scholarly journals On the Limitations and Implications of Modeling Heat Transport in Porous Aquifers by Assuming Local Thermal Equilibrium

2020 ◽  
Vol 56 (10) ◽  
Author(s):  
Manuel A. Gossler ◽  
Peter Bayer ◽  
Gabriel C. Rau ◽  
Florian Einsiedl ◽  
Kai Zosseder
Keyword(s):  
Heat Transport ◽  
Thermal Equilibrium ◽  
Local Thermal Equilibrium ◽  
Porous Aquifers

scholarly journals Precise Measurements of CH Maser Emission and Its Abundance in Translucent Clouds

2021 ◽  
Vol 257 (2) ◽  
pp. 47
Author(s):  
Ningyu Tang ◽  
Di Li ◽  
Gan Luo ◽  
Carl Heiles ◽  
Sheng-Li Qin ◽  
...  
Keyword(s):  
Thermal Equilibrium ◽  
Column Density ◽  
High Sensitivity ◽  
Local Thermal Equilibrium ◽  
Molecular Gas ◽  
Excitation Temperature ◽  
Hyperfine Transitions ◽  
Visible Wavelengths ◽  
Log Normal ◽  
Log Normal Distribution

Abstract We present high-sensitivity CH 9 cm ON/OFF observations toward 18 extragalactic continuum sources that have been detected with OH 18 cm absorption in the Millennium survey with the Arecibo telescope. CH emission was detected toward 6 of the 18 sources. The excitation temperature of CH has been derived directly through analyzing all detected ON and OFF velocity components. The excitation temperature of CH 3335 MHz transition ranges from −54.5 to −0.4 K and roughly follows a log-normal distribution peaking within [−5, 0] K, which implies overestimation by 20% to more than 10 times during calculating CH column density by assuming the conventional value of −60 or −10 K. Furthermore, the column density of CH would be underestimated by a factor of 1.32 ± 0.03 when adopting local thermal equilibrium assumption instead of using the CH three hyperfine transitions. We found a correlation between the column density of CH and OH following log N(CH) = (1.80 ± 0.49) and log N(OH −11.59 ± 6.87. The linear correlation between the column density of CH and H2 is consistent with that derived from visible wavelengths studies, confirming that CH is one of the best tracers of H2 components in diffuse molecular gas.

scholarly journals A theoretical analysis of local thermal equilibrium in fibrous materials

2015 ◽  
Vol 19 (1) ◽  
pp. 69-82
Author(s):  
Mingwei Tian ◽  
Ning Pan ◽  
Lijun Qu ◽  
Xiaoqing Guo ◽  
Guangting Han
Keyword(s):  
Thermal Equilibrium ◽  
Internal Heat ◽  
Constant Heat Flux ◽  
Local Thermal Equilibrium ◽  
Transfer Model ◽  
Fibrous Materials ◽  
Two Phase ◽  
Convective Boundary ◽  
Boundary Problems ◽  
Criterion System

The internal heat exchange between each phase and the Local Thermal Equilibrium (LTE) scenarios in multi-phase fibrous materials are considered in this paper. Based on the two-phase heat transfer model, a criterion is proposed to evaluate the LTE condition, using derived characteristic parameters. Furthermore, the LTE situations in isothermal/adiabatic boundary cases with two different heat sources (constant heat flux and constant temperature) are assessed as special transient cases to test the proposed criterion system, and the influence of such different cases on their LTE status are elucidated. In addition, it is demonstrated that even the convective boundary problems can be generally estimated using this approach. Finally, effects on LTE of the material properties (thermal conductivity, volumetric heat capacity of each phase, sample porosity and pore hydraulic radius) are investigated, illustrated and discussed in our study.

scholarly journals Liquid Brine in Ice Shelves

1975 ◽  
Vol 14 (70) ◽  
pp. 125-136 ◽  
Author(s):  
R. H. Thomas
Keyword(s):  
Steady State ◽  
Heat Transport ◽  
Thermal Equilibrium ◽  
Transport Model ◽  
Percolation Model ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Brine Layer ◽  
Good Agreement

Holes drilled into thin areas of the Brunt Ice Shelf encounter a layer of liquid brine less than 1 m thick approximately at sea-level. Assuming the brine to be moving horizontally, analysis of its effects on thermal equilibrium gives an estimate of steady-state annual brine flow that is in good agreement with the value deduced from a percolation model. The effect of firn density on percolation rates is such that the slope of an active brine layer increases rapidly as ice thickness increases. However, the heat transport model predicts that brine layers are unlikely to be active in both very thick and very thin ice shelves.

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