Stability analysis of a closed thermosyphon

1990 ◽  
Vol 1 (1) ◽  
pp. 1-23 ◽  
Author(s):  
M. A. Herrero ◽  
J. J. L. Velazquez
Keyword(s):  
Heat Flux ◽  
Natural Convection ◽  
Stability Analysis ◽  
Closed Loop ◽  
Stationary Solutions ◽  
External Heat ◽  
Intermediate Asymptotics ◽  
External Heat Flux

This paper deals with the motion of a fluid in a closed loop under the effect of natural convection and a given external heat flux. More precisely, we show that the stationary solutions of a system describing the intermediate asymptotics of the previous problem are structurally linearly unstable.

The Application of IRAs Optimizing Design in Vacuum Thermal Test

2013 ◽  
Vol 390 ◽  
pp. 708-713
Author(s):  
Yu Wei Sun ◽  
Xiao Ning Yang
Keyword(s):  
Heat Flux ◽  
Heated Surface ◽  
Design Guidelines ◽  
External Heat ◽  
Simulation Test ◽  
Thermal Tests ◽  
Typical Structure ◽  
Infra Red ◽  
Optimizing Design ◽  
External Heat Flux

The thermal vacuum environment simulation test is indispensible for the development of spacecrafts. And the simulation of the external heat flux exerted onto the spacecraft is one of the determining elements of the simulation test. In China, the infra-red simulation is a common method that used as simulation equipment of the external heat flux. The planar infra-red arrays is the most typical structure elements for planar spacecraft surface, but the margin effect of infra-red arrays influences the flux uniformity on heated surface severely. Based on Monte Carlo theory, some optimizing design guidelines had been drawn about planar infra-red arrays in past investigation. This paper introduces some testing and experiment that could confirm these guidelines, and these guidelines had been applied in some vacuum thermal tests of spacecrafts successfully.

Experimental study of commercial flame-retardant polycarbonate under external heat flux

2017 ◽  
Vol 131 (2) ◽  
pp. 1463-1470 ◽  
Author(s):  
Xuelin Zhang ◽  
Teng Zhang ◽  
Changhai Li ◽  
Hongshuang Wang ◽  
Xiao Chen ◽  
...  
Keyword(s):  
Experimental Study ◽  
Heat Flux ◽  
Flame Retardant ◽  
External Heat ◽  
External Heat Flux

Effectiveness-NTU Relationship for a Counterflow Heat Exchanger Subjected to an External Heat Transfer

2004 ◽  
Vol 127 (9) ◽  
pp. 1071-1073 ◽  
Author(s):  
Gregory F. Nellis ◽  
John M. Pfotenhauer
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Exchanger ◽  
Numerical Model ◽  
Analytical Solution ◽  
Convenient Method ◽  
Process Engineering ◽  
External Heat ◽  
External Heat Transfer ◽  
External Heat Flux

This paper presents the analytical solution for the effectiveness of a counterflow heat exchanger subjected to a uniformly distributed, external heat flux. The solution is verified against conventional ε-NTU relations in the limit of zero external heat flux. This situation is of interest in applications such as cryogenic and process engineering, and the analytical solution provides a convenient method for treating differential elements of a heat exchanger in a numerical model.

scholarly journals Initiation Parameters of Granulated Synthetic Polymers

2021 ◽  
Vol 29 (48) ◽  
pp. 114-122
Author(s):  
Peter Rantuch ◽  
Jozef Martinka ◽  
Tomáš Štefko ◽  
Igor Wachter
Keyword(s):  
Heat Flux ◽  
Polymeric Materials ◽  
Synthetic Polymers ◽  
Flow Time ◽  
External Heat ◽  
Small Thickness ◽  
Gaseous Products ◽  
Product Method ◽  
Different Shapes ◽  
External Heat Flux

Abstract Polymeric materials, which are currently very often used in various industries, are often transported and stored in the form of granules before processing. This method has several advantages, but in most studies the test samples are modified to different shapes and dimensions. This paper is therefore focused on the initiation of selected granular plastics. Samples of five polymeric materials were exposed to an external heat flux from 20 kW.m−2 to 40 kW.m−2. A spark initiator was used to ignite the released gaseous products of thermal decomposition of the polymer sample. FTP (flow-time product) method was applied to the obtained parameter - time to ignition, from which other initiation parameters were determined. The critical heat flux was determined in the range of 5.0 kW.m−2 - 11.8 kW.m−2. Despite the relatively small thickness (4 mm), the samples behaved as thermally thick. During the measurement, thin surface layer melted, and the rest of the polymer remained in its original granulated form. Ignition temperatures were calculated according to the Stefan-Boltzmann’s law between 273 °C - 402 °C.

scholarly journals Combustion Performance and Thermal Stability of Basalt Fiber-Reinforced Polypropylene Composites

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1826 ◽  
Author(s):  
Tang ◽  
Xu ◽  
Li
Keyword(s):  
Thermal Stability ◽  
Heat Flux ◽  
Thermal Decomposition ◽  
Heat Release ◽  
Decomposition Rate ◽  
Basalt Fiber ◽  
External Heat ◽  
Fiber Reinforced ◽  
Combustion Performance ◽  
External Heat Flux

In this study, the thermal stability and combustion performance of basalt fiber reinforced polypropylene (BFRPP) composite and pure polypropylene (PP) were compared. The results show that the basalt fiber has no positive effect on increasing the initial decomposition temperature of PP, but it could reduce the maximum thermal decomposition rate and increase the temperature of the maximum thermal decomposition rate. Adding basalt fiber to PP could slightly reduce the limiting oxygen index. At the same oxygen concentration, the BFRPP burned significantly more slowly than the PP. In addition, during the combustion, it was observed that the BFRPP showed a better anti-melt dripping effect than the PP. The results from the cone calorimeter test show that, under the same external heat flux, the time-to-ignition (TTI) of BFRPP was less than that of PP. This indicated that BFRPP was easier to ignite than PP. It was also found that the reciprocal of the square root of the TTI of both has a linear relationship with external heat flux. BFRPP has a lower peak heat release rate and total heat release than PP. Moreover, BFRPP produced less smoke than PP when burned.

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