DEW-POINT HYGROMETER FOR USE AT LOW TEMPERATURES

1939 ◽  
Vol 17d (2) ◽  
pp. 35-38 ◽  
Author(s):  
C. A. Winkler
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Low Temperatures ◽  
Dew Point ◽  
Slow Cooling ◽  
Point Temperature ◽  
Dew Point Temperature

An apparatus is described in which provision for slow cooling of a metal mirror by circulating over it liquid from a vessel in a thermoregulated bath, and the use of multiple thermocouple elements contained in the mirror, enable the dew-point temperature to be gradually approached and accurately determined. Precise measurements of relative humidity at low temperatures, where the moisture content of the air is small, are therefore possible. A precision of ± 0.5% relative humidity was readily attained at temperatures down to − 15 °C.

Observed changes in relative humidity and dew point temperature in coastal regions of Iran

2012 ◽  
Vol 110 (3) ◽  
pp. 385-393 ◽  
Author(s):  
P. Hosseinzadeh Talaee ◽  
A. A. Sabziparvar ◽  
Hossein Tabari
Keyword(s):  
Relative Humidity ◽  
Dew Point ◽  
Coastal Regions ◽  
Point Temperature ◽  
Dew Point Temperature

scholarly journals Relationship between Relative Humidity and the Dew Point Temperature in Abuja, Nigeria

OALib ◽  
2021 ◽  
Vol 08 (12) ◽  
pp. 1-13
Author(s):  
Enoch O. Elemo ◽  
Efua A. Ogobor ◽  
Benjamin G. Ayantunji ◽  
Otonye E. Mangete ◽  
George A. Alagbe ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Dew Point ◽  
Point Temperature ◽  
Dew Point Temperature

scholarly journals DRYING KINETICS OF PEELED COFFEE SUBMITTED TO DIFFERENT TEMPERATURES AND RELATIVE HUMIDITY OF THE AIR OF DRYING AFTER PARTIAL DRYING

2020 ◽  
Vol 28 ◽  
pp. 460-476
Author(s):  
Rodrigo Victor Moreira ◽  
Jefferson Luiz Gomes Correa ◽  
Ednilton Tavares de Andrade ◽  
Roney Alves da Rocha
Keyword(s):  
Relative Humidity ◽  
Effective Diffusivity ◽  
Drying Kinetics ◽  
Dew Point ◽  
Diffusivity Coefficient ◽  
Point Temperature ◽  
Dew Point Temperature ◽  
Different Temperatures ◽  
Kinetics Of

The mathematical modelling is fundamental for the understanding of the related processes the drying, that influences the quality of the coffee drink. The objective of this study was to evaluate the influence of different relative humidity of the drying air after partial drying on drying kinetics of peeled coffees. Coffee fruits were harvested in the cherry stage and processed by wet, resulting in the portion of peeled coffee. Eleven treatments of drying were accomplished, being nine results of the combination of three dry bulb temperatures and three dew point temperatures, more two treatments without the control of the dew point temperatures. The control of the relative humidity by the dew point temperature was made after the grains reached the partial drying. Among the studied models, those of Diffusion Approximation and Modified Midilli were the most adequate for describing the drying process of the first and second part of drying respectively. The effective diffusivity coefficient of water in coffee grains ranged from 0.81 x 10-11 to 1.84 x 10-11 m² .s-1 during the first part of the drying and ranged from 1.49 x 10-11 to 3.29 x 10-11 m² .s-1 during the second part of the drying, increasing significantly with the reduction of the dew point temperature and increase of the dry bulb temperature.

Evaluation of membrane-based air pre-dehumidification for a capillary radiant air conditioning system

2020 ◽  
pp. 1420326X2096738
Author(s):  
Zan-She Wang ◽  
Fang-Ting Yin ◽  
Ran Li ◽  
Zhao-Lin Gu
Keyword(s):  
Moisture Content ◽  
Air Conditioning ◽  
Dew Point ◽  
Liquid Desiccant ◽  
Air Conditioning System ◽  
Point Temperature ◽  
Dew Point Temperature ◽  
Temperature Range ◽  
Libr Solution ◽  
The Ideal

The polyvinylidene fluoride hollow fibre membrane air dehumidification tests were carried out between the liquid desiccant solutions and the wet air. Three liquid desiccant solutions of LiBr solution (50%), LiCl solution (35%) and CaCl2 solution (40%) were tested under different wet air conditions. The results showed that all the membrane dehumidification processes were stable. The air moisture content in the outlet of the membrane was maintained as 6.5 g/kg (da)–8.2 g/kg (da) when the air moisture content in the inlet of the membrane was operated from 17.1 g/kg (da) to 32.4 g/kg (da). The dehumidification amount of LiBr solution (50%) and LiCl solution (35%) was more productive. On this basis, a membrane-based air pre-dehumidification process for the capillary radiant air conditioning system was built. Since the ideal dew point temperature range of the indoor air is below 14–17°C according to the cold supply water, all the air moisture content at the membrane outlet is much lower than that of the ideal dew point temperature range, which means non-condensing occurs in the capillary tube surface. The membrane-based air pre-dehumidification process can easily form an adaptive regulation process of humidity with the capillary radiant air conditioning system under different environmental parameters.

Chart of Air-Vapor Mixture Properties at Different Pressures

1941 ◽  
Vol 8 (1) ◽  
pp. A14-A16
Author(s):  
R. C. Binder
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Total Pressure ◽  
Limited Range ◽  
Dew Point ◽  
Specific Humidity ◽  
Vapor Mixture ◽  
Close Approximation ◽  
Point Temperature ◽  
Dew Point Temperature

Abstract A discussion is given of the use of a total pressure-temperature diagram provided with reversible adiabatic and specific-humidity lines for mixtures of air and water vapor. The graphical relation between dew-point temperature, dry-bulb temperature, and specific humidity is given directly for any total pressure on this chart. From this relation the vapor pressure and relative humidity can be easily calculated. Certain chart lines give a close approximation to the wet-bulb temperature for a limited range. This pressure-temperature chart should be convenient and useful for a wide variety of problems which involve these fundamental thermodynamic properties.

scholarly journals A relative humidity calibration from 5°C to 45°C in a mixed-flow humidity generator

2012 ◽  
Vol 16 (1) ◽  
pp. 193-205 ◽  
Author(s):  
Nenad Milosevic ◽  
Nenad Stepanic ◽  
Marijana Babic
Keyword(s):  
Relative Humidity ◽  
Dew Point ◽  
Temperature Uniformity ◽  
Mixed Flow ◽  
Humidity Generator ◽  
Point Temperature ◽  
Traceability Chain ◽  
Dew Point Temperature ◽  
Reference Measurements ◽  
Humidity Environment

The paper presents a method used in the Vinca Institute of Nuclear Sciences for a reliable and traceable relative humidity calibration in the temperature range from 5?C to 45?C. Inside a controllable temperature and humidity environment, supplied by a mixed-flow humidity generator, measurements of hygrometers under calibration are compared with those of calibrated reference instruments. A traceability chain from temperature to reference relative humidity and next to the hygrometers under calibrations is provided by using a chilled-mirror dew-point temperature system and precise relative humidity probes. Corresponding calibration uncertainties are analyzed, particularly those associated to the temperature uniformity of controlled calibration environment. Two examples of relative humidity calibration with dew-point and relative humidity reference measurements in the range from 15 to 75% of RH and 5?C to 45?C are presented and discussed.

scholarly journals Possible impacts of climate change on fog in the Arctic and subpolar North Atlantic

2020 ◽  
Vol 6 (1) ◽  
pp. 31-43
Author(s):  
Richard E. Danielson ◽  
Minghong Zhang ◽  
William A. Perrie
Keyword(s):  
Relative Humidity ◽  
North Atlantic ◽  
Large Scale ◽  
Ensemble Member ◽  
Single Step ◽  
Dew Point ◽  
The Arctic ◽  
Point Temperature ◽  
Dew Point Temperature

Abstract. A conventional parameterization of midlatitude warm fog occurrence, based on in situ observations, is employed to estimate marine surface visibility in the Arctic and North Atlantic from three datasets: an ensemble member of the Hadley Earth System (HadGEM2) model and a nested regional WRF simulation that follow historical and future emissions scenarios for 1979–2100, and the ERA-Interim reanalysis for 1979–2004. Over large scales (of an entire year and region), all three gridded datasets agree well in terms of variables like surface air temperature, whose systematic differences seem small by comparison with its predicted change over the course of this century. On the other hand, systematic differences are more apparent in large-scale estimates of relative humidity and visibility. Large differences are attributed to a sensitivity to representation bias that is inherent in the formulation of each individual model and analysis. Two simple linear calibrations are examined, both of which assume that an in situ based parameterization is broadly consistent with the use of marine (ICOADS) observations of air and dew point temperature as an error-free reference. A single-step calibration is considered that takes the mean and variance of ICOADS frequency distributions as a reference. A two-step calibration is also performed in which ICOADS collocations are taken as a reference for the ERA reanalysis, which in turn is taken as a large-scale reference for the 1979–2004 HadGEM2 and WRF simulations. Both linear calibrations are applied (locally in time and space to air and dew point temperature) to the future climate scenarios of HadGEM2 and WRF. Although ICOADS observations are not error-free and parameterized visibility estimates are unlikely to capture much more than half the variance found in observations, attempts are made to present consistent regional changes in the frequency of high relative humidity, as a proxy for warm fog occurrence. The large-scale decrease in visibility over the 21st century is in the range of 8 %–12 % in the Arctic and 0 %–5 % in the North Atlantic.

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