Definitions and Fluid Properties

Question 1

Most significant properties which distinguish liquids from gases

Answer 1

bulk modulus of elasticity

density

Question 2

Fluid definition

Answer 2

a substance that continuously deforms when subjected to shear stresses

Question 3

Newton’s second law of motion

Answer 3

Force is proportional to time rate of change of momentum

Question 4

Temperature rise when a high-speed gas is brought to rest without heat transfer

Answer 4

Question 5

Equation for measuring fluid velocity through pressure rise when the fluid is brought to rest

Answer 5

Question 6

Heat transfer is positive if

Answer 6

…added to the system

….added to the fluid as it passes through control volume

Question 7

Work is positive if

Answer 7

….done by the system

(e.g. expansion of boundaries of a system)

…done by fluid as it passes through a control volume

(e.g. work done by a fluid as it passes through a turbine)

Question 8

Energy may be defined as the capacity to

Answer 8

do work

Question 9

e may be called the energy content, and consists of

Answer 9

kinetic energy

potential energy

internal energy

Question 10

the inequality of Clausius

Answer 10

Question 11

another second law axiom using entropy

Answer 11

Question 12

enthalpy

Answer 12

Question 13

usefule form of first and second laws of thermodynamics

(considering only pdv work being done)

Answer 13

Question 14

compressibility factor

Answer 14

Question 15

definition of specific heat at constant pressure

Answer 15

Question 16

definition of specific heat at constant volume

Answer 16

Question 17

for a perfect gas, equation relating R, cp, and cv

Answer 17

Question 18

definition of isentropic

Answer 18

adiabatic and reversible

Question 19

isentropic flow equations

Answer 19

Question 20

polytropic process

Answer 20

n=0 constant pressure process

n=1 isothermal process

n=gamma isentropic process

Question 21

Molecular spacing in gases

Answer 21

order of magnitude larger than the size of the individual molecules

Question 22

Molecular spacing in liquids

Answer 22

same order of magnitude of size as the molecules

Question 23

Density of standard air

Answer 23

1.225 kg/m3

Question 24

specific volume

Answer 24

volume occupied by a unit mass of a substance

Question 25

specific weight definition

Answer 25

force of gravity on the mass contained in a unit volume of a substance

Question 26

specific weight equation

Answer 26

Question 27

Is specific weight a true fluid property (strictly speaking)?

Answer 27

No, because it depends on the local gravitational acceleration.

Question 28

specific gravity equation

Answer 28

Question 29

When reporting specific gravity, what else should be noted?

Answer 29

temperatures of both the liquid in question and the reference temperature of water

Question 30

average bulk modulus of elasticity

Answer 30

Question 31

bulk modulus for water at 20 degC

Answer 31

Question 32

variation of K (bulk modulus) for water between 0 degC and 100 degC

Answer 32

a few percent

Question 33

isothermal elastic modulus of a gas

Answer 33

Question 34

isentropic elastic modulus of a gas

Answer 34

Question 35

equation for velocity of sound in any medium

Answer 35

Question 36

velocity of sound in a perfect gas

Answer 36

Question 37

surface tension units

Answer 37

energy per unit area of surface or force per unit length

Question 38

surface tension description

Answer 38

work done in bringing molecules to the surface (result of difference in mutual attraction between liquid molecules near a surface compared with those farther within the mass of liquid)

Question 39

increase in energy of a spherical bubble r when expanding to (r+dr)

Answer 39

Question 40

work done in expanding bubble (force from the difference in pressure inside and outside the bubble times the distance dr the force moves)

Answer 40

Question 41

equate the increase in energy to the work done for the expanding bubble

Answer 41

Question 42

general curved surface relation with principal radii r1 and r2

Answer 42

Question 43

equilibrium relation for liquid-gas interface in contact with a solid surface

Answer 43

Question 44

contact angle for wetting contact angle for non-wetting

Answer 44

Question 45

mercury contact angle for many surfaces

Answer 45

130-150 degrees | (non-wetting)

Question 46

capillary action

Answer 46

the rise of a column of liquid in a small tube due to surface tension

Question 47

capillary balance

Answer 47

weight of the liquid column in the tube and the peripheral force around the tube circumference

Question 48

capillary rise equation (solve for h in capillary balance equation)

Answer 48

Question 49

capillary action due to wetting contact angle capillary action due to non-wetting contact angle

Answer 49

rise of liquid depression of liquid

Question 50

surface tension of water in air

Answer 50

about 0.073 N/m

Question 51

approximate reduction of surface tension of water due to addition of wetting agents

Answer 51

about one-half

Question 52

If a liquid and its vapor coexist in equilibrium, the vapor is called a ____ vapor and the pressure exerted by this saturated vapor is called the _____ \_\_\_\_\_\_.

Answer 52

saturated vapor pressure

Question 53

Vapor pressure is a function of ______ for a given substance.

Answer 53

temperature