Characterization of the Humidity Calibration Chamber by Numerical Simulations

J. Salminen, H. Sairanen, P. Grahn, R. Högström, A. Lakka, M. Heinonen

Research output: Contribution to journalArticleScientificpeer-review

1 Citation (Scopus)

Abstract

At the Centre for Metrology MIKES of VTT Technical Research Centre of Finland (VTT MIKES), we have been developing a humidity calibration apparatus for radiosondes within an EMRP Project Metrology for Essential Climate Variables. The minimum air temperature and absolute humidity are -80°C and 2.576 * 10-4g·m-3 (corresponding the dew-point temperature -90°C), respectively. Recent developments for the apparatus extend its pressure operation range down to 7 hPa (abs). When operating in such dry conditions, the efficiency in calibration is highly limited by the time of humidity stabilization in a measurement chamber: Because the water vapor pressure is very low, the adsorption and desorption of water molecules at the chamber walls have a significant effect on the spatial and temporal humidity differences in the chamber. Inhomogeneity in humidity field inside the calibration chamber increases calibration uncertainty. In order to understand how varying parameters such as pressure, temperature, inflow speed and geometry of chamber effect on stabilization time of humidity field, computational fluid dynamics simulations were developed using Comsol software. Velocity and pressure of fluid, water vapor diffusion, temperature as well as adsorption/desorption of water molecules on the chamber walls were included in the simulations. Adsorption and desorption constants for water on the measurement chamber wall were determined experimentally. The results show that the flow speed and the surface area are the dominant parameters affecting the stabilization time of a calibration chamber. It was also discovered that more homogenous water vapor concentration field is obtained at low pressures.
Original languageEnglish
Article number84
JournalInternational Journal of Thermophysics
Volume38
Issue number6
DOIs
Publication statusPublished - 1 Jul 2017
MoE publication typeA1 Journal article-refereed

Fingerprint

humidity
chambers
simulation
water vapor
stabilization
desorption
metrology
adsorption
water
dew point
radiosondes
Finland
water pressure
temperature
computational fluid dynamics
vapor pressure
climate
molecules
inhomogeneity
low pressure

Keywords

  • calibration
  • calibration chamber
  • Comsol
  • FEM
  • cinite element method
  • humidity calibration
  • multiphysics
  • simulation
  • surface chemistry

Cite this

@article{c3fd57ab67724f7a825695af380d7ce1,
title = "Characterization of the Humidity Calibration Chamber by Numerical Simulations",
abstract = "At the Centre for Metrology MIKES of VTT Technical Research Centre of Finland (VTT MIKES), we have been developing a humidity calibration apparatus for radiosondes within an EMRP Project Metrology for Essential Climate Variables. The minimum air temperature and absolute humidity are -80°C and 2.576 * 10-4g·m-3 (corresponding the dew-point temperature -90°C), respectively. Recent developments for the apparatus extend its pressure operation range down to 7 hPa (abs). When operating in such dry conditions, the efficiency in calibration is highly limited by the time of humidity stabilization in a measurement chamber: Because the water vapor pressure is very low, the adsorption and desorption of water molecules at the chamber walls have a significant effect on the spatial and temporal humidity differences in the chamber. Inhomogeneity in humidity field inside the calibration chamber increases calibration uncertainty. In order to understand how varying parameters such as pressure, temperature, inflow speed and geometry of chamber effect on stabilization time of humidity field, computational fluid dynamics simulations were developed using Comsol software. Velocity and pressure of fluid, water vapor diffusion, temperature as well as adsorption/desorption of water molecules on the chamber walls were included in the simulations. Adsorption and desorption constants for water on the measurement chamber wall were determined experimentally. The results show that the flow speed and the surface area are the dominant parameters affecting the stabilization time of a calibration chamber. It was also discovered that more homogenous water vapor concentration field is obtained at low pressures.",
keywords = "calibration, calibration chamber, Comsol, FEM, cinite element method, humidity calibration, multiphysics, simulation, surface chemistry",
author = "J. Salminen and H. Sairanen and P. Grahn and R. H{\"o}gstr{\"o}m and A. Lakka and M. Heinonen",
note = "CA2: BA1701 CA2: BA17 AU2: Salminen, Juho AU2: Sairanen, Hannu AU2: H{\"o}gstr{\"o}m, Richard AU2: Heinonen, Martti",
year = "2017",
month = "7",
day = "1",
doi = "10.1007/s10765-017-2221-y",
language = "English",
volume = "38",
journal = "International Journal of Thermophysics",
issn = "0195-928X",
publisher = "Springer",
number = "6",

}

Characterization of the Humidity Calibration Chamber by Numerical Simulations. / Salminen, J.; Sairanen, H.; Grahn, P.; Högström, R.; Lakka, A.; Heinonen, M.

In: International Journal of Thermophysics, Vol. 38, No. 6, 84, 01.07.2017.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - Characterization of the Humidity Calibration Chamber by Numerical Simulations

AU - Salminen, J.

AU - Sairanen, H.

AU - Grahn, P.

AU - Högström, R.

AU - Lakka, A.

AU - Heinonen, M.

N1 - CA2: BA1701 CA2: BA17 AU2: Salminen, Juho AU2: Sairanen, Hannu AU2: Högström, Richard AU2: Heinonen, Martti

PY - 2017/7/1

Y1 - 2017/7/1

N2 - At the Centre for Metrology MIKES of VTT Technical Research Centre of Finland (VTT MIKES), we have been developing a humidity calibration apparatus for radiosondes within an EMRP Project Metrology for Essential Climate Variables. The minimum air temperature and absolute humidity are -80°C and 2.576 * 10-4g·m-3 (corresponding the dew-point temperature -90°C), respectively. Recent developments for the apparatus extend its pressure operation range down to 7 hPa (abs). When operating in such dry conditions, the efficiency in calibration is highly limited by the time of humidity stabilization in a measurement chamber: Because the water vapor pressure is very low, the adsorption and desorption of water molecules at the chamber walls have a significant effect on the spatial and temporal humidity differences in the chamber. Inhomogeneity in humidity field inside the calibration chamber increases calibration uncertainty. In order to understand how varying parameters such as pressure, temperature, inflow speed and geometry of chamber effect on stabilization time of humidity field, computational fluid dynamics simulations were developed using Comsol software. Velocity and pressure of fluid, water vapor diffusion, temperature as well as adsorption/desorption of water molecules on the chamber walls were included in the simulations. Adsorption and desorption constants for water on the measurement chamber wall were determined experimentally. The results show that the flow speed and the surface area are the dominant parameters affecting the stabilization time of a calibration chamber. It was also discovered that more homogenous water vapor concentration field is obtained at low pressures.

AB - At the Centre for Metrology MIKES of VTT Technical Research Centre of Finland (VTT MIKES), we have been developing a humidity calibration apparatus for radiosondes within an EMRP Project Metrology for Essential Climate Variables. The minimum air temperature and absolute humidity are -80°C and 2.576 * 10-4g·m-3 (corresponding the dew-point temperature -90°C), respectively. Recent developments for the apparatus extend its pressure operation range down to 7 hPa (abs). When operating in such dry conditions, the efficiency in calibration is highly limited by the time of humidity stabilization in a measurement chamber: Because the water vapor pressure is very low, the adsorption and desorption of water molecules at the chamber walls have a significant effect on the spatial and temporal humidity differences in the chamber. Inhomogeneity in humidity field inside the calibration chamber increases calibration uncertainty. In order to understand how varying parameters such as pressure, temperature, inflow speed and geometry of chamber effect on stabilization time of humidity field, computational fluid dynamics simulations were developed using Comsol software. Velocity and pressure of fluid, water vapor diffusion, temperature as well as adsorption/desorption of water molecules on the chamber walls were included in the simulations. Adsorption and desorption constants for water on the measurement chamber wall were determined experimentally. The results show that the flow speed and the surface area are the dominant parameters affecting the stabilization time of a calibration chamber. It was also discovered that more homogenous water vapor concentration field is obtained at low pressures.

KW - calibration

KW - calibration chamber

KW - Comsol

KW - FEM

KW - cinite element method

KW - humidity calibration

KW - multiphysics

KW - simulation

KW - surface chemistry

UR - http://www.scopus.com/inward/record.url?scp=85016746642&partnerID=8YFLogxK

U2 - 10.1007/s10765-017-2221-y

DO - 10.1007/s10765-017-2221-y

M3 - Article

VL - 38

JO - International Journal of Thermophysics

JF - International Journal of Thermophysics

SN - 0195-928X

IS - 6

M1 - 84

ER -