Lecture 1 - Introduction Flashcards
Formula for energy required to change temperature Q=
Mcp(T1-T2)
What is thermodynamics?
Thermodynamics focuses on transferring work into heat and heat into work
What is heat transfer?
Heat transfer looks at the movement of heat, no work is done
What is fluid dynamics?
The movement of fluid
What are the three types of system?
Closed system
Open system
Isolated system
What happens in an open system?
Heat and mass can be transferred
What happens in a closed system?
Heat can be transferred but mass cannot
What happens in an isolated system?
No heat or mass can be transferred to a system
What is the first law of thermodynamics?
When any closed system is taken through a cycle the net work delivered to the surroundings is proportional to the net heat taken from the surroundings
What is the simplified version of the first law of thermodynamics?
Energy in = energy out
What is the equation deduced from the first law of thermodynamics?
The non flow energy equation
What is internal energy a property of?
The fluid
What is the non flow energy equation?
Q - W = deltU
Heat - Work done = Change in internal energy
In an adiabatic process how can the non flow energy equation be simplified?
No heat transferred to or from the system; therefore Q = 0
-W = deltaU
What happens in an adiabatic expansion?
Work is done at the expense of the internal energy of the system
What happens in an adiabatic compression?
Work is done on the system by the surroundings, causing a rise in internal energy
How is the non flow energy equation simplified in a constant volume process?
Work done by the system is zero
W = 0
Q = deltaU
What happens to heat in a constant volume system?
Heat supplied across the system boundary for a closed system is equal to the change in internal energy of the system
If a constant pressure process is reversible how can the non flow energy equation be written?
deltaW = pdv
dQ - pdv = du
Since P is constant after integrating
Q - p(v2 -v1) = u2 - u1
What is enthalpy?
Enthalpy is the amount of heat content used or released in a system at constant pressure
Mathematical definition of enthalpy
u + pv = h
What is the difference between enthalpy and internal energy?
Reversible constant-volume processes: heat added is equal to the increase in internal energy
Constant pressure processes: heat added is equal to the enthalpy increase
Where did the majority of worlds power come from?
Oil
What has happened to the UK’s energy supply in recent years and why is this?
Big decrease in supply from coal, increase in gas supply as well as nuclear and renewables
What is the largest consumer of energy in the UK?
Industry and domestic which use approximately 34% of each
What is the advantage of gas turbine powerstations over coal stations?
Smaller
More compact
Much faster response
Much higher energy output (3MW vs 500MW)
1kWh is equal to how many joules?
1000W * 60s * 60s = 3.6MJ
What is a system?
Loosely defined as a region in space containing a quantity of fluid
