Phase Change in Liquid Face Seals

1978 ◽  
Vol 100 (1) ◽  
pp. 74-79 ◽  
Author(s):  
W. F. Hughes ◽  
N. S. Winowich ◽  
M. J. Birchak ◽  
W. C. Kennedy
Keyword(s):  
Phase Change ◽  
Temperature Variation ◽  
Approximate Solutions ◽  
Operating Conditions ◽  
Face Seals ◽  
Set Up

A study is made of boiling (or phase change) in liquid face seals. An appropriate model is set up and approximate solutions obtained. Some practical illustrative examples are given. The principal conclusions are: 1) Boiling may occur more often than has been suspected particularly when the sealed liquid is near saturation conditions. 2) The temperature variation in a seal clearance region may not be very great and the main reason for boiling is the flashing which occurs as the pressure decreases through the seal clearance. 3) There are two separate values of the parameter (h/ω2) (and associated radii where phase change takes place) which provide the same separating force under a given set of operating conditions. For a given speed seal face excursions about the larger spacing are stable, but excursions about the smaller spacing are unstable, leading to a growth to the larger spacing or a catastrophic collapse.

Phase Change in Liquid Face Seals II—Isothermal and Adiabatic Bounds With Real Fluids

1980 ◽  
Vol 102 (3) ◽  
pp. 350-357 ◽  
Author(s):  
W. F. Hughes ◽  
N. H. Chao
Keyword(s):  
Thermodynamic Properties ◽  
Phase Change ◽  
Leakage Rate ◽  
Operating Conditions ◽  
Isothermal Model ◽  
Reynolds Number Flow ◽  
Low Leakage ◽  
Real Fluid ◽  
Face Seals ◽  
Liquid Yield

Phase change effects in parallel and tapered liquid face seals are studied analytically. Both an isothermal and adiabatic model of low Reynolds number flow are considered by numerical integration of the descriptive equations for a real fluid. Real fluid thermodynamic properties are calculated for each step, using a computer program for the steam tables or thermodynamic properties of the fluid considered. Examples are presented for water. The general conclusions are: 1. For low leakage rate the isothermal model is more accurate and for high leakage rates the adiabatic model is more accurate. 2. Both parallel models, ordinarily neutrally stable with a liquid, yield the same general conclusions about stability. If the sealed fluid is near enough to saturation conditions, there will exist generally two values of the film gap, h, which yield the same separating force under a given set of operating conditions. For a given speed, face excursions about the larger value are stable, but excursions about the lower value are unstable, either growing to the larger h if displaced apart or collapsing if displaced together. 3. The transient of collapse is described by the adiabatic model which predicts a catastrophic collapse and then either failure or explosive return to a larger value of h. 4. Converging seals (ordinarily stable with a liquid at some given value of h) may become unstable, the phase change effect dominating the behavior and giving rise to collapse as described above. 5. The mass leakage rate is reduced significantly below the all liquid value when boiling occurs.

The Boiling Interface in a Misaligned Two-Phase Mechanical Seal

1997 ◽  
Vol 119 (2) ◽  
pp. 265-271 ◽  
Author(s):  
I. Etsion ◽  
M. D. Pascovici ◽  
L. Burstein
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Approximate Solutions ◽  
Operating Conditions ◽  
Mechanical Seal ◽  
Two Phase ◽  
Iterative Solutions

The boiling interface in a misaligned two-phase mechanical seal is analyzed using a complete thermohydrodynamic approach that requires complex simultaneous iterative solutions of the nonaxisymmetric heat transfer and phase-change problems. It is shown that under certain operating conditions, characterized by a modified Sommerfeld number, several approximate solutions with various levels of simplification can be utilized to calculate the boiling radius.

scholarly journals Experimental Study on Thermal Performance of Pre-formed Thin Heating Floor Filled with Shaped PCM

2021 ◽  
Vol 2076 (1) ◽  
pp. 012062
Author(s):  
Quanying Yan ◽  
Chao Ma ◽  
Wei Wang
Keyword(s):  
Phase Change ◽  
Thermal Performance ◽  
Operating Conditions ◽  
Normal System ◽  
Heating Systems ◽  
Supporting Material ◽  
Set Up ◽  
Change Material ◽  
Floor Heating ◽  
Change System

Abstract A shape-stabilized phase change material (PCM) with high-density polyethylene was prepared as the supporting material to be added to a pre-fabricated light and dry-type heating floor. A system for underfloor heating experiments was set up in the laboratory to test the effects of average supply and return water temperatures and different temperature differences on the thermal performance of two floor heating systems under 10 different operating conditions, respectively. The results show that the surface heat-flux density of a phase change floor (PCF) is higher than that of an ordinary one at the stable stage. The proportion of heat transfer to the heating room is about 13% higher in the phase change system compared to the normal system, and the heat loss is reduced by more than 10%. At the cooling stage, the surface temperature of PCF decreases slowly, compared to the rapid decrease of the ordinary one.

An Electrohydrodynamic (EHD) Meso Pump for Cryogenic Spot Cooling of Low Volume Complex Electronics

2003 ◽  
Author(s):  
M. Rada ◽  
M. Ohadi ◽  
A. Shooshtari
Keyword(s):  
Numerical Modeling ◽  
Low Temperature ◽  
Temperature Variation ◽  
Liquid Nitrogen ◽  
Cooling System ◽  
Operating Conditions ◽  
Low Volume ◽  
Liquid Nitrogen Cooling ◽  
Spot Cooling ◽  
Set Up

Low temperature cooling provides excellent operating conditions for some conventional and superconducting electronics applications. The cooling requirements for these applications include moderate to low power levels (down to fraction of Watts) and very strict spatial and temporal temperature variation (in the order of 0.1K or less). In this paper, experimental and modeling results of a liquid nitrogen cooling system, using an EHD meso pump are presented. The pumping mechanism uses the EHD ion-drag technique. The experimental set-up, procedures and results are presented, followed by a pumping curve obtained by numerical modeling.

Thermal Energy Storage Through Melting of a Commercial Phase Change Material in an Annulus with Radially Divergent Longitudinal Fins

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Tonny Tabassum Mainul Hasan ◽  
Latifa Begum
Keyword(s):  
Energy Storage ◽  
Phase Change ◽  
Phase Change Material ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Storage System ◽  
Operating Conditions ◽  
Melting Time ◽  
Bottom Part ◽  
Change Material

This study reports on the unsteady two-dimensional numerical investigations of melting of a paraffin wax (phase change material, PCM) which melts over a temperature range of 8.7oC. The PCM is placed inside a circular concentric horizontal-finned annulus for the storage of thermal energy. The inner tube is fitted with three radially diverging longitudinal fins strategically placed near the bottom part of the annulus to accelerate the melting process there. The developed CFD code used in Tabassum et al., 2018 is extended to incorporate the presence of fins. The numerical results show that the average Nusselt number over the inner tube surface, the total melt fraction, the total stored energy all increased at every time instant in the finned annulus compared to the annulus without fins. This is due to the fact that in the finned annulus, the fins at the lower part of the annulus promotes buoyancy-driven convection as opposed to the slow conduction melting that prevails at the bottom part of the plain annulus. Fins with two different heights have been considered. It is found that by extending the height of the fin to 50% of the annular gap about 33.05% more energy could be stored compared to the bare annulus at the melting time of 82.37 min for the identical operating conditions. The effects of fins with different heights on the temperature and streamfunction distributions are found to be different. The present study can provide some useful guidelines for achieving a better thermal energy storage system.

scholarly journals A 2-D model for Intermediate Temperature Solid Oxide Fuel Cells Preliminarily Validated on Local Values

Catalysts ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 36 ◽  
Author(s):  
Bruno Conti ◽  
Barbara Bosio ◽  
Stephen John McPhail ◽  
Francesca Santoni ◽  
Davide Pumiglia ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Operating Conditions ◽  
Solid Oxide ◽  
Intermediate Temperature ◽  
Physical Parameters ◽  
Local Concentration ◽  
Oxide Fuel ◽  
Molten Carbonate ◽  
Experimental Apparatus ◽  
Set Up

Intermediate Temperature Solid Oxide Fuel Cell (IT-SOFC) technology offers interesting opportunities in the panorama of a larger penetration of renewable and distributed power generation, namely high electrical efficiency at manageable scales for both remote and industrial applications. In order to optimize the performance and the operating conditions of such a pre-commercial technology, an effective synergy between experimentation and simulation is fundamental. For this purpose, starting from the SIMFC (SIMulation of Fuel Cells) code set-up and successfully validated for Molten Carbonate Fuel Cells, a new version of the code has been developed for IT-SOFCs. The new release of the code allows the calculation of the maps of the main electrical, chemical, and physical parameters on the cell plane of planar IT-SOFCs fed in co-flow. A semi-empirical kinetic formulation has been set-up, identifying the related parameters thanks to a devoted series of experiments, and integrated in SIMFC. Thanks to a multi-sampling innovative experimental apparatus the simultaneous measurement of temperature and gas composition on the cell plane was possible, so that a preliminary validation of the model on local values was carried out. A good agreement between experimental and simulated data was achieved in terms of cell voltages and local temperatures, but also, for the first time, in terms of local concentration on the cell plane, encouraging further developments. This numerical tool is proposed for a better interpretation of the phenomena occurring in IT-SOFCs and a consequential optimization of their performance.

Vibration of Rectangular Plates by the Ritz Method

1950 ◽  
Vol 17 (4) ◽  
pp. 448-453 ◽  
Author(s):  
Dana Young
Keyword(s):  
Ritz Method ◽  
Normal Modes ◽  
Approximate Solutions ◽  
The Other ◽  
Rectangular Plates ◽  
Elastic Plates ◽  
Modes Of Vibration ◽  
Ritz’S Method ◽  
Square Plate ◽  
Set Up

Abstract Ritz’s method is one of several possible procedures for obtaining approximate solutions for the frequencies and modes of vibration of thin elastic plates. The accuracy of the results and the practicability of the computations depend to a great extent upon the set of functions that is chosen to represent the plate deflection. In this investigation, use is made of the functions which define the normal modes of vibration of a uniform beam. Tables of values of these functions have been computed as well as values of different integrals of the functions and their derivatives. With the aid of these data, the necessary equations can be set up and solved with reasonable effort. Solutions are obtained for three specific plate problems, namely, (a) square plate clamped at all four edges, (b) square plate clamped along two adjacent edges and free along the other two edges, and (c) square plate clamped along one edge and free along the other three edges.

Artificial Neural Networks Used As a Rule Selector for Fuzzy Logic Controllers

1993 ◽  
Author(s):  
Shou-Heng Huang ◽  
Ron M. Nelson
Keyword(s):  
Fuzzy Logic ◽  
Fuzzy Logic Controller ◽  
Absolute Error ◽  
Operating Conditions ◽  
Delta Rule ◽  
Rule Sets ◽  
Artificial Neural ◽  
Artificial Neural Network Ann ◽  
Set Up ◽  
And Control

Abstract A feedforward, three-layer, partially-connected artificial neural network (ANN) is proposed to be used as a rule selector for a rule-based fuzzy logic controller. This will allow the controller to adapt to various control modes and operating conditions for different plants. A principal advantage of an ANN over a look up table is that the ANN can make good estimates to fill in for missing data. The control modes, operating conditions, and control rule sets are encoded into binary numbers as the inputs and outputs for the ANN. The General Delta Rule is used in the backpropagation learning process to update the ANN weights. The proposed ANN has a simple topological structure and results in a simple analysis and relatively easy implementation. The average square error and the maximal absolute error are used to judge if the correct connections between neurons are set up. Computer simulations are used to demonstrate the effectiveness of this ANN as a rule selector.

Investigation of the Flow Phenomenon Inside Gas Ejectors With Moist Gas Entrainment

2016 ◽  
Vol 9 (1) ◽  
Author(s):  
Yuping Wang ◽  
Mark Pellerin ◽  
Pravansu Mohanty ◽  
Subrata Sengupta
Keyword(s):  
Water Vapor ◽  
Phase Change ◽  
Gas Flow ◽  
Phase Distribution ◽  
Light Attenuation ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Second Phase ◽  
Symmetric Model ◽  
Design And Optimization

This paper focuses on the gas flow study of an ejector used in applications where moist gases are being entrained. Two parts of work are presented. In the first part, characteristics of gas flow inside an ejector, as well as the ejector's performance under various operating and geometric configurations, were studied with a three-dimensional computational model. Measurements were also performed for validation of the model. In the second part, focus was given to the potential condensation or desublimation phenomena that may occur inside an ejector when water vapor is included in the entrained stream. Experiments using light-attenuation method were performed to verify the presence of a second phase; then, the onset of phase change and the phase distribution were obtained numerically. A two-dimensional axis-symmetric model was developed based on the model used in the first part. User-defined functions were used to implement the phase-change criteria and particle prediction. A series of simulations were performed with various amounts of water vapor added into the entrained flow. It was found that both frost particles and water condensate could form inside the mixing tube depending on the operating conditions and water vapor concentrations. When the concentration exceeds 3% by mass, water vapor could condense throughout the mixing tube. Some preliminary results of the second phase particles formed, e.g., critical sizes and distributions, were also obtained to assist with the design and optimization of gas ejectors used in similar applications.

Solar Gasification of Biomass: A Molten Salt Pyrolysis Study

2004 ◽  
Vol 126 (3) ◽  
pp. 850-857 ◽  
Author(s):  
Roman Adinberg ◽  
Michael Epstein ◽  
Jacob Karni
Keyword(s):  
Solar Energy ◽  
Molten Salt ◽  
Operating Conditions ◽  
Thermochemical Conversion ◽  
Salt Medium ◽  
Feasible Option ◽  
Temperature Liquid ◽  
Set Up ◽  
Biomass Particles ◽  
Pyrolysis Of Biomass

A novel solar process and reactor for thermochemical conversion of biomass to synthesis gas is described. The concept is based on dispersion of biomass particles in a molten inorganic salt medium and, simultaneously, absorbing, storing and transferring solar energy needed to perform pyrolysis reactions in the high-temperature liquid phase. A lab-scale reactor filled with carbonates of potassium and sodium was set up to study the kinetics of fast pyrolysis and the characteristics of transient heat transfer for cellulose particles (few millimeters size) introduced into the molten salt medium. The operating conditions were reaction temperatures of 1073–1188 K and a particle peak-heating rate of 100 K/sec. The assessments performed for a commercial-scale solar reactor demonstrate that pyrolysis of biomass particles dispersed in a molten salt phase could be a feasible option for the continuous, round-the-clock production of syngas, using solar energy only.

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