Search results for "water vapor"
showing 10 items of 179 documents
Eulerian-Eulerian modelling and computational fluid dynamics simulation of wire mesh demisters in MSF plants
2014
Purpose – The purpose of this study is to focus on simulation of wire mesh demisters in multistage flash desalination (MSF) plants. The simulation is made by the use of computational fluid dynamics (CFD) software. Design/methodology/approach – A steady state and two-dimensional (2D) model was developed to simulate the demister. The model employs an Eulerian-Eulerian approach to simulate the flow of water vapor and brine droplets in the demister. The computational domain included three zones, which are the vapor space above and below the demister and the demister. The demister zone was modeled as a tube bank arrange or as a porous media. Findings – Sensitivity analysis of the model showed t…
Eulerian–Lagrangian modeling and computational fluid dynamics simulation of wire mesh demisters in MSF plants
2016
Abstract This study focuses on computational fluid dynamics model (CFD) for simulation of demisters in multistage flash desalination (MSF). The Eulerian–Lagrangian model (steady-state and two-dimensional) was developed to simulate the demister. The model was used to simulate the flow of water vapor and brine droplets in the demister. The computational domain includes the following three zones: the vapor space above the demister, the vapor space below the demister, and the demister. The demister zone was modeled as tube banks. A sensitivity analysis of the model revealed that vapor velocity is the main parameter that affects demister performance. Additionally, the analysis indicated that vap…
Structural evolution of LiOH: evidence of a solid–solid transformation toward Li2O close to the melting temperature
1998
Abstract The structural evolution of LiOH has been studied between 10 K and 1670 K using a combination of neutron and X-ray diffraction and calorimetric measurements. The room temperature tetragonal phase of LiOH has been observed down to 10 K. Above the room temperature a dehydration of solid LiOH into solid Li2O is observed at a temperature and speed which strongly changes with the thermal history and the partial pressure of water vapour. Depending on these conditions the transformation of LiOH in to Li2O before the fusion temperature can be complete, partial or suppressed. In this latter case, as previously reported in the literature, a first order structural phase transition of LiOH is …
Water vapor sensors based on the swelling of relief gelatin gratings
2015
We report on a novel device to measure relative humidity. The sensor is based on surface diffraction gratings made of gelatin. This material swells and shrinks according to the content of water vapor in air. By sending a light beam to the grating, diffracted orders appear. Due to the gelatin swelling or shrinking, first order intensity changes according to the relative humidity. Calibration curves relating intensity versus relative humidity have been found. The fabrication process of diffraction gratings and the testing of the prototype sensing devices are described.
Water Vapor Sensors Based on the Swelling of Relief Gelatin Gratings: Recent Advances and Development
2021
We report on a novel device to measure relative humidity. Materials used in the measurement of relative humidity are of different kinds. The sensor is based on surface diffraction gratings made of gelatin. This material swells and shrinks according to the content of water vapor in air. By sending a light beam to the grating, diffracted orders appear. Due to the gelatin swelling or shrinking, first order intensity changes according to the relative humidity. Calibration curves relating intensity versus relative humidity have been found. The fabrication process of diffraction gratings and the testing of the prototype sensing devices are described.
A quasi chemistry-transport model mode for EMAC
2010
Abstract. A quasi chemistry-transport model mode (QCTM) is presented for the numerical chemistry-climate simulation system ECHAM/MESSy Atmospheric Chemistry (EMAC). It allows for a quantification of chemical signals through suppression of any feedback between chemistry and dynamics. Noise would otherwise interfere too strongly. The signal is calculated from the difference of two QCTM simulations, a reference simulation and a sensitivity simulation. In order to avoid the feedbacks, the simulations adopt the following offline chemical fields: (a) offline mixing ratios of radiatively active substances enter the radiation scheme, (b) offline mixing ratios of nitric acid enter the scheme for re-…
On the demands on imaging spectrometry for the monitoring of global vegetation fluorescence from space
2013
Vegetation fluorescence when measured from space contributes only a tiny fraction of the signal coming on top of the reflected radiance by the Earth surface and the atmosphere. As a consequence, imaging spectrometers have to provide sufficient throughput and radiometric accuracy to enable accurate global monitoring of the daily to seasonal variations of the Earth's vegetation breath, which is particularly challenging if ground resolutions of a few hundred meters are targeted. Since fluorescence retrieval algorithms have to make corrections for atmospheric effects, it is necessary to provide sufficient spectral resolution, so that signal alterations due to the main parameters such as surface…
Improvements in land surface temperature retrieval from the Landsat series thermal band using water vapor and air temperature
2009
[1] Land surface temperature (LST) is involved in many land surface processes such as evapotranspiration, net radiation, or air temperature modeling. In this paper we present an improved methodology to retrieve LST from Landsat 4 TM, Landsat 5 TM, and Landsat 7 ETM+ using four atmospheric databases covering different water vapor ranges (from 0 to 8 g cm−2) to build the LST retrieval models and using both water vapor and air temperature as input variables. We also compare this with LST retrievals using only water vapor or only air temperature, as well as with an existing LST retrieval algorithm. In order to validate the results, we have selected 77 Landsat images taken between 2002 and 2006 …
Results from the Fourth WMO Filter Radiometer Comparison for aerosol optical depth measurements
2018
Abstract. This study presents the results of the Fourth Filter Radiometer Comparison that was held in Davos, Switzerland, between 28 September and 16 October 2015. Thirty filter radiometers and spectroradiometers from 12 countries participated including reference instruments from global aerosol networks. The absolute differences of all instruments compared to the reference have been based on the World Meteorological Organization (WMO) criterion defined as follows: 95% of the measured data has to be within 0.005 ± 0.001∕m (where m is the air mass). At least 24 out of 29 instruments achieved this goal at both 500 and 865 nm, while 12 out of 17 and 13 out of 21 achieved this at 368 and 412 nm,…
Lipids and biopackaging
1997
Packaging is important to preserve food quality. It is a barrier to water vapor, gas, aroma, and solute migration between the food and the environment. With the recent increase in ecological consciousness, research has turned toward finding biodegradable materials. The different kinds of biopackaging are discussed with special focus on edible films. The aim of this review is to focus on the influence of lipids used in edible films, mainly for their efficiency as water-vapor barriers. The structure, degree of saturation, chainlength, physical state, shape and dimension of crystals, and distribution of lipids into the film influence the functional properties of the film. In general, the perfo…