XV. On the thermal effects of fluids in motion - Part II

1854 ◽  
Vol 144 ◽  
pp. 321-364 ◽  
Keyword(s):  
Thermal Effects ◽  
Low Pressure ◽  
Cooling Effect ◽  
Cotton Wool ◽  
Low Pressures

In the last experiment related in our former paper, in which a low pressure of air was employed, a considerable variation of the cooling effect was observed, which it was necessary to account for in order to ascertain its influence on the results. We therefore continued the experiments at low pressures, trying the various arrangements which might be supposed to exercise influence over the phenomena. We had already interposed a plug of cotton wool between the iron and copper pipes, which was found to have the very important effect of equalizing the pressure, besides stopping any solid or liquid particles driven from the pump, and which has therefore been retained in all the subsequent experiments.

scholarly journals XXV. On the thermal effects of fluids in motion.— Part IV

1862 ◽  
Vol 152 ◽  
pp. 579-589 ◽  
Keyword(s):  
High Pressure ◽  
Thermal Effects ◽  
Carbonic Acid ◽  
Low Pressure ◽  
Cooling Effect ◽  
Porous Plug ◽  
Pressure Side ◽  
Atmospheric Air ◽  
Elastic Fluid ◽  
The Difference

In the Second Part of these researches we have given the results of our experiments on the difference between the temperatures of an elastic fluid on the high- and low-pressure sides of a porous plug through which it was transmitted. The gases employed were atmospheric air and carbonic acid. With the former, 0°·0176 of cooling effect was observed for each pound per square inch of difference of pressure, the temperature on the high-pressure side being 17°·25. With the latter gas, 0°·0833 of cooling effect was produced per lb. of difference of pressure, the temperature on the high-pressure side being 12°·844. It was also shown that in each of the above gases the difference of the temperatures on the opposite sides of the porous plug is sensibly proportional to the difference of the pressures.

Large Cryogenic Storage of Hydrogen in Carbon Nanotubes at Low Pressures

2001 ◽  
Vol 706 ◽  
Author(s):  
B. K. Pradhan ◽  
A. Harutyunyan ◽  
D. Stojkovic ◽  
P. Zhang ◽  
M. W. Cole ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Zero Point ◽  
Isosteric Heat ◽  
Low Pressure ◽  
Quantum Mechanical ◽  
Strong Adsorption ◽  
Point Motion ◽  
Post Synthesis ◽  
Walled Carbon Nanotubes ◽  
Low Pressures

AbstractWe report (6 wt %) storage of H2 at T=77 K in processed bundles of single-walled carbon nanotubes at P=2 atmospheres. The hydrogen storage isotherms are completely reversible. D2 isotherms confirm this anomalous low-pressure adsorption and further reveal the effects of quantum mechanical zero point motion. We propose that our post-synthesis treatment of the sample not only improves access for hydrogen to the central pores within individual nanotubes, but also may create a roughened tube surface with an enhanced binding energy for hydrogen. Such an enhancement is needed to understand the strong adsorption at low pressure. We obtain an experimental isosteric heat qst=125 ± 5 meV for processed SWNT materials.

Effects of Tooth Width on Gas Labyrinth and Windback Seals Operating at Low Pressure Ratios

2007 ◽  
Author(s):  
Gerald L. Morrison ◽  
Chae Hwan Lim
Keyword(s):  
Low Pressure ◽  
Labyrinth Seal ◽  
Screw Thread ◽  
Tooth Width ◽  
Accepted Standard ◽  
Additional Amount ◽  
The Difference ◽  
Low Pressures

The difference in leakage rates for labyrinth and windback seals is studied. It is determined that the leakage under the teeth of a windback seal is within ± 3% of a labyrinth seal with the same cavity/tooth design. The windback leaks an additional amount due to fluid passing through the long conduit composed of the continuous screw thread like channel. At low pressures and low differential pressures across the seal, the effect of tooth width upon the leakage in labyrinth and windback seals is opposite to the normal accepted standard of thinner teeth leak less.

A biphasic model of limb venous compliance: a comparison with linear and exponential models

2003 ◽  
Vol 95 (3) ◽  
pp. 1207-1215 ◽  
Author(s):  
Marcelo R. Risk ◽  
Vasilios Lirofonis ◽  
Ricardo L. Armentano ◽  
Roy Freeman
Keyword(s):  
Low Pressure ◽  
Coefficient Of Determination ◽  
Linear Modeling ◽  
Venous Compliance ◽  
Exponential Models ◽  
Biphasic Model ◽  
Venous Circulation ◽  
Compliance Curve ◽  
The Mean ◽  
Low Pressures

Compliance is not linear within the physiological range of pressures, and linear modeling may not describe venous physiology adequately. Forearm and calf venous compliance were assessed in nine subjects. Venous compliance was modeled by using a biphasic model with high- and low-pressure linear phases separated by a breakpoint. This model was compared with a linear model and several exponential models. The biphasic, linear, and two-parameter exponential models best represented the data. The mean coefficient of determination for the biphasic model was greater than for the linear and exponential models in the calf (biphasic 0.94 ± 0.04, exponential 0.81 ± 0.16, P = not significant; and linear 0.54 ± 0.05, P < 0.05) and forearm (biphasic 0.83 ± 0.17, exponential 0.79 ± 0.15, P = not significant; and linear 0.51 ± 0.06, P < 0.05). The breakpoint pressure in the biphasic model was higher in the calf than the forearm, 34.4 ± 3.9 vs. 29.1 ± 4.5 mmHg, P < 0.05. A biphasic model can describe limb venous compliance and delineate differences in venous physiology at high and low pressures. The steep low-pressure phase of the compliance curve extends to higher pressures in the calf than in the forearm, thereby enlarging the range of pressures over which hemodynamic regulation by the calf venous circulation occurs.

scholarly journals Venturi Wet Gas Flow Modeling Based on Homogeneous and Separated Flow Theory

2008 ◽  
Vol 2008 ◽  
pp. 1-25 ◽  
Author(s):  
Fang Lide ◽  
Zhang Tao ◽  
Xu Ying
Keyword(s):  
High Pressure ◽  
Pressure Drop ◽  
Gas Flow ◽  
Flow Model ◽  
Separated Flow ◽  
Flow Theory ◽  
Low Pressure ◽  
New Correlation ◽  
Wet Gas ◽  
Low Pressures

When Venturi meters are used in wet gas, the measured differential pressure is higher than it would be in gas phases flowing alone. This phenomenon is called over-reading. Eight famous over-reading correlations have been studied by many researchers under low- and high-pressure conditions, the conclusion is separated flow model and homogeneous flow model performing well both under high and low pressures. In this study, a new metering method is presented based on homogeneous and separated flow theory; the acceleration pressure drop and the friction pressure drop of Venturi under two-phase flow conditions are considered in new correlation, and its validity is verified through experiment. For low pressure, a new test program has been implemented in Tianjin University’s low-pressure wet gas loop. For high pressure, the National Engineering Laboratory offered their reports on the web, so the coefficients of the new proposed correlation are fitted with all independent data both under high and low pressures. Finally, the applicability and errors of new correlation are analyzed.

RESPIRATORY MOVEMENTS AND ENDURANCE OF FROGS AT LOW PRESSURES

1957 ◽  
Vol 35 (5) ◽  
pp. 593-601
Author(s):  
James C. Hall ◽  
Helen I. Battle
Keyword(s):  
Atmospheric Pressure ◽  
Prolonged Exposure ◽  
Low Pressure ◽  
Reduced Pressure ◽  
Lung Inflation ◽  
Initial Effect ◽  
Advanced Stages ◽  
Normal Atmospheric Pressure ◽  
Low Pressures ◽  
Respiratory Movements

Exposure of three species of frogs (Rana pipiens, R. clamitans, and R. sylvatica) to pressures of 1.5, 3.0, and 5.0 cm. Hg induces characteristic changes in the frequency and type of breathing. The immediate initial effect is that of increasing both mouth and lung oscillations for a brief period, prior to a gradual decline in rate. Lung oscillations persist longer than mouth oscillations, and on return to normal atmospheric pressure, are initiated earlier and at a rapid rate. During advanced stages of decompression, excess lung inflation is resultant from several consecutive inhalations, prior to a deep exhalation. R. pipiens is most resistant to low pressure, and R. sylvatica least resistant. Large individuals of a species survive longer than small. Survival is better with little oxygen in an atmosphere of nitrogen at normal atmospheric pressure than with a comparable oxygen supply at a reduced pressure. A brief acclimatization to pressures of 1.5 and 3.0 cm. Hg can be produced by prolonged exposure to 15 cm. Hg but not by intermittent exposures to low pressure.

Large cryogenic storage of hydrogen in carbon nanotubes at low pressures

2002 ◽  
Vol 17 (9) ◽  
pp. 2209-2216 ◽  
Author(s):  
B. B. Pradhan ◽  
A. A. Harutyunyan ◽  
D. Stojkovic ◽  
J. J. Grossman ◽  
P. Zhang ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Binding Energy ◽  
Tube Wall ◽  
Zero Point ◽  
Isosteric Heat ◽  
Low Pressure ◽  
Strong Adsorption ◽  
Point Motion ◽  
Walled Carbon Nanotubes ◽  
Low Pressures

We report up to 6 wt% storage of H2 at 2 atm and T = 77 K in processed bundles of single-walled carbon nanotubes. The hydrogen storage isotherms are completely reversible; D2 isotherms confirmed this anomalous low-pressure adsorption and also revealed the effects of quantum mechanical zero point motion. We propose that our postsynthesis treatment of the sample improves access for hydrogen to the central pores within individual nanotubes and may also create a roughened tube surface with an increased binding energy for hydrogen. Such an enhancement may be needed to understand the strong adsorption at low pressure. We obtained an experimental isosteric heat qst = 125 ± 5 meV. Calculations are also presented that indicate disorder in the tube wall enhances the binding energy of H2.

scholarly journals The Effect of Merging Subtropical Jet Stream and Polar Fronts Jet Stream on Heavy Rainfall in Southwest Asia

2021 ◽  
Author(s):  
Mohammad Saligheh
Keyword(s):  
South Asia ◽  
Weather Conditions ◽  
Low Pressure ◽  
Polar Front ◽  
Jet Stream ◽  
Zagros Mountains ◽  
Low Level ◽  
Subtropical Jet Stream ◽  
Subtropical Jet ◽  
Low Pressures

Abstract The purpose of this paper is to show the effect of high troposphere winds and currents on low troposphere events at sea level. For this study, precipitation data from atmospheric stations in South Asia and west of the Zagros Mountains were used. After preparing these data, 500 and 300 hectopascal level maps were used to interpret the weather conditions. Vertical transect flow maps were used to identify the position of the jet stream. The results showed that the merger of the polar front jet stream and the subtropical jet stream provide the conditions for accelerating atmospheric currents and reaching more humidity and stronger ascent conditions to South Asia. Jet streams merger have three major effects on low pressure. If the Jet stream vorticity is the same as the curvature vorticity, the low-pressure centers on the low level will be strengthened, otherwise they will weaken due to the opposite effects. The low pressure under the Jet stream divergence area helps to strengthen it. The difference in wind speed in the jet stream with low pressures, stranger low pressures in the low level.

Low-pressure superconductivity in lithium-doped methane predicted by first principles

2020 ◽  
pp. 2150032
Author(s):  
Ning Lu ◽  
Yu-Long Hai ◽  
Hai-Yan Lv ◽  
Wen-Jie Li ◽  
Chun-Lei Yang ◽  
...  
Keyword(s):  
Charge Transfer ◽  
High Temperature ◽  
Crystal Field ◽  
First Principles ◽  
Pressure Range ◽  
High Temperature Superconductor ◽  
Low Pressure ◽  
First Principles Calculations ◽  
A Charge ◽  
Low Pressures

To explore the high-temperature superconductor at low pressures, we have investigated the crystal structures, electronic properties, and possible superconductivity in the case of methane (CH4) doped by lithium in the pressure range of [Formula: see text][Formula: see text]GPa, based on the first-principles calculations. The results show that Li-intercalated CH4 (Lix(CH4)[Formula: see text]) can realize metallization and superconductivity at low pressures, even 5[Formula: see text]GPa. We find that there is a charge transfer between Li and CH4, but the metallization is driven by the change of crystal field induce by doping instead of charge transfer. The critical temperture is predicted from 3.8[Formula: see text]K at 5[Formula: see text]GPa for LiCH4 to 12.1[Formula: see text]K at 100[Formula: see text]GPa for Li(CH4)4. The low-pressure superconductivity of Lix(CH4)[Formula: see text] can be further optimized by adjusting component and pressure.

The pvt properties of water v*. the fluid to 1 kbar at 350-500 °c and along the saturation line from 150 to 350 °c

1985 ◽  
Vol 315 (1532) ◽  
pp. 235-246 ◽  
Keyword(s):  
Thermal Expansion ◽  
High Temperature ◽  
Expansion Method ◽  
Low Pressure ◽  
Saturation Line ◽  
Density Change ◽  
Pvt Properties ◽  
Gas Expansion ◽  
Low Pressures ◽  
Density Of Water

The density of water has been measured from low pressures to 1 kbar (1 bar = 10 5 Pa) at 25 K intervals from 350 to 500 °C and the density change on condensation has been measured from 150 to 350 °C by injecting water into a 35 cm 3 high-temperature vessel that can be completely filled in a single delivery from the screw injector used in earlier work. The thermal expansion of the vessel was determined by a gas-expansion method. The estimated uncertainty caused by the uncertainty of the volume of the vessel at low pressure is 0.02 kg m -3 at 150 °C and 0.08 kg m -3 at all other temperatures, and the uncertainty arising from the uncertainty in the compression of the vessel is 0.10 kg m -3 kbar -1 .

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