WATER - wiki.epfl.ch
Transcript of WATER - wiki.epfl.ch
OIL
WATER
OilTh,in = 100 °Ccp,h = 1.9 kJ/kgKmh = 2.6 kg/s
WaterTc,in = 40 °C; Tc, out = 80 °Ccp,h = 4.18 kJ/kgKmh = 1.0 kg/s
Th,in = 100 °C
Tc,in = 40 °CTc,out = 80 °C
1. Energy Balance
Qcold = mc⸱cp,c⸱ΔTc = 167200 W
Qhot = Qcold
Qhot = mh⸱cp,h⸱ΔTh
Th,out = Th,in - Qhot/mh⸱cp,h = 66.15 °C
2. Effectiveness method
ε = f(Cmin/Cmax, NTU) = 0.67
Cc = mc⸱cp,c = 4180 W/K = Cmin
Ch = mh⸱cp,h = 4940 W/K = Cmax
Cmin/Cmax = 0.85
NTU = UA/Cmin = 2.2 U = Cmin ⸱ NTU/A = 460 W/m2K
LMTC =
3. LMTD method
P = 0.67
R = 0.85F = 0.80 U = 455 W/m2K
Mercury
Water
Th,in = 65.6 °C
Tc,in = 21.1 °C
Th,out = 53.3 °CMercuryTh,in = 65.6 °C; Th,out = 53.3 °Ccp,h = 139,4 J/kgKmh = 0.83 kg/s
WaterTc,in = 21.1 °Ccp,h = 4.18 kJ/kgKmh = 0.028 kg/s
1. Energy Balance
Qhot = mh⸱cp,h⸱ΔTh = 1415 W
Qhot = Qcold
Qcold = mc⸱cp,c⸱ΔTc
Tc,in = Tc,out + Qcold/mc⸱cp,c = 33.2 °C
2. LMTD method
F = 1(it is a perfectly countercurrent arrangement)
LMTD = 32.6 K
A = 0.145 m2
Rfouling = U-1fouling - U
-1design
U-1design = ∑Ri
U-1fouling = ∑Ri + Rfouling
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Th,in = 160 °C
Tc,in = 25.0 °C
Th,out = 70.0 °C
Tc,out = 80.0 °C
Fouling condition
Qfouling = 0.7 Qdesign
Th,out,fouling = 90 °C
1. Energy Balance
Qfouling = 0.7 Qdesign
mcp(Tc,out,fouling - Tc,in) = 0.7mcp(Tc,out - Tc,in)
Tc,out,fouling = 0.7Tc,out + 0.3Tc,in = 63.5 °C
2. LMTD
LMTDdesign = 60.8 K
LMTDfouling = 79.7 K
3. Correction factors
Pdesign = 0.67
Rdesign = 0.61
Fdesign = 0.80
Pfouling = 0.52
Rfouling = 0.55
Ffouling = 0.95
4. Energy Balance + LMTD
Qfouling = 0.7 Qdesign
Ufouling A LMTDfouling Ffouling= 0.7 Udesign A LMTDdesign Fdesign
Ufouling = 0.7 Udesign LMTDdesign / LMTDfouling Fdesign / Ffouling= 899 W/m2K
5. Fouling resistance
Rfouling = U-1fouling - U
-1design = 6.1235e-04 m2K/W
WaterTc,in = 17 °CTc,out = 27 °Ccp,h = 4.18 kJ/kgK
SteamTh,in = Th,out = 40°Chlv = 2406 kJ/kg
1. Energy Balance
Q = msteamhlv = 6.6833e+05 kW
mwater = Q/(cpΔT)water = 1.5989e+04 kg/s
2. Effectiveness
ε = ΔTwater/ΔTmax = 0.43478NTU = UA/Cmin = 0.57
A = Cmin ⸱ NTU/U = 8105.4 m2