Processteknikens grunder (”PTG”) Introduction to Process Engineering v.2014 3. Energy conversion, balances, efficiency, equilibrium (Introduction to Thermodynamics) Ron Zevenhoven Åbo Akademi University Thermal and flow engineering / Värme- och strömningsteknik tel. 3223 ;
[email protected] Åbo Akademi University | Thermal and Flow Engineering | 20500 Turku | Finland 1/124 3.1: Energy Åbo Akademi University | Thermal and Flow Engineering | 20500 Turku | Finland 2/124 What is energy? /1 . ”Energy is any quantity that changes the state of a closed system when crossing the system boundary” (SEHB06) . ”Energy is the capacity to do work” (A83) . ”Energy is the capacity to do work or produce heat” (ZZ03) Åbo Akademi University | Thermal and Flow Engineering | 20500 Turku | Finland 3/124 What is energy? /2 . Energy cannot be produced or destroyed (First Law of Thermodynamics*) but it can be converted from one form into another, and vice versa. Energy can be degraded to lower quality, as a consequence of producing and converting heat (Second Law of Thermodynamics*) * sv: Termodynamikens Första och Andra Huvudsatsen Åbo Akademi University | Thermal and Flow Engineering | 20500 Turku | Finland 4/124 Types of energy /1 . In a closed system, energy is . These energies are all relative to a present (”stored”) as reference frame or reference state: potential energy* Ep and . potential energy relative to a kinetic energy** Ek position z = 0 in a gravity field (mechanical energy) and . kinetic energy relative to a non- internal energy*** U moving reference frame with (thermal energy) velocity v = 0 . For a mass m, with vertical . internal energy relative to zero position z in a gravity field and temperature T = 0, or surroundings velocity v defined as temperature T = T°.