scholarly journals Entropy change in a single Leontiev tube during energy separation of low-Prandtl gas mixture

2021 ◽  
Vol 2057 (1) ◽  
pp. 012029
Author(s):  
M S Makarov ◽  
S N Makarova
Keyword(s):  
Cylindrical Channel ◽  
Supersonic Nozzle ◽  
Entropy Change ◽  
Energy Separation ◽  
Gas Mixture ◽  
Simulation Data ◽  
Numerical Studies ◽  
Total Temperature

Abstract The results of numerical studies of energy separation of a helium-xenon gas mixture in a single Leontiev tube with a central cylindrical channel are presented. On the basis of the simulation data, a T-s diagram for energy separation is constructed. The changes in the total temperature depending on the entropy change in the central subsonic channel and in the annular supersonic nozzle are shown.

Investigations of Energy Separation Effect in Vortex Tube for Natural Gases

2013 ◽  
Vol 397-400 ◽  
pp. 205-208
Author(s):  
Wen Chuan Wang ◽  
Xiang Jun Fang ◽  
Shi Long Liu ◽  
Wen Long Sun
Keyword(s):  
Mass Fraction ◽  
Vortex Tube ◽  
Pressure Ratio ◽  
Three Dimensional ◽  
Energy Separation ◽  
Separation Effect ◽  
Natural Gases ◽  
Temperature Separation ◽  
Total Temperature ◽  
Cold Mass

This paper aims to investigate fixed composition natural gases including N2, CH4 and C2H4 energy separation effect in vortex tube. Energy separation phenomena of those gases were investigated by means of three-dimensional Computational Fluid Dynamics (CFD) method. Flow fields of natural gases in fixed inlet boundary conditions were simulated. The results main factors were found that affect the energy separation with cold mass fraction being 0.7 and pressure drop ratio being 3.90. At the same time, this paper has illustrated the effects and tendencies of energy separation with gases in the tube under the same cold mass flow fraction and cold pressure ratio. The results show mixture gases total temperature difference effect is unchanged varied with the cold mass fraction; CH4% has no effect on the vortex cold end temperature separation, but varied of CH4% has an influence in total temperature and hot end separation effect; total temperature separation effect of CH4% was divided into two sections, one is0%-80%, and the other 80%-100%.

scholarly journals Entropy Rules: Molecular Dynamics Simulations of Model Oligomers for Thermoresponsive Polymers

Entropy ◽  
2020 ◽  
Vol 22 (10) ◽  
pp. 1187
Author(s):  
Alexander Kantardjiev ◽  
Petko M. Ivanov
Keyword(s):  
Entropy Change ◽  
Atomic Scale ◽  
Solution Temperature ◽  
Water Molecules ◽  
Thermoresponsive Polymers ◽  
Simulation Data ◽  
Critical Solution Temperature ◽  
Extended Conformation ◽  
Dynamics Simulations ◽  
Experimental Findings

We attempted to attain atomic-scale insights into the mechanism of the heat-induced phase transition of two thermoresponsive polymers containing amide groups, poly(N-isopropylacrylamide) (PNIPAM) and poly(2-isopropyl-2-oxazoline) (PIPOZ), and we succeeded in reproducing the existence of lower critical solution temperature (LCST). The simulation data are in accord with experimental findings. We found out that the entropy has an important contribution to the thermodynamics of the phase separation transition. Moreover, after decomposing further the entropy change to contributions from the solutes and from the solvent, it appeared out that the entropy of the solvent has the decisive share for the lowering of the free energy of the system when increasing the temperature above the LCST. Our conclusion is that the thermoresponsive behavior is driven by the entropy of the solvent. The water molecules structured around the functional groups of the polymer that are exposed to contact with the solvent in the extended conformation lower the enthalpy of the system, but at certain temperature the extended conformation of the polymer collapses as a result of dominating entropy gain from “released” water molecules. We stress also on the importance of using more than one reference molecule in the simulation box at the setup of the simulation.

Magnetic refrigeration with GdN by Active Magnetic Refrigerator cycle

2011 ◽  
Vol 1310 ◽  
Author(s):  
Yusuke Hirayama ◽  
Hiroyuki Okada ◽  
Takashi Nakagawa ◽  
Takao. A. Yamamoto ◽  
Takafumi Kusunose ◽  
...  
Keyword(s):  
Magnetic Entropy Change ◽  
Hot Isostatic Pressing ◽  
Entropy Change ◽  
Magnetic Refrigeration ◽  
Zero Field ◽  
Active Magnetic Regenerator ◽  
Magnetic Field Change ◽  
Total Temperature ◽  
The Magnetic Field ◽  
Magnetic Regenerator

ABSTRACTA magnetic refrigeration test was performed using a test device filled with spherical GdN material synthesized by the hot isostatic pressing (HIP) method. Refrigeration with an active magnetic regenerator cycle was tested in the temperature range between 48 and 66 K, with the field changing from 1.2 to 3.7 T and 2.0 to 4.0 T at upper and lower sides of the regenerator bed filled with the GdN spheres, respectively. Temperature spans about of 2 K were obtained at both sides, and the total temperature span in each cycle attained about 5 K. The specific heat of the material was measured to calculate the magnetic entropy change ΔS and the adiabatic temperature change ΔT induced by the magnetic field change ΔH. It was suggested that for a given ΔH, larger ΔS and ΔT can be exploited when demagnetized to lower H, especially, to zero field.

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