Wyniki 1-10 spośród 14 dla zapytania: authorDesc:"Jacek Majewski"

Droplets size distribution in electrostatic spraying of water and water-based sprays

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The electrospraying of water and waterborne solutions (e.g. waterborne coatings and pesticides) is thoroughly investigated because of considerable gain in environment protection. However, water is rather uneasy to be electrosprayed, as some its properties, mainly high surface tension, high conductivity and high dielectric constant create difficulties for electrohydrodynamic (EHD) atomization of water. The droplet size and its distribution in a water shower are of key importance if industrial application of the process could become attractive. Streszczenie. Elektrostatyczne rozpylanie wody stanowi poważny problem z uwagi na szerokie zastosowanie roztworów wodnych w wielu gałęziach przemysłu i rolnictwa (np. malowanie obiektów lub opryski roślin) z udziałem substancji mających silne oddziaływanie na środowisko naturalne. Wielkość mikrokropelek wody lub jej roztworów oraz rozrzut ich wymiarów mają istotne znaczenie w wielu procesach przemysłowych. (Rozkład rozmiarów kropel podczas elektrostatycznego rozpylania wody i roztworów wodnych). Keywords: electrospraying of water, droplet size distribution, measurement of water droplets size. Słowa kluczowe: elektrostatyczne rozpylanie wody, rozrzut rozmiarów kropel, pomiary rozmiarów kropel wody. Introduction Although the history of electrostatic spraying of water (called also electro-hydrodynamic spraying, EHD) traces back to 1745, first mathematically supported research were reported by Lord Rayleigh in the last quarter of XIXth century, and industrial applications emerged only during the World War II. Today, the electrostatic spraying technologies are gaining of industrial interest due to quality improvement and/or cost reduction in many fields (e.g. finishing industry). The most popular today’s application of EHD are: paint spraying, continuous ink-jet printing, pesticide spraying, electroaerosol therapy (charged inhalers), smoke dissipation, EHD separation and precipitation, emulsion [...]

Methods for measuring ozone concentration in ozone-treated water

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The ozone measurements are gaining in importance as the area of environmental ozone applications to liquids and especially to water grows. Some a few methods can be enumerated, and each of them has only limited area of applications. The comparison of the methods shows that there still is a need for rugged, reliable, ozone-specific, direct measurement methods and sensors for measuring ozone concentration in ozonated water. Streszczenie. Przyrządy i metody do pomiaru stężenia ozonu w cieczach, a zwłaszcza w wodzie, nabierają coraz większego znaczenia w miarę rozszerzania się obszarów zastosowań ozonu ze względu na ochronę środowiska. Porównano kilka współcześnie stosowanych metod i wykazano, że każda z nich posiada tylko ograniczony obszar przydatności. (Metody pomiaru stężeń ozonu w wodzie ozonowanej) Keywords: water ozonation, dissolved ozone concentration measurement, water disinfection systems. Słowa kluczowe: ozonowanie wody, pomiary stężeń rozpuszczonego ozonu, układy do dezynfekcji wody. Introduction The global increase in pollution of surface fresh water as well as seawater is mainly caused by human industrial activity. This problem is even more urgent in highly populated areas of developed countries, since the environment becomes ecologically damaged - and this degradation is a factor enhancing e.g. the risk of waterspread epidemies [1]. On the other hand, consumers require from the manufacturers better quality of water and food for realizing healthy lifestyle. For these reasons, an intensive search for fast and efficient methods of water purification without residual taste, odour or toxic byproducts is continued. The method of water ozonation seems to satisfy these requirements to highly promising degree [2]. Although ozone was discovered in 1839 (by C. F. Schonbein) and used for tap water treatment in the Netherlands (1880’s), Nice (1907) and St. Petersburg (1910) [3], the water ozonation process is still widely i[...]

Measurement techniques concerning droplet size distribution of electrosprayed water

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The carefully-sized electrospraying of water is an important research problem because of wide use of sprays of water and aqueous solutions in many fields of industry and agriculture. The size of water droplets (or aqueous solutions) and its distribution is essential for various applications of aerosols. The measurement of size of electrosprayed water using laser-based measurement techniques is a non-intrusive and technologically advanced solution. Streszczenie. Wielkość mikrokropel wody oraz rozkład ich średnic mają istotne znaczenie w zastosowaniach aerosoli wytwarzanych metodą elektrostatycznego rozpylania. Pomiar średnic mikrokropel wody rozpylonej elektrostatycznie metodami opartymi na zastosowaniu lasera stanowi rozwiązanie bezkontaktowe i technicznie zaawansowane. (Metody pomiaru rozkładu średnic kropel wody rozpylanej elektrostatycznie). Keywords: electrospraying of water, droplet size distribution, droplet size measurement techniques. Słowa kluczowe: elektrostatyczne rozpylanie wody, rozkład średnic kropel, metody pomiaru średnic i ładunku kropel. Introduction The usefulness of many pulverized or dispersed substances in diverse fields and processes in both industrial end domestic activities (e.g. in paints, fuels, washing, or pharmaceuticals) is long known motivating factor for research and development of new techniques of pulverization, and measuring relevant features of the dispersed phase [1]. For many processes the most important characteristics is the particle size distribution (or, for sprays, the droplet size distribution, in short: DSD), since precise particle sizing has direct impact on the efficacy and quality of the product and helps reduce losses in both materials and energy. For example, ink jet printers or copier toners require carefully tailored DSD; similarly, saline aqueous solutions for drug inhalation can be targeted to specific part of the respiratory tract. Droplets under 3 μm in diameter are eject[...]

Measurement methods for size and charge distributions of electrosprayed water droplets DOI:10.12915/pe.2014.04.041

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The electrospraying of water and waterborne solutions (e.g. waterborne coatings and pesticides) is thoroughly investigated because of considerable gain in environment protection. The droplet size and charge distributions of water aerosol droplets are of key importance in many applications of the process in industry and in medical treatments. The measurement of the distributions of size and charge of electrosprayed water droplets using laser-based measurement techniques is a nonintrusive and technologically advanced solution. Streszczenie. Elektrostatyczne rozpylanie wody stanowi ważne zagadnienie z uwagi na zastosowania roztworów wodnych z udziałem substancji oddziaływujących na środowisko naturalne. Pomiar rozkładu wielkości kropelek oraz ich ładunków ma duże znaczenie w wielu procesach technologicznych i w zabiegach medycznych. (Metody pomiaru rozkładów wielkości i ładunku kropelek wody rozpylanej elektrostatycznie). Keywords: electrospraying of water, droplet size and charge distributions, droplet size and charge measurement methods. Słowa kluczowe: elektrostatyczne rozpylanie wody, rozkład wielkości i ładunków kropelek, metody pomiaru wielkości i ładunku kropelek. doi:10.12915/pe.2014.04.41 Introduction Electrospraying, also called electro-hydrodynamic spraying (or electro-hydrodynamic atomisation, EHDA), is a method that relies on breaking up a liquid jet into fine droplets by means of electrostatic forces. The size of the droplets obtained by this method ranges from a few nanometers to hundreds micrometers [1], depending on the parameters of the process of electrospraying. Several modes of operating an electrospray are distinguished; among them, in recent years the cone-jet mode has focused many research efforts [2], because it allows to obtain droplets with a narrow size distribution, practically monodispersed high quality spray. Although first experiments with electrospraying of liquids were described by Nollet in 1745, firs[...]

Polymer-based sensors for measurement of low humidity in air and industrial gases DOI:10.15199/48.2016.08.20

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Some problems concerning low humidity measurements using polymer-based humidity sensors are characterized. An exemplary calibration procedure applied to a humidity/temperature module is presented, as well as low-humidity range characteristics of humidity/temperature modules, and possible ways to extend the measurement range of these sensors towards low humidity levels of air and industrial gases are discussed. Streszczenie. Scharakteryzowano zagadnienia związane z pomiarami niskich wilgotności sensorami z polimerowym materiałem wilgotnościoczułym. Przedstawiono przykładową procedurę kalibracyjną zastosowaną do modułów termohigrometrycznych, i rozpatrzono możliwe sposoby rozszerzenia zakresu przetwarzania sensorów z polimerową warstwą wilgotnościoczułą na poziom wilgotności niskich w powietrzu i gazach przemysłowych.(Sensory z polimerową warstwą wilgotnościoczułą do pomiaru wilgotności niskich w powietrzu i gazach przemysłowych). Keywords: polymer-based humidity sensors, low humidity measurement, industrial gases humidity measurement. Słowa kluczowe: sensory z polimerową warstwą wilgotnościoczułą, pomiary wilgotności niskich, pomiary wilgotności gazów przemysłowych. Introduction The knowledge of humidity level in air and industrial gases is of paramount importance for the quality of end products in many modern technological processes, e.g. in semiconductor industry [1], pharmaceutical processing, or chemical gas purification [2]. Moreover, in some cases the water vapour content inside gas flowing through pipes should be monitored incessantly in order to detect possible leakage from the ambient into the pipe, and to trigger alarms in control installation. In such emergency situations, the response time of the monitoring sensors is crucial for avoiding deterioration of product or other consequences violating technological regime. Also, the pressures and temperatures applied in industry to gases can differ considerably from ambient cond[...]

Cross-sensitivity of hydrogen sensors to relative humidity DOI:10.15199/48.2018.07.32

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First devices for measuring hydrogen concentration in gas mixtures emerged around 1900 (used in airship filling systems) [1]. Intensive research on hydrogen sensors has begun in 1960s, and at present several electrical or electronic operating principles are well established and implemented in technologically advanced hydrogen-sensing devices. More than 400 models of hydrogen sensors are offered by about 100 manufacturers located mainly in Europe (ca. 50 %), North America (ca. 35 %), and East Asia (ca. 15 %). One of the reasons for that growing interest in hydrogen sensors is the long-term policy of the European Union and the USA to develop low-carbon energy technologies, including hydrogen as one of the most promising alternative sources of clean energy, till 2050 [2]. The biggest obstacle to the further progress in use of hydrogen in domestic life and automotive applications is the danger of explosion when the hydrogen concentration in air exceeds 4 vol% H2. Moreover, the hydrogen molecules are the smallest and the lightest of all gas molecules, and in the case of leakage they spread very fast in ambient air, forming an hydrogen-air mixture of very low ignition energy (0.02 mJ [3]). Reliable, fast and robust hydrogen-specific safety sensors are required. Some regulations allow to use oxygen sensors for quantifying hydrogen releases in vehicles, but this approach is disputed [4]. The most popular commercially available types of hydrogen safety sensors are: catalytic (ca. 30 %), electrochemical (ca. 30 %), thermal conductivity (ca. 15 %), and resistive (ca. 15 %). Market pull among the greatest car manufacturers imposed more stringent technical performance requirements for automotive hydrogen sensors than for the use in stationary systems [5]. The question of determining the cross-sensitivities of hydrogen sensors to various gases and vapours is one of the current research topics [6], but it is focused mainly on the interfe[...]

Metrological aspects of piezoresistors arrangements on the membrane in miniaturized pressure sensors

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A theoretical analysis concerning metrological features of thick film piezoresistors placed on circular edge-clamped membrane in pressure sensors is described. The change of resistance of a thick film piezoresistor, caused by the deflection of the membrane, related to the distance from the membrane centre and the width of the piezoresistor, is evaluated. Analytical expressions for different piez[...]

Determining of calibration equations for relative humidity sensors and modules


  Relative humidity (RH) sensors and modules are becoming increasingly important in many processes of modern industry (e.g. in the manufacturing processes of ultrapure materials for electronics devices). However, at present the standards for RH sensors’ and modules’ calibration can not offer a better accuracy than a few tenth of%RH. This fact has a strong influence on the accuracy of calibration data, and in consequence, on the fitting of calibration equations. As a rule, many authors of handbooks on sensors and calibration (e.g. [1, 4]) only discuss the “classic" regression method for the" y on x" regression case. Some researchers have determined the calibration equations using the inverse regression:" x on y" (e.g. [5]). The inverse regression requires to meet the condition of negligible y’s measurement errors [3]. An alternative to the regression methods is the minimax method of approximation. The goals of this work include providing proofs that it is reasonable to employ the minimax method to determining of calibration equations for RH sensors and modules, in comparison with the results obtained by the least-squares approximation method. In th[...]

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