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 A Study of Moist Air Condensation Characteristics in a Transonic Flow System

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 4052
Author(s):  
Jie Wang ◽  
Hongfang Gu
Keyword(s):  
Mach Number ◽  
Relative Humidity ◽  
Transonic Flow ◽  
Flow System ◽  
Plane Surface ◽  
Droplet Growth ◽  
Moist Air ◽  
Dry Air ◽  
Hydraulic Equipment ◽  
Non Equilibrium

When water vapor in moist air reaches supersaturation in a transonic flow system, non-equilibrium condensation forms a large number of droplets which may adversely affect the operation of some thermal-hydraulic equipment. For a better understanding of this non-equilibrium condensing phenomenon, a numerical model is applied to analyze moist air condensation in a transonic flow system by using the theory of nucleation and droplet growth. The Benson model is adopted to correct the liquid-plane surface tension equation for realistic results. The results show that the distributions of pressure, temperature and Mach number in moist air are significantly different from those in dry air. The dry air model exaggerates the Mach number by 19% and reduces both the pressure and the temperature by 34% at the nozzle exit as compared with the moist air model. At a Laval nozzle, for example, the nucleation rate, droplet number and condensation rate increase significantly with increasing relative humidity. The results also reveal the fact that the number of condensate droplets increases rapidly when moist air reaches 60% relative humidity. These findings provide a fundamental approach to account for the effect of condensate droplet formation on moist gas in a transonic flow system.

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

scholarly journals Indoor air quality of newly built low-energy preschools – Are chemical emissions reduced in houses with eco-labelled building materials?

2018 ◽  
Vol 28 (4) ◽  
pp. 506-519 ◽  
Author(s):  
Josefin Persson ◽  
Thanh Wang ◽  
Jessika Hagberg
Keyword(s):  
Air Quality ◽  
Relative Humidity ◽  
Indoor Air Quality ◽  
Air Temperature ◽  
Indoor Air ◽  
Building Materials ◽  
Ventilation System ◽  
Sampling Period ◽  
Low Energy ◽  
Low Energy Buildings

The use of an airtight frame in low-energy buildings could increase the risk of health-related problems, such as allergies and sick building syndromes (SBS), associated with chemical emissions from building materials, especially if the ventilation system is not functioning properly. In this study, the indoor air quality (IAQ) was investigated in newly built low-energy and conventional preschools by monitoring the indoor air temperature, relative humidity, particle-size distribution and levels of carbon dioxide (CO2), nitrogen dioxide (NO2), formaldehyde and total volatile organic compounds (TVOC). The thermal comfort was satisfactory in all preschools, with average indoor air temperature and a relative humidity at 21.4°C and 36%, respectively. The highest levels of TVOC (range: 130–1650 µg/m3 toluene equivalents) and formaldehyde (range: 1.9–28.8 µg/m3) occurred during the first sampling period associated with strong emissions from building materials. However, those preschools constructed with environmental friendly building materials (such as Swan Eco-label) had lower initial TVOC levels compared to those preschools constructed with conventional building materials. The IAQ and indoor chemical emissions were also strongly dependent on the functioning of the ventilation system. Preliminary risk assessment indicated that exposure to acrolein and crotonaldehyde might lead to respiratory-tract irritation among occupants.

scholarly journals The oxidation kinetics of depleted uranium and its low-alloy molybdenum alloys in moist air

2019 ◽  
Vol 63 (3) ◽  
pp. 100-104
Author(s):  
T. Chmela ◽  
P. Krupička
Keyword(s):  
Relative Humidity ◽  
Reaction Kinetics ◽  
Oxidation Kinetics ◽  
Reaction Rate ◽  
Depleted Uranium ◽  
Rate Equations ◽  
Moist Air ◽  
Molybdenum Alloys ◽  
Exponential Behaviour ◽  
Kinetics Of

Abstract The oxidation kinetics of depleted uranium and its low-alloy molybdenum alloys (U-2wt.%Mo, U-5wt.%Mo) were measured in a moist air (75% relative humidity) at 60 and 75 ° C. Coefficients of reaction rate equations were determined for linear oxidation kinetics. In the oxidation of depleted uranium at 75 ° C, a change in reaction kinetics from linear to exponential behaviour was observed after about 2500 hours.

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.

scholarly journals Spatial and Temporal Distribution of Temperature, Relative Humidity and Air Velocity in a Parallel Milking Parlour During Summer Period

2015 ◽  
Vol 15 (2) ◽  
pp. 517-526 ◽  
Author(s):  
Piotr Herbut ◽  
Sabina Angrecka ◽  
Grzegorz Nawalany ◽  
Krzysztof Adamczyk
Keyword(s):  
Relative Humidity ◽  
Air Temperature ◽  
Ventilation System ◽  
Temporal Distribution ◽  
Operating Conditions ◽  
Air Velocity ◽  
Summer Period ◽  
Air Movement ◽  
Air Stream ◽  
Relative Air Humidity

Abstract The research aimed at determining the most significant parameters affecting the microclimate of milking parlours, such as temperature, relative humidity and air movement in a parallel milking parlour in real operating conditions. The research was conducted in the summer period, when the risk of heat stress in cattle is higher. To check welfare of cows during milking, days with air temperature >25°C and days with temperature equal or lower than 25°C were analysed. Observation and analysis were performed for air flow in milking parlour, range of supplied air stream and how air movement affects cattle. It was observed that the irregular distribution of air movement led to the development of diverse air velocity in different zones of the milking parlour (0.2-9.0 m∙s-1). As a consequence, the conditions inside the barn were not homogenous for all the cattle. A significant effect of the cows and external air temperature (which depends indirectly on orientation of the milking parlour relative to cardinal directions) on temperature increase (approx 6°C) was concluded, with relative air humidity at the level of 85-90%, during the milking, which led to systematic decrease of microclimatic comfort for cattle. Based on the conducted research, it was concluded that the design of ventilation systems in parallel milking parlours should be preceded by increased research not only on ventilation system efficiency but also on the distribution of flow ventilated air.

scholarly journals The effect of atmospheric humidity on the metabolism of the fasting mealworm ( Tenebrio molitor L., Coleoptera)

1932 ◽  
Vol 111 (772) ◽  
pp. 376-390 ◽  
Keyword(s):  
Relative Humidity ◽  
Dry Matter ◽  
Total Water ◽  
Moist Air ◽  
Atmospheric Humidity ◽  
Dry Air ◽  
Two Temperatures ◽  
The Difference ◽  
Food Reserves ◽  
Metabolic Water

Previous work has shown that fasting mealworms will live at room tempera­ture for two hundred days, and even at 30°C. they usually live for over a month. During the first two days of starvation the mealworms are restless, and they pass a certain amount of excrement. After this they lie quite still, and pass extremely little excreta. The loss in weight of starving mealworms is different in dry and moist air at one temperature, or in air with the same relative humidity at two temperatures. At 23° C. the mealworms evidently regulate their metabolism, because while they lose weight at different rates in air of various relative humidities, yet they keep the ratio of dry matter to water in their bodies constant (Buxton, 1930). In carrying this work further, I have attempted to find whether the rate at which fasting mealworms evaporate water is proportional at any temperature to the saturation deficiency of the air. Now the fasting mealworm not only evaporates water present in its body at the start of the experiment, but also considerable quantities of water produced by the metabolism of food reserves during starvation. We can estimate the amount of water present in the mealworms at the start of starvation, and can find how much is left at the end of the experiment; the difference represents part of the total water evaporated. But this method does not indicate any metabolic water which is produced and also evaporated during starvation. If one wishes to know the total water evaporated, it can be collected in a stream of air, or else the loss of food reserves must be estimated and the metabolic water produced calculated from these results. I preferred to use the second method, as it is not easy to measure the actual amount of water given off by insects except into dry air.

Annual Analysis of Boundary Conditions on Air Flow through Building Envelope

2016 ◽  
Vol 824 ◽  
pp. 379-386
Author(s):  
Michaela Horáčková
Keyword(s):  
Mechanical Ventilation ◽  
Relative Humidity ◽  
Boundary Conditions ◽  
Ventilation System ◽  
Building Envelope ◽  
Flow Through ◽  
The Difference ◽  
One Year ◽  
Measured Pressure

Leakage in the building envelope may occur airflow as well as its surface. It brings series of adverse consequences, including the flow of diffuse. The airflow building envelope is allowed through a pressure gradient, which is caused by the difference in temperature and wind effects; if necessary a mechanical ventilation system. Article introduces the analysis which was performed on experimental objects of different wind exposition in situ. In this analysis was measured pressure, relative humidity and air temperature in the interior and exterior, for a period of one year. In the conclusion is evaluated the effect of these boundary conditions on the very existence of the airflow through building envelope.

Is air moisture relevant on radiative heat exchange inside built environments?

2019 ◽  
Vol 37 (4) ◽  
pp. 1291-1316
Author(s):  
Nuno Serra ◽  
Viriato Semiao
Keyword(s):  
Relative Humidity ◽  
Air Temperature ◽  
Flow Characteristics ◽  
Scale Model ◽  
Radiative Heat Exchange ◽  
Built Environments ◽  
Moist Air ◽  
Content Type ◽  
Relative Differences ◽  
Real Scale

Purpose This paper aims to clarify the necessity of taking into account the commonly neglected radiation in built environments. Ignoring radiation within acclimatized spaces with moist air, which is a participating medium, can yield inaccurate values of the relevant variables, endangering the Heating, ventilation, and air conditioning design accuracy and leading to energy inefficiencies and discomfort. Design/methodology/approach The paper uses computational fluid dynamics to predict non-isothermal flows with radiation, for both mixing and displacement ventilation strategies. The tool is applied to a lab-scale model (scale 1:30), and the results are compared with experimental data and predictions without radiation. Furthermore, the radiation influence is also assessed at real-scale level, including a parametric study on the effect of the air relative humidity on radiation. Findings The paper demonstrates the unequivocal impact of radiation on the flows thermal-kinematics at real-scale: ignoring radiation yields average air temperature differences of 2ºC. This becomes more evident for larger air optical thicknesses (larger relative humidity): changing it from 20 per cent to 50 per cent and 70 per cent yields maximum relative differences of 100 per cent for the velocity components and 0.4ºC for the air temperature. Nevertheless, the results for the lab-scale case are not so conclusive about the effect of moist air radiation on the thermal flow characteristics, but they evidence its impact on the flow kinematics (maximum relative differences of velocity components of 35 per cent). Originality/value The paper fulfills an identified need to clarify the relevant effects of air moisture on radiation and on the flow turbulence and thermal-kinematic characteristics for forced convective flows inside built environments.

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