Engineering Thermodynamics
Thermodynamics is bookkeeping with a direction attached: the first law says the books must balance, the second says which way the entries can go. These topics animate the boundary and the flows across it.
Start from the beginning →8 topics you can watch now, 14 still to come.
Foundations
Systems, boundaries, properties and states — the vocabulary everything else is written in.
- System, Boundary and SurroundingsStart here. Draw three different boundaries round the same piston and watch the answer change each time.
- The Zeroth Law and TemperatureThree bodies drift into equilibrium, and the law that sounds trivial turns out to be the only reason a thermometer works.
- Properties, state and equilibrium
- Processes and cycles
The first law
Energy is conserved — applied to closed systems, then to flows.
- The First Law for a Closed SystemJoule's experiment: raise the same internal energy twice, once by heat and once by work, and watch the bar land in the same place.
- Enthalpy and the Steady Flow Energy EquationEnthalpy derived rather than declared — flow work always travels with internal energy, so the two are grouped once and never parted.
- Specific heats
- Compressors, nozzles and diffusers in detail
The second law
Why energy being conserved is not enough to make it useful.
- Why the First Law Is Not EnoughA machine whose energy books balance perfectly, and which nobody has ever built — then the two statements that explain why.
- The Carnot CycleWalk the four processes with the piston moving alongside, and find an efficiency that depends on nothing but two temperatures.
- Entropy and the Principle of IncreaseEntropy derived from Carnot rather than asserted — and one bar that is never allowed to fall.
- Heat engines, refrigerators and COP
- Availability and irreversibility
Properties of pure substances
Steam tables, and what a phase diagram is actually recording.
- Phase change and the p-v-T surface
- Dryness fraction and steam tables
- Mollier diagram
- Ideal gas and real gas equations
Power and refrigeration cycles
The arrangements engineers actually build.
- Brayton cycle
- Rankine cycle and reheat/regeneration
- Vapour compression refrigeration
- Psychrometry
About Engineering Thermodynamics
Thermodynamics is bookkeeping raised to a physical law, and then a second law that says the bookkeeping is not symmetric. The first law says energy is conserved; the second says that of all the conserving processes, only some actually happen. Almost every result in the subject is a consequence of that asymmetry.
Getting the definitions right early matters more here than in most subjects. What counts as the system, where its boundary lies, and what crosses that boundary determine every sign in every equation. A large share of confusion in thermodynamics is really confusion about the boundary.
Entropy is the idea students find slipperiest, and the one most worth the effort. It is the property that distinguishes a process that can be undone from one that cannot, and it sets a hard ceiling on the efficiency of every engine — a limit no design will ever engineer around.
What to know first
- Basic mechanics — work, energy, pressure
- Comfort reading a property table or chart
Where it gets used
- Understanding why no engine or refrigerator beats its ideal efficiency
- Reading an engine or refrigeration cycle on a property diagram
- Assessing an energy-saving claim for whether it is even permitted