Full-scale friction

The above assumed values for the friction factors are somewhat larger than the factors measured on full-scale friction tests on the similar projects however, the listed values are based on those used in similar containments. 

To measure all the parameters pertinent to simulating reactor conditions, Ny-lund and co-workers (1968, 1969) presented data from tests carried out on a simulated full-scale, 36-rod bundle in the 8-MW loop FRIGG at ASEA, Vasteras, Sweden (Malnes and Boen, 1970). Their experimental results indicate that the two-phase friction multiplier in flow through bundles can be correlated by using Becker s correlation (Becker et al., 1962),... 

This is valid for any Newtonian fluid in any (circular) pipe of any size (scale) under given dynamic conditions (e.g., laminar or turbulent). Thus, if the values of jV3 (i.e., the Reynolds number 7VRe) and /V, (e/D) for an experimental model are identical to the values for a full-scale system, it follows that the value of N6 (the friction factor) must also be the same in the two systems. In such a case the model is said to be dynamically similar to the full-scale (field) system, and measurements of the variables in N6 can be translated (scaled) directly from the model to the field system. In other words, the equality between the groups /V3 (7VRc) and N (e/D) in the model and in the field is a necessary condition for the dynamic similarity of the two systems. 

Table 2 Sample and full-scale dynamometers used for characterization of friction materials...

Their major advantage is that a linear electrical output is produced as a function of displacement within 0.01% of full scale, without the use of additional hardware or signal conditioning. This makes potentiometers very easy to use, simple to design and inexpensive. Linearity results if the potentiometer is isolated from the load (which is easy to accomplish). The construction of these potentiometers determines their resolution, their temperature stability and noise levels. The major disadvantage of potentiometers is that they contain mechanical moving parts, that are subject to wear. Also, the frictional and inertial components of these potentiometers should be kept low in order to minimize dynamic system distortion caused by mechanically loading the source of the displacement movement. 

Fig. 13.31 Friction stir weld process development tool at the Marshall Space Flight Center (MSFC) shown with an 8.2 m (27 ft) diameter barrel segment of the 2195 Al-Li Space Shuttle external tank LH2 tank (left). Full-scale LH2 tank (right) at the National Aeronautics and Space Administration (NASA) Michoud Assembly Facility in New Orleans. Courtesy of NASA MSFC...

Figure 5.13 shows an example of the variation of P with depths during negative skin friction based on a full scale tension pile test. The maximum negative skin friction developed was about 0.25 a (P = 0.25), with an average value of about 0.2 cr. ... 

As a result of born nature of silk, silky synthetic fabrics have been developed on its full scale. As shown in Table-1, continuous pursuits of silky synthetic fibers have been carried out without satisfactions with past achievements. Polyester fibers are featured with trilobal cross sections,and their surfaces were peeled off with an alkaline weight reduction by which its mutual frictional resistance amang fibers were minimized just like silk yarns. 

In the following, a procedure for incorporation of relevant full-scale measurements related e.g. to internal flow parameters and surface floater motions is described. The method which is applied for calculation of failure probabilities is described in more detail. The various relevant sources of imcertainty are taken into accoimt (e.g. hydrodynamic drag coefficient, floater offset, friction coefficient etc.). 

Two full scale tests conducted by author C13, 14] proved the feasibility of using additives in large pipe systems. During full scale experiments practically no temperature changes due to the additives in the heat exchanger were observed which is in contradiction to the above mentioned laboratory results where a marked friction loss decrease was accompanied by a deterioration of the heat transfer. 

The results from testing of GEN3 and GEN4 materials indicated that neither was suitable for the brake application. The testing did show that the small-scale friction test system developed by Prof Kalin at the University of Ljubljana is capable of simulating the friction/wear environment of a full-size dynamometer test system. 

This energy is converted from mechanical to frictional energy (heat). It can represent the difference in a measurement signal for a given process property value when approached first from a zero load and then from a full scale as shown in Figs. 3.4 and 3.5. They provide examples of recovery to near zero strain. It shows that material can withstand stress beyond its proportional limit for a short time, resulting in different degrees of the hysteresis effect. 

The purpose of this chapter is to present the experimental results for the full-scale LAD outflow tests in liquid hydrogen. Test conditions were taken over a wide range of liquid temperatures (20.3-24.2 K), tank pressures (100-350 kPa), and outflow rates (0.010-0.055 kg/s) thermally and operationally representative of an in-space propellant transfer from a depot storage tank or to a smaller scale in-space engine. Horizontal LAD tests were conducted to measure independently the frictional and dynamic losses down the channel. Flow-through-screen tests were performed to measure independently the dominate pressure loss in LEO, the FTS resistance. Meanwhile, 1-g inverted vertical LAD outflow tests were conducted to obtain performance data for two full-scale 325 x 2300 LAD channels. One of the channels had a perforated plate and a custom-built internal thermodynamic vent system to enhance performance. Model predictions from Chapter 3 are compared to each set of experimental data. 

In addition, the simplified ID steady state pressure drop model for screen channel liquid acquisition devices has been developed and compared to the FTS, horizontal LAD, and full-scale LAD outflow experimental data. Both experimental data and model confirm that, in 1-g outflow from a cryogenic propellant tank, the hydrostatic pressure drop is the leading order term, followed by the FTS pressure drop, and frictional and dynamic losses down the channel. The model qualitatively tracks the LH2 1-g inverted outflow test results the model predicts the breakdown point within 9% for the TVS cooled channel and 18% for the standard channel. Discrepancies between 1-g model and data are primarily attributed to a non-uniform FTS pressure distribution along the channel. Results show that both LAD channels behaved close to anticipated performance and that this simplified ID model can be used to qualitatively track LAD performance in a dynamic outflow environment. 

Table 1 shows comparisons between pressure drop data for a full-scale channel assembly and the PATRIARCH code predictions. The latter have been based on empirically determined two-phase friction multipliers which seem to have a wide range of validity under SGHW conditions. In general, three two-phase pressure drop friction factors for rod clusters lie between the predictions of the Martlnelli-Nelson and Thom correlations for single round tubes. 

This sharp decoupling also explains the saturation of the diffusion for TZ > 10. For 7Z > 10, due to almost full decoupling of the solute motion from the solvent dynamics there is hardly any contribution from the density mode and the friction is determined by the binary part. Thus in the time scale at which the solute dynamics takes place, the solvent remains nearly static. Now once the solute becomes very small, it does not feel the static structure of the solvent around it and can diffuse through the interparticle distances. Thus further decrease in the size of the solute does not decrease the binary friction leading to the near saturation of the diffusion when plotted against the solute-solvent size ratio. 

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