Generally applicable approaches for estimating the “quasi-static”, which means without fluid–structure interaction and frequency-dependent water-hammer wave speed in steel-lined pressure tunnels are ...analyzed. The external constraints and assumptions of these approaches are discussed in detail. The reformulated formulas are then compared to commonly used expressions. Some special cases of wave speed calculation such as unlined pressure tunnels and open-air penstocks are investigated. The quasi-static wave speed is significantly influenced by the state of the backfill concrete and the near-field rock zone (cracked or uncracked). In the case when these two layers are cracked, the quasi-static wave speed is overestimated in between 1% and 8% compared to uncracked concrete and near-field rock layers. Depending on the stiffness of steel liner and penstock, the fluid–structure interaction leads to significant difference in wave speeds values. Compared to the quasi-static case, the fluid–structure interaction approach, applied to steel-lined tunnels, results up to 13% higher wave speed values in the high-frequency range (higher than 600
Hz) and up to 150% lower values for frequencies between 150 and 300
Hz in the considered test case.
A new monitoring approach for detecting, locating, and quantifying structurally weak reaches of steel-lined pressure tunnels and shafts is presented. These reaches arise from local deterioration of ...the backfill concrete and the rock mass surrounding the liner. The change of wave speed generated by the weakening of the radial-liner supports creates reflection boundaries for the incident pressure waves. The monitoring approach is based on the generation of transient pressure with a steep wave front and the analysis of the reflected pressure signals using the fast Fourier transform and wavelet decomposition methods. Laboratory experiments have been carried out to validate the monitoring technique. The multilayer system (steel-concrete-rock) of the pressurized shafts and tunnels is modeled by a one-layer system of the test pipe. This latter was divided into several reaches having different wall stiffnesses. Different longitudinal placements of a steel, aluminum, and PVC pipe reach were tested to validate the identification method of the weak section.
AbstractThe local deterioration of the mechanical properties of steel-lined pressure shafts and tunnels induces a decrease of the celerity and an increase of the energy attenuation of water hammer ...waves. This deterioration may arise from the weakening of the backfill concrete and the surrounding rock mass, which provide the radial support of the steel liner. A new online monitoring system implemented and tested at the Grimsel II pumped-storage shaft in Switzerland is presented. The difficulties encountered during the in situ measurements are outlined. The new monitoring approach is based on acquiring and analyzing the dynamic pressure data generated by the normal operation of pumps and turbines. The wave celerity and the exponential attenuation coefficient of water hammer waves are estimated based on pressure records. Monitoring charts for these indicators are established using the statistical quality control method. The results show a stable monitoring scheme that needs longer acquisition data series to consolidate its control limits.
In this work, numerical results focused on the enhancement of water-air heat exchanger thermal performance are presented. New designs consisting of using diffusers between the front end openings of ...the vehicle and the first exchanger facing the airflow are suggested. The diffuser will reduce the velocity magnitude but over a larger area through the exchanger. This will reduce the air velocity non-uniformity upstream the exchanger and then increase its thermal performance. An in-house code is established to evaluate the thermal performance of the exchanger based on known parameters; namely, the ratio of the area of the air inlet opening to the area of the exchanger, the distance between the air inlet opening and the first exchanger at its downstream, the angle of the diffuser, and the water and air mass flow rates. It was shown that the thermal performance of the exchanger can be enhanced by up to 67% when the diffuser is present depending on the configuration.
Fans are often tested without downstream blockage and, thus, the performance is considerably different when the fan is mounted in a vehicle as part of a cooling system and where high blockage effect ...is present downstream. The aim of the present work is to analyze by laser Doppler velocimetry LDV measurements the topology of the flow induced by a fan incorporated in a simplified underhood model reproducing engine blockage and to study the blockage effect of the engine positioning on the flow induced by the fan. The distance between the fan and the engine block affects the mean flow axial velocity U. The vertical velocity component W is greatly influenced by the variation of the distance between the fan and the engine block, both in magnitude and topology.
This work reports on experiments carried out on a real passenger vehicle in a large wind tunnel to investigate the effects of car inclination on underhood cooling. The vehicle’s underhood is ...instrumented by thermocouples that measure the temperatures of many underhood components during different car functioning modes. Measurements are carried out for three thermal functioning points at car speeds 90, 110 and 130 km/h. In these experiments the engine was in operation and the front wheels positioned on the test facility with power-absorption-controlled rollers. Three car inclinations are investigated: flat, uphill and downhill. The results show that car inclination, even if very small, can have significant effects on underhood cooling and must be taken into consideration in numerical simulations and controlled in experimental tests. It was shown that down-hill and up-hill inclinations increase temperatures of components, air zones and engine parameters in the underhood, with higher effect for the down-hill inclination. Temperature increases in constant-speed driving phase are higher than in thermal soak phase.
Abstract A reusable Robertshaw red rubber double-lumen endotracheal tube (DLT) was placed to facilitate lung isolation for thoracoscopy in a 49-year-old atopic patient. In spite of its smooth ...insertion, it was then not possible to remove the DLT. Direct laryngoscopy showed severe laryngeal edema. After 48 hours of medical treatment with steroids, the trachea was extubated. The laryngeal edema could have been the result of physical and chemical irritation by the reusable rubber DLT itself, or from the substances formed during repeated cleaning and sterilization of the DLT. Atopic patients who are prone to developing latex allergy are also more liable to develop severe reactions to chemical, mechanical, and physical irritation from reusable red rubber DLTs or from the chemical solution used for its cleaning and sterilization.
The hydrophobicity of five proteins was estimated by reversed-phase chromatography (RPC), hydrophobic-interaction chromatography (HIC), and precipitation with ammonium sulfate. These data were ...correlated to partition behavior in aqueous two-phase systems.
A parameter (
1
m
∗
) that was derived from the precipitation curves is based on the solubility of proteins in an electrolyte solution. The correlation between
1
m
∗
and the retention times in HIC and RPC was poor due to interaction effects with the chromatography matrices and probably partial unfolding of the proteins; however, this parameter (
1
m
∗
) was expected to be a measure of hydrophobicity of proteins that relates better than the chromatographic data to experiments where the hydrophobic behavior of proteins in an aqueous solution is used for their separation.
The partition behavior of the five proteins in aqueous two-phase systems (ATPS) in the absence and presence of NaCl was investigated. A poor correlation was found between log K (K is the partition coefficient) in ATPS and the hydrophobicity values measured by RPC and HIC; however, a very good correlation was found between log
1
m
∗
which is a measure of protein hydrophobicity based on the solubility of the protein during precipitation and log K, particularly in
PEG
PO
4
systems with added NaCl. The parameter (
1
m
∗
) also demonstrated a good correlation with log K in PEG/dextran systems. A simple correlation for the prediction of partitioning in specific ATPS based on this parameter has been evaluated. An expression describing its resolution power, R, and a parameter describing the hydrophobicity of the system, P
0, was determined making the correlation potentially predictive for other proteins in the ATPSs used. Hydrophobicity of proteins was better exploited in
PEG
PO
4
systems than in PEG/dextran ones as a much higher resolution (R) is obtained in the former.
Fans are often tested without downstream blockage and, thus, the performance is considerably different when the fan is mounted in a vehicle as part of a cooling system and where high blockage effect ...is present downstream. The aim of the present work is to analyze by laser Doppler velocimetry LDV measurements the topology of the flow induced by a fan incorporated in a simplified underhood model reproducing engine blockage and to study the blockage effect of the engine positioning on the flow induced by the fan. The distance between the fan and the engine block affects the mean flow axial velocity U. The vertical velocity component W is greatly influenced by the variation of the distance between the fan and the engine block, both in magnitude and topology. KCI Citation Count: 5
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