltage Switchgear

Abstract The drastic fluctuations in temperature and humidity in the switchgear environment can lead to condensation, posing the threat to the safe and dependable operation of power equipment. In response to the limitations of current anti-condensation measures, a new anti-condensation system for high-voltage switchgear is proposed. Firstly, this research provides an overview of the cause of condensation and the present situation of relevant prevention technologies. Secondly, a new anti-condensation system for high-voltage switchgear is presented. Drawing upon existing anti-condensation technology, this system effectively addresses prevalent issues such as high air humidity and facile condensation in high-voltage switchgear. Electric field simulation calculations, conducted using COMSOL simulation software, demonstrate that the system does not compromise the normal operation of the switchgear. Finally, practical applications show that the robust operational stability of the system. It consistently achieves precise heat dissipation and dehumidification in high-voltage switchgear, which has high application value.

Sub-ppm short-chain fatty acids detection with La(III) modified SnO2 gas sensors

La(III) modified nanocrystalline SnO2 with lanthanum content [La]/([Sn] +[La]) = 0; 0.5; 1 and 2 mol. % were prepared by flame spray pyrolysis and characterized by X-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Identification of surface segregation of La(III) containing phases was performed via Raman spectroscopy. Acidic properties of pure and La(III) modified SnO2 were characterized by temperature-programmed desorption of ammonia (TPD-NH3) with mass spectral determination of desorption products. It was demonstrated that decrease in the Lewis acidity of the SnO2 surface leads to the specific increase in sensor response when detecting gases with acidic properties like short-chain fatty acids (SCFAs) and H2S. The obtained materials are capable to detect SCFAs at ppb concentration level, including high air humidity conditions (RH = 80 %).

Effect of humidity and oxygen on friction, wear and durability of a polymer-bonded molybdenum disulfide (MoS2)-based dry film lubricant (DFL) coating system in large amplitude fretting

Investigations into effects of humidity and oxygen on a polymer-bonded MoS2-based dry film lubricant (DFL) coating, on grit-blasted Ti–6Al–4V using a cylinder-on-flat configuration, are reported. Sustained low friction and low wear occurred in both low-humidity air and low-humidity argon, producing significant extension of fretting wear lifetimes. A cracked-paved structure was observed in low-humidity air which was not observed in low-humidity argon. The Mo-DFL coatings were observed to be highly sensitive to humidity. As humidity increased, a notable rise of friction and wear ensued which reduced the system lifetime. Different friction evolution was observed in high-humidity air and high-humidity argon before failure, with a short-lived but established low friction phase in high-humidity air and a consistent high friction phase in high-humidity argon. Although oxidation of the MoS2 to MoO3 is a key process of degradation of DFLs of this type, this oxidation reaction does not operate in the absence of humidity.

E. Coli inactivation by humidified air barrier discharge plasmas and the chemical stability of amino acids

In this study, we use atmospheric air dielectric barrier discharge (DBD) plasma to inactivate E. coli (E. coli) by changing the air humidity levels. In order to analyze the inactivation process of E. coli during the humidified air DBD plasma treatment, we analyze the byproducts of 12 representational amino acids and compare their chemical stability. The experimental results show that the E. coli surface density (CFU cm−2) on a steel disc decreased significantly when the air humidity was increased from 20% to 60%, and humidified air DBD plasma at 60% humidity is very effective in inactivating E. coli. A consistently potent deactivation effect on E. coli can be seen in plasma afterglow treatment experiments over a storage time of two minutes, indicating that plasma-activated long-lived reactive oxygen and nitrogen species play a crucial role in controlling the E. coli inactivation. Compared to the low humidity (20%) condition, the concentration of reactive species produced by the plasma at high humidity (60%) increased 2-fold for 2-hydroxyterephthalic acid and 5-fold for hydrogen peroxide while ozone production was halved. Amino acid experiments showed that amino acids may be oxidized, hydroxylated and nitroxylated by reactive species. The reduction of amino acids by air DBD plasma was even more pronounced at high air humidity compared to low air humidity. Our analysis indicates that the significant inactivation of E. coli by humified air DBD plasma is related to the chemical instability of amino acids.

Optimization of the performance of CsPbI2Br perovskite solar cells in air by adding polyethylene-graft-maleic anhydride and its mechanism

In this study, by adding Polyethylene-graft-maleic anhydride (PGMA) to the inorganic CsPbI2Br perovskite film, the coordination bonds and hydrogen bonds between PGMA and CsPbI2Br cooperate to passivate defects, regulate energy level and stabilize the perovskite structure and eventually improve the device performance. We systematically study the effects of PGMA addition on the morphology, structure, light absorption, defect concentration and carrier lifetime, hydrophobicity, and optical stability and room temperature black phase stability of CsPbI2Br films, and the photoelectric performance and air stability of PSCs, as well as their mechanism. The experimental results show that the addition of 3 wt% of PGMA greatly improves the photoelectric conversion efficiency (PCE) of CsPbI2Br PSCs by 40.19 % because of the synergistic passivation effects and energy level tuning. The hydrogen bonds between –CH2 in PGMA and I−/Br− in CsPbI2Br, along with the coordination of carbonyl groups with Cs+/Pb2+, improve carrier transport and collection by inactivating flaw and managing the level, reducing the non-radiative recombination losses. In addition, the PSCs with 3 wt% of PGMA maintain 80 % of their initial efficiency even after 600 h in high humidity air environment due to the synergistic effect of coordination bonds and hydrogen bonds. Our study provides valuable insights into the use of PGMA to improve the performance of all-inorganic CsPbI2Br PSCs and the practicality of perovskite solar cells.

Thermodynamic analysis of drying cycles utilizing a desiccant wheel thermoelectric modules and heat pipe for the drying of hazel nuts in the East Blacksea climatic conditions

The use of renewable energy sources to maintain appropriate thermal humidity and temperature conditions in food drying technologies, especially in humid climate zones, is a current area of research. In the Eastern Black Sea Region, the high relative and specific humidity of the atmospheric air lead to a low drying rate of the products. Therefore, in this study, to enhance the drying rate of the products, three models and their psychometric cycles were studied on decreasing the specific humidity of the drying air and increasing the moisture saturation degree of the drying air. The innovative hazelnut drying models proposed for the climatic conditions of the Eastern Black Sea region incorporate several components, including thermoelectric modules (TEM), photovoltaic thermal (PV/T) systems, desiccant wheels (DW), heat pipes (HP) and heat exchangers (HX). The thermodynamic analysis was conducted on the theoretical cycles belonging proposed models. Emphasis was given to the development of Model-C, taking into account the drying conditions specific to hazelnuts in the Eastern Black Sea region, among the cycles named Model-A, Model-B and Model-C. The energy efficiencies and SEMER values of Model-A, Model-B and Model-C were presented based on selected atmospheric conditions. Each model is valid under its characteristic operating conditions, and the energy efficiencies, SEMER values and the exergetic efficiencies for Model-A, Model-B and Model-C were determined as (4.66%-0.271 kg-H2O kWh−1–62%), (9.87%-0.1542 kg-H2O kWh−1–22%) and (9.13%-0.1381 kg-H2O kWh−1–10%), respectively. Also, presented models of hazelnut drying supported by renewable energy have achieved high sustainable index (SI) values. Consequently, these models ensure the sustainability of energy in the drying sector and facilitate the assessment of their environmental, economic and social impacts. The utilization of renewable energy in the models will lead to a reduction in CO2 emissions during the drying process. These results indicate that TEM systems are a viable option for food drying in the future.

Increased heat stress for the population of urbanized areas against the background of global climate change

The combination of high temperature and relative humidity of the atmospheric air creates heat stress, which has a serious impact on the environment, society and the health of the population in urban areas. Using the example of the city of Kyiv, the paper investigated long-term changes in heat stress depending on global climate changes. Averaged monthly long-term climate data of the urban environment were studied, starting from 1981, based on monitoring data using the Copernicus Climate Change Service toolkit and data from the Borys Sreznevsky Central Geophysical Observatory. Predictive dynamics of temperature by conventional and wet bulb was investigated using OriginPro8 software. Data on the dependence of the frequency and unevenness of precipitation during the last decades are presented. The dependences of the value of the heat index (NI) on the temperature and air humidity for different observation periods were obtained. Over the past decade, Kyiv has seen a significant increase in average heat stress and the frequency of days and events with extreme heat stress. According to the obtained forecast estimates, in 2050 the heat index should increase by almost 30%, and the risk to the health of the population in the surrounding area and for workers in the open air will be interpreted as "high" levels at a relative humidity of 80%; "moderate" at a relative humidity of 50% and "low" at a relative humidity of 20%. The forecast temperature dynamics according to the conventional and according to the wet thermometer in the month of July at the end of different years is: 2021–2030 – 24.136°С and 26.24°С; 2030–2050 – 26.371°С and 28.918°С, respectively, with other equal conditions of the urban environment. An additional possibility of influence on the thermal dome appears already at the design stage, thanks to the variability of the placement of the projected buildings on the general plan, and the formation of individual buildings, in the correct area ratio green plantings to stone surfaces of facades and paving. The research data will be useful for the possible reduction of the size of the thermal dome over the city during the planning and reconstruction of the housing stock and the development of climate neutrality measures for the cities of Ukraine.