scholarly journals Influence of Air Temperature and Humidity on Dehydration Equilibria and Kinetics of Theophylline

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Amira Touil ◽  
Roman Peczalski ◽  
Souad Timoumi ◽  
Fethi Zagrouba
Keyword(s):  
Relative Humidity ◽  
Air Temperature ◽  
Solid Phase ◽  
Gravimetric Analysis ◽  
Dehydration Rate ◽  
Processing Times ◽  
Theophylline Monohydrate ◽  
Temperature And Humidity ◽  
Polymorphic Forms ◽  
Kinetics Of

The effect of hygrothermal conditions (air temperature and relative humidity) on the dehydration of theophylline monohydrate was investigated. Firstly, the equilibrium states of theophylline were investigated. The data from gravimetric analysis at constant temperature and humidity were reported as desorption isotherms. The PXRD analysis was used to identify the different polymorphic forms of theophylline: the monohydrate, the metastable anhydrate, and the stable anhydrate. Solid-solid phase diagrams for two processing times were proposed. Secondly, the dehydration kinetics were studied. The water content evolutions with time were recorded at several temperatures from 20°C to 80°C and several relative humidities from 4% to 50%. Different mathematical models were used to fit the experimental data. The spatially averaged solution of 2D Fickian transient diffusion equation best represented the water mass loss versus time experimental relationship. The dehydration rate constant was found to increase exponentially with air temperature and to decrease exponentially with air relative humidity.

Drying of Rough Rice in Oven: An Experimental Study

2015 ◽  
Vol 365 ◽  
pp. 77-81 ◽  
Author(s):  
J.V. Silva ◽  
E.M.A. Pereira ◽  
T.H.F. Andrade ◽  
Antônio Gilson Barbosa de Lima
Keyword(s):  
Experimental Study ◽  
Relative Humidity ◽  
Moisture Content ◽  
Product Quality ◽  
Air Temperature ◽  
Drying Rate ◽  
Rough Rice ◽  
Drying Conditions ◽  
Kinetics Of ◽  
Mechanical Movement

This paper aims to present an experimental study of rough rice (BRSMG CONAI cultivar) drying by using a stationary method. The grain was dried in an oven with air mechanical movement under controlled conditions of velocity, temperature and relative humidity. In order to obtain balanced moisture content, the samples studied were kept at 40 and 70°C. Results of the drying and heating kinetics of the grain during the process are shown and analyzed. It was found that higher drying rate and lower time for drying as higher air temperature (70°C) is used. It can be concluded that the reduction of the moisture content of the grain, is considered very complex and, depending on the method and drying conditions, can substantially provokes breaking and cracks, which reduces final product quality.

Effect of Relative Humidity on Drying Kinetics of Agricultural Products

2014 ◽  
Vol 699 ◽  
pp. 257-262
Author(s):  
Sulastri Sabudin ◽  
Mohd Zairul Hakimi Remlee ◽  
Mohd Faizal Mohideen Batcha
Keyword(s):  
Relative Humidity ◽  
Air Temperature ◽  
Energy Efficient ◽  
Human Population ◽  
Room Temperature ◽  
Food Preservation ◽  
Agricultural Products ◽  
Drying Behavior ◽  
Drying Rates ◽  
Kinetics Of

The demand for food has been ever increasing in proportion with the growing human population. This includes agricultural products including fruits. Hence, food preservation for extended usage through drying is gaining importance. This study reports the drying behavior of several agricultural products, namely sweet potato, carrot, ginger, turmeric, passion fruit and its rind. Focus has been given to the effect of relative humidity on drying for these products at room temperature. Experiments were carried out at 27°C by varying relative humidity at 40%, 60% and 80%. It was found that the relative humidity has a strong effect on drying, with lower relative humidity providing higher drying rates. In humid surrounding like Malaysia which has an average humidity more than 70%, controlling humidity of drying air may result in an energy efficient process in comparison to raising the drying air temperature

INFLUENCE OF TEMPERATURE AND HUMIDITY ON THE EMERGENCE BEHAVIOUR OF ANAX JUNIUS (ODONATA: AESHNIDAE)

1973 ◽  
Vol 105 (7) ◽  
pp. 975-984 ◽  
Author(s):  
Robert Trottier
Keyword(s):  
Relative Humidity ◽  
Water Temperature ◽  
Air Temperature ◽  
Water Surface ◽  
Average Speed ◽  
Anax Junius ◽  
Air Temperatures ◽  
Stage 4 ◽  
Temperature And Humidity ◽  
Three Stages

AbstractEmergence from the water of Anax junius Drury normally occurred after sunset. The onset was affected independently by water temperature and air temperature; low water temperature and high air temperature delayed the onset of emergence. In the field, the net vrtical distance travelled above the water, before ecdysis, was positively correlated with air temperature. In the laboratory, the vertical distance travelled above the water was greatest when air and water temperatures were approximately the same. The average speed of climbing to the first resting position above the water surface was faster at high than low water temperature, but the average speed of climbing from there to the final position, where ecdysis occurred, was reduced due to the effects of air temperature and humidity. Air temperatures below 12.6 °C were found to retard ecdysis and larvae returned to the water and emerged early the following day making the final process of emergence and ecdysis diurnal instead of nocturnal. The duration of ecdysis was shorter at high than low air temperatures and only the first three stages, as arbitrarily defined, were longer at low than high relative humidity; stage 4, shortened with low relative humidity. This study shows that A. Junius, emerging from the water is affected at first by the temperature experienced when submerged, but it becomes gradually and cumulatively affected by air temperature and humidity while climbing to the ecdysial position and moulting.

scholarly journals Quantifying the impact of heat on human physical work capacity; part II: the observed interaction of air velocity with temperature, humidity, sweat rate, and clothing is not captured by most heat stress indices

2021 ◽  
Author(s):  
Josh Foster ◽  
James W. Smallcombe ◽  
Simon Hodder ◽  
Ollie Jay ◽  
Andreas D. Flouris ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Empirical Study ◽  
Air Temperature ◽  
Physical Work ◽  
Climate Index ◽  
Physical Work Capacity ◽  
Air Movement ◽  
Wide Range ◽  
Temperature And Humidity ◽  
The Impact

Abstract Increasing air movement can alleviate or exacerbate occupational heat strain, but the impact is not well defined across a wide range of hot environments, with different clothing levels. Therefore, we combined a large empirical study with a physical model of human heat transfer to determine the climates where increased air movement (with electric fans) provides effective body cooling. The model allowed us to generate practical advice using a high-resolution matrix of temperature and humidity. The empirical study involved a total of 300 1-h work trials in a variety of environments (35, 40, 45, and 50 °C, with 20 up to 80% relative humidity) with and without simulated wind (3.5 vs 0.2 m∙s−1), and wearing either minimal clothing or a full body work coverall. Our data provides compelling evidence that the impact of fans is strongly determined by air temperature and humidity. When air temperature is ≥ 35 °C, fans are ineffective and potentially harmful when relative humidity is below 50%. Our simulated data also show the climates where high wind/fans are beneficial or harmful, considering heat acclimation, age, and wind speed. Using unified weather indices, the impact of air movement is well captured by the universal thermal climate index, but not by wet-bulb globe temperature and aspirated wet-bulb temperature. Overall, the data from this study can inform new guidance for major public and occupational health agencies, potentially maintaining health and productivity in a warming climate.

Temporal and Spatial Patterns of Temperature and Humidity in Taxodium distichum Shelterbelts of Jiangmen, South China

2012 ◽  
Vol 610-613 ◽  
pp. 1150-1154 ◽  
Author(s):  
Lu Zhang ◽  
Zhi Yao Su ◽  
Xiang Lin Wang
Keyword(s):  
Relative Humidity ◽  
Spatial Patterns ◽  
Air Temperature ◽  
Seasonal Pattern ◽  
Taxodium Distichum ◽  
Blank Field ◽  
Sugarcane Field ◽  
Temporal And Spatial Patterns ◽  
Temperature And Humidity ◽  
Temporal And Spatial

Temporal and spatial patterns of temperature and humidity in shelterbelts of Taxodium distichum were investigated using routine observation and gradient observation methods in sampling plots placed in Taxodium distichum shelterbelts, sugarcane, and open (blank) fields, respectively. The results showed that: 1) Taxodium distichum shelterbelts mitigated air temperature in July. Air temperature of Taxodium distichum shelterbelts was 0.7 °C and 1.7 °C lower than that of sugarcane field and blank field in July, respectively, while less change of air temperature in January was recorded. Air temperature at 20 cm from the ground in the Taxodium distichum shelterbelts was the highest in April, October and January, but the lowest in July; 2) Relative humidity in the Taxodium distichum shelterbelts was higher than in blank field through the four seasons, but lower than in sugarcane field in July, October and January. Relative humidity in sugarcane field and Taxodium distichum shelterbelts was higher near the ground, and relative humidity in sugarcane field increased significantly; 3) One-way ANOVA followed by Tukey’s HSD indicated that both air temperature and relative humidity were significantly different with a seasonal pattern among shelterbelts of Taxodium distichum, sugarcane field and open field (P＜0.001).

scholarly journals An investigation on hygroscopic properties of 15 black carbon (BC) from different carbon sources: Roles of organic and inorganic components

2020 ◽  
Author(s):  
Minli Wang ◽  
Yiqun Chen ◽  
Heyun Fu ◽  
Xiaolei Qu ◽  
Bengang Li ◽  
...  
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Organic Carbon ◽  
Black Carbon ◽  
Water Uptake ◽  
Carbon Sources ◽  
High Relative Humidity ◽  
Gravimetric Analysis ◽  
Hygroscopic Properties ◽  
Kinetics Of

Abstract. The hygroscopic behavior of black carbon (BC) has a significant impact on global and regional climate change. However, the mechanism and factors controlling the hygroscopicity of BC from different carbon sources are not well understood. Here, we systematically measured the equilibrium and kinetics of water uptake by 15 different BC (10 herb-derived BC, 2 wood-derived BC, and 3 soot) using gravimetric water vapor sorption method combined with in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). In the gravimetric analysis, the sorption/desorption equilibrium isotherms were measured under continuous-stepwise water vapor pressure conditions, while the kinetics was measured at a variety of humidity levels obtained by different saturated aqueous salt solutions. The equilibrium water uptake of the BC pool at high relative humidity (> 80 %) positively correlated to the dissolved mineral content (0.01–13.0 wt %) (R2 = 0.86, P = 0.0001) as well as the content of the thermogravimetrically analyzed organic carbon (OCTGA, 4.48–15.25 wt %) (R2 = 0.52, P = 0.002) and the alkali-extracted organic carbon (OCAE, 0.14–8.39 wt %) (R2 = 0.80, P = 0.0001). In contrast, no positive correlation was obtained with the content of total organic carbon or elemental carbon. Among the major soluble ionic constituents, chloride and ammonium were each correlated with the equilibrium water uptake at high relative humidity. Compared with the herbal BC and soot, the woody BC had much lower equilibrium water uptake, especially at high relative humidity, likely due to the very low dissolved material content and OC content. The DRIFTS analysis provided generally consistent results at low relative humidity. The kinetics of water uptake (measured by pseudo-second order rate constant) correlated to the content of OCTGA and OCAE as well as the content of chloride and ammonium at low relative humidity (33 %), but to the porosity of bulk BC at high relative humidity (94 %). This was the first study to show that BC of different types and sources has greatly varying hygroscopic properties.

scholarly journals An analysis of moist air energy potential during the process of paper band drying

2006 ◽  
Vol 60 (7-8) ◽  
pp. 188-194 ◽  
Author(s):  
Vladimir Valent ◽  
Milorad Krgovic ◽  
Srecko Nikolic
Keyword(s):  
Relative Humidity ◽  
Air Temperature ◽  
Ventilation System ◽  
Specific Consumption ◽  
Moist Air ◽  
Energy Potential ◽  
Dry Air ◽  
Thermodynamic State ◽  
Flow Through ◽  
Kinetics Of

The energy potential of moist air venting from the dryer of the installation for drying paper bands was analyzed. The thermodynamic state of air is defined by the air temperature at the outlet of the dryer and the dew temperature of the air. For the temperature at the outlet of the dryer (55-85?C) and selected dew temperatures (45-65?C), the specific consumption of dry air was determined. For selected kinetics of paper band drying, 10-35 kgH2O/(m2h), the modification of energy potential of the air as a function of air temperature at the outlet of the dryer and the temperature of dew air was specified. The air flow through the dryer was also correlated with the operation of the ventilation system and recuperation of energy. An analysis of the thermodynamic state of moist air venting from the dryer and the calculation of its energy potential confirmed that increase of the dew temperature of the air decreases its energy potential. With the intensity of vaporization Ivm,isp = 10 kgH2O/(m2h), the decrease is 6%. With Ivm,isp = 35 kgH2O/(m2h), the decrease is much greater and amounts to 21.6%. With increasing dew temperature, the specific consumption of dry air decreases, as well as the relative humidity of the air.

scholarly journals Effect of Lockdown,Temperature,and Humidity on the Pattern of COVID-19 in Erbil Province,Kurdistan Region, Iraq

2021 ◽  
Vol 20 (2) ◽  
pp. 56-67
Author(s):  
Rundk Hwaiz ◽  
◽  
Katan Ali ◽  
Namir Al-Tawil
Keyword(s):  
Relative Humidity ◽  
Air Temperature ◽  
Death Rate ◽  
Weather Conditions ◽  
World Health ◽  
The Novel ◽  
Number Of Patients ◽  
Temperature And Humidity ◽  
Novel Coronavirus ◽  
Health Organization

Background: COVID-19 was first reported in Erbil province in Iraq on March 19, 2020. The effect of lockdown on reducing the spread of the novel coronavirus and the effect of weather conditions (air temperature and humidity) on the daily reported number of cases and death rate of COVID-19 were investigated during April to July, 2020. Objective: To investigate the effect of lock down on reducing the spread of the novel coronavirus pandemic and the effect of weather conditions (air temperature and humidity) on the daily reported number of cases and death rate of COVID-19. Patients and Methods: The data collected during three different periods, the first (total lockdown), followed by the second period of lockdown relaxation, which was followed by the third period (interrupted relaxation of lockdown) that reported hundreds of new cases daily. The real-time PCR .assay was performed on suspected COVID-19 patients according to the protocol established by the World Health Organization. Results: Temperature and relative humidity were recorded in Erbil city in Iraq. Patients’ age ranged (2-70) years old. Out of (1469) patients confirmed positive with COVID-19, 57.7% of them were males, 31.3% were females, and the rest (11%) were children. The mean number of patients per day was 32.77 during the period of interrupted relaxation lockdown which was significantly higher than in the total-lock down period (3.88 patient), and the relaxation lockdown period (1.93 patient). The mortality rate per day was 0.77 during the period of interrupted relaxation lockdown was significantly higher than the rates (0.0%) of the other periods. Moreover, increasing the temperature increased the number of confirmed cases in July while, low relative humidity significantly increased the rate of reported cases. Conclusion: The increase in the number of reported cases of COVID-19, might be related to the interruption of lockdown. Moreover, the daily reported cases and mortality rates increased by increasing the temperature from April to June.

scholarly journals Lightning Behaviour during the COVID-19 Pandemic

F1000Research ◽  
2021 ◽  
Vol 10 ◽  
pp. 906
Author(s):  
Fazandra Yusfiandika ◽  
Chun Lim Siow ◽  
Chandima Gomes ◽  
Aravind Chockalingam ◽  
Lee Cheng Pay
Keyword(s):  
Statistical Analysis ◽  
Relative Humidity ◽  
Air Temperature ◽  
Human Activities ◽  
Correlation Study ◽  
T Test ◽  
Lightning Strikes ◽  
Variation Trend ◽  
Temperature And Humidity ◽  
Atmospheric Changes

Background COVID-19 has drastically dampened human activities since early 2020. Studies have shown that this has resulted in changes in air temperature and humidity. Since lightning activities are dependent on air temperature and humidity, this study is conducted to evaluate the correlation between the intensity of lightning activities with the atmospheric changes, and investigates the changes, in lightning activities due to atmospheric changes during the COVID-19 pandemic. Methods The hypothesis was tested through a t-test and Pearson’s correlation study. The variation trend of lightning strikes count (LSC) in Europe and Oceania during the five months COVID-19 lockdown period (March – July) compared to the same period in the previous five years from 2015 to 2019 is investigated. Results Statistical analysis shows the LSC in Europe and Oceania during the lockdown period dropped significantly by more than 50% and 44% respectively compared to the same period in previous five years. Furthermore, LSC was found to be positively correlated with air temperature and relative humidity in Europe. However, in Oceania, LSC seems to be only positively correlated with air temperature but negatively correlated with relative humidity. Conclusions This study seems to suggest that lightning activities have significantly changed during this pandemic due to reduction in human activities.

The Effect of Drying Air Temperature and Humidity on the Drying Kinetic of Kenaf Core

2013 ◽  
Vol 315 ◽  
pp. 710-714 ◽  
Author(s):  
Suhaimi Misha ◽  
Ali Sohif Mat ◽  
Mohd Hafidz Ruslan ◽  
Kamaruzzaman Sopian ◽  
Elias Salleh
Keyword(s):  
Relative Humidity ◽  
Air Temperature ◽  
Coefficient Of Determination ◽  
Suitable Model ◽  
Chi Square ◽  
Experimental Conditions ◽  
Kenaf Core ◽  
Thin Layer Drying ◽  
Drying Kinetic ◽  
Temperature And Humidity

Drying kinetics of kenaf core was investigated in a Low Temperature and Humidity Chamber Test. The drying experiments were carried out at temperature of 45, 50 and 55°C and air relative humidity of 10, 20 and 30% using a constant air velocity of 1.0 m/s. The moisture content data at various drying air conditions were converted to moisture ratio and plotted against time to obtain the drying curves for each experimental data. The curves were fitted to eight different thin layer drying models to determine a suitable model for drying of kenaf core. The fit quality of the models was evaluated based on their coefficient of determination (R2), reduced chi-square (χ2) and root mean square error (RMSE). Among the eight models, Two Term model is the best model for describing the drying behavior of kenaf core. The drying air temperature gave more significant effect on the drying kinetic of kenaf core compared to the drying air relative humidity under the experimental conditions studied.

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