Effect Of Air Relative Humidity Research Articles

The Effect of Air Relative Humidity on the Drying Process of Sanitary Ware at Low Temperature: An Experimental Study

Drying is a thermodynamic process in which the moisture contained in the solid is removed by evaporation through the supply of an appreciable amount of thermal energy. It is recognized as a critical and intricate stage in the manufacturing process of ceramic materials. In general, drying at higher temperatures and lower air-relative humidity provokes severe hydric, thermal, and mechanical fractures in the ceramic parts, thus reducing product quality after the process. Then, this process must be realized under controlled conditions. From an industrial point of view, the drying process of sanitary ware takes place in two stages: drying at low temperatures (less than 40 °C) and drying at high temperatures (above 50 °C). Thus, the purpose of this work is to experimentally investigate the drying process at low temperatures in sanitary toilets. Drying experiments were conducted in an oven with the same temperature (35 °C) and different relative humidity of the drying air. The results of the moisture content, temperature, and dimension variations along the process, as well as drying and heating rates, are reported and analyzed. The results indicate that the higher the air’s relative humidity, the slower the moisture removal. Herein, aspects of the product quality after the drying process are also discussed.

A comprehensive analysis of the moist air transonic flow in a nozzle with a very low expansion rate

• Experimental study of the moist air transonic flow in a nozzle with a low expansion rate. • Mathematical models of homogeneous condensation. • The study of the effect of air relative humidity on the expansion process. • The study of the interaction between condensation and pressure waves. Inevitable and undesirable as it is, phase transition has a significant impact on the fluid flow efficiency in many energy processes. This paper deals with the impact of water vapour condensation and liquid water evaporation in the moist air expansion in a nozzle with a low expansion rate. The presented comprehensive analysis includes a numerical study supported by analytical and experimental research. The experimental study concerning measurements of atmospheric air transonic flows was carried out using an in-house experimental test rig. A nozzle with a low expansion rate of P ̇ ≈ 1000 s - 1 was investigated experimentally at different inlet air relative humidity values included in the range of 25 to 51 %. The nozzle was measured for supersonic outlet conditions, as well as with elevated back pressure (78 kPa). The technique of Schlieren photography and static pressure measurement on the nozzle wall were used for qualitative identification of both condensation and shock waves. The presented numerical modelling was conducted using commercial computational fluid dynamics software extended with an in-house condensation model. The code was validated against experimental data and data available in the literature. The analysis of the flow in the nozzle with a very low expansion rate revealed very interesting structures of pressure waves. The impact of relative air humidity on the condensation process and the interaction of the condensation wave with aerodynamic oblique as well as normal shock waves were investigated. It is observed that the higher the air relative humidity value, the more difficult it is to identify aerodynamically induced oblique shock waves in the flow. Finally, considering that the efficiency drop induced by the phase change can reach up to 10 %, the impact of condensation on the expansion process efficiency is presented.

Effect of Differentiated Relative Humidity of Air on the Quality of Traditional Speciality Guaranteed “Krakowska Sucha Staropolska” Sausage

The aim of the study was to determine the effects of air relative humidity (RH: 60 and 80%) during the drying process of “krakowska sucha staropolska” (KSS) sausages on selected quality characteristics. The composition and production process of KSS sausages complied the requirements of traditional specialities guaranteed. It was found that the use of lower RH of drying air allowed a time reduction of 20%. Lowering the RH of air during the drying process did not affect the cross-sectional colour and odour of the sausages, colour components, TBARS values, protein, fat and salt content. However, the acceleration of the drying process resulted in very dried outer layers and less dry interior of KSS sausages. As a result, the sausages had lower scores in the sensory evaluation of hardness and overall acceptability. For this reason, shortening the drying process of sausages by using air with lower relative humidity is not recommended.

The effect of air relative humidity on the evaporation temperature of water-ethanol droplets

Using the method of infrared thermography, an experimental study of the temperature of evaporating droplets of a water-ethanol solution of different concentrations suspended on polypropylene thread at different air relative humidity was carried out. It is shown that the amplitude of the diminution in droplet temperature during evaporation decreases with an increase in relative air humidity for all considered concentrations of the water-ethanol solution. It is shown that the pattern of decreasing the minimum temperature of cooling of the evaporating droplets with increasing ethanol concentration is characteristic of all the studied air relative humidity. The obtained experimental data are generalized and can be used when calculating the heat and mass transfer of evaporating droplets of the water-ethanol solution.

The effect of air relative humidity on the intensity of evaporating of water–ethanol droplets

The results of experimental studies of the evaporation of the water-ethanol droplets with various concentrations of ethanol suspended on a thread are presented. Using high-speed microphotography, we studied the dynamics of changes in the size of evaporating droplets at various relative humidity of the surrounding air. As a result of experiments, it was found that the relative humidity of the surrounding air had a significant effect on the process of droplet evaporation. For all the considered concentrations of ethanol, it was found that the higher the concentration, the shorter the evaporation time of the droplets. Generalization of the experimental data on the evaporation time of the water-ethanol droplets of the corresponding concentration of ethanol at a relative humidity of 95% was carried out.

Effects of air relative humidity on spectral characteristics of dielectric barrier discharge plasma assisted combustion reactor

Using dielectric barrier discharge (DBD), a cylinder plasma assisted combustion (PAC) reactor was designed and applied to real aero-engines. Through the acquired optical emission spectroscopy (OES), the effects of air relative humidity (RH) on important active products (e.g. excited nitrogen molecules and hydroxyl radical) of this reactor discharges were investigated. In addition, vibrational temperature of N2* was calculated by Boltzmann plots. The OES of OH radials at 309 nm was analyzed. The results indicated that most OES of second positive system (SPS) N2*(CΠ3u→BΠ3g) had lower intensity at higher RH. The OES of first negative system (FNS) N2+ (391.4 nm) enhanced at 25 ~ 50% RH and reduced at 50~95%. Vibrational temperature of N2* reduced with the increased RH. When RH was lower than 35%, the OES of OH(A∑2→XΠ2) decreased with the increase of RH. While RH was higher than 35%, OH intensity increased. These research results could provide a vital basis for further studying the effects of DBD PAC reactor on combustion performances of aero-engines.

Effects of air relative humidity and ventilation rate on particle concentrations within a reduced-scale room

An improved understanding of particle movement in ventilated rooms would help reduce airborne disease transmission in healthcare facilities. More empirical data are needed on the movement of small ...

Effects of Air Relative Humidity and Temperature on Photodegradation Processes in Beech and Spruce Wood

Spruce and beech samples were irradiated by UV light in humid (100% air humidity) and dry conditions to clarify the effects of vapor on photodegradation. UV-irradiated samples were also soaked in distilled water for comparison. The color change and the IR absorption spectra were measured. The wet condition generated considerably greater discoloration than did the dry condition. The intensity of the color change was higher at elevated temperature (53 °C) than at 32 °C. The results showed that the presence of water as vapor increased the degradation of lignin. The nonconjugated carbonyl groups absorbing around 1760 cm-1 were found not to be stable, and the number of these chemical groups decreased in the presence of vapor when compared against the dry condition. The rising temperature amplified this degradation effect.

Studies on Stress Relaxation Process in Biodegradable Starch Film

In the paper the effects of keratin and polyvinyl alcohol additives on the stress relaxation course in thermoplastic starch film were presented. The 3-parameter Zener model was used to describe the behavior of film under loading taking into account sample sizes and initial deformation velocity. The effects of air relative humidity, initial deformation velocity and the way of sample cutting on model parameters were also determined. The increase of keratin content resulted in the decrease of E0 parameter, whereas the increase of polyvinyl alcohol caused its increase.

The effect of air relative humidity on the appearance and structure of subcutaneous pork fat unsalted or treated with NaCl, KCl or K-lactate

This study evaluated the effect of different air relative humidities (RH) and temperatures (T) on the appearance and structure of subcutaneous fat unsalted or treated with NaCl, KCl or K-lactate. Subcutaneous fat samples were stored for 60 days at different RH and T (from 63.5% to 87.7% at 5 °C and from 57.7% to 84.3% at 25 °C). The water content of the subcutaneous fat samples depended on the air RH and T and on the salting treatment. Within each salting treatment, fat samples with lower water contents showed oil drip on the surface, except for samples treated with K-lactate, which did not show oil drip at any RH or T. The air RH below which oil drip appeared depended on the salting treatment. Adipocytes from the external layer of the samples with oil drip showed a wrinkled appearance under the light microscope, which was related to water loss. Hardness of subcutaneous fat decreased with increasing water content in a non-linear way, similar to that described for lean tissue in the literature.

Efeito de ciclos de umidade relativa e temperatura do ar na resistência de juntas colodas com lâminas de Eucalyptus grandis W. Hill ex Maiden, Eucalyptus saligna Smith e chapas de fibra de densidade média (MDF)

Este trabalho teve como objetivo avaliar o efeito de ciclos de umidade relativa e temperatura do ar na resistência da linha de cola, em juntas coladas entre lâminas de madeira de Eucalyptus grandis, Eucalyptus saligna e lâminas de chapa de fibras de média densidade (MDF) cujas densidades foram iguais a 0,60, 0,66, e 0,72g/cm³, respectivamente. Foram empregados adesivos de poliacetato de média viscosidade e uréia-formaldeído nas gramaturas de 150,0g/m² e 180,0g/m², respectivamente, em face simples. O teor médio de umidade no momento da colagem foi igual a 14%. Foram observadas diferenças significativas tanto na resistência da linha de cola quanto na percentagem de falha na madeira provocada pela composição das amostras, etapa de equilíbrio e tipo de adesivo. Os valores mais elevados de resistência foram observados nas juntas coladas com madeira de Eucalyptus saligna após a primeira etapa de equilíbrio, enquanto os menores valores ocorreram nas juntas combinando lâminas de eucalipto e MDF. Considerando apenas as lâminas de madeira, os valores mais elevados de falha na madeira foram observados nas juntas coladas entre lâminas de Eucalyptus grandis. Nas amostras compostas de madeira de eucalipto e lâminas de MDF, a porcentagem de falha foi total e o rompimento ocorreu exclusivamente no interior da chapa de MDF. Observou-se interação significativa entre a composição das amostras lâminas e o tipo de adesivo, em que os valores mais altos de resistência ocorreram nas juntas coladas com madeira de Eucalyptus saligna e adesivo à base de uréia-formaldeído.

Effect of gas humidity on the potential of pseudoreference Pt/air electrode in amperometric solid-state gas sensors

The effect of air relative humidity (RH) on the potential of two different Pt/air electrodes was examined. One electrode was platinum in contact with a hydrophilic Nafion (Pt-Nafion/air), the other was platinum in contact with a plasticized polyvinyl chloride containing a hydrophobic electrolyte (Pt-PVC/air). Over the RH range, from 11 to 72%, the potential of the Pt-Nafion/air electrode decreases non-linearly with increasing RH from 880 to 710 mV versus Ag/AgCl electrode. The potential decrease at the steepest part of the dependence (for RH from 30 to 70%) amounts to about −4 mV/%RH. The potential of the Pt-PVC/air electrode increases linearly with increasing RH from 324 to 337 mV versus Ag/AgCl electrode, with a slope of 0.21 mV/%RH. The change of the reference electrode potential with changing RH might influence the properties of the sensors where the current is measured on the increasing or descending part of the current–potential curve (e.g. the sensors with an indicator electrode exposed to test gas without a diffusion barrier).

Effect of air relative humidity on ham rind and subcutaneous salted fat during the resting period

This study evaluated the effect of different air relative humidities (RH) on the nature and structure of the rind of dry-cured ham and of salted subcutaneous fat. After salting 16 hams were stored for 40 days at 4°C, and at two different RHs (50–55 and 80–85%). Salted subcutaneous fat samples were stored for 30 days at 15°C and at different RH (57.7, 70.8, 75.3 and 80.0%). Storage of hams at 50–55% RH after salting produced a whiteness on some parts of the rind, due to precipitation of salt inside the rind. Fat samples stored at 80.0% RH showed no oil drip and the fat cells observed microscopically were similar to non-salted cells. In contrast, fat samples stored at 57.7 and 70.8% RH showed oil drip and the fat cells from the external layer showed a wrinkled aspect in the optical microscope. Samples stored at 75.3% RH showed only a slight oil drip at the edges.

The effect of humidity and state of water surfaces on deposition of aerosol particles onto a water surface

Deposition processes of particles with dry diameter larger than about 10 μm are dominated by gravitational settling, while molecular diffusion and Brownian motion predominate the deposition processes of particles smaller than 0.1 μm in dry diameter. Many air pollution derived elements exhibit characteristics common to sub-micron particles. The objective of the present study is to examine the effects of meteorological conditions within the turbulent transfer layer on the deposition velocity of particles with dry diameter between 0.1 and 1 μm. It is for these sub-micron particles that particle growth by condensation in the deposition layer, the broken water surface effect and the enhanced transfer process due to atmospheric turbulence in the turbulent transfer layer play important roles in controlling the particle deposition velocity. Results of the present study show that the `dry air’ assumption of Williams’ model is unrealistic. Effects of ambient air relative humidity and water surface temperature cannot be ignored in determining the deposition velocity over a water surface. Neglecting effects of ambient air relative humidity and water surface temperature will result in defining atmospheric stability incorrectly. It is found that the largest effect of air relative humidity on deposition velocity occurs at an air–water temperature difference corresponding to the point of `displaced neutral stability'. For a given wind speed of U=5 m s −1 the additive effects of water surface temperature, T w, changes from 5 to 25°C and ambient air relative humidity variations from 85 to 60%, respectively, lead to a maximum difference in v d of about 20%. For a higher wind speed of 10 m s −1, however, the corresponding change in v d reduces to less than 5%. This is further confirmation that wind speed is one of the strongest variables that governs the magnitude of v d. The present study also found that the broken surface transfer coefficient, k bs, given as a multiple of the smooth surface transfer coefficient, k ss, is physically more meaningful than assigning it a constant value independent of particle size. The method used in this study requires only a single level of atmospheric data coupled with the surface temperature measurement. The present method is applicable for determining deposition velocity not only at the conventional measurement height of 10 m but also at any other heights that are different from the measurement height.

Cushioning Properties of Corrugated Fiberboard and the Effects of Moisture Content

The effect of air relative humidity on the shock absorbing properties of three types of corrugated fiberboard (single face, single wall, and double wall) was studied. Samples were conditioned at four different relative humidities ranging from 55% to 95% and then tested using an appropriate cushion tester. The results show that there is a significant influence of the moisture content of the corrugated fiberboard material on the cushioning characteristics. These results are particularly important when designing packages for fresh horticultural products, especially in cases where a favorable situation for strengthening the compressive resistance is unfavorable for shock absorbing or energy dissipating during an impact.