EXPERIMENTAL ANALYSIS OF TWO-PHASE EJECTOR SYSTEM WITH VARYING MIXING CROSS-SECTIONAL AREA USING NATURAL REFRIGERANT CO2

2010 ◽  
Vol 18 (04) ◽  
pp. 297-307 ◽  
Author(s):  
MASAFUMI NAKAGAWA ◽  
ARIEL R. MARASIGAN ◽  
TAKANORI MATSUKAWA
Keyword(s):  
Cross Sectional Area ◽  
Pressure Recovery ◽  
Inlet Pressure ◽  
Inlet Temperature ◽  
Sectional Area ◽  
Two Phase ◽  
Entrainment Ratio ◽  
Evaporator Temperature ◽  
Cross Sectional ◽  
Ejector System

The use of two-phase ejector in improving the performance of transcritical CO2 refrigeration system needs further experimental verification particularly the effects of its geometrical design. In this study, experimental data were gathered for ejectors with different mixing cross-sectional areas at different operating temperature and pressure. The results have shown that a smaller mixing area yields higher efficiency due to its higher pressure recovery and entrainment ratio, but its advantages are limited to lower ejector inlet pressure Pc. A larger mixing area is required for higher cooling capacity which can be achieved at higher ejector inlet pressure or lower ejector inlet temperature but excessive increase in this area considerably decreases the efficiency of the system. In this study, the ejector with the largest mixing area was the most inefficient and reduced the COP up to 10% compared to most efficient type. It demonstrates the significant effect of ejector's geometrical features, particularly the mixing cross-sectional area and its related geometrical ratio, in the performance of CO2 ejector system. The effect of motive nozzle inlet condition on pressure recovery profile has been more evident for ejector with smaller mixing area while the evaporator temperature has the least effect in the performance of the system. In the conditions used in this study, using ejector yielded a COP improvement of up to 35% compared to the conventional system.

Effects of the Cross-Sectional Area of a Volute on Suction Recirculation and Cavitation in a Centrifugal Pump

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Hyeon-Seok Shim ◽  
Kwang-Yong Kim
Keyword(s):  
Centrifugal Pump ◽  
Three Dimensional ◽  
Cross Sectional Area ◽  
Navier Stokes ◽  
Sectional Area ◽  
Two Phase ◽  
Cross Sectional ◽  
Sst Model ◽  
The Cross ◽  
Critical Cavitation

Abstract The effects of the cross-sectional area of a volute on suction recirculation and cavitation in a centrifugal pump were investigated. The pump performance and fluid flow were analyzed using both steady and unsteady three-dimensional Reynolds-averaged Navier–Stokes analyses. The shear stress transport (SST) model was adopted as a turbulence closure model, and a simplified Rayleigh–Plesset cavitation model and a homogeneous two-phase mixture model were used to simulate the cavitating flow inside the pump. A constant to determine the designed circumferential velocity of the volute was selected as the geometric parameter for a parametric study. The hydraulic efficiency, head coefficient, blockage in front of the impeller, and critical cavitation number for a head-drop of 3% were selected as the performance parameters to evaluate the hydraulic performance. The results show that unlike the blockage, the hydraulic and suction performances were affected significantly by the volute shape. Both steady and unsteady flow analyses showed that the onset and development of suction recirculation were relatively unaffected by the volute geometry and the best efficiency point of the pump.

Research on AirFlush®: distribution of water and air in tubular and capillary membrane modules

2003 ◽  
Vol 3 (5-6) ◽  
pp. 409-414 ◽  
Author(s):  
J. Verberk ◽  
H. van Dijk
Keyword(s):  
Cross Sectional Area ◽  
Air Distribution ◽  
Phase Flow ◽  
Sectional Area ◽  
Two Phase ◽  
Cross Sectional ◽  
Dead End ◽  
Capillary Membrane ◽  
Membrane Modules ◽  
The Cross

Dead-end ultrafiltration has proved itself as a technique for reclamation of backwash water of sand filters and as a pretreatment step before spiral wound reverse osmosis. A direct result of dead-end filtration is a flux decrease in time caused by the accumulation of material in the membrane pores and on the membrane surface. Different cleaning techniques are used to remove this accumulated material. Recently a new technique has been introduced, the AirFlush®. This technique makes use of air to create higher turbulence as compared to a water flush. At Delft University of Technology in co-operation with X-flow and Norit Membrane Technology research has been started into the fundamentals of the combined air and water flush. As in many industrial processes, an equal division of water and air over an installation is very important. To check the distribution of water and air over the cross-sectional area of tubular and capillary membrane modules two different test installations have been built. The results from the experiments show that for tubular membrane modules the water and air distribution over the cross-sectional area of the module is not always equally divided. Improvements have to be obtained by a better air distribution system. For capillary membrane modules the distribution of water and air over the cross-sectional area is more equally divided. The results from the experiments are discussed taking into account the theory of two-phase flow. It is shown that from the theory of two-phase flow the good distribution for the capillary membrane module can be explained by the large frictional pressure drop compared to the hydrostatic pressure drop.

Pelvic Canal Narrowing Caused by Triple Pelvic Osteotomy in the Dog

1994 ◽  
Vol 07 (03) ◽  
pp. 110-113 ◽  
Author(s):  
D. L. Holmberg ◽  
M. B. Hurtig ◽  
H. R. Sukhiani
Keyword(s):  
Postoperative Complications ◽  
Pelvic Osteotomy ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Canal Width ◽  
Operative Complications ◽  
Post Operative Complications

SummaryDuring a triple pelvic osteotomy, rotation of the free acetabular segment causes the pubic remnant on the acetabulum to rotate into the pelvic canal. The resulting narrowing may cause complications by impingement on the organs within the pelvic canal. Triple pelvic osteotomies were performed on ten cadaver pelves with pubic remnants equal to 0, 25, and 50% of the hemi-pubic length and angles of acetabular rotation of 20, 30, and 40 degrees. All combinations of pubic remnant lengths and angles of acetabular rotation caused a significant reduction in pelvic canal-width and cross-sectional area, when compared to the inact pelvis. Zero, 25, and 50% pubic remnants result in 15, 35, and 50% reductions in pelvic canal width respectively. Overrotation of the acetabulum should be avoided and the pubic remnant on the acetabular segment should be minimized to reduce postoperative complications due to pelvic canal narrowing.When performing triple pelvic osteotomies, the length of the pubic remnant on the acetabular segment and the angle of acetabular rotation both significantly narrow the pelvic canal. To reduce post-operative complications, due to narrowing of the pelvic canal, overrotation of the acetabulum should be avoided and the length of the pubic remnant should be minimized.

DETERMINATION OF THE FUNCTION OF THE ROD’S CROSS-SECTIONAL AREA USING VIBRATION EIGENFREQUENCIES

2020 ◽  
Vol 0 (4) ◽  
pp. 19-24
Author(s):  
I.M. UTYASHEV ◽  
◽  
A.A. AITBAEVA ◽  
A.A. YULMUKHAMETOV ◽  
◽  
...  
Keyword(s):  
Cross Sectional Area ◽  
Variable Cross ◽  
Sectional Area ◽  
Longitudinal Vibrations ◽  
Cross Sectional ◽  
Method Error ◽  
Various Boundary Conditions ◽  
Elastic Fixation ◽  
Crosssectional Area

The paper presents solutions to the direct and inverse problems on longitudinal vibrations of a rod with a variable cross-sectional area. The law of variation of the cross-sectional area is modeled as an exponential function of a polynomial of degree n . The method for reconstructing this function is based on representing the fundamental system of solutions of the direct problem in the form of a Maclaurin series in the variables x and λ. Examples of solutions for various section functions and various boundary conditions are given. It is shown that to recover n unknown coefficients of a polynomial, n eigenvalues are required, and the solution is dual. An unambiguous solution was obtained only for the case of elastic fixation at one of the rod’s ends. The numerical estimation of the method error was made using input data noise. It is shown that the error in finding the variable crosssectional area is less than 1% with the error in the eigenvalues of longitudinal vibrations not exceeding 0.0001.

Changes in the parameters of nasal breathing and parameters of the upper respiratory tract during orthognathic operations in patients with II and III skeletal class of jaw anomalies

2020 ◽  
pp. 22-27
Author(s):  
S.Sh. Gammadaeva ◽  
M.I. Misirkhanova ◽  
A.Yu. Drobyshev
Keyword(s):  
Respiratory Tract ◽  
Nasal Cavity ◽  
Nasal Septum ◽  
Cross Sectional Area ◽  
Upper Respiratory Tract ◽  
Sectional Area ◽  
Nasal Breathing ◽  
Cross Sectional ◽  
Skeletal Class ◽  
Upper Respiratory

The study analyzed the functional parameters of nasal breathing, linear parameters of the nasal aperture, nasal cavity and nasopharynx, volumetric parameters of the upper airways in patients with II and III skeletal class of jaw anomalies before and after orthognathic surgery. The respiratory function of the nose was assessed using a rhinomanometric complex. According to rhinoresistometry data, nasal resistance and hydraulic diameter were assessed. According to the data of acoustic rhinometry, the minimum cross-sectional area along the internal valve, the minimum cross-sectional area on the head of the inferior turbinate and nasal septum and related parameters were estimated. According to the CBCT data, the state of the nasal septum, the inferior turbinates, the nasal aperture, the state of the nasal cavity, and the linear values of the upper respiratory tract (nasopharynx) were analyzed. The patients were divided into 4 groups according to the classification of the patency of the nasal passages by

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