Methods of calculating radiative-conductive heat exchange in the components of electrovacuum instruments

1979 ◽  
Vol 36 (2) ◽  
pp. 204-209
Author(s):  
V. S. Koshelev ◽  
G. M. Tsymbalov ◽  
V. N. Shevtsov
Keyword(s):  
Heat Exchange ◽  
Conductive Heat

scholarly journals Heat exchange of a roller with a particle from polymeric material when it is pressed into tissue

2019 ◽  
Vol 298 ◽  
pp. 00086
Author(s):  
Vladimir Fedyaev ◽  
Valentin Khaliulin ◽  
Marat Faskhutdinov ◽  
Alexey Belyaev ◽  
Liliya Sirotkina
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Initial Conditions ◽  
Thermal Contact ◽  
Polymer Particle ◽  
Heat Propagation ◽  
Conductive Heat ◽  
Polymer Particles ◽  
Heat Conservation ◽  
The Heat Balance

We study the heat transfer of polymer particles with a roller that presses the material of the particles into the fabric. Provided that the speed of movement of the tissue with the particles relative to the roller is small, the heat exchange of the pressed particles with the environment is not taken into account, a mathematical model of conductive heat transfer in the contacting roller, polymer particle and reinforcing fabric is proposed. This model includes heat conservation equations written with respect to average temperatures of the roller, particles, fabric, as well as boundary and initial conditions. Assuming that there is perfect thermal contact between the polymer particles and the fabric, in the direction of heat propagation the average thickness of the pressed tissue particle is small, the layer of material of particles and fabric is considered thermally thin, the temperature in it varies slightly in thickness. As a result, the initial system of three equations is reduced to one equation with respect to the temperature of the roller, which is supplemented by the corresponding boundary and initial conditions. In the case when the temperature along the radius of the roller varies along its radius linearly, the specific heat flux on the surface of the roller is estimated. After that, this expression is substituted into the heat balance equation of a thermally thin layer consisting of particle material and tissue, which is integrated after certain transformations.

scholarly journals Thermal conductivity of firn at Lomonosovfonna, Svalbard, derived from subsurface temperature measurements

2019 ◽  
Vol 13 (7) ◽  
pp. 1843-1859 ◽  
Author(s):  
Sergey Marchenko ◽  
Gong Cheng ◽  
Per Lötstedt ◽  
Veijo Pohjola ◽  
Rickard Pettersson ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Exchange ◽  
Effective Thermal Conductivity ◽  
Vertical Profile ◽  
Systematic Errors ◽  
Conductive Heat ◽  
Glacier Surface ◽  
Optimization Routine ◽  
Subsurface Temperatures ◽  
Over Time

Abstract. Accurate description of snow and firn processes is necessary for estimating the fraction of glacier surface melt that contributes to runoff. Most processes in snow and firn are to a great extent controlled by the temperature therein and in the absence of liquid water, the temperature evolution is dominated by the conductive heat exchange. The latter is controlled by the effective thermal conductivity k. Here we reconstruct the effective thermal conductivity of firn at Lomonosovfonna, Svalbard, using an optimization routine minimizing the misfit between simulated and measured subsurface temperatures and densities. The optimized k* values in the range from 0.2 to 1.6 W (m K)−1 increase downwards and over time. The results are supported by uncertainty quantification experiments, according to which k* is most sensitive to systematic errors in empirical temperature values and their estimated depths, particularly in the lower part of the vertical profile. Compared to commonly used density-based parameterizations, our k values are consistently larger, suggesting a faster conductive heat exchange in firn.

scholarly journals Melting and Heat Exchange at the Bottom of a Snow Cover

1985 ◽  
Vol 6 ◽  
pp. 276-277 ◽  
Author(s):  
Kenji Kojima ◽  
Hideaki Motoyama
Keyword(s):  
Heat Exchange ◽  
Snow Cover ◽  
Early Period ◽  
Melting Rate ◽  
Heat Fluxes ◽  
Conductive Heat ◽  
Test Field ◽  
Daily Amount ◽  
Daily Average ◽  
The Past

The melting rate of the bottom of a snow cover during the winter and its variation with time were studied in relation to heat exchange at the ground-snow interface. Continuous observations were made of bottom-melt, using a lysimeter, during the past four winters beginning December 1980, at our test field in Moshiri, Hokkaido, which is known for severe coldness and deep snow. During the four months in this area the amount of bottom-melt ranged from 45 - 70 mm in total and from 0.4 - 0.6 mm per day on average. In winters with much snow the daily amount of bottom-melt decreased gradually from a maximum of about 1.5 mm.d-1 in early December, reached its minimum of 0.2 - 0.3 mm d-1 day in February, and then increased again. In a winter with a smaller amount of snow it varied greatly with time during the early period of the winter and became zero temporarily. Such variations of the melting rate could be explained by conductive heat fluxes observed in the ground and snow. The daily average of the former was about 5 W.m-2 at a depth of 0.1 m in early December and decreased to about 2.5 W.m-2 in early April.

scholarly journals Thermal Performance of Cemented Paste Backfill Body Considering Its Slurry Sedimentary Characteristics in Underground Backfill Stopes

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7400
Author(s):  
Chao Huan ◽  
Sha Zhang ◽  
Xiaoxuan Zhao ◽  
Shengteng Li ◽  
Bo Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Simulation Model ◽  
Flow Direction ◽  
Seepage Flow ◽  
Parameter Determination ◽  
Conductive Heat ◽  
Cemented Paste Backfill ◽  
Exchange Performance ◽  
Paste Backfill

The combined mine backfill–geothermal (CMBG) system can be used to effectively extract geothermal energy by installing a heat exchange tube (HET) in the underground backfilled stopes of mines, which can be used as the heat supply for buildings in mines and the surrounding areas. The efficient performance of this system strongly depends on the thermal exchange process between the HET and its surrounding cemented paste backfill body (CPB). In this study, a validated simulation model is established to investigate the heat exchange performance of CPB, in which the nonuniformly distributed thermal properties in CPB are fully considered. The results indicate that the increase in the porosity has a negative effect on the heat exchange performance of CPB. With the increase in the porosity, the decreased rate of the conductive heat transfer in CPB could be up to approximately 18%. In conditions with seepage flow, the heat transfer capacity of CPB could be effectively improved. Generally, a higher hydraulic conductivity corresponds to a higher heat transfer performance of CPB. When the seepage velocity rose from 2 × 10−6 to 6 × 10−6 m/s, the thermal conductivity of CPB achieved a 114% increase from 1.843 to 3.957 W/(m·K). Furthermore, it was found that the thermal energy accumulates along the seepage flow direction, enhancing the thermal influencing radius of the HET in this direction. Thus, the arrangement of HETs should fully take into account the seepage flow effect. This proposed simulation model could provide a reference for parameter determination and optimization of CMBG systems.

Conductive Heat Exchange with a Gel-Coated Circulating Water Mattress

2004 ◽  
pp. 1742-1746 ◽  
Author(s):  
Anselm Br??uer ◽  
Larissa Pacholik ◽  
Thorsten Perl ◽  
Michael John Murray English ◽  
Wolfgang Weyland ◽  
...  
Keyword(s):  
Heat Exchange ◽  
Conductive Heat ◽  
Circulating Water
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