GPE-EPIC 14-17 June 2009 - Venice (Italy)
2nd International Congress on Green Process Engineering 2nd European Process Intensification Conference
EVOLUTION OF VELOCITY AND TURBULENCE DISSIPATION RATE IN THE EXTRAPOLATION OF EXCHANGER SIZE
LEMENAND Thierry, DELLA VALLE Dominique, DUPONT Pascal and PEERHOSSAINI Hassan Thermofluids, Complex Flows and Energy Research Group, Laboratoire de Thermocinétique de Nantes, CNRS UMR 6607, Nantes, France
OBJECTIVES STUDIED FLOW
RESULTS
CONCLUSIONS
Convective velocity U
convTurbulent Dissipation Rate ε
0,0 0,2 0,4 0,6 0,8 1,0
0,0 0,2 0,4 0,6 0,8 1,0 1,2
Uconv (m/s)
y/R Inlet Re=15000
54 mm 20 mm
0,0 0,2 0,4 0,6 0,8 1,0
0,0 0,2 0,4 0,6 0,8 1,0 1,2
Uconv (m/s)
y/R Outlet Re=15000
54 mm 20 mm
0,0 0,2 0,4 0,6 0,8 1,0
1E-3 0,01 0,1 1
ε (m2s-3)
y/R Inlet Re=15000
54 mm 20 mm
0,0 0,2 0,4 0,6 0,8 1,0
0 2 4 6 8 10 12 14 16 18
ε (m2s-3)
y/R Outlet Re=15000
54 mm 20 mm
0,0 0,2 0,4 0,6 0,8 1,0
0,000 0,005 0,010 0,015 0,020 0,025 0,030 0,035
ε D/Uconv
3
y/R Inlet Re=15000
54 mm 20 mm
0,0 0,2 0,4 0,6 0,8 1,0
0,0 0,2 0,4 0,6 0,8 1,0
ε D/Uconv
3
y/R Outlet Re=15000
54 mm 20 mm
Test section 1st tab array
Fluctuant velocity U
rms0,0 0,2 0,4 0,6 0,8 1,0
0,00 0,04 0,08 0,12 0,16
Urms (m/s)
y/R Inlet Re=15000
54 mm 20 mm
0,0 0,2 0,4 0,6 0,8 1,0
0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 0,45
Urms (m/s)
y/R Outlet Re=15000
54 mm 20 mm
0,0 0,2 0,4 0,6 0,8 1,0
0,00 0,05 0,10 0,15 0,20 0,25
Urms/Uconv
y/R Inlet Re=15000
54 mm 20 mm
0,0 0,2 0,4 0,6 0,8 1,0
0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 0,45 0,50
Urms/Uconv
y/R Outlet Re=15000
54 mm 20 mm
The work consists to study the shape modification of the velocity and the turbulent dissipation rate in the size extrapolation and to test the traditional extrapolation laws, while comparing, in the two
flows, scales of turbulence at constant Reynolds number.
We have performed LDA measurements in the flow field in two static mixers (of diameters 20 mm and 54 mm) of HEV type (High
Efficiency Vortex).
The flow in this geometry is highly non uniform.
The turbulence is produced by small fins fixed at the walls of an empty duct.
The longitudinal vortices and the wake effects predominate over the wall turbulence.
The same geometry is at the base of the two flows obtained by a simple homothety.
Re=15000 D=20mm or 54mm
The extrapolation of Urmsby and ε by provide good results upstream of the flow and in the center downstream from the flow.
Further investigations are necessary to explain the behavior differences in the wake and in the shear layer.
LDA measurements for different Reynolds numbers will be make to test the Reynolds number effect.
We will study the length scales evolution and the shape modification of the turbulent spectra in the size extrapolation.
rms conv
U
U extrapolation
3 conv
D U
ε extrapolation
conv flow
U =U
rms conv
U
U conv3
D U
ε
⇒
⇓
⇓
( )
u'2 32=A Λ
2 2
1 5Urms2
U U
= +
