Heat, energy, and engines

Energy is conserved, but it degrades

The first law of thermodynamics says energy is never created or destroyed, only converted — chemical to heat in a flame, heat to motion in an engine, motion to electricity in a generator. The second law adds the catch: every conversion wastes some energy as low-grade heat, and heat only flows downhill, hot to cold, on its own.

Together these two laws explain engines (burn fuel hot, dump waste heat cold, harvest the difference as work), refrigerators (pumping heat uphill costs work — that is why the back of the fridge is warm), and why no machine, ever, will be 100% efficient.

Fluids: the other half of the story

Liquids and gases carry energy and exert forces too. Moving fluid trades pressure for speed (how wings generate lift), sticky fluids resist flow (viscosity — honey vs water), and those ideas size everything from water pipes to jet engines. In polymer engineering, viscosity is daily business: molten plastic must flow through molds, and resin must soak through fiber cloth before it cures.

Temperature runs polymer manufacturing

Chemical reactions speed up roughly exponentially with temperature — the Arrhenius law. Curing a thermoset laminate is a controlled version of this: hotter cure runs faster, but the reaction itself releases heat, and a thick part that traps that heat can overheat from the inside. Getting a wing skin cured evenly is thermodynamics, heat flow, and chemistry cooperating. The cure kinetics simulation lets you play with exactly this trade-off between temperature, time, and degree of cure.