Two-Phase Thermal Systems for Space Application–European Development and Test Results

1987 ◽  
Author(s):  
Helmut Kreeb ◽  
Hans Georg Wulz
Keyword(s):  
Space Application ◽  
Test Results ◽  
Thermal Systems ◽  
Two Phase ◽  
European Development

FROUDE’S LAW OF SIMILITUDE – CONTEMPORARY AND FUTURE SEAKEEPING TESTING

2021 ◽  
Vol 153 (A2) ◽  
Author(s):  
R P Dallinga ◽  
R H M Huijsmans
Keyword(s):  
Model Test ◽  
Scale Effects ◽  
Higher Order ◽  
Air Pressure ◽  
Test Results ◽  
Viscous Effects ◽  
Two Phase ◽  
Scale Models ◽  
Non Linear

Historically “scale effects” in the interpretation of tests with scale models in waves using Froude’s Law of Similitude are mostly associated with viscous effects. Nowadays, with a much more complete modelling of reality and a focus on higher order non-linear phenomena, scaling of model test results implies a wider range of assumptions than the validity of Froude’s Law. Our contribution to the conference is a visionary review of contemporary and future problems in the interpretation of these tests. In this context we will discuss the developments in test techniques, including the development of a new Two-Phase Laboratory facilitating seakeeping and sloshing tests at reduced air pressure.

Model Testing and Analysis Study on Shear Strength of Rock Mass Containing Multiple Cracks under Compression-Shearing Loading

2008 ◽  
Vol 33-37 ◽  
pp. 617-622
Author(s):  
Wei Shen Zhu ◽  
Bin Sui ◽  
Wen Tao Wang ◽  
Shu Cai Li
Keyword(s):  
Shear Strength ◽  
Rock Mass ◽  
Rock Sample ◽  
Failure Process ◽  
Jointed Rock ◽  
Multiple Cracks ◽  
Test Results ◽  
Failure Model ◽  
Two Phase ◽  
Bridge Failure

Two-phase modelling testing was performed to study the shear strength of rock bridges of jointed rock mass in this paper. The failure process of rock sample containing multiple collinear cracks was observed. Based on theory of fracture mechanics and analytical method, a rock-bridge failure model was proposed and the expression of shear strength was derived. Comparison of calculated shear strength and the model test results was made and they agree well.

Preswirl and Mixed-Flow (Mainly Liquid) Effects on Rotordynamic Performance of a Long (L/D = 0.75) Smooth Seal

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Dung L. Tran ◽  
Dara W. Childs ◽  
Hari Shrestha ◽  
Min Zhang
Keyword(s):  
Dynamic Instability ◽  
Silicone Oil ◽  
Dynamic Stiffness ◽  
Radial Clearance ◽  
Inlet Temperature ◽  
Test Results ◽  
Transition Flow ◽  
Two Phase ◽  
Rotordynamic Coefficients ◽  
Transition Flow Regime

Abstract Measured results are presented for rotordynamic coefficients and mass leakage rates of a long smooth annular seal (length-to-diameter ratio L/D = 0.75, diameter D = 114.686 mm, and radial clearance Cr = 0.200 mm) tested with a mixture of silicone oil (PSF-5cSt) and air. The test seal is centered, the seal exit pressure is maintained at 6.9 bars-g while the fluid inlet temperature is controlled within 37.8–40.6 °C. It is tested with three inlet-preswirl inserts, namely, zero, medium, and high (the preswirl ratios (PSRs), i.e., the ratio between the fluid's circumferential velocity and the shaft surface's velocity, are in ranges of 0.10–0.18, 0.30–0.65, and 0.65–1.40 for zero, medium, and high preswirls, respectively), six inlet gas-volume fractions GVFi (0%, 2%, 4%, 6%, 8%, and 10%), four pressure drops PDs (20.7, 27.6, 34.5, and 41.4 bars), and three speeds ω (3, 4, and 5 krpm). The targeted test matrix could not be achieved for the medium- and high-preswirl inserts at PD ≥ 27.6 bars due to the test-rig stator's dynamic instability issues. Spargers were used to inject air into the oil, and GVFi values higher than 0.10 could not be consistently achieved because of unsteady surging flow downstream from the sparger mixing section. Leakage mass flow rate m˙ and rotordynamic coefficients are measured, and the effect of changing inlet preswirl and GVFi is studied. The test results are then compared with predictions from a two-phase, homogeneous-mixture, bulk-flow model developed in 2011. Generally, both measurements and predictions show little change in m˙ as inlet preswirl changes. Measured m˙ remains unchanged or slightly increases with increasing GVFi, but predicted m˙ decreases. Measured m˙ is comparable to predicted values but consistently lower. Dynamic-stiffness coefficients are measured using an ensemble of excitation frequencies and curve-fitted well by frequency-independent stiffness Kij, damping Cij, and virtual mass Mij coefficients. Planned tests with the medium- and high-preswirl inserts could not be accomplished at PD = 34.5 and 41.4 bars because the seal stator became unstable with any finite injection of air. The test results show that the instability arose because the seal's direct stiffness K became negative and increased in magnitude with increasing GVFi. The model predicts a drop in K as GVFi increases, but the test results dropped substantially more rapidly than predicted. Also, the model does not predict the observed strong tendency for K to drop with an increase in preswirl in moving from the zero-to-medium and medium-to-high preswirl inserts. The authors believe that the observed drop in K due to increasing GVFi is not explained by either (a) a reverse Lomakin effect from operating in the transition flow regime or (b) the predicted drop in K at higher GVFi values from the model. A separate and as yet unidentified two-phase flow phenomenon probably causes the observed results. The negative K results due to increasing GVFi and moving from the zero to medium, and medium to high preswirl observed here could explain the instability issue (sudden subsynchronous vibration) on a high-differential-pressure helico-axial multiphase pump (MPP), reported in 2013. Effective damping Ceff combines the stabilizing effect of direct damping C, the destabilizing effect of cross-coupled stiffness k, and the influence of cross-coupled mass mq. As predicted and measured, increasing inlet preswirl significantly increases k and decreases Ceff, which decreases the seal's stabilizing properties. Ceff increases with increasing GVFi—becomes more stable.

scholarly journals Prediction of Two-Phase Critical Flow Rate

1965 ◽  
Vol 87 (1) ◽  
pp. 53-57 ◽  
Author(s):  
S. Levy
Keyword(s):  
Flow Rate ◽  
Thermal Equilibrium ◽  
Present Model ◽  
Critical Flow ◽  
Test Results ◽  
Two Phase ◽  
Mean Velocity ◽  
Critical Flow Rate ◽  
Pressure Losses ◽  
Gas Void Fraction

An analytical model to predict two-phase critical flow rate is proposed. The model is based upon thermal equilibrium, a “lumped” treatment of the two-phase velocity (each phase is represented by a single mean velocity), and upon the neglect of frictional and hydrostatic pressure losses. A comparison of the proposed predictions with available test results and previous analyses shows that: (a) The present model agrees very well with the published test data; (b) In contrast to all other analyses, the model requires no assumption about the gas void fraction.

Photovoltaic-Thermal Collector System for Domestic Application

Solar Energy ◽  
2005 ◽  
Author(s):  
T. T. Chow ◽  
J. Ji ◽  
W. He
Keyword(s):  
Energy Performance ◽  
Primary Energy ◽  
Heat Energy ◽  
Solar Thermal ◽  
Test Results ◽  
Thermal Systems ◽  
Collector System ◽  
Solar Thermal Collector ◽  
Reduced Temperature ◽  
Direct Attachment

Photovoltaic-thermal (PV/T) systems integrate photovoltaic and solar thermal technologies into one single system with dual production of electricity and heat energy. A typical arrangement is the direct attachment of PV modules on to a solar thermal collector surface. For a given collector surface area, the overall system energy performance is expected higher than the conventional “side-by-side” PV and solar thermal systems. In the development of PV/T collector technology using water as the coolant, the most common design follows the sheet-and-tube thermal absorber concept. Fin performance of the thermal absorber has been identified as one important factor that affects much the overall energy performance of the collector. Accordingly, an aluminum-alloy flat-box type PV/T collector prototype was constructed and tested. Our test results indicate that a high combined thermal and electrical efficiency can be achieved. The primary-energy-saving efficiency for daily exposure approaches 65% at zero reduced temperature operation. With a simple and handy design, the product is considered to be very suitable for domestic application.

Prediction of Two-Phase Pressure Drop and Density Distribution From Mixing Length Theory

1963 ◽  
Vol 85 (2) ◽  
pp. 137-150 ◽  
Author(s):  
S. Levy
Keyword(s):  
Single Phase ◽  
Continuous Medium ◽  
Phase System ◽  
Mixing Length ◽  
Test Results ◽  
Two Phase ◽  
Pressure Drops ◽  
Mixing Length Theory ◽  
Phase Pressure ◽  
Good Agreement

Single-phase turbulent mixing length methods are used to predict two-phase flow. Two-phase density and velocity distributions and two-phase pressure drops are derived by treating the two-phase system as a continuous medium where the turbulent exchanges of momentum and density are equal. Good agreement is obtained between test results and analytical predictions.

Numerical investigation on the gas–liquid entraining and separating effects on self-priming performance in a flow-ejecting centrifugal pump

2018 ◽  
Vol 233 (2) ◽  
pp. 232-248 ◽  
Author(s):  
Guidong Li ◽  
Yang Wang ◽  
Jieyun Mao
Keyword(s):  
Centrifugal Pump ◽  
Separation Efficiency ◽  
Simulation Analysis ◽  
Guide Vane ◽  
Test Results ◽  
Baffle Plate ◽  
Two Phase ◽  
Performance Curves ◽  
Separating Property ◽  
Frequency Domain Properties

To investigate the influence of entraining and separating effect of gas–liquid two-phase on self-priming performance in the flow-ejecting centrifugal pump, three different schemes of adding the baffle plate behind the guide vane were proposed. Experiments on self-priming performance for three different guide vane schemes were carried out, and numerical calculations on entraining property in the ejector and separating property in the chamber were analyzed by means of the Eulerian–Eulerian multiphase flow model. Meanwhile, the frequency domain properties of pressure pulsation and the pump performance curves were obtained to further verify the feasibility of the scheme in practical application. The results show that the simulation analysis agreed well with the test results. The area and magnitude of high velocity region and vorticities in the ejector of scheme 2 are remarkably larger than those of other schemes. Gas–liquid separation efficiency in a pump chamber also significantly improves when the baffle plate behind the guide vane is mounted at an appropriate position. Furthermore, different guide vane schemes have certain impact on the characteristics of internal and unsteady flow pulsation phenomena in model pump but are within the acceptable operation range. The head and efficiency of scheme 2 are also slightly higher than those of the prototype in the full operation range.

Test results of a pumped two-phase mounting plate with ammonia

1987 ◽  
Author(s):  
T. SWANSON ◽  
M. MCCABE, JR. ◽  
M. GROTE
Keyword(s):  
Test Results ◽  
Two Phase

Line Force in a Two-Phase Orthotropic Medium

1982 ◽  
Vol 49 (1) ◽  
pp. 55-61 ◽  
Author(s):  
R. S. Wu ◽  
Y. T. Chou
Keyword(s):  
Free Surface ◽  
Elastic Field ◽  
Space Application ◽  
Orthotropic Medium ◽  
Method Of Images ◽  
Two Phase ◽  
Special Cases ◽  
Line Force ◽  
Technological Interest

Based on the generalized method of images, the elastic field of an in-plane line force acting in a two-phase orthotropic medium is analyzed. Several special cases of technological interest are deduced from the general solution, including the case of a line force applied on the free surface of a half space. Application of the results to the determination of the elastic field of an edge dislocation in a semi-infinite orthotropic medium is illustrated.

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