Thermodynamics definitions

Question 1

Reversible process

Answer 1

For fluid undergoing reversible process, both the fluid and the surroundings can always be returned to their original states

Question 2

Isentropic efficiency

Answer 2

For identical start and end pressures, a ratio of reversible power to real world power. A measure of how much a steady flow process approximates to an isentropic process.

Question 3

Adiabatic

Answer 3

No heat transfer between the fluid and its surroundings.

Question 4

Cycle

Answer 4

A series of processes which returns a system to it initial state

Question 5

Reservoir

Answer 5

Thermodynamic system with a heat capacity large enough that can supply or absorb a finite amount of heat and remain at constant temperature

Question 6

Source

Answer 6

System which supplies heat

Question 7

Sink

Answer 7

System which accepts heat

Question 8

Isentropic

Answer 8

A process in which there is no friction and no heat transfer. Also means constant entropy

Question 9

Entropy

Answer 9

A thermodynamic property representing the unavailability of a system’s thermal energy for conversion into mechanical work. Measures degree of disorder in the system.

Question 10

Closed system

Answer 10

Space containing fluid with boundary between the fluid and its surroundings

Question 11

Property

Answer 11

Numerical values which define the system. Independent of the path taken to reach its state.

Question 12

State postulate

Answer 12

‘simple’ equilibrium whose state can be determined by 2 independent properties

Question 13

Gauge pressure

Answer 13

Pressure referenced to atmospheric pressure

Question 14

Absolute pressure

Answer 14

Pressure referenced to vacuum at p=0

Question 15

2-point temp scale

Answer 15

Defined by properties of a thermometric substance. T=0 at melting point

Question 16

Thermodynamic temp scale

Answer 16

Not dependent on properties of a substance. Absolute zero when k=0

Question 17

Zeroth law

Answer 17

Two objects at the same temperature are at thermal equilibrium

Question 18

Process

Answer 18

Transforms system from 1 equilibrium state to another

Question 19

Path

Answer 19

Transition between start and end of a process

Question 20

Equilibrium

Answer 20

Net force = 0 when multiple forces are acting on an object

Question 21

Quasi-equilibrium

Answer 21

System always remains close to equilibrium as it moves from its start to end point of process.

Question 22

Work

Answer 22

force x distance through which the force acts

Question 23

Stationary system

Answer 23

Any change in ke/pe of system is small

Question 24

Internal energy

Answer 24

Summation of all the microscopic energies in a substance. Is a property

Question 25

1st law thermodynamics

Answer 25

When any closed system is taken through a cycle, the net work done by the system upon the surroundings is equal to the net heat supplied to the system from the surroundings.

Question 26

Independent property

Answer 26

Properties which can be combined

Question 27

Extensive properties

Answer 27

Properties which depend on system size

Question 28

Specific heat capacity

Answer 28

Quantity of energy required to raise the temperature of one unit mass by one degree.

Question 29

Enthalpy

Answer 29

A combination property. It’s the sum of internal energy and a term with the sense of work, pv. H = U + PV.

Question 30

Isochoric

Answer 30

Constant volume

Question 31

Isobaric

Answer 31

Constant pressure

Question 32

Isothermal

Answer 32

No heat transfer

Question 33

Flow work

Answer 33

Work to deform part of a boundary displacing volume V at pressure P.

Question 34

Open system

Answer 34

Fluid continuously passes into and away from a system

Question 35

Steady flow rate

Answer 35

Constant mass flow rate

Question 36

Axiom

Answer 36

Something which can’t be disproved, but clearly no case exists which disproves it

Question 37

Isolated system

Answer 37

No heat, work or mass crosses the system boundary

Question 38

Kevin Plank statement of second law of thermodynamics

Answer 38

It’s impossible for any device operating in a cycle to receive heat from a single reservoir and produce an amount of work,

Question 39

Clausius statement of second law of thermodynamics

Answer 39

It’s impossible to have a device that works in a cycle and transfers heat from a cooler body to a hotter body without work being done on the system.