Spatial distribution of formamide from EVA foam mats: CFD simulation and inhalation exposure assessment for children

The radionuclides released from NPPs (Nuclear Power Plants) as a result of accidents will significantly affect human health by causing cancer, genetic diseases, or acute radiation sickness. To investigate and evaluate the influence of the airborne hazardous materials on human bodies in an indoor environment in urban areas near NPPs, it is necessary to calculate the inhalation dose. In this study, a method for the assessment of the inhalation dose of indoor radionuclides was proposed. This method consists of the combination of the basic equation of natural ventilation and the empirical equation for calculation of the inhalation dose. The method was applied in a modeled densely urban domain, and CFD simulations were conducted to obtain the wind pressure distribution on the building surfaces. Moreover, the impacts of certain important parameters, including the ventilation coefficient, the age group of humans, the wind velocity, the urban street width, and the building height, were discussed in this paper. The results show that all of these parameters affect the indoor inhalation dose. In most cases, the indoor dose obtained at the same floor was higher with a higher ventilation coefficient, breathing rate, wind velocity, and street width or a lower building height. Furthermore, people living in the middle floors will generally be exposed to a lower inhalation dose than those in other floors especially the top floor.

Forced air pre‐cooling after harvest of fruit was an indispensable part of modern cold chain logistics. A comprehensive thermodynamics evaluation system of forced air pre‐cooling for cherry was established in this paper using the finite volume method and verified with experimental results. The results showed that the 7/8 pre‐cooling time decreased with increasing air velocity. However, when the air velocity was higher than 2 m/s, the 7/8 pre‐cooling time was not significantly shortened. In addition, 7/8 pre‐cooling time and air velocity coincided with the power function: t7/8 = 42.603v−0.687. The energy consumption of forced air pre‐cooling decreased first (0.5–1.5 m/s) and then increased (1.5–3 m/s) with the increase in air velocity, and the largest difference reached 9.30%. Finally, the inhomogeneity of pre‐cooling was also analyzed. The larger the air velocity was, the lower and earlier of the peak value of inhomogeneity in the forced air pre‐cooling process. When the air velocity exceeded 2 m/s, the change rate of the inhomogeneity of 7/8 pre‐cooling time was less than 5%.Practical applicationsForced air pre‐cooling after harvest of fruit was an indispensable part of modern cold chain logistics. However it can significantly reduce water loss, fruit wilting and rot during storage. In this paper, the air parameters of cherries 7/8 pre‐cooling time, energy consumption and inhomogeneity of pre‐cooling were analyzed by CFD simulation and experiment. According to the results, we can acquire the explicit relationship between 7/8 pre‐cooling time and air velocity. And the influence of air velocity on energy consumption and the inhomogeneity of pre‐cooling. The purpose was to get optimal air parameters for forced air pre‐cooling of cherries.

The age-old question, “How much is enough?” needs to be answered with regard to the practice of adding higher and higher air velocities in an effort to lower respirable coal dust concentrations in longwall installations. What is the level at which a further increase in air velocities no longer dilutes, but entrains and suspends respirable dust? At some point entrainment becomes the dominant factor and respirable dust levels will become constant, or even increase with further increases in air velocity. When the problem of entrainment exceeds the benefit of dilution, any further increase in air velocities is a waste of available air that could be used elsewhere in the mine where it is needed. This article presents a case study, approximately 2 years in length, done by Jim Walter Resources' engineering staff, which evaluates the effect of wide variations in air velocity (770 to 1500 ft/min) on respirable dust concentrations on seven longwalls in the Blue Creek coal seam in Central Alabama. Production levels are incorporated into the analysis to establish that no reasonable mathematical relationship exists between further increases in already high air velocities and reductions in respirable dust levels.

Experimental and computational studies on gas–solid fluidization in a cylindrical column with and without internals

An experiment was performed to investigate lift-off, blow-off and combustion characteristics of a lifted coaxial diffusion flame according to fuel jet and air velocity. A jet diffusion flame which is attached on the nozzle rim begins to be lifted with increase of air velocity, and finally becomes blow-off at higher air velocity. In experiment, blow-off limit increased with increase of fuel jet velocity, however lift-off occurred at lower air velocity. Flame structure and combustion characteristics were examined by schlieren photos, temperature distributions and emisions concentration distributions. Flame temperature became higher at midstream and its RMS became larger at up and downstream with increase of air velocity. Local NO concentration decreased but CO₂ concentration increased with increase of air velocity, which shows combustion reaction becomes close to be stoichiometric at higher air velocity in spite of lift-off.

Live performance of male broilers subjected to constant or increasing air velocities at moderate temperatures with a high dew point

Modeling and simulation of air humidification by hollow fiber membrane contactors are investigated in the current study. A computational fluid dynamic model was developed by solving the k-epsilon turbulence 2D Navier.Stokes equations as well as mass conservation equations for steady-state conditions in membrane contactors. Finite element method is used for the study of the air humidification under different operating conditions, with a focus on the humidity density, total mass transfer flux and velocity field. There has been good agreement between simulation results and experimental data obtained from literature. It is found that the enhancement of air stream decreases the outlet humidity from 0.392 to 0.340 (module 1) and from 0.467 to 0.337 (module 2). The results also indicated that there has been an increase in air velocity in the narrow space of shell side compared with air velocity wide space of shell side. Also, irregular arrangement has lower dead zones than regular arrangement which leads to higher water flux.

This study applied Adaptive Neuro-Fuzzy Inference System (ANFIS) to predict the moisture ratio (MR) during the drying process of yam slices (Dioscorea rotundata) in a hot air convective dryer. Also the effective diffusivity, activation energy, and rehydration ratio were calculated. The experiments were carried out at three (3) drying air temperatures (50, 60, and 70 °C), air velocities (0.5, 1, and 1.5 m/s), and slice thickness (3, 6, and 9 mm), and the obtained experimental data were used to check the usefulness of ANFIS in the yam drying process. The result showed efficient applicability of ANFIS in predicting the MR at any time of the drying process with a correlation value (R2) of 0.98226 and root mean square error value (RMSE) of 0.01702 for the testing stage. The effective diffusivity increased with an increase in air velocity, air temperature, and thickness and the values (6.382E -09 to 1.641E -07 m2/s). The activation energy increased with an increase in air velocity, but fluctuate within the air temperatures and thickness used (10.59–54.93 KJ/mol). Rehydration ratio was highest at air velocity×air temperature×thickness (1.5 m/s×70 °C × 3 mm), and lowest at air velocity × air temperature×thickness (0.5 m/s×70 °C × 3 mm). The result showed that the drying kinetics of Dioscorea rotundata existed in the falling rate period. The drying time decreased with increased temperature, air velocity, and decreased slice thickness. These established results are applicable in process and equipment design, analysis and prediction of hot air convective drying of yam (Dioscorea rotundata) slices.

In this research, physical properties of corn and barley seeds were first determined and then, to obtain the change in pressure drop, power consumption and mechanical seed damage as a function of air velocity during suction conveying of corn and barley, a suction-type pneumatic conveying system was designed and constructed and finally the pneumatic conveying characteristics of corn and barley seeds were determined under seven air velocities. The results indicated that the geometric and arithmetic mean diameters and sphericity of corn seeds were 80, 63 and 20%, respectively, more than the barley seeds. Pressure drop increased nonlinearly and linearly with an increase in air velocity for corn and barley seeds, respectively. However, power consumption was nonlinearly increased with air velocity for both seeds. Mechanical damage of both seeds increased linearly as the air velocity was increased. There was a turning point at which the pressure drop increased rapidly with an increase in air velocity. The lowest pressure drop for corn and barley occurred at the air velocity of 20 and 15 m s-1, respectively. Therefore, for reducing the specific energy consumption and mechanical damage to corn and barley seeds at the conveying capacity of 15 ton h-1, the air velocity in pneumatic conveying must be decreased below 20 and 15 m s-1, respectively. Key words: Pneumatic conveying, conveying characteristics, pressure drop, power consumption, mechanical damage.

Investigation on blockage boundary condition of dense-phase pneumatic conveying in bending slits

Global warming combined with increased production (i.e. more piglets, more milk and consequently more heat) means that sows are more often challenged by heat stress. The objective was to develop an effective temperature (ET) equation to predict how air temperature, velocity and humidity affect the respiration rate (RR), rectal temperature (RT) and skin temperature (ST) as an expression of heat stress in gestating sows in order to elucidate the relationship between the thermal parameters and the sows' perception of the environment. The experimental room was equipped with a negative pressure ventilation system with diffuse air inlet through the ceiling, electrical heaters, steam generators and dehumidifiers. An air distribution unit was constructed to generate vertical air velocity. A total of 16 gestating sows were exposed to three temperatures (25°C, 29°C and 33°C), two levels of relative humidity (30% and 70%) and three levels of air velocity (0.2ms-1, 1ms-1 and 2.5ms-1). The RR, RT and ST were recorded every 30min throughout the three 2-h test periods. The estimated effects of humidity and velocity in relation to effect of temperature was nearly independent of whether it was determined from RR or RT, whereas the effect of humidity was much smaller when determined from ST. High coefficients of determination (>0.97) were found for the second order relationship between the estimated ET and RR, RT and ST. An increase in relative humidity from 50 to 70% corresponded to an increase in ET of 0.9°C, while an increase in air velocity from 0.2 to 1.0ms-1 corresponded to a decrease in ET of 1.2°C. The applied ET equation was useful for expressing the combined effect of temperature, humidity and velocity on animals exposed to heat stress. However, multiplying the effect of velocity by the temperature gradient between the animal and the surrounding air did not improve the estimation.

The purpose of this study is to evaluate the effect of air curtains on indoor environment and dehumidification energy consumption for different air supply angle and velocity. The numerical investigation is conducted in a low-humidity plant located in the atmospheric boundary layer. The standard k-epsilon turbulence model is used in the simulation study. The optimum air supply angle and velocity are evaluated based on temperature and humidity distribution. The simulation cases range in air supply angle from 0° to 20° and velocity from 6 m/s to 14 m/s, which is studied by means of orthogonal experiments. Simulation results show that air curtain can reduce the average indoor temperature of the plant by up to 3.9°C and reduce the average moisture content by up to 86.6%. The energy saving assessment of the dehumidification rotor system shows a parabolic variation in energy consumption with increasing air velocity at a certain air supply angle. The optimum energy consumption occurs in the range of 9–11 m/s for air supply velocity. When air supply velocity is over 11 m/s, the airflow exchange is enhanced by air curtain at the plant opening, resulting in higher energy consumption from air leakage for dehumidification.

The purpose of this study is to evaluate the effect of air curtains on indoor environment and dehumidification energy consumption for different air supply angle and velocity. The numerical investigation was conducted in a low-humidity plant located in the atmospheric boundary layer. The standard k-epsilon turbulence model was used in simulation study. The optimum air supply angle and velocity were evaluated based on temperature and humidity distribution. The simulation cases range in air supply angle from 0° to 20° and velocity from 6m/s to 14m/s, which were studied by means of orthogonal experiments. Simulation results show that air curtain can reduce the average indoor temperature of the plant by up to 3.9°C and reduce the average moisture content by up to 86.6% compared to the cases without air curtains. The energy saving assessment of the dehumidification rotor system shows a parabolic variation in energy consumption with increasing air velocity at a certain air supply angle. The optimum energy consumption occurs at the range of 9-11m/s for air supply velocity. When air supply velocity is over 11m/s, the airflow exchange is enhanced by air curtain at the plant opening, resulting the higher energy consumption from air leakage for dehumidification.

Avoidance of allergens and air pollutants in respiratory allergy

Occupational exposure to chemicals occurs mainly through inhalation and the skin. The inhalation exposure assessment is regulated by law, while in Poland the method of conducting measurements for dermal exposure has not been indicated in the law. However, due to the restrictions 71 and 76 from Annex XVII of REACH for 1-methyl-2-pyrrolidone (NMP) and N,N-dimethylformamide (DMF), exposure assessment by the dermal route is necessary. These restrictions require to ensure that exposure of workers is below the derived no-effect levels (DNELs) for dermal exposure. The aim of the work was assessment of suitability of selected non-measurement forecasting models for the estimation of dermal occupational exposure to chemicals for the purposes of assessing compliance of working conditions with the restrictions 71 and 76 of the REACH regulation. Three tools estimating dermal exposure, recommended by European Chemical Agency (ECHA), were selected: ECETOC TRA, RISKOFDERM and IH SkinPerm, which were used to estimate 2 exemplary workplaces. Results of the estimations of dermal exposure showed that non-measuring models are useful for fulfilling the obligations under restrictions 71 and 76 of Annex XVII of REACH. The type of exposure scenario and amount of data available for the workplace are crucial for the selection of the model. The ECETOC TRA was considered the best model for this type of analysis, whose main advantages are direct comparison of the output data in mg/kg/day with the DNEL value and use of standardized descriptors system. Exposure modeling is a good and cheap way to determine the dermal exposure magnitude at workplaces, also to comply with the requirements of restrictions 71 and 76 of Annex XVII of REACH. The application of modeling in the case of occupational exposure by the dermal route is one of the solutions when it is necessary to comply with the DNEL for dermal exposure. Med Pr Work Health Saf. 2023;74(6):487-500.