Work in thermodynamic processes W=FΔd W=PAΔd W= - PΔV
Processconditions first law Isobaricboth temp ΔU=Q+W and volume change Isovolumetricno workΔV=0 so W=0 so ΔU=Q Isothermalno change ΔU=Q+W=0 in T or U so Q= - W Adiabaticno energyQ=0 transfer asso ΔU=W heat
PV diagrams and thermodynamic processes (quick quiz 12.2) Identify the paths
PV diagram of a cycle
Newcome Steam engine
Otto cycle Otto Engine
Diesel cycle Diesel Engine
Efficiency of an engine Work out Energy in e = W Q H
Sadi Carnot Reflections on the Motive Power of Fire Efficiency of a heat engine Theoretical maximum Began the understanding that became the second law of thermodynamics. –entropy
The Carnot Engine
Carnot Engine No real engine operating between two energy reservoirs can be more efficient than a Carnot engine operating between the same two reservoirs. e c = T H -T C T H
Three engines operate between reservoirs separated in temperature by 300 K. The reservoir temperatures are: a) T h =1000 K T c =700 K b) T h =800 KT c =500 K c) T h =600 KT c =300 K Rank the engines in order of their theoretical maximum efficiency.
Second Law of Thermodynamics No heat engine operating in a cycle can absorb energy from a reservoir and use it entirely for the performance of an equal amount of work. You cant have a totally efficient engine. In any closed system, entropy always increases.
Out: Which of these processes are isothermal, isovolumetric, or adiabatic: a)A tire being rapidly inflated b)A tire expanding gradually at a constant temperature c)A steel tank of gas being heated