• Title/Summary/Keyword: Clearance flow

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RENAL REGULATION OF UREA EXCRETION DURING UREA INFUSION IN ACUTE HEAT EXPOSED BUFFALOES

  • Chaiyabutr, N.;Buranakarl, C.;Loypetjra, P.
    • Asian-Australasian Journal of Animal Sciences
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    • v.5 no.1
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    • pp.81-90
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    • 1992
  • Five buffaloes kept in normal ambient temperature ($30^{\circ}C$) showed no significant changes in the heart rate, respiratory rate, packed cell volume, plasma constituents and renal hemodymics during intravenous infusion of urea for 4 h. The rate of urine flow, fractional urea excretion, urinary potassium excretion and osmolar clearance significantly decreased while the renal urea reabsorption markedly increased during urea infusion. The decrease of fractional potassium excretion was concomitant with the reduction of the rate of urine flow and urine pH. In animals exposed to heat ($40^{\circ}C$) the rectal temperature heart rate and respiratory rate significantly increased while no significant changes in GFR and ERPF were observed. An intravenous infusion of urea in heat exposed animals caused the reduction of the rate of urine flow with no changes in renal urea reabsorption, urine pH and fractional electrolyte excretions. During heat exposure, there were marked increases in concentrations of total plasma protein and plasma creatinine whereas plasma inorganic phosphorus concentration significantly decreased. It is concluded that an increase in renal urea reabsorption during urea infusion in buffaloes kept in normal ambient temperature depends on the rate of urine flow which affect by an osmotic diuretic effect of electrolytes. The limitation of renal urea reabsorption in heat stressed animals would be attributed to an increases in either plasma pool size of nitrogenous substance or body metabolism.

A SIMPLIFIED METHOD TO PREDICT FRETTING-WEAR DAMAGE IN DOUBLE $90^{\circ}$ U-BEND TUBES

  • Choi, Seog-Nam;Yoon, Ki-Seok;Choi, Taek-Sang
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.616-621
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    • 2003
  • Fluid-elastic instability is believed to be a cause of the large-amplitude vibration and resulting rapid wear of heat exchanger tubes when the flow velocity exceeds a critical value. For sub-critical flow velocities, the random turbulence excitation is the main mechanism to be considered in predicting the long-term wear of steam generator tubes. Since flow-induced interactions of the tubes with tube supports in the sub-critical flow velocity can cause a localized tube wear, tube movement in the clearance between the tube and tube support as well as the normal contact force on the tubes by fluid should be maintained as low as possible. A simplified method is used for predicting fretting-wear damage of the double $90^{\circ}$U-bend tubes. The approach employed is based on the straight single-span tube analytical model proposed by Connors, the linear structural dynamic theory of Appendix N-1300 to ASME Section III and the Archard's equation for adhesive wear. Results from the presented method show a similar trend compared with the field data. This method can be utilized to predict the fretting-wear of the double $90^{\circ}$U-bend tubes in steam generators.

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Solid-liquid mixture flow characteristics in an inclined slim hole annulus (Slim hole 경사 환형관내 고-액 혼합유동 특성에 관한 연구)

  • Suh, Byung-Taek;Han, Sang-Mok;Woo, Nam-Sub;Kim, Young-Ju;Hwang, Young-Kyu
    • Proceedings of the SAREK Conference
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    • 2008.06a
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    • pp.1315-1320
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    • 2008
  • An experimental study was carried out to study the solid-liquid mixture upward flow in a vertical and inclined annulus with rotating inner cylinder. Lift forces acting on a fluidized particle plays a central role in many importance applications, such as the removal of drill cuttings in horizontal drill holes, sand transport in fractured reservoirs, sediment transport and cleaning of particles from surfaces, etc. Field measurements have revealed that the pressure drop over a borehole during drilling of a slim oil well or a well with a long reach can depend significantly on the rotation speed of the drill pipe. An accurate prediction of the annular frictional pressure drop is therefore important for conditions where the annular clearance is small. Effect of annulus inclination and drill pipe rotation on the carrying capacity of drilling fluid, particle rising velocity, and pressure drop in the slim hole annulus have been measured for fully developed flows of water and of aqueous solutions.

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A Numerical Analysis and Experiment for Micro-Fans (축류 마이크로 홴의 전산해석 및 성능시험)

  • Cho, Jin-Soo;Pyun, Tae-Kyoon;Park, Wang-Sik;Chun, Chang-Kun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.24 no.7
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    • pp.895-906
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    • 2000
  • A three dimensional linear frequency-domain lifting surface panel method was used for the aerodynamic analysis of axial flow type micro-fans. As proven by the duct modeling, the tip clearance of the micro-fans tested is large enough to ignore the calculated effect of the duct system. As the numerical results and experimental data agreed well in the operating point region, the method was applicable in the parametric studies to determine the design parameters of axial flow fans. Experiments on micro-fans were carried out based on KS B 6311. The newly designed micro-fan showed improvements in both static pressure rise and volumetric flow rate compared to the existing fans at a given operating condition. No detection of surging and the smooth characteristic curve proved the improvement in performance. To reduce the fan noise in the fan design, it was necessary to make use of the frequency spectrum analysis data. Measurement of sound pressure level for micro-fans was conducted based on KS B 6361 and KS A 0705. The peak - which occurs at blade passage frequency and its higher harmonics due to the fan noise - was not detected. This justifies the design methodology of the blade.

Effect of Turbine Blade tip shape on the Total Pressure Loss of a Turbine Cascade (블레이드 팁 형상이 터빈 캐스케이드 전압 손실에 미치는 영향에 대한 연구)

  • Lee, Ki-Seon;Park, Seoung-Duck;Noh, Young-Chul;Kim, Hak-Bong;Kwak, Jae-Su;Jun, Yong-Min
    • The KSFM Journal of Fluid Machinery
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    • v.12 no.2
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    • pp.39-45
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    • 2009
  • Leakage flow through turbine blade tip gap causes strong leakage vortex near the blade suction side and induces large aerodynamic losses. In this study, the conventional plane tip and various squealer tip blades were tested in a linear cascade in order to measure the effect of the tip shape on the total pressure loss. Three tip gap clearances of 0.6%, 1.3%, and 2.0% of blade span were tested. Flow measurement was conducted at one chord downstream from the trailing edge with a five-hole probe. Results showed that the leakage vortex was stronger than passage vortex and the mass averaged overall total pressure loss through the cascade was the lowest for suction side blade tip case. For all tested cases, the area averaged overall total pressure loss was increased as the tip clearance increased.

A Study on Null Characteristics of 4-way Spool Valve (4방향 스풀밸브의 중립특성에 관한 연구)

  • Ham, Young-Bog;Yun, So-Nam;Lee, Geun-Ho;Kim, Sung-Dong
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.8
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    • pp.165-171
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    • 2000
  • In this study the 4-way spool valve characteristics are clearly defined and clearly defined and proposed new type of spool valve. This paper presents governing equations of the flow through clearances between sleeve and spool as a model of orifice flow for null characteristics analysis and programmed analysis software of it. This software is possible to basically analysis that not only which case of open center closed center or critical center but _ -displacement of spool lab position boundary region and spool opening of the valve and to estimate the pressure variation in the spool and external leak flow variation. We are convinced that the scale of load pressure difference is changed as lab condition of valve and this scale is changed with boundary point on the annular clearance. It is vary useful to designer and user of spool valve with this design data and analysis software.

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Performance analysis of a scroll compressor considering quasi one-dimensional leakage modeling and heat transfer loss (준 1차원 누설모델링 및 열전달 손실을 고려한 스크롤압축기의 성능해석)

  • Gang, Tae-Gyu;Park, Gyeong-U;Jeong, Yeon-Gu;Park, Hui-Yong
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.10
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    • pp.1339-1349
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    • 1997
  • A numerical method of calculating the performance of a scroll compressor for refrigerant R-22 and R-134a is presented in this paper. A series of involute curves are employed for the scroll wrap design and the compression volume is investigated geometrically. The radial leakage flow rate through tip clearance is calculated by the two-dimensional compressible flow. On the basis of the results, quasi one-dimensional leakage modeling can be applied to the performance analysis of a scroll compressor, more effectively. Furthermore, the heat transfer effect between scroll wrap and working fluid in compression chamber is considered for the performance analysis. As the results of this study, the effects of the radial and tangential leakage flow rate and heat transfer on the scroll compressor performance are derived precisely. These results may provide the guideline for the design and development of a real scroll compressor.

Theoretical Analysis of Sealless Piston for Hydraulic Cylinders (시일이 없는 유압 실린더용 피스톤의 이론해석)

  • Park, T.J.
    • Transactions of The Korea Fluid Power Systems Society
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    • v.3 no.3
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    • pp.1-7
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    • 2006
  • In this paper, a theoretical analysis is carried out to study the lubrication characteristics of sealless piston for hydraulic cylinders. The analytical pressure distributions are obtained solving one-dimensional Reynolds equation with partially tapered moving piston. Nearly analytical expressions for lateral forces acting on the piston and leakage flow rate through the clearance are also presented. Using the analytical expressions, the influence of design parameters on lubrication characteristics can be easily evaluated without numerical analysis. Composite-shaped piston which minimizes the leakage flow rate is the optimum in sealless piston for hydraulic cylinder.

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An Experimental Study on Friction Reduction in Journal Bearings (저어널 베어링에서의 마찰감소현상에 대한 실험적 연구)

  • 이득우;김경웅
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.10 no.3
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    • pp.298-304
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    • 1986
  • The friction reduction by dilute polymer solutions was investigated experimentally in journal bearings. Flow pattern visualization and torque measurements were performed for a concentric case (.epsilon.=0). The effects of polymer concentration, bearing clearance, and polymer molecular weight on friction reduction were examined. The frictional torque and the intensity of vortices of the case of polymer solution were reduced compared with those of base oil only.

AH EXPERIMENTAL STUDY ON THE EFFECTS OF MULTIBANDED ORTHODONTIC APPLIANCES ON DENTAL CARIES ACTIVITY (전대환교정장치가 치아우식활성도에 미치는 영향에 관한 실험적 연구)

  • Kim, Hye Kyoung
    • The korean journal of orthodontics
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    • v.6 no.1
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    • pp.47-54
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    • 1976
  • This study was conducted to investigate the effects of multibanded orthodontic appliances on dental caries activity. The subjects consisted of 50 males and females with multibanded orthodontic appliance and the same number of caries free group. The following conclusions were obtained, 1. There was significant difference between the experimental group and control group in the tests of Snyder colorimetric test, acid :buffering capacity and oral glucose clearance test (at $5\%$ level of significance). 2. There was no significant difference between the experimental group and control group in the tests of unstimulated salivary flow fate, stimulated salivary flow rate and salivary viscosity test (at $5\%$ level of significance). 3. Dental caries activity was higher in experimental group than in control group.

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