• Title, Summary, Keyword: fluid viscosity

Search Result 672, Processing Time 0.037 seconds

A Calculation for the Viscosity of Fluid at the Critical Point

  • Kim, Won-Soo;Chair, Tong-Seek
    • Bulletin of the Korean Chemical Society
    • /
    • v.23 no.11
    • /
    • pp.1524-1526
    • /
    • 2002
  • It is very difficult to measure the fluid viscosity at the critical point, there are seldom found experimental values of fluid viscosity at the critical point. Few theories can explain the critical viscosity quantitatively. A theory of viscosity previously proposed by authors10 is applied to the fluid at the critical point. This theory can be simplified as a simple form with no adjustable parameters, allowing for easy calculation. Viscosities at the critical point for some substances have been calculated, and calculated results are satisfactory when compared with the observed values.

Laminar Heat and Fluid Flow Characteristic with a Modified Temperature-Dependent Viscosity Model in a Rectangular Duct

  • Sohn Chang-Hyun;Chang Jae-Whan
    • Journal of Mechanical Science and Technology
    • /
    • v.20 no.3
    • /
    • pp.382-390
    • /
    • 2006
  • The present study proposes a modified temperature-dependent non-Newtonian viscosity model and investigates the flow characteristics and heat transfer enhancement of the viscoelastic non-Newtonian fluid in a 2:1 rectangular duct. The combined effects of temperature dependent viscosity, buoyancy, and secondary flow caused by the second normal stress difference are considered. Calculated Nusselt numbers by the modified temperature-dependent viscosity model give good agreement with the experimental results. The heat transfer enhancement of viscoelastic fluid in a rectangular duct is highly dependent on the secondary flow caused by the magnitude of second normal stress difference.

Characteristics of Shear-Thinning Fluid Viscosity under Traversal Vibration (진동장에서의 전단박화 유체 점도의 특성 연구)

  • Ku Yun-Hee;Lee Ji-Hyung;Shin Sehyun
    • Proceedings of the KSME Conference
    • /
    • /
    • pp.317-320
    • /
    • 2002
  • The effect of vibration on the viscosity of a shear-thinning fluid was investigated with a newly designed pressure-scanning capillary viscometer. The viscometer was designed to measure non-Newtonian viscosity continuously over a range of shear rates at a time. Low frequency vibration was applied perpendicularly to the direction of the flow. The effect of the transversal vibration was investigated for both Newtonian fluids and non-Newtonian fluids. The experimental results showed that the vibration had no effect on the viscosity of the Newtonian fluids. However, the vibration caused a significant reduction of the shear-thinning fluid viscosity. The viscosity reduction was strongly dependent on both vibration frequency and shear rate. In addition, the viscosity reduction was affected by the amplitude of vibration, and, the bigger amplitude applied, the more viscosity reduction occurred.

  • PDF

A Study on the Measurement of the Fluid Viscosity by Using the Torsional Vibration of a Circular Rod (원형 봉의 비틀림 진동에 의한 유체 점도 측정 연구)

  • Chun, Han-Yong;Kim, Jin-Oh
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.26 no.6
    • /
    • pp.1016-1025
    • /
    • 2002
  • This paper deals with the measurement of the fluid viscosity by using the torsional vibration of a circular rod excited by a torsional vibrator at one end. The effect of an adjacent viscous fluid on the torsional vibration of the rod has been studied theoretically and expressed in terms of the mechanical impedance. The theoretically-obtained trend that the mechanical impedance is proportional to the square root of the viscosity times the density of the fluid has been confirmed by the impedance measurement. The paper demonstrates that a torsionally-vibrating rod can be used as a sensor to measure the viscosity of a fluid.

Effect of Fluid Viscosity on the Suspension of a Single Particle in Channel Flow (채널 유동에서 점성이 단일 입자 혼합 유동의 suspension에 미치는 영향)

  • Choi, Hyoung-Gwon
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.33 no.3
    • /
    • pp.194-200
    • /
    • 2009
  • Suspension of a single solid particle in a channel flow with a constant pressure gradient is studied numerically. The interaction of a circular particle with a surrounding Newtonian fluid is formulated using a combined formulation. Numerical results are presented using two dimensionless variables: the sedimentation Reynolds number and the generalized Froude number. From the present results, it has been shown that a solid particle is suspended at a smaller generalized Froude number as the viscosity of the surrounding fluid increases. The time taken for equilibrium position is found to be smaller as fluid viscosity increases when both : the sedimentation Reynolds number and the generalized Froude number are the same while, at the same situation, the dimensionless time taken for equilibrium position is to be nearly the same regardless of fluid viscosity when a dimensionless time variable is introduced

봉의 비틀림 고유진동에 대한 인접 점성유체의 영향

  • 김진오;전한용
    • Journal of KSNVE
    • /
    • v.10 no.1
    • /
    • pp.168-173
    • /
    • 2000
  • This paper deals with the theoretical study on the effect of the viscosity of an adjacent viscous fluid on the characteristics of the torsional vibration of a rod with fixed-free boundary conditions. Expressions for the natural frequency and damping factor have been obtained as functions of the viscosity of the fluid by exact and asymptotic analyses. The results provide quantitative information of the natural frequency reduction and damping rate affected by the fluid viscosity.

  • PDF

Mechanical Impedance at the Interface between a Torsionally-Vibrating Rod and a Viscous Fluid (비틀림 진동 봉과 점성 유체의 경계면에서의 역학적 임피던스)

  • 전한용;김진오
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • /
    • pp.153-159
    • /
    • 2002
  • This paper deals with the measurement of the fluid viscosity by using the torsional vibration of a circular red excited by a torsional vibrator at one end. The effect of an adjacent viscous fluid on the torsional vibration of the rod has been studied theoretically and expressed in terms of the mechanical impedance. The theoretically-obtained trend that the mechanical impedance is proportional to the square root of the viscosity times the density of the fluid has been confirmed by the impedance measurement. The paper demonstrates that a torsionally-vibrating rod can be used as a sensor to measure the viscosity of a fluid.

  • PDF

Heat Transfer Behavior of Viscoelastic Fluid including buoyancy effect with Modified Temperature Dependent Viscosity Model in a Rectangular Duct (수정점도 모델을 이용한 직사각형 덕트에서의 부력을 고려한 점탄성 유체의 열전달 특성)

  • Sohn C. H.;Jang J. H.
    • 한국전산유체공학회:학술대회논문집
    • /
    • /
    • pp.192-198
    • /
    • 1999
  • The present study proposes modified temperature-dependent non-Newtonian viscosity model and investigates flow characters and heat transfer enhancement of the viscoelastic non-Newtonian fluid in a 2:1 rectangular duct. The proposed modified temperature dependent viscosity model has non-zero value near the high temperature and high shear rate region while on the existing viscosity models have zero value. Two versions of thermal boundary conditions involving difference combination of heated walls and adiabatic walls are analyzed in this study. The combined effect of temperature dependent viscosity, buoyancy, and secondary flow caused by second normal stress difference are ail considered. The Reiner-Rivlin model is adopted as a viscoelastic fluid model to simulate the secondary flow caused by second normal stress difference. Calculated Nusselt numbers by the modified temperature-dependent viscosity model gives under prediction than the existing temperature-dependent viscosity model in the regions of thermally developed with same secondary normal stress difference coefficients with experimental results in the regions of thermally developed. The heat transfer enhancement of the viscoelastic fluid in a 2:1 rectangular duct is highly dependent on the secondary flow caused by the magnitude of second normal stress difference.

  • PDF

Study of Cam and Follower Contacts with the Mixed Concepts of EHL and Boundary Lubrication (EHL과 경계 윤활의 혼합 개념에 의한 캠과 종동물의 접촉 현상에 대한 연구)

  • 장시열
    • Tribology and Lubricants
    • /
    • v.15 no.4
    • /
    • pp.343-353
    • /
    • 1999
  • The role of viscosity index improver's(Ⅶ) additives for modem engine lubrication is complex. Under the condition of atmosphere or low shear rate, the characteristics of Ⅶ added lubricant is verified and quoted frequently for mathematical model of lubricant behavior. However, recent research shows that added lubricant has the characteristics of shear thinning at high shear rate condition although it performs well enough over the whole range of working temperature. At high shear rate, they show significant decrease of apparent viscosity irrespective of temperature. Many experimental researches verify that Ⅶ added lubricant shows boundary film layer formation on the solid surface as well as shear thinning effect by its polymeric molecular characteristics. The intend of our research is to verify the effects of Ⅶ from the viewpoint of continuum mechanics, because conventional Reynolds'equation with only pressure-viscosity relation cannot fully predict the lubricant behavior under the Ⅶ added condition. In these aspects, Reynolds'equation of Newtonian fluid model lacks the reflection of real fluid behavior and there is no way to explain the non-linear characteristics of Ⅶ added lubricant. In this research, we mathematically modeled the Ⅶ added lubricant behaviors which are the characteristics of non-Newtonian fluid behavior at high shear rate and boundary film formation on the solid surface. The consideration of elastic deformation in the contact region is also included in our computation and finally the converged film pressure and the film thickness with elastic deformation are obtained. The results are compared with those of Newtonian fluid model.

Pump Performance Analyses with High Viscous Fluids (점성이 높은 유체를 사용하는 펌프의 성능해석)

  • Kim, Dong-Joo;Roh, Hyung-Woon;Suh, Sang-Ho
    • The KSFM Journal of Fluid Machinery
    • /
    • v.7 no.2
    • /
    • pp.21-26
    • /
    • 2004
  • In this study the effects of fluid viscosity on the pump performances for a conventional centrifugal pump were experimentally investigated. The study aimed to compare the pump characteristics between water and viscosity fluids. In order to measure the flow rate and pressure, v-notch welt and bourdon pressure gauges were used for the codes of KS B6301 and KS B6302. The working fluids were water, aqueous sugar and glycerin solutions. The results were summarized as follows : The experimental results were summarized as follows : the pump characteristics of the total head, shaft power, and efficiency with high viscosity fluids were different from those of water. When the viscosity of the applied fluid was increased, the total head and efficiency were more decreased than those of water. The decreasing gradients of the total head and the efficiency were larger than water due to the increased disk friction losses at the duty operation point. However, the shut-off head was almost constant regardless the viscosity of applied fluids. Each efficiency curves for the sugar $20w\%$ and glycerin $20w\%$ solutions was decreased up to $15.1\%$ and $34.4\%$ than that of water, respectively.