Thermodynamic Units and Properties

Question 1

What is Specific Volume?

Answer 1

Volume per unit mass

Question 2

What is mass?

Answer 2

Amount of stuff in a material

Question 3

What is density?

Answer 3

Mass per unit volume.

Note: specific volume is the inverse of density.

Question 4

What is weight?

Answer 4

Force exerted by an object due to the acceleration of gravity exerted on its mass.

wt=mg/g(c)

Question 5

What are Intensive properties?

Answer 5

Independent of mass.
Anything specific (specific volume), temperature, pressure, density.

Question 6

What are Extensive properties?

Answer 6

Varies with the amount of mass in a substance.
Ex: mass itself, total volume.

Question 7

Convert Fahrenheit to Rankine

Answer 7

R=F+460

Question 8

Covert Kelvin to Celsius.

Answer 8

K=C+273

Question 9

Pressure conversions.

Answer 9

0.491 psi=1” Hg
0.433 psi=1’ water
14.7 psi=408” water (or 33.95’)
14.7 psi=29.9” Hg
1 psi=2.3’ water

Note: NRC bank uses 15 psi and 30”Hg.

Question 10

Pressure of a column of water

Answer 10

P=(rho•g•z)/g(c)

rho=density

Question 11

Convert from Patm and Pguage.

Answer 11

Patm=Pguage+15

Question 12

What is potential energy?

Answer 12

Energy due to height (position).

PE=mgz/g(c)

ft-lbf

Question 13

What is kinetic energy?

Answer 13

Energy due to velocity.

KE=(m•v^2)/(2•g(c))

ft-lbf

Question 14

What is internal and specific internal energy?

Answer 14

Microscopic form of energy due to temperature. U, in btu’s

Specific internal energy;
u=U/mass
btu/lbm

Question 15

What is PV energy and specific PV energy?

Answer 15

Flow energy (pressure x volume)

Specific flow energy is per unit mass.
Pv=PV/m
Units ft-lbf/lbm

Question 16

What is Work?

Answer 16

A process done by or done on a system.

Mechanical work and flow work.

Question 17

Define Mechanical Work.

Answer 17

W=F•d

Force on an object thru it’s displacement.

Question 18

Define Flow Work.

Answer 18

Work required to maintain continuous steady flow of fluid.

W(flow)=F•L (L=length)
Since P=F/A, ->F=P•A. ->W(f)=P•A•L

Since A•L=V ->W(f)=P•V
Units of btu’s

Question 19

What is Power?

Answer 19

Rate of doing work or rate of energy transfer. Per unit time.

Question 20

Define HP.

Answer 20

1HP=550ft-lbf/sec

Also P=F•v/550
v=velocity.
F=force.
P=power.

Question 21

What is Heat (Q)?

Answer 21

Energy in the form of temperature.

Specific heat is q=Q/m

Question 22

What is Sensible Heat?

Answer 22

Heat added or removed to change temperature.

Question 23

What is Latent Heat?

Answer 23

Heat added or removed to cause a change in phase of a substance.

Question 24

What is Superheat?

Answer 24

Heat added to dry saturated steam to raise its temperature above saturation.