MeOH and EtOH evaporating flow mechanisms in square and circular microchannels
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Transcript of MeOH and EtOH evaporating flow mechanisms in square and circular microchannels
Methanol and Ethanol Evaporating Flow
Mechanisms in Square and Circular
Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems, LTCES
Center for Innovation, Technology and Policy Research, IN+
Instituto Superior Tรฉcnico, Technical University of Lisbon
Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
APPLICATIONS
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Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
MOTIVATION
3
โข Microchannels
โ etched directly into the component
โข dielectric fluids
โ thermal resistances
โข integrate the microchannel structure into a layer that is closer to the heat producing device. This
removes layers of material in the thermal resistance path which can significantly improve the cooling of
the heat source
โข Flow boiling
โ heat removal rates
โ pumping power
โ โฌโฌ
Macrochannel Flow Pattern Maps simply fail to apply
Instabilities are prominent
Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
EXPERIMENTAL APPARATUS
4
Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
EXPERIMENTAL CONDITIONS
5
SCS_521CCS_543
Properties of the fluids (Tsat, 0.1MPa)
0 50 100 150 2000
200
400
600
800
q"s [kW.m-2
]
G [
kg.
m-2
.s-1
]
CH3OH CCS
542
CH3OH SCS
521
C2H
5OH CCS
542
C2H
5OH SCS
521
methanol
ethanol
Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
MEASUREMENTS
6
0 2 4 6 8 10 12 14 16 18 2010
20
30
40
time [s]
Pre
ssure
[kPa]
0 20 40 60 80 100
280
300
320
340
360
380
400
Tem
pera
ture
[K
]
Length [mm]
0 2 4 6 8 10 12 14 16 18 2020
250
300
350
400
450
time [s]
Tem
pera
ture
[K
]
outlet measured pressure
inlet measured pressure
0 0.5 1 1.5 2 2.5 3
4
6
8
10
Time [s]
Pre
ssure
Dro
p [
kPa]
0 20 40 60 80 100
0
2
4
6
8
h [
kW
.m-2
.K-1
]
Length [mm]
๐ท๐๐๐๐๐๐๐
๐ป๐๐๐๐๐๐๐๐๐๐
Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
PRESSURE DROP
7
โ๐ inlet
stagnation
chamber
โ๐ outlet
stagnation
chamber
โ๐๐๐๐inlet
contraction
โ๐๐๐ฅ๐outlet
expansion
โ๐๐๐ป๐,๐๐non-heated
entrance length
โ๐๐๐ป๐,๐๐ข๐กnon-heated
exit length
โ๐๐ป๐= ๐๐๐ โ ๐๐๐ข๐กheated length
โ๐๐๐๐= 1 โ๐ด๐๐ ๐ด๐๐ ๐
2
+ ๐พ๐๐๐1
2๐บ2๐๐ฟ
๐พ๐๐๐ = 0.0088๐ผ2 โ 0.1785๐ผ + 1.6027 ๐พ๐๐ฅ๐= - 2 x 1.33๐ด๐๐
๐ด๐๐ ๐1 โ
๐ด๐๐
๐ด๐๐ ๐
๐๐๐ = ๐๐๐๐๐ ,๐๐๐๐๐ก โ โ๐๐๐๐ โ โ๐๐๐ป๐,๐๐
โ๐๐๐ฅ๐,๐ ๐=1
2๐พ๐๐ฅ๐๐บ
2๐๐ฟ,๐
two-phase
โ๐๐๐ฅ๐,๐ก๐= ๐บ2๐ด๐๐ ๐ด๐๐ ๐
๐ด๐๐ ๐ด๐๐ ๐
โ 1 ๐๐ฟ,๐ 1 โ ๐ฅ๐๐ฅ๐๐ก2 1 +
5
๐๐๐+
1
๐๐๐2
๐๐๐ข๐ก = ๐๐๐๐๐ ,๐๐ข๐ก๐๐๐ก + โ๐๐๐ฅ๐ + โ๐๐๐ป๐,๐๐ข๐ก
๐๐๐ ๐๐๐ข๐ก
single-phase single-phase
๐๐๐๐๐ ,๐๐๐๐๐ก ๐๐๐๐๐ ,๐๐ข๐ก๐๐๐ก
Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
TEMPERATURE
8
๐๐ค,๐๐ = ๐๐ค,๐๐ข๐ก โ๐๐ " ๐ด๐๐ ๐๐ ๐ข๐
๐ ๐๐๐๐๐ท๐๐ท๐
2๐๐ฟ๐ป๐
๐ ๐ = 1
๐ ๐ = 0.785
๐๐ = ๐๐,๐๐ +๐๐ " ๐๐ค ๐ง
๐ ๐๐ฟ ๐๐,๐ฟ
๐๐ = ๐๐ ๐๐ก
๐๐ ๐๐ก = 1 โ๐ง
๐ฟ๐ป๐๐๐ ๐๐ก ๐๐๐๐๐๐ก +
๐ง
๐ฟ๐ป๐๐๐ ๐๐ก ๐๐๐ข๐ก๐๐๐ก
(Single-phase region)
(Two-phase region)๐ฟ๐ ๐๐ก = ๐ ๐๐ฟ ๐๐,๐ฟ ๐๐ ๐๐ก,0 โ ๐๐,๐
๐๐ " ๐๐ค
๐ป๐๐๐๐๐ ๐๐๐๐
๐ป๐๐๐๐๐
one dimensional heat conduction
Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
HEAT TRANSFER COEFFICIENT
9
โ =๐๐ "
๐๐ค,๐๐ โ ๐๐
๐๐ " =
๐ผ2๐
๐ด๐ป๐โ โ๐๐๐ ๐ ๐๐ค,๐๐ข๐ก โ ๐๐๐๐ โ ๐๐ ๐๐๐๐
4 โ ๐๐ค,๐๐ข๐ก4
60 90 120 1500
5
10
15
20C2H5OH
havg [
kW
.m-2.K
-1]
q"s [kW.m-2]
G=662kg.m-2.s
-1
G=483kg.m-2.s
-1
G=303kg.m-2.s
-1
G=214kg.m-2.s
-1
G=125kg.m-2.s
-1
SCS_521,
๐๐ = ๐๐ ๐๐ก
(Two-phase region)
square 521mm, ethanol
Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
HEAT TRANSFER COEFFICIENT
10
=โ โ โ๐ ๐โ๐๐
0.0 0.2 0.40
4
8
12CH3OH
havg [
kW
.m-2.K
-1]
Quality [-]
G=661kg.m-2.s
-1
G=482kg.m-2.s
-1
G=302kg.m-2.s
-1
G=214kg.m-2.s
-1
Local Vapor Quality [-]
hlo
cal[k
W.m
-2.K
-1]
0.0 0.2 0.40
4
8
12C2H5OH
havg [
kW
.m-2.K
-1]
Quality [-]
G=662kg.m-2.s
-1
G=483kg.m-2.s
-1
G=304kg.m-2.s
-1
G=214kg.m-2.s
-1
G=125kg.m-2.s
-1
Local Vapor Quality [-]h
local[k
W.m
-2.K
-1]
๐๐" = 91kW.m-2, ๐ป๐๐๐ =343K ๐๐
" = 99kW.m-2, ๐ป๐๐๐ =357K
square 521mm, methanol square 521mm, ethanol
Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
HEAT TRANSFER COEFFICIENT
11
-0.2 0.0 0.2 0.40
4
8
12C2H5OH
havg [
kW
.m-2.K
-1]
Quality [-]
q"
s=60kW.m
-2
q"
s=88kW.m
-2
q"
s=124kW.m
-2
Exit Vapor Quality [-]h
local[k
W.m
-2.K
-1]
-0.2 0.0 0.2 0.40
4
8
12CH3OH
havg [
kW
.m-2.K
-1]
Quality [-]
q"
s=45kW.m
-2
q"
s=66kW.m
-2
q"
s=92kW.m
-2
Exit Vapor Quality [-]
hlo
cal[k
W.m
-2.K
-1]
66 < ๐ฎ < 700kg.m-2.s-1, ๐ณ = ๐ณ๐ฏ๐ป 130 < ๐ฎ < 700kg.m-2.s-1, ๐ณ = ๐ณ๐ฏ๐ป
circular 543mm, methanol circular 543mm, ethanol
Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
HEAT TRANSFER COEFFICIENT
12
Correlation Application range Comments Maximum deviation
Haynes and Fletcher(2003) R11 and R123; Copper, ๐บ= 0.11 โ 1.84 kg m-2 s-1; = 0.0 โ 1.0;
๐๐ "= 11-170kW.m-2; ๐ทโ= 0.92,1.95mm
subcooled and saturated flow
boiling
+3.0%
Kandlikar and Balasubramanian (2004) R113, R134b, R123; ๐บ = 50 โ 570kg m-2 s-1; =0.00 โ 0.98;
๐๐ "= 5 โ 91kW.m-2; ๐ทโ= 0.19 โ 2.92mm
strong presence of nucleate
boiling
+3.3%
Saitoh et al. (2007) R134a, SUS304, ๐บ= 150-450kg m-2 s-1; = 0.2 โ 1.0;
๐๐ "= 5-40kW.m-2; ๐ทโ= 0.51, 1.12, 3.1mm
convective and nucleate boiling
contributions
+10.2%
Yu et al (2002) Water, SS, ๐บ= 50 โ 200kg m-2 s-1; = 0.0 โ 0.9;
๐= 200kPa; ๐ทโ= 2.98mm
nucleate boiling dominates
over a large ๐บ and range
+21.5%
0.0 0.1 0.2 0.3 0.40
20
40
60
80C2H5OH
havg [
kW
.m-2.K
-1]
Quality [-]
Experimental
Kandlikar
Yu et al.
Saitoh et al.
Haynes and Fletcher
๐๐" = 55kW.m-2; 130 < ๐ฎ < 700kg.m-2.s-1
Exit Vapor Quality [-]
hlo
cal[k
W.m
-2.K
-1]
square 521mm, ethanol
Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
FLOW PATTERNS
13
โข Definitions adapted from Collier and Thome (1994) and Carey (2007)
โ Determined from simultaneous measurements of โ๐, ๐๐ค,๐๐ข๐ก and high speed imaging
Bubbly flow
Confined flow
Elongated flow
Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
FLOW PATTERN MAPS
14
๐ผ ๐ต ๐ถ๐ต = 0.763๐ ๐๐๐๐ต๐
๐๐๐๐
0.41
๐ถ ๐ต ๐ด = 0.00014๐ ๐๐๐1.47๐๐๐๐
โ1.23
Revellin and Thome (2007)Revellin and Thome (2007)
0.0 0.2 0.4 0.6 0.8 1.00
200
400
600
800CH3OH, CCS
Bubbly flow
Confined flow
Elongated flow
IB/CB
CB/A
Mass
Flu
x, G
[kg.m
-2.s
-1]
Quality [-]Exit Vapor Quality [-]
0.0 0.2 0.4 0.6 0.8 1.00
200
400
600
800CH3OH, SCS
Bubbly flow
Confined flow
Elongated flow
IB/CB
CB/A
Mass
Flu
x, G
[kg.m
-2.s
-1]
Quality [-]Exit Vapor Quality [-]
๐๐" = 81kW.m-2, ๐ป๐๐๐ =342K ๐๐
" = 73kW.m-2, ๐ป๐๐๐ =360K
square 521mm, methanolcircular 543mm, methanol
Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
CLOSURE
15
โ๐
๐
๐ป๐,๐๐๐
โข inlet contraction and outlet expansion as well as nonโheated lengths were quantified and subtracted from the total two-phase
flow pressure drops
โข determination of local ๐ป๐๐๐ and ๐ป๐ and of flow pattern regimes
โข ๐๐ค,๐๐ข๐ก varies non-linearly along the channel
โข determination of local ๐ป๐,๐๐,๐ป๐, ๐ and of flow pattern regimes
โข ๐๐๐๐๐๐
โข is higher for low and independent on ๐บ incipience of boiling
โข is lower for high and independent on ๐บ dry patches on the wall causing heat transfer decline
โข ๐๐๐๐๐๐,๐๐๐๐๐๐
โข is higher for low ๐๐ " and dependent on ๐บ (๐บ =662kg.m-2.s-1) reduced space for convective flow to develop
โข is lower for low ๐บ and independent on ๐๐ " dominance of nucleate boiling and annular evaporation; the effect of ๐๐
" on
โ overcomes the effect of ๐บ
โข comparison of the experimental results with correlations for subcooled boiling and flow boiling show similar trends, but the
experimental values are below prediction
Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
CLOSURE
16
๐ญ๐๐๐ ๐๐๐๐๐๐๐๐๐๐๐
โข flow patterns and flow pattern transitions for diabatic evaporation of ethanol and methanol obtained from ๐ป, ๐ and high speed
imaging
โข flow patterns are qualitatively identical for both fluids and cross sections
โข similar trends with the model proposed by Revellin and Thome (2007)
โข deviations Instabilities occurring inside the channel, due to pressure fluctuations, explosive boiling and long dryout periods that
degrade the heat transfer
โข further experimental research is needed to generate more data at higher vapor qualities and different heat fluxes and mass
fluxes, for the developing of more accurate flow pattern maps
Methanol and Ethanol Evaporating Flow Mechanisms in Square and Circular Microchannels
Laboratory of Thermofluids, Combustion and Energy Systems
Professor Nunes de Carvalho and his team for thin film deposition.
Financial support:
Project โSURWET-COOLSโ, PTDC/EME-MFE/109933/2009
Portuguese Science and Technology Foundation, grant SFRH-BD-76596-2011
QUESTIONS
17
Simultaneous measurements of Temperature, pressure and high-speed imaging
in well defined homogeneous transparent channel walls with constant wall heat flux
is a major asset to assist in the comprehension of fluid flow behavior in microscale flows
Acknowledgements