Formules examen energie.
Grootheden met hun eenheden
W = Arbeid [J]
- W > 0: arbeid toevoegen aan systeem
- Arbeid per eenheid massa (w = W/m) = [J/kg]
- arbeid = druk. volume w = p.v (slide 68: intro thermo)
Q = warmte [J]
- Q > 0: warmte toevoegen aan systeem
- Warmte per eenheid massa (q = Q/m) = [J/kg]
U = inwendige energie [KJ/kg = 1000J/kg]
P = druk [Pa = N/m2] [1 bar = 105 PA]
- Bar = atmosferische druk
- bara = absolute druk
- barg = relatieve druk
T = temperatuur [K, C° = 273,15 K]
V = Volume [m3]
- Specifiek volume = volume per massa-eenheid (v = V/m) = [m3/kg]
EXTRA
p. V en T hebben functioneel verband => Als twee van deze grootheden zijn bepaald binnen het
werkfluidum dan weet je ook de derde grootheid. Je weet dat ook de toestand.
m = Massa [kg]
ρ = dichtheid/specifieke massa/soortelijk gewicht [kg/m3]
- ρ = 1 / v = 1/ (V/m)
ḿ = Massadebiet [kg/s]
- ḿ = ρ. A . c
A .c
- ḿ = (1/v). A . c =
v
ḿ. v
A= (slide 49: intro thermodynamica)
c
c = snelheid van fluidum [m/s]
P = vermogen [W = 1J/s]
- Pth = thermisch vermogen = dQ/Dt = Q́
- Pm = mechanisch vermogen = dW/dt = Ẃ
- J = Ws
- 1 kWh = 3.6 MJ
- kWh = 1000 watt gedurende een uur
h = enthalpie [J]
= u + p.v = inwendige energie + product van druk en specifiek volume
Eenheden: J +( N/m2). m3
= toestand van de energie, hoe de druk binnen het systeem werkt en dan ook nog eens druk
zet op de omgeving
= energie van het systeem zelf en de energie die bestaat met de *
omgeving.
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