Relative Humidity Values Research Articles

Experimental investigation and mathematical modeling of the unsteady drying kinetics of durum wheat grains

Dehydration of durum wheat often occurs under conditions where the effects the drying temperature, the water activity and the elasticity of the grains are significant to influence the drying kinetics. We here investigate the unsteady isothermal desorption process of a moisture from durum wheat grains by employing the static gravimetric method conducted at 30°C and 40°C and at controlled relative humidity values of 6.26% and 74.7%. Moreover, to explain our measured data, we have derived a new elastic diffusion model that extends Fick’s laws by taking into account the effect of the elasticity of the deformable grains. To consider the grain shrinkage during dehydration, we express the diffusion governing equation into the “grain material” coordinates system. We discuss in more detail the unidirectional radial mass transfer via scaling analysis and numerical solutions followed by a successful comparison between the model predictions and our measured data. A diffusion-elasticity coupling constant emerges naturally in the diffusion equation and its effects on the drying kinetics as well as on the grain radius retraction are examined. We found out that the elasticity enhances mass transport within the investigated grains and thus decreases the drying time.

Simulation and Experimental Study of Light and Thermal Environment of Photovoltaic Greenhouse in Tropical Area Based on Design Builder

In order to study the adaptability of photovoltaic greenhouses to climate in tropical areas, a photovoltaic greenhouse model (photovoltaic panel coverage rate: 76.9%) was built in this study according to a 1:1 proportion. The distribution law of the indoor illuminance, temperature, and humidity were studied simultaneously in the photovoltaic greenhouse by actual measurements and simulation. The filed data are shown as follows: (1) Illuminance: in limited rain winter, the average illuminance and light transmittance were 7.02 kLux and 25.77%, respectively (10:00–16:00); but in different weather conditions during summer, the average illuminance and light transmittance were 15.47 kLux and 32.35%, respectively (9:00–16:00). (2) Temperature and humidity: the indoor temperatures of the greenhouse were between 22.1 and 29.3 °C in limited rain winter, with a relative small temperature difference between indoor and outdoor environments; the relative humidity values were between 69% and 97%; but in summer, the temperatures at all indoor test site were higher than outdoor sites, with an average temperature difference of 2.7 °C and relative humidity values between 46% and 94%. According to the simulation by Design Builder, the average light transmittances were 33.09% in winter and 37.54% in summer, the temperature difference between winter and summer was less than 1 °C, and the relative humidity decreased with the increase of temperature, which basically coincided with the filed data. The results of the analysis showed that the illuminance, temperature and humidity of the photovoltaic greenhouse can satisfy the production requirements of shade-enduring and neutral crops. At the same time, by comparing the illumination, temperature and humidity of the photovoltaic greenhouse with that of an ordinary greenhouse, the former had good adaptability to climate in tropical areas, which can achieve the goal of photovoltaic generation and agricultural production synchronously.

Analysis of Ventilation Efficiency in the Earth Covered Magazine for Ammunition Storage Using Numerical Simulation

Internal environment parameters such as temperature, relative humidity and airflow velocity in ammunition storage facilities have a significant impact on the condition and overall life of ammunition, especially on the process of ammunition degradation in situations when their values deviate from required standards for safe storage. High temperatures inside the magazine, as well as in the ammunition packaging, can have a very negative effect on the structure of ammunition and explosives, and high values of relative humidity can result in corrosion and rapid decomposition of chemical compounds. Therefore, a properly designed ventilation system should ensure that the values of internal temperature and relative humidity are within the permitted limits, which is a very important aspect of the storage process itself, so that ammunition and explosives can be completely safe and ready for transport, use and handling. Experimental studies conducted in several magazines of ammunition and explosives in Bosnia and Herzegovina (BiH), had aim to monitor changes of environmental parameters such as temperature, relative humidity and airflow velocity. During these experimental measurements, high values of relative humidity were in these magazines observed, as well as uneven airflow in some ventilation ducks. The main cause of such measured values can be related to the inadequate performance of the natural ventilation system of the analysed magazines. Using numerical simulations (finite volume method) in the ANSYS – Fluent program, the analysis of the existing ventilation system of earth covered magazine in BiH from the aspect of airflow velocity was performed, as well as analysis of modifications that can improve airflow within the analysed magazine. The results of numerical simulation for the existing state of analysed magazine corresponded to the results of airflow measurements at certain places in the magazine. It was confirmed that the existing ventilation system does not provide proper ventilation, which further causes higher relative humidity values. The results of numerical simulation for the proposed modifications of the ventilation system have shown significantly better air circulation in the magazine, i.e. that a more efficient natural ventilation was achieved.

CFD modelling of the condensation, evaporation, coagulation and crystallization processes in the cooling tower emissions

The aim of the paper is to develop the CFD model for the environmental impact assessment of the cooling tower. The methods applied for this problem are the single-phase turbulent multispecies flow modelling with the DPM Lagrangian particle tracking. The simulations have been carried out in the steady state SIMPLE solver using the ANSYS Fluent software. User Defined Functions have been defined to enhance the accuracy and versatility of the modelling approach in terms of turbulence, fog formation, evaporation, coagulation and crystallization modelling. The Chalk Point cooling tower experiment, laboratory tests with freezing droplets and analytical correlations are used to verify the customized parts of the new CFD model. The arbitrary small-town geometry is used to demonstrate the simulation capabilities of the fog and drift deposition as well as the temperature and relative humidity values near ground and buildings. The results indicate that the new CFD model is able to predict the cooling tower plume parameters, icing and salt contamination risks as well as drift deposition.

Damage risk assessment of building materials with moisture hysteresis

Heat and Moisture Transfer (HMT) simulations are used to evaluate moisture related damage risks in building envelopes. HMT simulations are commonly performed accepting the hypothesis of not considering the moisture hysteresis of materials. The results of HMT simulation of a timber wall with hysteresis are presented, and compared to the results of three simplified models, showing the effects of hysteresis on the simulation results and on the assessment of the risk of decay. Moisture content is the most influenced variable, while temperature and relative humidity are slightly affected. The wood decay risk analysis is performed using the simplified 20% moisture content rule. Similar temperature values and relative humidity values are calculated as simplified models, while the moisture content annual average values have differences up to 2.3%. The wood decay risk obtained with the simplified models could be overestimated if the simulation is performed using the desorption curve, while it could be underestimated with the adsorption curve. The best approximation is obtained with the mean sorption curve, while the desorption curve and the adsorption curve could be used to calculate the upper and lower boundary of the moisture contents respectively.

Heat and moisture transfer studies on walnuts during hot air drying in a fixed-bed column dryer

• Heat and moisture transfer model was developed for fixed-bed column walnut drying. • Temperature and moisture distributions in the column and single walnuts were simulated. • Mechanisms of heat and moisture transfer during the drying process were discussed. • Good predictability achieved for drying under step-down temperature conditions. This research was conducted to better understand the mechanisms of heat and moisture transfer of walnuts during drying in a fixed-bed column dryer with heated air, and to develop a mathematical model to simulate this process. Drying experiments were performed under constant temperature and step-down temperature conditions (43, 55, 65 and 75 °C) with fixed air velocity of 0.7 m/s. The nonequilibrium transfers of liquid moisture, water vapor and heat within the single walnuts (both shell and kernel), as well as between the walnuts and drying air in the column were simulated and studied using a finite element method. The numerical results showed that the distribution of temperature and moisture content in the single walnuts played an important role in the heat and moisture transfer in the deep-bed column. The drying characteristics of walnuts were significantly affected by the non-uniformity of drying conditions surrounding the walnuts (particularly for air temperature and humidity) along the column heights. The predicted values of walnut moisture contents, temperatures, and air relative humidity at different column heights agreed well with the experimental values (R adj 2 > 0.972) under different drying conditions. This study established the theoretical basis for improving and optimizing the walnut drying process in deep-bed dryers. The developed mathematical model can be used to describe the drying characteristics and understand the mechanisms of walnuts drying in deep bed dryers.

Estimate of The Dynamical Change of Air TemperAture, Relative Humidity and Dew Point TemperaTure for Some Selected Station in Iraq

Relative humidity can be inferred from the dew point values. When the air temperature and dew point temperatures are very close, the air has high relative humidity. The converse is true when there is a large difference between the air temperature and the dew point temperature, indicating the presence of low humidity air. To understand the expected changes in the climatic elements in the atmosphere, changes in temperature behavior, dew point, and relative humidity have been studied This study used data obtained from the European Center (ECMWF), which includes monthly and annual mean temperatures, dew, and relative humidity during the period (1988-2018) for selected stations in Iraq. The highest values of temperature and dew were recorded in July and August, and they were accompanied by a decrease in relative humidity. The highest value of relative humidity was recorded in December and January, accompanied by a decrease in temperature and dew, as we note through the results that there is an inverse relationship between relative humidity, temperature, and dew point Relative humidity changes when the temperature rises or falls, and the relative humidity may be higher in the morning when the temperature drops. The lowest amount of relative humidity during the day is when the temperature rises, the highest temperature value was recorded on 21July 2017 (12:00 PM) for Basra Station, while the highest relative value is humidity in Basra Governorate. Mosul station on January 21, 2014 (12:00 AM), and the reason is due to meteorological factors and the nature of the geographical area.

3E Analysis of the Effect of Different Type of Fans on Cooling Performance Applied to an Industrial Deep Freezer

In this study, two different industrial refrigerators were designed, manufactured and tested to analyze the impact of different types of fans (Type 1 and Type 2) used in industrial cooling systems on the performance of the cooling system. In order to test the fan performance and airflow effects, two axial fan configurations with different structures and different motor technology (EC and shaded-pole induction) were tested in two separate industrial refrigerator test rooms in accordance with TS EN ISO 23953-2 standards. R290 (Propane) was used as a refrigerant in the systems. The average temperature and relative humidity values of the environment where the experiment was conducted were measured as 25 °C and 60 % (Class 3), respectively. During the experiments, the total of 51.71 kWh energy was consumed in system 1, while the total of 54.22 kWh energy was consumed in system 2 and the difference between the energy consumption of the two systems was calculated as 4.85%. The average temperatures of the inlet and outlet of the evaporator of the system 1 and 2 were -21.57 °C, -18.97 °C and -23.43 °C, -20.94 °C, respectively. The average refrigerant temperatures for the system 1 and 2 were calculated as -24.65 °C, -26.44 °C, respectively. While the average coefficient of performance value of the type 1 system was 1.74, it was calculated as 1.54 for the type 2 cooling system. The average second-law efficiencies for the two cooling systems were calculated as 30.85 % and 29.81 %, respectively. In addition, the environmental economy analysis was carried out using the amount of CO2 that was prevented from emitting and the CO2 emission price calculated accordingly.

Monitoring and Assessment of Indoor Environmental Conditions after the Implementation of COVID-19-Based Ventilation Strategies in an Educational Building in Southern Spain.

Since students and teachers spend much of their time in educational buildings, it is critical to provide good levels of indoor environmental quality (IEQ). The current COVID-19 pandemic has shown that maintaining a good indoor air quality level is an effective measure to control the transmission of the SARS-CoV-2 virus. This study used sensors to monitor key IEQ factors and assess several natural ventilation scenarios in a classroom of the University of Granada. Subsequently, the IEQ factors (temperature, relative humidity, CO2 concentration, acoustic environment, and air velocity) were evaluated for the selected ventilation scenarios in the occupied classroom, and the field monitoring was carried out in two different assessment periods, winter and summer. The obtained results show that the CO2 concentration levels were well below the recommended limits. However, the maintenance of the recommended thermal and acoustic IEQ factors was significantly affected by the natural ventilation strategies (temperature and relative humidity values were very close to the outside values, and the background sound pressure level was over 35 dBA during the entire assessment). The proper measurements and careful selection of the appropriate ventilation scenarios become of utmost importance to ensure that the ventilation rates required by the health authorities are achieved.

Laboratory Measurement and Boundary Conditions for the Water Vapour Resistivity Properties of Typical Australian Impermeable and Smart Pliable Membranes

The duo of better insulated and more air-tight envelopes without appropriate consideration of water vapour diffusion and envelope moisture management has often demonstrated an increased potential of moisture accumulation, interstitial condensation, and mould growth within the building envelope. To inform a resilient, energy efficient, and healthy building design, long-term transient hygrothermal modelling are required. Since 2008, concern has been raised to the Australian building regulators regarding the need to establish the vapour diffusion properties of construction materials, in order to develop a hygrothermal regulatory framework. This paper discusses the results from laboratory testing of the vapour diffusion properties of two common reflective pliable membranes, and one smart pliable membrane. The two reflective pliable membranes are often used within the exterior walls of Australian buildings. The smart pliable membrane is a relatively new, internationally available product. The three membranes were tested as per ISO 12,572 at 23 °C and 50% RH. To establish if the vapour resistivity properties were constant, under different relative humidity conditions, the membranes were further tested at 23 °C and relative humidity values of 35%, 65%, and 80%. The results of the three pliable membranes show that the vapour resistivity properties varied in a non-linear (dynamic) manner subject to relative humidity. In conclusion, this research demonstrates that regardless of the class, each of the tested membrane types behaved differently under varying relative humidity and pressure gradients within the testing laboratory.

The role of temporal resolution of meteorological inputs from reanalysis data in estimating air humidity for modelling applications

Reliable values of relative humidity are basic inputs for modelling in many disciplines and in the most disparate scientific fields. Unfortunately, humidity variables remain less focused than other meteorological parameters and generally suffer from considerable uncertainty mainly due to the fact that their observations are not widely available, fostering the use of the observations of other meteorological quantities to estimate them. The aim of this work is to assess the loss in daily maximum and minimum relative humidity accuracy when sampling interval becomes coarser than one hour. For this purpose, meteorological data from the ERA5 dataset, the most advanced reanalysis product released by the European Centre for Medium-Range Weather Forecasts (ECMWF), are used. Among the many advantages of ERA5 over the previous release ERA-Interim are the finer temporal resolution and data archived at the hourly time step. Near-surface relative humidity is derived using 1- and 3-hourly reanalysis data of 2-m temperature, 2-m dew-point temperature and surface pressure. Deviations from the actual values, as obtained from reference measures acquired at 15 minute intervals, are evaluated. Results show that the biases of the ERA5-based values are consistently reduced compared to its predecessor and that the performance of the calculated 1-hourly time resolution relative humidity data is almost equivalent to using observations. Reducing the sampling interval from three to one hour provides a significant improvement in data quality. The results indicate significant increases in errors in the estimates when the temporal resolution of the meteorological inputs becomes coarser than one hour, exceeding also the numerical and approximation errors due to simplifying assumptions in the theoretical and empirical formulas used. The positive impact of improving temporal resolution from ERA-Interim to ERA5 reanalysis is also quantified by the number of the correct relative humidity extremes increasing by 50%.

Accelerated Aging Effects on the Hygrothermal Behaviour of Hemp Concrete: Experimental and Numerical Investigations

In this article, both numerical and experimental investigations were carried out on the durability of hemp concrete. For this, an accelerated aging process was performed using cycles of immersion, freezing and drying. Then, an experimental campaign was enabled to determine heat and mass transfer properties, as well as the microstructure for both aged and reference materials. Observations using a digital microscope showed the appearance of cracks at the interfaces and an increase of the porosity of about 6%. These microstructural modifications imply a non-negligible evolution of heat and mass transfer properties. Thus, a numerical model for the prediction of heat and mass transfer was developed. The prediction of physical phenomena was computed using both aged and reference material properties. It highlights the aging effects on the behaviour of the hemp concrete. The numerical simulation results showed significant discrepancies between the predicted relative humidity values for the two configurations (aged and reference) of about 18% and a maximum phase shift of 40 min, due to the amplification of the mass transfer kinetics after aging. Nevertheless, few deviations in temperature values were found. Thus, after aging, sensible heat fluxes were overestimated compared to the reference case, unlike latent heat fluxes, where an underestimation was shown.

Effects of temperature and relative humidity on the COVID-19 pandemic in different climates: a study across some regions in Algeria (North Africa).

After more than a year from the first confirmed cases of coronavirus (COVID-19) disease, the role of meteorological factors in the transmission of the virus still needs to be correctly determined. In this scenario of deep uncertainty, the present study aims to investigate the effects of temperature and relative humidity on daily new cases of COVID-19. For this purpose, the COVID-19’s development of infection in fourteen Algerian cities characterized by different climatic conditions, during the period from April 1, 2020, to August 31, 2020, has been investigated. A detailed time series analysis along with linear regression was used to state a possible correlation among some climate’s factor variability (temperature and relative humidity) and daily new confirmed cases of COVID-19. The results showed a weak correlation between daily new cases of COVID-19 and meteorological factors throughout the selected regions. In addition, we concluded that the COVID-19 could fit to high or low values of temperature and relative humidity, and other factors not climates could affect the spreading of the virus like demography and human contact. So, after the discovery of the vaccine and before vaccination of 70% of the world’s population, living with the virus has become an inevitable reality, and it is mandatory to apply the sanitary procedures to slow down the COVID-19 transmission.Graphical abstract

Determining of Climatic Parameters Using CFD in Different Window Span in Naturally Ventilated Greenhouses

The aim of this study was to compare with the measured inner air temperature and relative humidity values and the simulated values determined with Computational Fluid Dynamics (CFD) in the naturally ventilated gable-roofed single glass greenhouse located North-South direction, having 45o and 90° window spans and under no cultivation.
 The measured values were recorded every 2 hours from 8 am to 18 pm using the relative humidity and air temperature sensors placed in 7 different locations. Measurements were made in case of the 45° and 90° window span openness. For CFD simulations, the SolidWorks 2011 software was used. The values of air temperature and relative humidity inside the greenhouse were simulated depending on the outside ambient conditions and structural and physical properties of greenhouse. Then, the measured values were compared with the simulated values and error rate for each sensors were determined.
 As a result, it was determined minimum error rates of the measured and simulated air temperature and relative humidity in greenhouses is 4.8% and 4.7%, respectively. The study showed that the CFD can be used as a powerful tool for determining inner climatic factors in naturally ventilated greenhouses.

Year long monitoring of indoor air quality and ventilation in school classrooms in Victoria, Australia

Children under 15 years spend over six hours per day in school buildings and are particularly vulnerable to the effects of poor indoor air quality (IAQ). However long-term monitoring of indoor environmental conditions is limited in Australian schools. This study evaluates IAQ in ten Australian school classrooms in the temperate settings of Victoria. Temperature, relative humidity, CO2 concentration, PM2.5 and PM10 were monitored over a period of one year. The temperature and relative humidity values in the monitored classrooms ranged between 18.7°C and 23.8°C and 44–63 RH%, respectively, indicating that the conditions have been mechanically controlled. The average air change (ACH) rates in the 10 school classrooms varied considerably (range: 0.7–4.83 ACH). The ventilation rates ranged from 1.6 Ls−1 to 11.5 Ls−1 per person with 7 out of the 10 classrooms showing ventilation rates below the recommended minimum. This study points to the need for increasing ventilation rates in classrooms.

Synergistic approach to simultaneously improve response and humidity-independence of metal-oxide gas sensors

The chemiresistive response of metal-oxide gas sensors depends on ambient conditions. Humidity is a strongly influential parameter and causes large deviations in signals and, consequently, an inaccurate detection of target gases. Developing sensors unaffected by humidity, as documented by extensive works of research, comes at the cost of response — a significant drop in sensor response inevitably accompanies an increase in humidity-independence. This trade-off between humidity-independence and gas response is one of the major obstacles that limit practical applications of metal-oxide gas sensors. This study presents a novel approach to improve both the features by incorporating the rare-earth element, yttrium, into the host SnO2 sensor. The Y-doped SnO2 nanofibers are highly stable across relative humidity values ranging from 0% to 87%, and show improved selectivity and sensitivity in the detection of up to 20 ppb of NO2 target gas with the limit of detection at 103.71 ppt. Based on experimental results and van der Waals (vdW)-corrected DFT calculations, these improvements can be attributed to the synergistic effect of oxygen vacancy created by the introduction of aliovalent Y and the formation of Y2O3 nanoparticles that play a critical role in making the sensor surface hydrophobic.

A Study of Food Poisoning Cases in Turkey from 2016 to 2020 According to the Written and Visual Media

This study aims to examine and statistically analyze the cases of food poisoning in Turkey between 2016 and 2020, and the number of people affected by these cases. The data on food poisoning were obtained from news sources published in the written and visual media while weather temperature and relative humidity values were obtained from the Ministry of Agriculture and Forestry. Frequency distributions and Kruskal Wallis and Bonferroni non-parametric tests were used to evaluate the data. A total of 504 cases of food poisoning (100.8 cases/year, 42 cases/month) were experienced in Turkey between 2016 and 2020, and the estimated number of people affected by those cases is 27,196. Surprisingly, most cases of food poisoning occurred in autumn and winter while the lowest number of cases took place in summer. Students and employees were most affected by food poisoning. No direct correlation of food poisoning with ambient temperature and relative humidity was determined. The study is the first research conducted in Turkey in this area, and can be used to develop strategies and policies for food safety.

Detection of hydrogen sulfide using polyaniline incorporated with graphene oxide aerogel

This paper presents the fabrication of polyaniline and graphene oxide aerogel composite (PGA) thin film-based sensors for H2S gas sensing application. The optical and morphological properties of these composite films were characterised correspondingly by UV–visible spectroscopy and scanning electron microscopy. To prepare the gas sensors, thin films of PANI and PGA composites were deposited onto interdigitated electrodes by spin coating method. The response of these sensors towards H2S gas was evaluated by monitoring the change in electrical conductivity at room temperature under two relative humidity values of 60% RH and 80% RH. The PGA composite thin film-based gas sensors showed a higher response compared with the pure PANI-based sensor. The gas sensor made of PGA-3 showed a good response of 3.87 in 67 s (60% RH), which is 4.6 times higher than that of pure PANI and 2.5 times higher than that of PGA-1 at 1 ppm. The first-principles simulations were carried out to investigate the H2S sensing mechanism of PGA heterostructure. The adsorption of H2S at different locations of pure PANI and PGA composites was analysed. The band gap for PGA showed more significant change after adsorption than that of pure PANI, which indicated the higher sensitivity for detecting H2S.

Mechanistic Investigation of the Role of Relative Humidity in Stainless Steel Pitting Morphology

This study investigated the underlying causes of the distinct differences in pit morphology of ground 304 stainless steel observed following exposure to seawater brines at two different levels of relative humidity (RH). Full immersion studies in key brine chemistries associated with the two RH values of 76% and 40% were systematically conducted and the resulting morphology in each case examined using scanning electron microscopy. Consistent with previous reported results of long-term atmospheric and full immersion exposures in seawater chemistry,1,2 the morphology observed at 40% RH was irregular and cross-hatched while pits exposed to 76% RH were ellipsoidal and crystallographically faceted (Fig.1). The mechanisms for these observed differences in pit morphology were examined by collecting and analyzing the anodic and cathodic kinetics data in solutions corresponding to the chemistries of interest. These results were utilized to examine the hypothesis that the differences in morphology were caused by differences in total cathodic current supply required for continued pit growth (Fig. 2). References T. D. Weirich et al., J. Electrochem. Soc., 166, C3477–C3487 (2019).J. Srinivasan et al., J. Electrochem. Soc., 168, 021501 (2021). Acknowledgements This work is supported at the Ohio State University by Sandia National Laboratories (SNL). SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. This document is SAND2021–4571A. Figure 1

Application of Gagge’s energy balance model to determine humidity-dependent temperature thresholds for healthy adults using electric fans during heatwaves

Heatwaves are one of the most dangerous natural hazards causing more than 166,000 deaths from 1998–2017. Their frequency is increasing, and they are becoming more intense.Electric fans are an efficient, and sustainable solution to cool people. They are, for most applications, the cheapest cooling technology available. However, many national and international health guidelines actively advise people not to use them when indoor air temperatures exceed the skin temperature, approximately 35 °C.We used a human energy balance model, to verify the validity of those recommendations and to determine under which environmental (air temperature, relative humidity, air speed and mean radiant temperature) and personal (metabolic rate, clothing) conditions the use of fans would be beneficial.We found that current guidelines are too restrictive. Electric fans can be used safely even if the indoor dry-bulb temperature exceeds 35 °C since they significantly increase the amount of sweat that evaporates from the skin. The use of elevated air speeds (0.8 m/s) increases the critical operative temperature at which heat strain is expected to occur by an average of 14 °C for relative humidity values above 22 %. We also analyzed the most extreme weather events from 1990 to 2014 recorded in the 115 most populous cities worldwide, and we determined that in 93 of them the use of fans would have been beneficial.We developed a free, open-source, and easy-to-use online tool to help researchers, building practitioners, and policymakers better understand under which conditions electric fans can be safely used to cool people.