2 edition of Thermal transpiration measurements on helium. found in the catalog.
Thermal transpiration measurements on helium.
Daniel Turner Klees
|Statement||A thesis ... for the degree of Master of Science [Department of Physics]|
|The Physical Object|
|Pagination||57 l., typed.|
|Number of Pages||57|
The terrestrial hydrological cycle is strongly influenced by transpiration—water loss through the stomatal pores of leaves. In this report we present studies showing that the energy content of radiation absorbed by the leaf influences stomatal control of transpiration. This observation is at odds with current concepts of how stomata sense and control transpiration, and we suggest an Mori, J., & Honda, S. (). Estimation of thermoacoustic field in a helium circulation system based on perturbative 54th Annual Conference of the Society of Instrument and Control Engineers of Japan, SICE (pp. ). Institute of Electrical and Electronics Engineers ://
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Abstract A new experimental technique was employed to measure the thermal transpiration effect (thermomolecular pressure difference) for Ar, N 2, and CO between 77 and 97°K and for helium-3 and helium-4 between and 7°K.A cascade device consisting of seven large tubes connected top to bottom with capillaries was partially immersed in either liquid nitrogen or liquid helium while a The thermal transpiration effect, which means a significant pressure difference between the two ends of a pipe due to a large temperature difference, has been discussed in ion mobility measurements in helium gas at K.
A modified Takaishi–Sensui’s empirical formula for the pressure correction is obtained from the experimental results. We propose Thermal transpiration measurements on helium.
book use this formula instead of the Thermal transpiration across an array of parallel capillaries ∼mm in transverse dimension has been measured for helium and nitrogen gas in the pressure range 1–:// Thermal transpiration of helium and nitrogen in silica μm capillaries between temperatures of and K has been measured in the pressure range of Pa –to 10 kPa by the differential method using apparatus in which the gases are back-filled into a clean UHV-compatible :// Measurements have been made of the pressure ratio, R, due to thermal transpiration in hydrogen, helium, argon, and nitrogen between a warm temperature of °K and cold temperatures of or ° is found that R depends on X, the product of the pressure and tube diameter according to the empirical relation, Thermal transpiration measurements were made at the steady and unsteady states for several gases on a membrane of porous ceramic.
At the steady state the heat of transport was examined as a function of the average gas pressure. At the unsteady state, comparisons were presented between gas permeabilities determined The thermal transpiration effect, which means a significant pressure difference between the two ends of a pipe due to a large temperature difference, has been discussed in ion mobility measurements in helium gas at K.
A modified Takaishi-Sensui's empirical formula for the pressure correction is obtained from the experimental results. We propose to use this formula instead of the The sublimation and vapor pressure of Ar 36 were measured in the temperature range K. Pressures below 1 Torr were measured with a McLeod gauge and corrected for effects of thermal transpiration and mercury streaming.
The estimated accuracy of these pressure measurements ranges from 1% near 1 Torr to 10% near 10 :// have been the cause of the higher thermal conductivity values.
The accuracy of the thermal conductivity data can be assessed well by the use of the parameter j=A/C.1], (5) Thermal transpiration measurements on helium. book C. is the constant volume specific heat and 1] is the viscosity. For a monatomic gas such as helium the value of j should be very nearly j values calculated using ://?.
the heat exchangers of a helium-cooled reactor require knowledge of some of the thermophysical properties of the helium gas, and the same applies to the treatment of observed data in heat transfer experiments.
The properties treated in this report are the density, the specific heats, the thermal conductivity, and the :// The experimental measurements of the absolute thermal transpiration differential pressure generated in a capillary tube by helium, argon, carbon dioxide, and air are compared to the theoretical differential pressure calculated by Loyalka.
The thermal creep flow calculated using the BGK model and Maxwell’s diffuse‐specular reflection operator at the wall is quantitatively correct for these On the basis of an experimental study in a large temperature range, it is shown that “helium densities” of adsorbents measured at room temperature could be erroneous due to a non-negligible effect of helium adsorption.
It is proposed that the density obtained with helium at high temperature, for instance, at the regeneration temperature of the adsorbent, be considered as the adsorbent :// Hellemans, R. Physica 34 Van Itterbeek, A. Van Dael, W.
THE ADSORPTION OF HELIUM, ARGON AND NITROGEN ON GRAPHITE by R. HELLEMANS, A. VAN ITTERBEEK and W. VAN DAEL Instituut voor Lage Temperaturen en Technische Fysica, Leuven, Belgi Synopsis Adsorption isotherms of He, Ar and N2 on graphite are measured in the temperature range between 90 at Application Note Page 5 Rev.
9/03 b. To calculate the cold free space: ρ = − bath std s s cs cm T m T V V where: Vcs = calculated cold free space with sample present (standard cm 3) Vcm = cold free space measured for the empty tube (standard cm 3) ms = mass of sample to be analyzed (grams) ρs = approximate sample true density (grams/cm 3) Tbath = bath temperature (Kelvin) Experimental Measurements The injected ion drift tube apparatus used in these studies has been described in detail previously The carbon clusters were generated by pulsed laser vaporization of a carbon rod in a continuous flow of helium buffer gas.
Ions that exit the source were focused into a quadrupole mass spectrometer, which is / Thermolecular pressure differences due to thermal transpiration were measured to find the corrections for low-temperature vapor-pressure thermometry using helium The experimental apparatus consisted basically of several stainless-steel, pressure-sensing tubes, each connected to the same pressure container inside a cryostat.
The upper, or warm, ends of the tubes were connected to Experimentally determined results on the measurement of hydrogen equilibrium pressure as a function of hydrogen concentration and temperature in α-titanium have been corrected for thermal transpiration effects in the apparatus.
An empirical relationship, which Measurements have been made of the pressure ratio, R, due to thermal transpiration in hydrogen, helium, argon, and nitrogen between a warm temperature of °K and cold temperatures of or pump that works by the principle of thermal transpiration, has no moving parts, and consequently offers high reliability.
A 6-mask process was used to fabricate the pump from a glass substrate and a silicon wafer. A single stage pump and two integrated pressure sensors occupy mm x 2 mm. Measurements show that this device can evacuate ~yogesh/pdfs/conferencepapers/ due to thermal transpiration.
The effect of thermal transpiration has been measured for three CDG transducers and four gases – nitrogen, argon, helium and hydrogen – in a range of pressures from 10 –2 Pa to Pa.
Normalization of the pressure scale for different gases can easily be performed using the two well-known gas parameters, Vacuum/volume 33/number 6/pages to / Printed in Great Britain X/83$+ Pergamon Press Ltd Thermal transpiration correction in capacitance manometers K F Poulter, M-J Rodgers, P J Nash, T J Thompson and M P Perkin, Division of Mechanical and Optical Metrology, National Physical Laboratory, Teddington, Middlesex, UK received 1 June ; in revised form 1 JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, VOL.
14, NO. 4, AUGUST Fig. The principle of thermal transpiration states that two chambers at differing temperatures generate a pressure differential due to differences in the rate of molecular ﬂux from either chamber. difference does not create a pressure difference between ~yogesh/pdfs/journalpublications/JMEMS_KnudsenPump_8_pdf.
CORRECTION OF PRESSURE DATA FOR THERMAL TRANSPIRATION EFFECTS IN PNEUMATIC LINES By James A. Daggerhart Distribution of this report is provided in the interest of information exchange. Responsibility for the contents resides in the author or organization that prepared it.
Prepared under Grant No. NGR by Fifty-one papers (and three keynote addresses) on contemporary theoretical issues and experimental techniques pertaining to the underlying factors that control heat-conduction behavior of materials.
The latest findings on insulation, fluids, and low-dimensional solids and composites are reviewed as?id=ujRFHBWYmoUC. Thermal accommodation coefficients for helium, argon gases, and their mixtures on stainless steel have been obtained by measur- ing the cooling rates of a stainless steel sphere suspended in the where E L is transpiration per unit leaf area (mol m −2 s −1), Ψ S is bulk soil water potential (MPa), Ψ L is leaf water potential (MPa) and ρgh is the gravitational pull (g) on a water column of density ρ ( MPa m −1) at height h (m).
The influence of gravity on water potential persists whether or not water is moving through the xylem, whereas hydraulic effects resulting from using helium gas as the coolant, and four tests using distilled water as the coolant.
All tests were made for various rates of coolant mass flow. To provide a basis for evaluating the effectiveness of transpiration cooling, a test was performed without coolant. This test provided measurements Closure to “Discussion of ‘Transpiration-Induced Buoyancy and Thermal Diffusion-Diffusion Thermo in a Helium-Air Free Convection Boundary Layer’” (, ASME J.
Heat Transfer, 86, p. ) /Closure-to-Discussion-of-Transpiration-Induced. A parametric study for determining conditions for the optimum performance of such a pump requires, in addition to the thermal transpiration measurements, appropriate independent measurements for determining the geometric properties of the porous :// //A-Study-of-Thermal-Transpiration-for-the.
relative thermal velocities. While the terms tend to be used interchangeably in IMS, they are in fact not identical in a wider context. Scattering or dephasing measurements carried out at very low pressures, wherein collisions eject the ions from stable trajectories , allow to determine Helium (from Greek: ἥλιος, romanized: Helios, lit.
'Sun') is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas, the first in the noble gas group in the periodic boiling point is the lowest among all the is the second lightest and second most abundant element in the observable The thermal transpiration effect is illustrated in Figure 4, which presents several sets of data obtained during absolute-mode calibration of a Pa CDG using helium and argon.
The upper two sets of data show that the response of the heated CDG becomes highly non-linear as pressure is decreased and is 4 parts in too high at the lowest Abstract Thermal transpiration is the macroscopic movement induced in a rarefied gas by a temperature gradient.
The gas moves from the lower to the higher temperature zone. An original method is proposed here to measure the stationary mass flow rate of gas created by thermal transpiration in a micro-tube heated at its 25gR.
An Experimental and Numerical Study of the Final Zero-Flow Thermal Transpiration Stage. This is the Thermal Transpiration phenomenon. In the present work, thermal transpiration has been studied both through an experimental approach, which exploits an original measuring system, and through a numerical approach, which is modeled on the basis Numerical analysis of the Poiseuille flow and the thermal transpiration of a rarefied gas through a pipe with a rectangular cross section based on the linearized Boltzmann equation for a hard sphere molecular gas.
Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films, Vol. 28, Issue. 4, p. provides precise measurements of moisture content down to ppbV. Another premium product, QCM analyzers require minimal maintenance. If the main interest is for moisture content rather the dew point temperature, then QCM technology is a good choice.
Thermal Conductivity Binary Gas analyzer This technology is used to Thermal transpiration effects for gases at pressures above torr. Isao Yasumoto. New High Resolution Ion Mobility Mass Spectrometer Capable of Measurements of Collision Cross Sections from to K.
Jakub Ujma, Kevin Giles, Michael Morris, and Perdita E. :// An experimental study on the efficiency of transpiration cooling in hypersonic laminar and turbulent flow regimes is T i=0,k is determined by the infrared measurements.
rate of helium is factor seven and ten higher than air and argon, respectively. In addition, the heat capacity and thermal conductivity of helium are larger.
Even The main objective of this experimental investigation on the gas flow slip regime is to measure the mass flow rate in isothermal steady flows through cylindrical micro tubes.
Two technical procedures devoted to mass flow rate measurements are compared, and the measured values are also compared with the results yielded by different approximated analytical solutions of the gas dynamics Thermal transpiration (thermo-molecular flow) 45 1.
20 Thermal conductivity 46 Thermal conductivity at high pressures (Kn «1) 46 Thermal conductivity at low pressures (Kn»1) 50 Diffusion of gases 54 Fick’s diffusion laws 54 Self-diffusion. Get this from a library! High accuracy thermal conductivity measurements near the lambda transition of helium with very high temperature resolution: final report for NASA-FIR grant #NAG [William M Fairbank; John A Lipa; United States.
National Aeronautics and Space Administration.] Thermal Conductivity Gauge (Pirani) This measurement principle utilizes the thermal conductivity of gases for the purpose of pressure measurements in the range from mbar/Torr to atmospheric pressure.
Today, only the principle of the controlled Pirani gauge is~nsl/Lectures/urls/Marcos Rojas-Cárdenas, Irina Graur, Pierre Perrier, J Gilbert Meolans.
An Experimental and Numerical Study of the Final Zero-Flow Thermal Transpiration Stage. Journal of Thermal Science and Technology, The Japan Society of Mechanical Engineers and The Heat Transfer Society of Japan7, pp - /jtst hal