scholarly journals The exchange of energy between gas atoms and solid surfaces

1930 ◽  
Vol 129 (809) ◽  
pp. 146-161 ◽  
Keyword(s):  
Temperature Jump ◽  
Average Energy ◽  
Accommodation Coefficient ◽  
Rotational Energy ◽  
Solid Surfaces ◽  
Translational Energy ◽  
Gas Molecules ◽  
The Difference

If gas molecules with average energy corresponding to a given temperature strike the surface of a solid at a different temperature, the average energy of the gas molecules leaving the surface does not in general correspond to the temperature of the solid but depends also on their average energy before staking it. In order to exclude complications due to the transfer of rotational energy we shall consider only monatomic gases. Let the average translational energy of the molecules before striking the surface at temperature T 2 correspond to a temperature T 1 , and let the average translational energy of the molecules after leaving the surface correspond to a temperature T 2 ' (see fig. 1). Modifying slightly a suggestion made by Maxwell* in a different connection, Smoluchowski assumed that the change in the temperature of the gas molecules brought about by striking the surface is proportional to the difference between the temperature of the surface and that of the gas molecules before striking it ; that is, that T 2 - T 1 = a , (T 2 - T 1 ). (1) The constant of proportionality a was later called the accommodation coefficient by Knudsen. Smoluchowski applied this idea to explain the so-called temperature jump at the surface of a solid.

scholarly journals Exchange of energy between diatomic gas molecules and a solid surface

1935 ◽  
Vol 152 (877) ◽  
pp. 515-529 ◽  
Keyword(s):  
Quantum State ◽  
Solid Surface ◽  
Translational Motion ◽  
Accommodation Coefficient ◽  
Rotational Energy ◽  
Translational Energy ◽  
Weighting Factors ◽  
Quantum Numbers ◽  
Gas Molecule ◽  
Gas Molecules

When gas molecules are incident on a solid the exchange of energy may be measured by Knudsen’s accommodation coefficient. If the gas molecules before collision have a mean energy corresponding to the temperature T 2 and the solid surface is at temperature T 1 , then the gas molecules after collision will have a mean energy corresponding to a temperature T´ 2 , T´ 2 being a function T 1 and T 2 . The accommodation coefficient α is then defined as α = Lt T1 → T 2 (T´ 2 ─ T 2 )/(T 1 ─ T 2 ). Hitherto* it has only been possible to develop a theory for monatomic gases, the atoms of which possess translational energy alone. This paper is an attempt to include the effects which must arise from the rotation of diatomic molecules. The first step in the calculation of the accommodation coefficient is to obtain the probability p (Wr; nm | n 1 m 1 ) that when a gas molecule with transitional energy W r and rotational energy corresponding to the quantum state m collides with a solid atom in quantum state n , a transition will take place to the state specified by the quantum numbers n 1 and m 1 , the balance of energy being taken up by the translational motion of the molecule. The accommodation coefficient α is then found by averaging p (Wr; nm | n 1 m 1 ) over all accessible values of W r , n , m , n 1 , m 1 , with the proper weighting factors.

Microscopic Interpretation of Arrhenius Parameters

2018 ◽  
Author(s):  
Niels Engholm Henriksen ◽  
Flemming Yssing Hansen
Keyword(s):  
Activation Energy ◽  
Transition State ◽  
Transition State Theory ◽  
Average Energy ◽  
Zero Point ◽  
State Theory ◽  
Exponential Factor ◽  
Quantum Tunnelling ◽  
Microscopic Interpretation ◽  
The Difference

This chapter reviews the microscopic interpretation of the pre-exponential factor and the activation energy in rate constant expressions of the Arrhenius form. The pre-exponential factor of apparent unimolecular reactions is, roughly, expected to be of the order of a vibrational frequency, whereas the pre-exponential factor of bimolecular reactions, roughly, is related to the number of collisions per unit time and per unit volume. The activation energy of an elementary reaction can be interpreted as the average energy of the molecules that react minus the average energy of the reactants. Specializing to conventional transition-state theory, the activation energy is related to the classical barrier height of the potential energy surface plus the difference in zero-point energies and average internal energies between the activated complex and the reactants. When quantum tunnelling is included in transition-state theory, the activation energy is reduced, compared to the interpretation given in conventional transition-state theory.

scholarly journals Measurement of Thermal Accommodation Coefficients Using Laser-Induced Incandescence

2007 ◽  
Author(s):  
K. J. Daun ◽  
P. H. Mercier ◽  
G. J. Smallwood ◽  
F. Liu ◽  
Y. Le Page
Keyword(s):  
Deformation Rate ◽  
Surface Deformation ◽  
Accommodation Coefficient ◽  
Polyatomic Gases ◽  
Thermal Accommodation ◽  
Laser Induced Incandescence ◽  
Translational Mode ◽  
Accommodation Coefficients ◽  
Thermal Accommodation Coefficient ◽  
Gas Molecules

Laser-induced incandescence (LII) is used to measure the thermal accommodation coefficient between soot sampled from a well-characterized flame and various monatomic and polyatomic gases. These measurements show that the thermal accommodation coefficient between soot and monatomic gases increases with molecular mass due to the decreasing speed of incident gas molecules and corresponding decrease in surface deformation rate, and that energy is transferred preferentially from the surface to the translational mode of the polyatomic gas molecules over internal energy modes.

scholarly journals The gas flow pattern through small size Resistive Plate Chambers with 2 mm gap

2021 ◽  
Vol 16 (11) ◽  
pp. P11022
Author(s):  
Y. Pezeshkian ◽  
A. Kiyoumarsioskouei ◽  
M. Ahmadpouri ◽  
G. Ghorbani
Keyword(s):  
Gas Flow ◽  
Fluid Dynamic ◽  
Gas Flow Rate ◽  
Argon Gas ◽  
Dynamic Methods ◽  
Gas System ◽  
Gas Molecules ◽  
Simulation Results ◽  
Resistive Plate Chambers ◽  
The Difference

Abstract A prototype of a single-gap glass Resistive Plate Chamber (RPC) is constructed by the authors. To find the requirements for better operation of the detector's gas system, we have simulated the flow of the Argon gas through the detector by using computational fluid dynamic methods. Simulations show that the pressure inside the chamber linearly depends on the gas flow rate and the chamber's output hose length. The simulation results were compatible with experiments. We have found that the pressure-driven speed of the gas molecules is two orders of magnitude larger in the inlet and outlet regions than the blocked corners of a 14 × 14 cm2 chamber, and most likely the difference in speed is higher for larger detectors and different geometries.

Ballistics and visual targeting in flea-beetles (Alticinae)

1995 ◽  
Vol 198 (9) ◽  
pp. 1931-1942 ◽  
Author(s):  
J Brackenbury ◽  
R Wang
Keyword(s):  
Flea Beetle ◽  
Rotational Energy ◽  
The Body ◽  
Translational Energy ◽  
High Contrast ◽  
Significant Preference ◽  
Flea Beetles ◽  
Mode 2 ◽  
Optical Grid ◽  
Targeting Accuracy

The kinematics of jumping was measured in seven species of flea-beetle (Alticinae). The accuracy of two species during targeted jumping was also investigated. Take-off accelerations ranged from 15 to 270 times gravity. Rotational energy accounted for 4­21 % of the total translational energy. Two species were able to control jump direction and landing. When presented with a high-contrast optical grid, Chalcoides aurata exhibited two alternative jump modes. In mode 1 or wingless jumping, the body rotated continuously, the insect rarely landed on its feet and no discrimination was shown between landing on the black or white stripes of the grid. In mode 2 jumping, recruitment of the wings eliminated rotation and virtually ensured a feet-first landing; there was also a significant preference for jumping towards the black stripes. Aphthona atrocaerulea could alter take-off angle in order to strike targets at inclinations of 0­90 ° to the horizontal. Targets consisting of a white illuminated cross on a black background were struck with equal accuracy, regardless of distance (within the normal jumping range). The beetle aimed specifically for the centre of the target and not for the high-contrast boundary. The distribution of hits about the target centre was radially symmetrical. Although take-off was wingless, rotation could be abolished in mid jump, within 10 ms, by extending the wings. This virtually guaranteed a feet-first landing. Targeting accuracy is discussed in the context of biomechanical steering mechanisms and visual control.

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