Thermodynamics Flashcards
What is an isolated system?
No heat or matter is transferred
What is a closed system?
Where there is an exchange of heat energy
What is a open system?
When there is an exchange of both heat energy and matter
First law of thermodynamics
Change in Internal Energy = Energy transferred to system - Work Done by System
What equation is used for Non-Flow Processes?
PV = NKT
What is the 1st Law of Thermodynamics for a isothermal process?
Q = W
What is the equation for the change in internal energy for a non-flow process?
Change in internal energy = Q - PChangeinVol
Change in internal energy for an isochoric process
Change in internal energy = Q
What is the change in internal energy for an adiabatic process?
-W
What is the Molar Heat Capacity?
The heat energy required to raise the temperature of 1mol of an ideal gas to be raised by 1K
What is the Molar Heat Capacity equation for an isochoric equation?
Change in Internal Energy = nCvChangeinTemo
What is the Molar Heat Capacity equation for an isobaric equation?
Change in Internal Energy = nCpChange in temp - pChangeinVol
What is Enthalpy(H)
It is the heat energy transferred in a process at constant pressure
What is the Enthalpy equation?
Change in H = Change in internal energy + pchangeinV
How to use a PV graph to find work?
The work is the area under the PV diagram
How to identify an isotherm?
The value of PV is always constant
What difference is there between an isotherm and adiabatic curve?
An adiabatic curve is steeper than a isotherm curve
How to identify an isochoric process?
An isochoric is a straight vertical line on a PV graph
How to identify an isobaric process?
A straight horizontal line on a PV graph
How to calculate the net Work Done in a cyclic process?
Area enclosed within the loop
Process of 4-stroke Petrol Engine?
Induction, Compression, Expansion and Exhaust
What is the Second Law of Thermodynamics?
The entropy of a closed system always increase
What is Entropy?
A measure of disorder in a system
Given time a system will always tend towards disorder
Happens spontaneously and does not need energy
How does heat flow work in a source?
A heat source will always flow towards a heat sink
Thermal equilibrium is the state of highest entropy
How does the heat engine process work?
Source at Temperature Th provides heat energy Qh
Heat allows process to occur which does Work
Sink at Temperature Tc absorbs heat energy Qc
How to find efficiency of heat engine process?
Qh -Qc / Qh
How to find theoretical maximum efficiency?
Th - Tc / Th
What is the Coefficient of Performance?
A measure of how much heat energy is transferred for the work done
What is the CoP for a refrigerator or air conditioner?
Qc / Qh - Qc
or
Tc / Th - Tc
What is the CoP for a heat pump?
Qh/Qh-Qc
or
Th/Th-Tc
