Modification of Equations of State in the Metastable Region for High-speed Vapor Compression

2020 ◽  
Vol 41 (7) ◽  
pp. 1278-1282
Author(s):  
R. I. Nigmatulin ◽  
D. Yu. Toporkov
Keyword(s):  
High Speed ◽  
Equations Of State ◽  
Vapor Compression ◽  
Metastable Region

scholarly journals Thin Gas Film Isothermal Condensation in Aerodynamic Bearings

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Eliott Guenat ◽  
Jürg Schiffmann
Keyword(s):  
High Speed ◽  
Waste Heat ◽  
Load Capacity ◽  
Saturation Pressure ◽  
Operating Conditions ◽  
Fluid Film ◽  
Small Scale ◽  
Vapor Compression ◽  
Density Profiles ◽  
Film Pressure

Abstract High-speed small-scale turbomachinery for waste heat recovery and vapor compression cycles is typically supported on gas-lubricated bearings operating close to the saturation conditions of the lubricant. Under particular conditions, the gas film might locally reach the saturation pressure with potentially hazardous effects on the performance of the gas bearing. The present work introduces a model based on the Reynolds equation and the development of cavitation modeling in liquid-lubricated bearings for condensing gas bearings. The effect of condensation on load capacity and pressure and density profiles is investigated for two one-dimensional bearing geometries (parabolic and Rayleigh step) and varying operating conditions. The results suggest that the load capacity is generally negatively affected if condensation occurs. An experimental setup consisting of a Rayleigh-step gas journal bearing with pressure taps to measure the local fluid film pressure is presented and operated in R245fa in near-saturated conditions. The comparison between the evolution of the fluid film pressure under perfect gas and near saturation conditions clearly suggests the occurrence of condensation in the fluid film. These results are corroborated by the very good agreement with the model prediction.

Global General Relativity

1979 ◽  
Vol 368 (1732) ◽  
pp. 19-21
Keyword(s):  
General Relativity ◽  
High Speed ◽  
Equations Of State ◽  
Perturbation Expansion ◽  
Theoretical Work ◽  
Field Equations ◽  
Gravitational Fields ◽  
Highly Nonlinear ◽  
Mathematical Techniques ◽  
Algebraic Forms

Much of the theoretical work that has been carried out in General Relativity, particularly in the earlier years of the subject, has been concerned with finding explicit solutions of Einstein’s field equations, either in the vacuum case or, with suitable equations of state, when matter is present. These have been very useful in giving us some sort of feeling for the nature of more general ‘ physically reasonable ’ solutions, but they can, at best, only be rough approximations to such solutions. Exact solutions must, owing to the limitations of human energy and ingenuity, and to the complexity of Einstein’s equations, involve a number of simplifying assumptions, such as special symmetries or particular algebraic forms for the metric or curvature. Sometimes it is legitimate to regard such a special solution as the first term in some perturbation expansion towards something more realistic. But in the highly nonlinear situations of strong gravitational fields, such as in gravitational collapse to a black hole, or perhaps also in cosmology, it is often not clear when the results of such perturbation calculations (themselves often very complicated) can be trusted. High-speed computers can come to our aid (Smarr 1979, this symposium), of course, and can often give important insights in particular situations. But complementary to these are the global qualitative mathematical techniques that have been introduced into relativity over the past several years (Hawking & Ellis 1973; Penrose 1972).

scholarly journals Coronal Hole Dynamics

1983 ◽  
Vol 36 (1) ◽  
pp. 93
Author(s):  
D Summers
Keyword(s):  
Coronal Hole ◽  
High Speed ◽  
Equations Of State ◽  
Fluid Model ◽  
Coronal Holes ◽  
Nonlinear Ordinary Differential Equation ◽  
Spherically Symmetric ◽  
Algebraic Equations ◽  
Cross Sectional ◽  
Outflow Velocity

The dynamics of high speed streams of solar plasma emanating from a coronal hole is investigated by use of a two-fluid model with polytropic equations of state. Steady outflow is considered along a flow tube which has a radial orientation with respect to the Sun, and a cross-sectional area proportional to r' where r is the heliocentric radius and s is a divergence parameter (~2). All the flow variables are assumed to be functions of r only. The equations of continuity, momentum and state may be used to obtain a single, nonlinear, ordinary differential equation for the outflow velocity, and the problem reduces to the numerical solution of three pairs of simultaneous algebraic equations. It is found that the velocity profiles are generally highly dependent on the divergence parameter s, as well as the polytropic indices. Numerical results are given for a variety of cases most relevant to the solar corona. As s increases from 2, the value appropriate to purely spherically symmetric expansion, the outflow velocity increases throughout the range from the coronal base out to infinity, over a certain parameter range. Although the terminal outflow speed for s > 2 may be far in excess of the purely spherically symmetric value, we find that high speed streams emanating from coronal holes cannot be accounted for by geometrical effects alone. The results may have important applications in the general theory of stellar winds.

scholarly journals UJI PRESTASI MESIN PENDINGIN KOMPRESI UAP YANG MENGGUNAKAN REFRIGERAN R22 DENGAN METODE PENGUJIAN AKTUAL DAN SIMULASI

2018 ◽  
Vol 3 (2) ◽  
pp. 73-82
Author(s):  
Audri Deacy Cappenberg ◽  
Haris Ramadan
Keyword(s):  
High Speed ◽  
Cooling System ◽  
Simulation Software ◽  
Vapor Compression ◽  
Low Speed ◽  
Performance Factors ◽  
Thermodynamic Simulations ◽  
And Performance ◽  
Vapor Compression Cooling ◽  
Different Characteristics

AbstrakSistem pengkondisian udara yang mengatur temperatur dan  kelembaban udara dalam ruangan, dalam pengoperasiannya membutuhkan refrigeran yang mudah menyerap dan melepaskan kalor. Setiap refrigerant memiliki karakteristik yang berbeda-beda yang mempengaruhi efek refrigerasi dan koefesien prestasi yang dihasilkan. R 22 adalah salah satu refrigeran yang memiliki karakteristik yang baik pada mesin pendingin. Software Genetron properties adalah sebuah software simulasi yang dapat menghitung aliran fluida atau refrigerant pada mesin pendingin. Genetron properties melakukan simulasi termodinamika untuk siklus kompresi uap dan memberikan hasil dalam bentuk tabulasi dan pada diagram Mollier diagram (h-s diagram). Pengujian prestasi mesin pendingin yang menggunakan  R-22 dilakukan secara aktual dan simulasi dengan menggunakan software genetron properties. Hasil pengujian dan perhitungan menunjukkan bahwa : Kerja kompresor, COP dan performance factor  pada mesin pendingin kompresi uap ketika high speed  adalah 0,528 kW,  8,42 dan 0,1187;  saat low speed adalah 0,528 kW; 8,52 dan 0,117.  COP dari   hasil pengujian dengan software genetron properties ketika high speed 2,193 saat low speed 1,415 hal ini dikarenakan mesin pendingin kompresi uap dalam keadaan tidak optimalKata Kunci : Mesin Pendingin, Kompresi Uap, COP AbstractAir conditioning system that regulates temperature and humidity in the room, in operation requires refrigerants that are easy to absorb and release heat. Each refrigerant has different characteristics that affect the effects of refrigeration and the performance coefficients produced. R 22 is one of the refrigerants that has good characteristics on cooling system. Genetron properties is a simulation software that can calculate fluid flow or refrigerant on a cooling sistem. Genetron properties perform thermodynamic simulations for vapor compression cycles and provide results in tabulation and Mollier diagram diagrams (h-s diagrams). Testing the performance of cooling system using R-22 is done in actual and simulated using genetron properties software. The test results and calculations show tha the work of compressor, COP and performance factors on vapor compression cooling system when high speed is 0.528 kW, 8.42 and 0.1187; when low speed is 0.528 kW; 8.52 and 0.117. COP from the results of testing with genetron software properties when high speed 2,193 at low speed 1,415 this is because the vapor compression of cooling system is in an optimal condition Keyword: Cooling system, vapor compression, COP

Development of a Direct Condensing Radiator for Use in a Spacecraft Vapor Compression Refrigeration System

1973 ◽  
Vol 95 (4) ◽  
pp. 1053-1064 ◽  
Author(s):  
J. L. Williams ◽  
E. G. Keshock ◽  
C. L. Wiggins
Keyword(s):  
High Speed ◽  
System Modeling ◽  
High Speed Photography ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Flow Conditions ◽  
Tube System ◽  
Vapor Compression Refrigeration ◽  
Parametric Analyses ◽  
Stable Flow

The development and feasibility testing of a hybrid spacecraft heat rejection system that incorporates a single radiator capable of functioning as either a conventional space radiator or as a condenser in a refrigeration cycle is described. Emphasis is placed on development of the radiator/condenser (RC), which is considered to be the most critical component of the hybrid system. The selection, design and fabrication of candidate RC configurations are described together with preliminary parametric analyses necessary to establish pressure drop, heat transfer and flow stability characteristics. Verification testing in one-g and zero-g environments is described; the latter condition being obtained by means of a C-135 aircraft. The testing included flow visualization (i.e., high-speed photography) of the condensation processes in a parallel channel quartz tube system modeling the RC. Representative qualitative photographs are presented. Results indicate stable flow conditions prevail for both one-g and zero-g operation.

Methods for and Benefits of Centrifugal Compressor Design Audits

2003 ◽  
Author(s):  
Robert J. McKee ◽  
Justin R. Hollingsworth ◽  
Anthony J. Smalley
Keyword(s):  
Torsional Vibration ◽  
High Speed ◽  
Performance Test ◽  
Equations Of State ◽  
Pressure Rise ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Design Stage ◽  
Flow Angle ◽  
Process Gas

As gas pipeline and industrial compressors become more powerful and more complex, it has become beneficial to conduct technical audits of these machines in the design stage. Detailed analysis of critical or advanced compressors by independent evaluators have identified operating limitations, resonant responses, potential vibrations, weak components, the onset of stall, and other instabilities, and have recommended ways to eliminate a variety of potential problems before the compressor is placed in operation. The suitability of a compressor and its driver for the planned service should be thoroughly evaluated, so that each component and the system not only satisfy the design conditions, but also extreme operating conditions. This paper presents a description of the tools available for design audits and gives examples of benefits that have resulted from recent audits. The rotordynamics of any large high-speed compressor should be carefully evaluated to identify potential instabilities, high vibration levels, and even destructive responses of the machine. Powerful rotordynamic analysis tools and specific knowledge exists to accurately predict bearing and seal stiffness and damping, lateral critical speeds, and damped forced responses. Some examples of significant results obtained from rotordynamic evaluations are presented, and typical problems that have been identified and eliminated are highlighted. Torsional vibration analyses for compressor trains are an essential aspect of a design audit that have identified vibration problems and weak components. Examples of torsional vibration responses and problems that can be identified and corrected are included in this paper. The aerodynamics of a compressor is a design audit topic to which attention should be paid. Thermophysical properties of the process gas, as it is compressed, are important quantities which can be accurately determined by modern equations of state. The internal velocity distribution and pressure rise per impeller and diffuser can be evaluated to identify areas of excess loss, poor work transfer, or restrictions within a compressor. Flow angles such as at the impeller and diffuser entrances can be predicted and evaluated. The diffuser inlet flow angle is a critical indicator of the onset of rotating stall. This type of aerodynamic analysis also provides important input for performance test planning and evaluation. This paper concludes with a summary of benefits of design audits for pipeline and industrial compressors.

scholarly journals Pagosa Simulation of Hypervelocity Impact and Fragmentation From Hypersonic Explosions

2019 ◽  
Author(s):  
Xia Ma ◽  
David Culp ◽  
Brandon Smith
Keyword(s):  
High Speed ◽  
High Efficiency ◽  
Equations Of State ◽  
National Laboratory ◽  
Time Integration ◽  
Material Point ◽  
Hypervelocity Impact ◽  
High Rate ◽  
Material Strength ◽  
Detonation Transition

Abstract We use PAGOSA’s FLIP+MPM capability to simulate hypervelocity impact and fragmentation from hypersonic explosions. The scenario to be simulated involves a complex chain explosion from fragmentation impact which was caused by another explosion. The simulations also use the SURF model for shock to detonation transition (SDT) and the MATCH model for mechanical ignition and deflagration of high explosives. These models in PAGOSA working together are crucial for modeling complex system for real world applications. This shows the powerful modeling and predicting capability of PAGOSA that others cannot do. Since experimental data are not available for any complex scenario like this, we did verification and validation (V&V) in each separate steps, These include the fragmentation simulated by FLIP+MPM, the Shock to Detonation Transition (SDT) modeled by SURF and mechanical ignition and deflagration modeled by MATCH. PAGOSA is a shock hydrodynamics program developed at Los Alamos National Laboratory (LANL) for the study of high-speed compressible flow and high-rate material deformation. PAGOSA is a three-dimensional Eulerian finite difference code, solving problems with a wide variety of equations of state (EOSs), material strength, and explosive modeling options. It has high efficiency for simulations running on massively parallel supercomputers. It is a multi-material code using volume of fluid (VOF) interface reconstruction and second order fully explicit time integration. Standard von Neumann artificial viscosity is used. Newly added material point method (MPM) plus Fluid-Implicit Particle (FLIP) capability can simulate high-speed metal fragmentation.

Microfabrication research at the National Submicron Facility

1983 ◽  
Vol 41 ◽  
pp. 86-89
Author(s):  
E.D. Wolf
Keyword(s):  
Integrated Circuits ◽  
Particle Physics ◽  
High Speed ◽  
New Technology ◽  
High Energy ◽  
High Energy Particle ◽  
New Science ◽  
Wide Range ◽  
Intermediate Domain ◽  
Circuit Function

Most microelectronics devices and circuits operate faster, consume less power, execute more functions and cost less per circuit function when the feature-sizes internal to the devices and circuits are made smaller. This is part of the stimulus for the Very High-Speed Integrated Circuits (VHSIC) program. There is also a need for smaller, more sensitive sensors in a wide range of disciplines that includes electrochemistry, neurophysiology and ultra-high pressure solid state research. There is often fundamental new science (and sometimes new technology) to be revealed (and used) when a basic parameter such as size is extended to new dimensions, as is evident at the two extremes of smallness and largeness, high energy particle physics and cosmology, respectively. However, there is also a very important intermediate domain of size that spans from the diameter of a small cluster of atoms up to near one micrometer which may also have just as profound effects on society as “big” physics.

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