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Results for “CRITICAL PRESSURE”
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Pool boiling of methane between atmospheric pressure and the critical pressure.
Pool boiling of methane over pressure range from 1 atm to critical pressure in both nucleate and stable film boiling regimes
Two-phase flows and heat transfer within systems with ambient pressure above the thermodynamic critical pressure
In systems where the design inlet and outlet pressures P sub amb are maintained above the thermodynamic critical pressure P sub c, it is often assumed that heat and mass transfer are governed by single-phase relations and that two-phase flows cannot occur. This simple rule of thumb is adequate in many low-power designs but is inadequate for high-performance turbomachines, boilers, and other systems where two-phase regions can exist even though P sub amb P sub c. Heat and mass transfer and rotordynamic-fluid-mechanic restoring forces depend on momentum differences, and those for a two-phase zone can differ significantly from those for a single-phase zone. By using a laminar, variable-property bearing code and a rotating boiler code, pressure and temperature surfaces were determined that illustrate nesting of a two-phase region within a supercritical pressure region. The method of corresponding states is applied to bearings with reasonable rapport.
Two-phase flows and heat transfer within systems with ambient pressure above the thermodynamic critical pressure
In systems where the design inlet and outlet pressure P sub amb are maintained above the thermodynamic critical pressure P sub c, it is often assumed that heat and mass transfer are governed by single-phase relations and that two-phase flows cannot occur. This simple rule of thumb is adequate in many low-power designs but is inadequate for high-performance turbomachines, boilers, and other systems where two-phase regions can exist even though P sub amb P sub c. Heat and mass transfer and rotordynamic-fluid-mechanic restoring forces depend on momentum differences, and those for a two-phase zone can differ significantly from those for a single-phase zone. By using a laminar, variable-property bearing code and a rotating boiler code, pressure and temperature surfaces were determined that illustrate nesting of a two-phase region within a supercritical pressure region. The method of corresponding states is applied to bearings with reasonable rapport.
Evolution of critical pressure with increasing Fe substitution in the heavy-fermion system URu 2 - x Fe x Si 2
Measurements of electrical resistivity, ρ(T ), were performed under quasihydrostatic pressure up to P ~ 2.2 GPa to determine the pressure dependence of the so-called hidden order (HO) and large-moment antiferromagnetic (LMAFM) phases for the URu 2-x FexSi2 system with x = 0.025, 0.05, 0.10, 0.15, and 0.20. As the Fe concentration (x) is increased, we observed that a smaller amount of external pressure, P c , is required to induce the HO → LMAFM phase transition. A critical pressure of P c ~ 1.2 GPa at x = 0.025 reduces to P c ~ 0 at x = 0.15, suggesting the URu 2-x Fe x Si 2 system is fully expressed in the LMAFM phase for x ≥ x* c = 0.15, where x * c denotes the ambient pressure critical concentration of Fe. Furthermore, when using a bulk modulus calculation to convert x to chemical pressure, P ch (x), we consistently found that the induced HO → LMAFM phase transition occurred at various combinations of x c and P c such that P ch (x c ) + P c ≈ 1.5 GPa, where xc denotes those critical concentrations of Fe that induce the HO→LMAFM phase transition for the URu 2-x Fe x Si 2 compounds under pressure. We performed exponential fits of ρ(T ) in the HO and LMAFM phases in order to determine the pressure dependence of the energy gap, , that opens over part of the Fermi surface in the transition from the paramagnetic (PM) phase to the HO/LMAFM phase at the transition temperature, T 0 . Finally, this change in the pressure variation of Δ(P) at the HO→LMAFM phase transition is consistent with the values of P c determined from the T 0 (P) phase lines at the PM→HO/LMAFM transition.
Microwave voltage breakdown at critical pressures
Microwave voltage breakdown at critical pressures /Ranger spacecraft/
On the dependence of the upper critical pressure of a cylindrical shell on the boundary conditions for the tangential displacements
Effect of boundary conditions for tangential displacement on upper critical pressure value of cylindrical shell
Heat transfer from an incandescent wire in saturated liquid nitrogen from atmospheric to the critical pressure
Film boiling and heat transfer from platinum wire in saturated liquid nitrogen up to critical pressure
The investigation of critical pressure burning of fuel droplets Annual report, 1 Jan. - 31 Dec. 1970
Experimental and theoretical results of critical pressure burning of fuel droplets
Heat transfer from an incandescent wire in saturated liquid nitrogen from atmospheric to the critical pressure
Heat transfer from incandescent platinum wires in saturated liquid nitrogen, examining film boiling from atmospheric to critical pressure
Saturated film boiling of nitrogen from atmospheric to the critical pressure
Liquid nitrogen saturated film boiling from wire at pressures up to critical, discussing liquid- vapor interface configuration
The effect of initial flaw configuration on leak critical pressure vessel design
The effect of initial flaw shape and depth on the cycles required to produce a pressure leak condition in parent and welded 2219-T87 aluminum was examined for thicknesses from 0.04 to 0.3 inch. Initial flaw aspect ratios of 0.5, 0.3, and 0.15 were examined for tests conducted at a frequency of 4 Hz at room temperature and at 300 F. A computer program developed by Forman was used to predict the cycles to leak curve as a function of initial crack aspect ratio, material thickness, and specimen type and the results compared with the experimental data. Sources of error in the crack propagation analysis and the interface with NDI capabilities are discussed.
Some Measurements of the Effect of Gaseous Imperfections on the Critical Pressure Ratio in Air and the Speed of Sound in Nitrogen
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Process feasibility study in support of silicon material, task 1
Analyses of process system properties were continued for materials involved in the alternate processes under consideration for semiconductor silicon. Primary efforts centered on physical and thermodynamic property data for dichlorosilane. The following property data are reported for dichlorosilane which is involved in processing operations for solar cell grade silicon: critical temperature, critical pressure, critical volume, critical density, acentric factor, vapor pressure, heat of vaporization, gas heat capacity, liquid heat capacity and density. Work was initiated on the assembly of a system to prepare binary gas mixtures of known proportions and to measure the thermal conductivity of these mixtures between 30 and 350 C. The binary gas mixtures include silicon source material such as silanes and halogenated silanes which are used in the production of semiconductor silicon.
A Geophysical Flow Experiment in a Compressible Critical Fluid
The first objective of this experiment is to build an experimental system in which, in analogy to a geophysical system, a compressible fluid in a spherical annulus becomes radially stratified in density through an A.C. electric field. When this density gradient is demonstrated, the system will be augmented so that the fluid can be driven by heating and rotation and tested in preparation for a microgravity experiment. This apparatus consists of a spherical capacitor filled with critical fluid in a temperature controlled environment. To make the fluid critical, the apparatus will be operated near the critical pressure, critical density, and critical temperature of the fluid. This will result in a highly compressible fluid because of the properties of the fluid near its critical point. A high voltage A.C. source applied across the capacitor will create a spherically symmetric central force because of the dielectric properties of the fluid in an electric field gradient. This central force will induce a spherically symmetric density gradient that is analogous to a geophysical fluid system. To generate such a density gradient the system must be small (approx. 1 inch diameter). This small cell will also be capable of driving the critical fluid by heating and rotation. Since a spherically symmetric density gradient can only be made in microgravity, another small cell, of the same geometry, will be built that uses incompressible fluid. The driving of the fluid by rotation and heating in these small cells will be developed. The resulting instabilities from the driving in these two systems will then be studied. The second objective is to study the pattern forming instabilities (bifurcations) resulting from the well controlled experimental conditions in the critical fluid cell. This experiment will come close to producing conditions that are geophysically similar and will be studied as the driving parameters are changed.
Observation of superconductivity in the pressurized Weyl-semimetal candidate TaIrTe 4
We report the observation of superconductivity in the pressurized type-II Weyl semimetal (WSM) candidate TaIrTe 4 by means of complementary high-pressure transport and synchrotron x-ray diffraction measurements. We find that TaIrTe 4 shows superconductivity with transition temperature (TC) of 0.57 K at the pressure of ~23.8GPa. Then, the T C value increases with pressure and reaches ~2.1K at 65.7 GPa. In situ high-pressure Hall coefficient (R H ) measurements at low temperatures demonstrate that the positive R H increases with pressure until the critical pressure of the superconducting transition is reached, but starts to decrease upon further increasing pressure. Above the critical pressure, the positive magnetoresistance effect disappears simultaneously. Our high-pressure x-ray diffraction measurements reveal that at around the critical pressure, the lattice of the TaIrTe 4 sample is distorted and its volume is reduced by ~19.2%, the value of which is predicted to result in the change of the electronic structure significantly. Furthermore, we propose that the pressure-induced distortion in TaIrTe4 is responsible for the change of topology of the Fermi surface, and such a change favors the emergence of superconductivity. Our results reveal the correlation among the lattice distortion, topological physics, and superconductivity in the WSM, a hot topic in condensed-matter physics.
Formation of short-range magnetic order and avoided ferromagnetic quantum criticality in pressurized LaCrGe 3
LaCrGe 3 has attracted attention as a paradigm example of the avoidance of ferromagnetic (FM) quantum criticality in an itinerant magnet. In this work, we combined thermodynamic (specific heat and thermal expansion), transport, x-ray, and neutron scattering as well as μSR measurements to obtain insights on the temperature-pressure phase diagram of LaCrGe 3 . Consistent with previous studies of the phase diagram by transport measurements, our thermodynamic data shows clearly that the FM transition at T FM changes its character from second order to first order when it is suppressed to low temperatures by pressure. In addition, previous studies demonstrated that for high pressures a new phase occurs below T 2 , which was proposed to be a long-wavelength antiferromagnetic state (AFM q ). In this paper, we provide evidence from our thermodynamic data that this phase transition is preceded by yet another phase transition at T 1 >T 2 . Our μSR data indicate that full magnetic volume fraction is only established below T 2 , but that this magnetism is characterized by a short correlation length. Within the experimental resolution, our neutron-scattering data is not able to identify any magnetic Bragg peaks. Overall, the microscopic magnetic data is therefore consistent with the formation of FM clusters in the proximity of the avoided FM quantum critical point in LaCrGe 3 . This conclusion is at odds with the previous proposal of AFM q order and raises questions on the role of disorder in this stochiometric compound.