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[en] The pressure drops through contractions in horizontal single and two-phase flow were investigated. A total of 167 measurements were made for four different entrance shapes to study the effects of the entrance shape on the pressure drop through a contraction in horizontal single and two-phase flow. From this data, pressure drops were calculated and compared with the pressure drops predicted by analytical models for single and two-phase flow. For single phase flow the agreement between the data and predictions is within ±25%, whereas for two-phase flow Hoopes model, which gives a better agreement than the homogeneous model, underpredicts the data as much as 45%. In addition, the effects of void fraction and liquid phase mass velocity on the pressure drop through the sudden flow channel constraction were investigated for two-phase flow. (Author)
Journal
[en] Ten methods of the total two-phase pressure drop prediction based on five existing models and correlations have been examined for their accuracy and applicability to pressurized water reactor conditions. These methods were tested against 209 experimental data of local and bulk boiling conditions: Each correlations were evaluated for different ranges of pressure, mass velocity and quality, and best performing models were identified for each data subsets. A computer code entitled 'K-TWOPD' has been developed to calculate the total two phase pressure drop using the best performing existing correlations for a specific property range and a correction factor to compensate for the predicted error of the selected correlations. Assessment of this code shows that the present method fits all the available data within ±11% at a 95% confidence level compared with ± 25% for the existing correlations. (Author)
Journal
[en] It is desirable to calibrate impactors in order to gain quantitative information from the measurements made with them. Calibration of an impactor requires high reproduceability of the experimental conditions. In particular, the nature of the surface on which the deposit of particles is formed must be such that each impact is effective: the best results are obtained by coating the plates with an adhesive mixture of dioctylphthalate and Canada balsam. With this procedure, the shape of the curves for yield of stages is similar to that of theoretical curves. The geometry of the impactor with which the present study deals is such that certain dimensional relationships remain unchanged from one stage to the next. Furthermore, the curves for each stage can be reduced to a single curve by adopting a system of reduced co-ordinates. From this curve the different stages can easily be proportioned so as to localize at the desired point of the spectrum the cut-offs made by each stage. The same curve also indicates the effect of the rate at which air passes through the instrument on the stopping power of each stage. In the present case a throughput of 24 litres/min was selected; for four stages it corresponds to a pressure-drop of approximately 200 mm/Hg. The first and last cut-offs are at 0.5 and 4 μm, respectively. Depending on the use of the sample and the number of fractions desired, one or two intermediate stages can be eliminated. (author)
[fr]
Pour tirer des renseignements quantitatifs des mesures faites avec les impacteurs, il est souhaitable de les étalonner. L'étalonnage d'un impacteur requiert une grande reproductibilité des conditions expérimentales. En particulier, la nature de la surface sur laquelle se forme le dépôt de particules doit être telle que chaque impact soit efficace. Les meilleurs résultats en ce sens ont été obtenus en enduisant les lamelles d'un mélange adhésif dioctyphtalate, baume du Canada. Avec ce procédé, la forme des courbes de rendement par étage se rapproche de celle des courbes théoriques. La géométrie de l'impacteur, objet des présents travaux, est telle que certains rapports dimensionnels sont invariants d'un étage à l'autre. Les courbes relatives à chaque étage peuvent d'ailleurs se ramener à une courbe unique en adoptant un système de coordonnées réduites. A partir de cette courbe, il est alors aisé de dimensionner les différents étages, de manière à localiser aux endroits souhaités du spectre, les coupures faites par chaque étage. Cette même courbe permet de juger de l'influence du débit d'air traversant l'appareil sur le pouvoir d'arrêt de chaque étage. Dans le cas présent, un débit de 24 litres/min a été choisi. 11 correspond, pour quatre étages, S une perte de charge voisine de 200 mm de mercure. Les coupures extrêmes se situent respectivement vers 0,5 et 4 μm. Suivant l'utilisation du prélèvement et le nombre de fractions désirées, un ou deux étages intermédiaires peuvent être supprimés. (author)Source
International Atomic Energy Agency, Vienna (Austria); 783 p; Dec 1967; p. 351-377; Symposium on Instruments and Techniques for the Assessment of Airborne Radioactivity in Nuclear Operations; Vienna (Austria); 3-7 Jul 1967; IAEA-SM--95/10; ISSN 0074-1884; 
; 2 refs., 23 figs., 1 tab.
; 2 refs., 23 figs., 1 tab.
[en] Single phase natural circulation is of interest in various energy systems, including solar heaters, nuclear reactors, geothermal power production, engine and computer cooling. The present paper deals with an experimental study on the influence of pressure drops on the behavior of a single-phase natural circulation loop. In a simple rectangular loop (MTT-1) located at DITEC, three series of tests have been carried out, with localized pressure drops (orifices of 6 mm, 10 mm and 14 mm diameter in the vertical legs) and different power levels. The experimental data are analyzed and compared with previous results obtained with smooth pipes, demonstrating the stabilizing effect of the pressure drops on the overall behavior of the loop
Journal
International Communications in Heat and Mass Transfer; ISSN 0735-1933; ; CODEN IHMTDL; v. 26(5); p. 597-606
; CODEN IHMTDL; v. 26(5); p. 597-606
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