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HEAT TRANSFER DURING BOILING AND CONDENSATION IN MICROCHANNELS
Júlio César Passos
Universidade Federal de Santa Catarina
Centro Tecnológico - Departamento de Engenharia Mecânica
LEPTEN/Boiling
Laboratórios de Engenharia de Processos de Conversão e Tecnologia de Energia
Motivation
DVolume
AreaSurface 1
• High heat transfer coefficient during flow boiling and flow condensation. • The surface area to volume ratio increases with the decrease of the diameter.
• Refrigeration and air conditioning account for a significant proportion of electricity usage.
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Contents • Motivation, • Macro and micro scale, • Confined pool boiling • Two-phase flow regimes in microchannels • Flow boiling in microchannels (LEPTEN/UFSC results) • Conclusions of the Part A • Condensation in microchannels (Theoretical analysis) • Flow condensation in microchannels (LEPTEN/UFSC results) • Conclusions of the Part B
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Macro and micro scale
• Criterium for considering micro and macro scale
Confinement number: Kew and Cornwell (1997)
5.0
2
1
2
h
c
vl D
L
DgCo
h
• Kandlikar and Steinke (2003) propose:
mDm h 20010 for considering micro channel.
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Confinement number and transition diameter from micro to macro
Fluid Tsat
(oC) P
(bar) l
kg.m-3)
v kg.m-3)
mNm-1
Lc
(mm)
Dtran (mm)
Co=0.5
Water 99.6 1 959 0.6 59.0 2.50 5.0
FC72 55.9 1 1603 13.1 12.0 0.88 1.75
R134a - 26.4 1 1378 5.2 15.5 1.07 2.14
R134a 33 8.4 1176 41 7.02 0.80 1.60
HFE7100 59.6 1 1373 9.6 15.7 1.08 2.17
n-Pentane 35.9 1 603.6 2.9 14.3 1.56 3.11
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
q=20 k
W/m
2
s=0.2 mm Tw=63.1
oC s=0.5 mm Tw=64.4
oC s= 1 mm
Tw=65.5oC
q=40 k
W/m
2
s=0.2 mm Tw=75.5
oC s=0.5 mm Tw=68.1
oC s= 1 mm
Tw=69.3oC
Confined pool boiling
in Passos et al. (2005) ETFS, Elsevier, Vol. 30, pp. 1-7.
Heat
s
Heat (C)
(NC)
Flow boiling in microchannels
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Two-phase flow visualization in a microchannel
Two-phase air-water test rig,
at LEPTEN-UFSC.
In Barreto, E.X., Oliveira, J.L.G., Passos, J.C., Frictional pressure drop and void fraction analysis in air-water
two-phase flow in a microchannel, IJMF/ELSEVIER, Vol. 72, pp. 1-10, 2015.
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
jg= 0.12 0.12 0.80 0.80 6.40 0.12 0.80 0.80 6.40 18.60 18.60 26.7 jl= 0.53 3.50 3.50 1.37 3.50 0.10 0.95 0.70 1.37 2.65 3.50 3.50
jg and jl in m/s In Barreto, E.X., Oliveira, J.L.G., Passos, J.C., Frictional pressure drop and void fraction analysis in air-water
two-phase flow in a microchannel, IJMF/ELSEVIER, Vol. 72, pp. 1-10, 2015.
Two-phase flow visualization in a microchannel
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
jg and jl in m/s jg= 0.80 6.40 6.40 10.50 18.60 34.80
jl= 0.10 0.10 0.53 0.53 0.53 0.53
In Barreto, E.X., Oliveira, J.L.G., Passos, J.C., Frictional pressure drop and void fraction analysis in air-water
two-phase flow in a microchannel, IJMF/ELSEVIER, Vol. 72, pp. 1-10, 2015.
Two-phase flow visualization in a microchannel
A
xm
A
mj
g
g
..
A
xm
A
mj l
l
)1(...
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
In Barreto, E.X., Oliveira, J.L.G., Passos, J.C., Analysis of air-water flow patterns in parallel microchannels: a
visualization study, ETFS/ELSEVIER, Vol. 63, pp. 1-8, 2015.
Two-phase flow visualization in
7 parallel microchannels
The gas quality in the inlet manifold is given.
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Scale effects on macro and micro scale: forces per unit area
Inertia force
2
2
22'' G
D
DVFi
Surface tension force
DD
DF
2
'' cos
: specific mass of the fluid (kg.m-3)
: surface tension (N.m-1=J.m-2) : contact angle of the interface liquid-vapor
In: Kandlikar, S.G., Scale effect on flow boiling heat transfer in microchannels: A fundamental perspective, Int. J. of Thermal Sciences, vol. 49, pp. 1073-1085, 2010.
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Forces per unit area (cont.)
Shear force
D
G
D
V
D
DD
V
F
2
2
''
Gravity (buoyancy) force
gD
D
gDF vl
vlg
2
3''
: fluid viscosity (Pa.s) .
: accelaration due to gravity (m.s-2)
g
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Forces per unit area (cont.)
Evaporation momentum force
vfg
QMh
qF
1"2
''
: heat flux on the tube surface (Wm-2) "q
: latent heat of vaporization (J.kg-1) fgh
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Scale effect on flow boiling
Effect of the tube diameter on different types of forces during boiling of water
In: Kandlikar, S.G., Scale effect on flow boiling heat transfer in microchannels: A fundamental perspective, Int. J. of Thermal Sciences, vol. 49, pp. 1073-1085, 2010.
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Scale effect on flow boiling (cont.) In Kandlikar (2010)
Effect of the tube diameter on different types of forces during
boiling of water
Effect of the tube diameter on different types of forces during
boiling of R-123.
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Scale effect on flow boiling (cont.)
In Kandlikar (2010)
Effect of the tube diameter on different types of forces during boiling of water
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Main characterisitics
Boiling flow in Microchannels
h
Dp
Surface tension force
Gravity force
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Flow configurations
During flow boiling, the presence of annular flow or intermittent flow regimes are predominant due to capillary effects. The stratified flow regime is more rare.
Yan e Lin (1998), IJHMT, v. 41, pp. 4183 – 4194.
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Boiling flow patterns and transitions
Bubbly flow at x=3.8%
Bubbly/Slug flow at x=4%
Slug flow at x=4.3%
Slug/Semi-Annular flow at x=7.6%
Semi-Annular flow at x= 15%
Wavy Annular flow at x=23%
Smooth Annular flow at x=23%
[U1]
In Revellin and Thome, 2007, Int. J. of Heat and Fluid Flow, Vol. 28, pp.63-71. Flow Patterns and transitions for
R245fa, d=0,5 mm, L=70,70 mm, G=500 kg/m2s and Tsat=35 oC.
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Boiling flow patterns (Revellin and Thome (2007)
[U1]
In Revellin and Thome, 2007, Experimental investigation of R-134a and R-245fa two-phase flow in
microchannels for different flow conditions, Int. J. of Heat and Fluid Flow, Vol. 28, pp.63-71.
Schematic diagram of the test section
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Flow regimes
[U1]
Flow patterns observed by Cornwell and Kew (1993) during
flow boiling of R113 in 2 x 0.9mm2 parallel rectangular channels.
q”=3 to 33 kW/m2
Low quality High quality
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Flow visualiation by
Hara et al. (2010)
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Flow maps: adapted by Revellin et al. (2006)
Bubbly Intermittent
Annular
Intermittent/Annular
Vapor superficial velocity (m/s)
Liq
uid
su
per
fici
al v
elo
city
(m
/s)
Air-Water D=1.097 mm
R-134a D=0.509 mm
Modified transition lines Transition lines (Tripplet et al., 1999)
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Flow regimes: effect of the diameter on the transition lines
[U1]
Fluido: R-134a a 30º C; q”=60kW/m2 (Revellin and Thome (2007))
Vapor quality
Mass v
elo
city,
G (
kg/m
2s)
Dryout
Annular
CB IB
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Case study:
Pressure drop and heat transfer coefficient during the R-134a convective
boiling inside microchannels
Results obtained in the thesis of
Evandro Rodrigo Dario
R-134a CONVECTIVE BOILING INSIDE MULTIPARALLEL MICROCHANNELS AND ANALYSIS OF THE MALDISTRIBUTION AIR-WATER MASS FLOW RATE
WITHIN THE INLET MANIFOLD CONNECTED TO MICROCHANNELS
Advisor: Júlio César Passos; Co-advisor: Lounès Tadrist POSMEC/UFSC e Aix Marseille Université
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Flow boiling inside parallel microchannels forçada
Scheme of the R134a circuit, LEPTEN/Boiling, in Dario (2013).
Test section (Dario, 2013)
L=150 mm Heated length, Lheat=120 mm
Dh=0.77±0.1 mm
(1) Microchannels (copper tubes) (2) Copper plates (3) Skin heaters (4) Teflon blocks (5) Manifolds
Experimental data in the flow patterns proposed by Revellin e Thome (2007)
in Dario (2013)
Annular Dryout CB
IB
Experimental data
Local quality, x
Mas
s ve
loci
ty. K
g/m
2s
The different contributions to the pressure drop
R-134a, G= 1002 Kg/m2s, Pin= 605 kPa
Thesis of Dario (2013), and Dario et al. (2015) accepted to the Int.
Conference on Boiling and Condensation , Boulder-CO/USA
Pressure drop: Comparison of experimental data with semi-empirical models
[U1]
Lee and Mudawar (2005) consider the R134-a boiling flow inside 53 parallel channels with
Dh=0.35 mm For the Homogeneous model 1
l
v
u
uS
?
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Thesis of Dario (2013), and Dario et al. (2015) accepted to the Int.
Conference on Boiling and Condensation , Boulder-CO/USA
Onset of nucleate boiling
(a) Heat flux;
(b) Inlet pressure;
(c)Mass velocity; (d) Pressure drop; (e) Wall
temperature.
Time (s)
Two phase flow Single phase flow
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Boiling curves
ONB
Hea
t fl
ux,
”
At T 7
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Boiling curves
ONB
At T 7
Hea
t fl
ux,
kW
/m2K
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Boiling curves
smkgG 2/1001
smkgG 2/503
smkgG 2/252
Hea
t fl
ux
At T7
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Heat transfer coefficient as function of quality on the flow pattern map of
Revellin and Thome (2007)
Dry
ou
t
HT
C, CB
IB
Vapor quality, x
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Experimental points obtained by
Dario (2003) in his thesis.
Heat transfer coefficient as function of quality on the flow pattern map of
Revellin and Thome (2007)
Dryout
CB IB
HT
C,
Vapor quality, x
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Experimental points obtained by
Dario (2003) in his thesis.
Heat transfer coefficient as function of quality on the flow pattern map of
Revellin and Thome (2007)
Dario (2013)
HT
C,
Dryout
IB CB
Vapor quality, x
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
BOILING FLOW INSIDE AN ANNULAR CROSS SECTION MICROCHANNEL
The next results were obtained in the Master of Science of Evandro Rodrigo Dario
Advisor: Júlio César Passos LEPTEN/POSMEC/UFSC – March 2008.
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Convective boiling in microchannels
n-Pentane G=253 kg/m²s q”= 25 kW/m2
n-Pentane G=169 kg/m²s q”= 12.5 kW/m2
MSc of Dario (2008)
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Test section
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Boiling flow visualization (1)
G = 148 kg/m2s
Liquid-vapor interface
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
G = 190 kg/m2s
Boiling flow visualization (2)
On increasing the mass velocity and the heat flux the liquid-vapor interface becomes less defined. On increasing the heat flux increase the number of active nucleation sites. Occurs the trend to stratify the flow with big bubbles on the upper region of the channel.
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
G = 274 kg/m2s
Boiling flow visualization (4)
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Conclusions
• The flow regime maps needs to be improved in order to predict dryout heat fluxes for a wide operational conditions and fluids;
• There is still insufficient data for heat transfer coefficient in
convective boiling inside microchannels of organic fluids, in particular CO2.
• Inlet two-phase flow represents a typical condition in the evaporators of a refrigerant system and can affect the heat transfer coefficient because the early dryout caused by the maldistribution of mass flow rate.
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Flow condensation in microchannels
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Chiller condenser
http://www.carriercca.com
MPE-MultiPort Extruded Aluminium tubes
used in microcondensers
www.hydro.com
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
State of the art
Condensers employing microchannel (MC) in aluminum profiles MPE have been used successfully in automotive
air condicioners for around 25 years.
Available experimental heat transfer data for condensation in MC are widely scattered.
A great number of researchers obtained the HTC by using the Wilson plot methods, such data have high
uncertainty.
In: Wang and Rose (IJHMT, vol. 54 (2011), pp. 2525-2534) 4th Brazilian Meeting of Boiling , Condensation and
Multiphase Flows UNICAMP – March 27 2015
Literature review – Effect of the
channel shape
• Numerical solution for annular regime, Wang and Rose (2006).
53
Wang and Rose (2006, 2011) is based on the
assumptions of Nusselt (1916) but includes the
streamwise shear stress on the condensate film
surface as well as the transverse pressure
gradient due to surface tension in the presence
of change in condensate surface curvature. The surface tension has negligible effect.
Nusselt (1882-1957)
Ernst Kraf Vilhelm Nusselt
Published, in 1916,
“Die Oberflachenkondensation des
Wasserdampfes”, Z. Ver. Deut. Ing., Vol.
60, 541, 1916.
4th Brazilian Meeting of Boiling , Condensation and
Multiphase Flows UNICAMP – March 27 2015
The Nusselt model for film condensation
gρρμ
1
dy
udvl
l
2
2
y=0, u=0 ,
y=d,
Boundary conditions
2
l
2
vl
δ
y
2
1
δ
y
μ
δρρgu(y)
0dy
du
y
Laminar =
smooth interface
30deR
Laminar
with waves
1800deR
Turbulent region
1800Re30 d
30deR
(1)
(2)
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
The Nusselt model (2)
.
md
.
mdhdq lv
..
mdm
.
m
dxbq ."
sup
.
mdhdq lv
dxbqdq ."
sup
lv
satl
lv h
TTk
h
q
dx
d
.
sup
"
sup
d
.
mdhdq lv
dxbqdq ."
sup
dx
dg
dx
d
l
vll d
d 2
4
1
sup4
lvvll
atll
hg
xTTkx
d
s
xd x;
Jahh lvlv 68,01'
correction
Ja: Jakob number
dxx
x
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
The Nusselt model (3)
dl
x
kh
4
1
sup
'3
4
xTT
hkgh
atl
lvvll
xl
s
sup
"
sup ssatx TThq
The local hx
decrease with x.
4
1
sup
'3
943.0
LTT
hkgh
atl
lvvll
Ll
s
After integration
4
1
sup
3'
943.0
TTk
LhgNu
atll
lvvll
L
s
Properties at:
2
supTTT
sat
f
satlvv Tathand
'
sup
'
.
lv
satL
lv h
TTAh
h
qm
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Advisor: Júlio César Passos; Co-Advisor: Saulo Güths LEPTEN/POSMEC/UFSC – defended in March 06 2015.
CONVECTIVE CONDENSATION WITHIN AN ALLUMINIUM PROFILE-MPE CONTAINING
EIGHT PARALLEL MICROCHANNELS
The next results were obtained in the Master of Science of Guilherme Piazza Zanette
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Experimental setup: R-134a condensation loop
Main elements of the experimental set up
1 Heat chamber 6 Filter
2 Superheater 7 Micro-pump
3 Mass flowmeter 8 Thermal baths
4 Test section A Test section bypass
5 Post-condenser B Experimental setup bypass
Schematic diagram of the test section
1 – MPE profile (Multi-Port Extruded);
2 – Manifolds;
3 – Copper Plates;
4 – Heat Fluxmeters;
5 – Heat Sinks;
6 – Plexy Glass Structure.
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Test section – MPE profile
• Multi-Port Extruded
• Commercial Profile
• Aluminium 3003
• Eight Microchannels
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Dimensions of the test section – MPE
LABMETRO/CERTI
Central Channels
Lateral Channels
Average Deviation
Hydraulic Diameter
Total Length
Mean Roughness
Thickness
m
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Heat flux meter
Copper plate
Aluminium
profile-MPE
Heat
Flux
meter
Heat Flux meter
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Flow regimes 76.060.0 Co
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Vapor quality
Average heat transfer coefficients
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
ha
vera
ge (W
/m2K
)
Advisor: Júlio César Passos LEPTEN/POSMEC/UFSC –May 24 2011.
HEAT TRANSFER AND PRESSURE DROP DURING THE CONDENSATION OF R-134a IN PARALLEL
MICROCHANNELS
The next results were obtained in the Master of Science of Gil Goss Jr.
GOSS Jr., G.;PASSOS, J.C. Heat transfer during the condensation of R134a inside eight parallel microchannels, International Journal of Heat and Mass Transfer, v.59, p. 9–19, 2013.
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Test section
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
(1)Microchannels
(2) Copper plate
(3) Cooler Peltier
(4) Copper plate (5) Heat sink
Flow regimes
Test conditions
230 kg.m-2.s-1 < G < 445 kg.m-2.s-1
17 kW.m-2 < q” < 53 kW.m-2 0.55 < xv < 1
7.3 bar < p < 9.7 bar 28 oC < Tfluid < 38 oC
0 < Rel < 616 6621 < Rev < 28145
Eo=50 and Co=1.1
Condensation flow regime map of Coleman and Garimella
Annular/Mist Mist
Annular
Disperse
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Vapor quality
Condensation of the R134a
Test section: microchannel with 0.8 mm diameter
Cooling flow: ethylene-glycol
in the annular space LEPTEN-UFSC
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Visualization: R-134a flow condensation (Microchannel with 0.8 mm diameter), LEPTEN/UFSC results
a) Annular flow (p=6.0 bar; m=183 g/s)
b) Annular flow with waves (p=6.7 bar; m=217 g/s)
c) Intermittent flow (p=6.6 bar; m=182 g/s)
d) Bubbly flow (p=6.4 bar; m=177 g/s) Liquid slug Taylor bubble
Liquid ring
Liquid rings
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Video (LEPTEN-UFSC)
R-134a flow condensation
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Conclusions
• Experimental heat transfer data for condensation in microchannels are widely scattered (Wang and Rose, 2011)
• The Wilson-plot technique is not appropriated for determining the HTC, in microchannels;
• The experimental determination of HTC for condensation
presents additional challenges; • For the heat transfer phenomenon, the formulations developed
for conventional channels do not work with the same precision in microchannels (Goss Jr. and Passos, 2013);
• Further research is need.
4th Brazilian Meeting of Boiling , Condensation and
Multiphase Flows UNICAMP – March 27 2015
Thank you very much for your attention!
4th Brazilian Meeting of Boiling , Condensation and Multiphase Flows
UNICAMP – March 27 2015
Many thanks to the organizers of the JEM-2015 for the invitation!