The Experts below are selected from a list of 162 Experts worldwide ranked by ideXlab platform
Hans Janssen - One of the best experts on this subject based on the ideXlab platform.
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Hygric properties of porous building materials (IV): Semi-permeable membrane and Psychrometer methods for measuring moisture storage curves
Building and Environment, 2019Co-Authors: Chi Feng, Hans JanssenAbstract:Abstract The moisture storage curve is an important hygric property of porous building materials. It describes the moisture storage characteristic of a material via the relation between the moisture content and the moisture potential. Current experimental protocols for measuring moisture storage curves are not satisfactory, as they often require extensive facilities while still lacking the capability to handle the adsorption process in most of the over-hygroscopic range. This paper proposes two novel and simple methods – the semi-permeable membrane method and the Psychrometer method – to solve these issues. Measurements on calcium silicate, autoclaved aerated concrete and ceramic brick are performed and validated by comparing the experimental outcomes obtained from these two novel methods and from other existing protocols. It is proven that the semi-permeable membrane method and the Psychrometer method are applicable for both adsorption and desorption processes, the latter both from saturated and capillary moisture content. Limited by the accuracy of the Psychrometer and the condensation caused by temperature fluctuations, these two methods show their best applicable range for capillary pressures below −1·105 Pa. The semi-permeable membrane method and the Psychrometer method also feature in low cost, simple handling and application efficiency.
Chi Feng - One of the best experts on this subject based on the ideXlab platform.
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Hygric properties of porous building materials (IV): Semi-permeable membrane and Psychrometer methods for measuring moisture storage curves
Building and Environment, 2019Co-Authors: Chi Feng, Hans JanssenAbstract:Abstract The moisture storage curve is an important hygric property of porous building materials. It describes the moisture storage characteristic of a material via the relation between the moisture content and the moisture potential. Current experimental protocols for measuring moisture storage curves are not satisfactory, as they often require extensive facilities while still lacking the capability to handle the adsorption process in most of the over-hygroscopic range. This paper proposes two novel and simple methods – the semi-permeable membrane method and the Psychrometer method – to solve these issues. Measurements on calcium silicate, autoclaved aerated concrete and ceramic brick are performed and validated by comparing the experimental outcomes obtained from these two novel methods and from other existing protocols. It is proven that the semi-permeable membrane method and the Psychrometer method are applicable for both adsorption and desorption processes, the latter both from saturated and capillary moisture content. Limited by the accuracy of the Psychrometer and the condensation caused by temperature fluctuations, these two methods show their best applicable range for capillary pressures below −1·105 Pa. The semi-permeable membrane method and the Psychrometer method also feature in low cost, simple handling and application efficiency.
Antonio Ribeiro Da Cunha - One of the best experts on this subject based on the ideXlab platform.
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Medidas automatizadas de psicrômetro de termopar aspirado versus não aspirado
Sociedade Brasileira de Meteorologia, 2014Co-Authors: Antonio Ribeiro Da Cunha, Volpe, Clovis AlbertoAbstract:The thermocouple is used for obtaining the air temperature with sensitivity and optimum precision, beyond great advantage over the mercury or alcohol thermometer, because it generates electrical signals that can be stored in automated systems. However, when it comes to obtaining the relative humidity from thermocouple, it is needed caution due to other factors involved. In this study two sets of thermocouple Psychrometers, aspirated and no-aspirated were evaluated, relative to a Vaisala set, from 17 to 31/01/2008 (15 days). From measurements of dry and wet bulb temperatures, the relative humidity value was obtained, and it was possible to compare them with the Vaisala set measurements. The two types of Psychrometers showed precision and accuracy in measurements of air temperature, and only precision in measurements of relative humidity, being that the aspirated Psychrometer presented more precision. Despite the no-aspirated Psychrometer has lesser precision in measurements, it is more robust because it is independent of a 12 VDC micro-fan, making it, a sensor with lesser risk of inadequate measures. Both aspirated and no-aspirated Psychrometers do not measure accurately the relative air humidity during night period.O termopar ou par termoelétrico é utilizado na obtenção da temperatura do ar com ótima precisão, sensibilidade e com grande vantagem sobre o termômetro de mercúrio ou álcool, pois geram sinais elétricos que podem ser armazenados em sistemas automatizados. No entanto, quando se trata da obtenção da umidade relativa a partir de termopar, o processo se torna mais cauteloso devido a outros fatores envolvidos. Neste estudo, avaliaram-se dois conjuntos psicrômetros de termopar, aspirado e não aspirado, em relação a um conjunto Vaisala, no período de 17 a 31/01/2008 (15 dias). A partir de medidas de temperaturas de bulbos seco e úmido foram obtidas medidas da umidade relativa, e com isso, foi possível compará-las com as medidas obtidas pelo conjunto Vaisala. Os dois tipos de psicrômetros apresentaram precisão e exatidão nas medidas de temperatura do ar, e apenas precisão nas medidas de umidade relativa do ar, sendo que o psicrômetro aspirado foi o mais preciso. Apesar do psicrômetro não aspirado ter apresentado menor precisão nas medidas, ele é mais robusto porque independe do micro-ventilador de 12 VDC, o que faz dele um sensor com menos riscos de medidas inadequadas. Ambos os psicrômetros, aspirado e não aspirado, não medem com exatidão a umidade relativa do ar no período noturno
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Programação, conexão e avaliação de psicrômetro aspirado de termopar de baixo custo em micrologger para estudos agrometeorológicos
Revista Brasileira de Meteorologia, 2013Co-Authors: Antonio Ribeiro Da CunhaAbstract:ABSTRACT : PROGRAMMING, CONNECTION AND AVALIATION OF A LOW COSTASPIRA TED THERMOCOUPLE Psychrometer IN MICROLOGGER FOR AGROMETEOROLOGICAL STUDIES : As the psychrometric method is considered standard for the measurement of relative humidity, many studies have used aspirated thermocouple Psychrometers connected to microloggers but, however, they do not detail how the aspiration of the air stream is done. However, one of the major difficulties of aspirated thermocouple Psychrometers is to program and to connect it in micrologger, because specific programming and connection are requires, and still some skills in getting accurate measurements. This work aimed to provide the programming and the connection of the aspirated thermocouple Psychrometer type T for the CR10X microloggers and CR23X of Campbell Scientific, evaluating the quality of measurements of temperature and air relative humidity in relation the a sensor Vaisala HMP50. The non-continuous measurements were made in the period 2006/09/04 to 2007/07/11 at Jaboticabal, SP. The air temperature measurements were similar between the Vaisala sensors and aspirated thermocouple Psychrometer, but the relative humidity measurements were significantly
Eng Choon Leong - One of the best experts on this subject based on the ideXlab platform.
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Expedited soil–water characteristic curve tests using combined centrifuge and chilled mirror techniques
Geotechnical Testing Journal, 2017Co-Authors: Harianto Rahardjo, Eng Choon Leong, Xue Feng Nong, D. T. T. Lee, Yok-king FongAbstract:A soil–water characteristic curve (SWCC) shows soil’s ability to provide water availability and the rate that this water can be transmitted and replenished. However, the current commonly used method to determine the SWCCs of soils (the axis-translation method) is time consuming. This study combines two relatively new but established methods (centrifuge and chilled mirror Psychrometer) to find a rapid and reliable way to obtain the SWCC for a large range of suctions. For comparison, the SWCC was also independently measured using the axis-translation method (Tempe cell and pressure plate). The comparisons show that the SWCC parameters (air-entry values, residual suctions, and slope of SWCC) determined using the combined centrifuge and chilled mirror Psychrometer methods agree well with the same SWCC parameters determined using the Tempe cell and pressure plate methods (axis-translation method). At the same time, the time taken was cut down from a few months for the axis-translation method to about two days for the combined centrifuge and chilled mirror Psychrometer.
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Indirect Measurement of Suction
Geotechnical and Geological Engineering, 2008Co-Authors: Rifat Bulut, Eng Choon LeongAbstract:This paper reports on indirect soil suction measurement methods. Indirect suction measurement techniques measure the moisture equilibrium condition of the soil instead of suction. The moisture equilibrium condition of the soil can be determined by primary means as in vapor pressure, secondary means as through another porous medium or tertiary means as in measuring other physical properties of the porous medium that indicates its moisture equilibrium condition. Indirect suction measurement techniques employing primary means include thermocouple Psychrometers, transistor Psychrometer and chilled-mirror Psychrometer. Indirect suction measurement techniques employing secondary means includes the filter paper method and indirect suction measurement techniques employing tertiary means include thermal conductivity sensors and electrical conductivity sensors. These techniques have been widely used in engineering practice and in research laboratories. However, each of these techniques has its own limitations and capabilities, and active research into improving these techniques is ongoing in universities, research laboratories, and private sector. This paper outlines working principles, calibration, measurement, and application areas of these methods based on recent literature and practice.
Rifat Bulut - One of the best experts on this subject based on the ideXlab platform.
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a comparison of total suction measurements with thermocouple Psychrometer filter paper technique and chilled mirror device
GeoHunan International Conference: Challenges and Recent Advances in Pavement Technologies and Transportation GeotechnicsAmerican Society of Civil Eng, 2009Co-Authors: Daniel Mabirizi, Rifat BulutAbstract:Soil suction is one of the most important parameters describing the moisture stress condition of unsaturated soils, and its measurement is equally important for realistic applications of unsaturated soil mechanics. The thermocouple Psychrometers, filter paper method and chilled-mirror device are three soil suction measurement techniques that have found their places in describing the behavior of unsaturated soils in geotechnical engineering practice. However, as it is inherent with all the suction measurement methods there are still difficulties and uncertainties associated with these soil suction measurement techniques. In this paper, the filter paper, chilled-mirror Psychrometer, and thermocouple Psychrometer methods are evaluated and compared based on some recent observations and test results. These methods are used to measure total suctions of some high plasticity clay soils under very strict temperature control conditions. From the test results, the capabilities and limitations of the three methods are analyzed.
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Indirect Measurement of Suction
Geotechnical and Geological Engineering, 2008Co-Authors: Rifat Bulut, Eng Choon LeongAbstract:This paper reports on indirect soil suction measurement methods. Indirect suction measurement techniques measure the moisture equilibrium condition of the soil instead of suction. The moisture equilibrium condition of the soil can be determined by primary means as in vapor pressure, secondary means as through another porous medium or tertiary means as in measuring other physical properties of the porous medium that indicates its moisture equilibrium condition. Indirect suction measurement techniques employing primary means include thermocouple Psychrometers, transistor Psychrometer and chilled-mirror Psychrometer. Indirect suction measurement techniques employing secondary means includes the filter paper method and indirect suction measurement techniques employing tertiary means include thermal conductivity sensors and electrical conductivity sensors. These techniques have been widely used in engineering practice and in research laboratories. However, each of these techniques has its own limitations and capabilities, and active research into improving these techniques is ongoing in universities, research laboratories, and private sector. This paper outlines working principles, calibration, measurement, and application areas of these methods based on recent literature and practice.