CHAPTER (2) FLUID PROPERTIES SUMMARY DR. MUNZER EBAID MECH.ENG.DEPT.

Size: px

Start display at page:

Download "CHAPTER (2) FLUID PROPERTIES SUMMARY DR. MUNZER EBAID MECH.ENG.DEPT."

Trevor Sparks
5 years ago
Views:

1 CHAPTER () SUMMARY DR. MUNZER EBAID MECH.ENG.DEPT. 08/1/010 DR.MUNZER EBAID 1

2 System Is defined as a given quantity of matter. Extensive Property Can be identified when it is Dependent on the total mass of the system such as Mass-(M) & Weight- (W). Intensive Property Can be identified when it is Independent of the total mass of the system such as Pressure (p), density ( ) ρ 08/1/010 DR.MUNZER EBAID

3 Specific Weight Weight volume mg ρ g γ V Specific GravityS specific specific weight weight of of fluid water γ γ f w ( ρg) ( ρg) fluid water ρ ρ f w 08/1/010 DR.MUNZER EBAID 3

4 Ideal Gas Law: (Equation of State) PV nrut m PV ( nrut ) m nm Ru P T V m P ρrt Where: n Number of moles m Molecular mass (nm)mmass of the gas R u Universal gas constant R Gas Constant 08/1/010 DR.MUNZER EBAID 4

5 Specific Heat Capacity The term originated primarily through the work of Scottish physicist Joseph Black Specific Heat at Constant Volume C V Is defined as the Amount of Heat required to raise the unit mass of a given substance by one degree at constant volume. Specific Heat at Constant Pressure C p Is defined as the Amount of Heat required to raise the unit mass of a given substance by one degree at constant pressure. 08/1/010 DR.MUNZER EBAID 5

6 Specific Enthalpy (h) / ( J/kg K) The enthalpy in a fluid is defined as: h u + p ρ The difference cp - cv is constant for an ideal gas. cp - cv R The Ratio of Specific Heats The Ratio of Specific Heats can be expressed as: k cp / cv Where: k the ratio of specific heats 08/1/010 DR.MUNZER EBAID 6

7 Consider the flow shown Fig. 1 where the velocity distribution is typical of a laminar flow next to a solid boundary. The following observation can be identified which are: The velocity gradient at the boundary is finite. The velocity gradient dv, becomes smaller, with distance from the boundary. dy The velocity at the boundary is zero. dv By definition, τ, Then dy Where: τ dv τ μ dy Shear stress applied dv dy Velocity gradient (Shear Strain) 08/1/010 DR.MUNZER EBAID 7

8 Units of Viscosity: μ τ dv dy N m m s m N s m Common Unit for Viscosity is Poise. (1 poise ). Ns 0.1 m Units of Kinematic Viscosity: μ ν ρ Ns kg m m 3 m s 08/1/010 DR.MUNZER EBAID 8

9 Kinematic Velocity ν μ m ( ρ s ) 1. Variation of viscosity with temperature for gases Sutherland Constant μ μ 0 T T 0 3 T T S S (S) are found from Table (A.). Variation of viscosity with pressure for gases Viscosity is minmal for pressure less than 10 atmospheres 08/1/010 DR.MUNZER EBAID 9

10 3. Variation of viscosity with temperature For Liquids μ Ce b T The variation of Dynamic Viscosity for fluids with temperature is given in (Fig. A.) in the Appendix of the text book. 08/1/010 DR.MUNZER EBAID 10

11 The variation of Kinematic Viscosity for fluids with temperature is given in (Fig. A.3) in the Appendix of the text book. 08/1/010 DR.MUNZER EBAID 11

12 Newtonian and Non-Newtonian Fluids Newtonian fluids are identified when only dv τ α dy Shear Thinning: (paints, printer ink ) Shear thickening: (gypsum-water mixture) 08/1/010 DR.MUNZER EBAID 1

13 Elasticity The elasticity of a fluid is related to the amount of deformation (expansion or contraction) for a given pressure change. Expressing this in a mathematical form, dv dp α V dv V Then Where E Degree of Elasticity dp E V V For an Adiabatic process (No heat transfer) E V kp Where K C C P V dp E V ρ ρrt dρ p 08/1/010 DR.MUNZER EBAID 13

14 surface Tension The cohesive forces between molecules down into a liquid are shared with all neighboring atoms. Those on the surface have no neighboring atoms above, and exhibit stronger attractive forces upon their nearest neighbors on the surface. This enhancement of the intermolecular attractive forces at the surface is called Surface Tension Surface Tension The surface tension Force is given by F s σ L 08/1/010 DR.MUNZER EBAID 14

15 Surface Tension Forces Case (b) F σ πr pπr σ σ P r P π σ r P 4σ r Case (c) Case (d F σl Wt σ F F + F σ σ, i σ, o 08/1/010 DR.MUNZER EBAID 15

16 Vapour Pressure The pressure exerted by a vapor; often understood to mean saturated vapor pressure (the vapor pressure of a vapor in contact with its liquid form and increases with temperature). Vapor pressure depends on various factors which are: The nature of the liquid. Temperature. The presence of dissolved substances. 08/1/010 DR.MUNZER EBAID 16

17 END OF SUMMARY DR. MUNZER EBAID 08/1/010 DR.MUNZER EBAID 17

Part II Fundamentals of Fluid Mechanics By Munson, Young, and Okiishi

Part II Fundamentals of Fluid Mechanics By Munson, Young, and Okiishi WHAT we will learn I. Characterization of Fluids - What is the fluid? (Physical properties of Fluid) II. Behavior of fluids - Fluid