diapositiva 1 · 2020-02-12 · 13th international conference multiphase flow in industrial plants...
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![Page 1: Diapositiva 1 · 2020-02-12 · 13th International Conference MULTIPHASE FLOW IN INDUSTRIAL PLANTS New Database 4 The new pressure drop database is obtained from experimental tests](https://reader034.vdocuments.mx/reader034/viewer/2022050403/5f80eb49cf4b344eda1fdd11/html5/thumbnails/1.jpg)
13th International Conference
MULTIPHASE FLOW IN INDUSTRIAL PLANTS
MFIP 2014
Davide DEL COL, Marco AZZOLIN, Alberto BISETTO and Stefano BORTOLIN
Department of Industrial Engineering
University of Padova
A PREDICTING METHOD OF FRICTIONAL PRESSURE DROP
DURING TWO-PHASE FLOW IN SMALL DIAMETER CHANNELS
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13th International Conference
MULTIPHASE FLOW IN INDUSTRIAL PLANTS
Outline
2
Introduction and motivation
New database
Description of the test rig
Experimental technique
Description of the model and comparison with
experimental data
Conclusions
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13th International Conference
MULTIPHASE FLOW IN INDUSTRIAL PLANTS
Introduction
3
Two-phase flow in minichannels is widely present
in evaporators and condensers.
Pressure drop have a strong influence
on the two-phase heat transfer
It is crucial to have reliable pressure drop prediction methods
for two-phase heat transfer modeling and optimization
Increasing interest in refrigerants possessing low GWP
due also to growing number of regulations and laws
In 2012 the European Commission
proposed to cut F-gas emissions
by two-thirds by 2030
European Union’s F-gas regulations:
from 2017 automotive
air-conditioning GWP < 150
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13th International Conference
MULTIPHASE FLOW IN INDUSTRIAL PLANTS
New Database
4
The new pressure drop database is obtained from
experimental tests with
Natural
refrigerant R290 (propane)
HFO R1234ze(E)
Mixtures R32/R1234ze(E)
Fluid Mass velocity [kg m-2 s-1] Pressure [bar] Saturation temperature [°C]
R1234ze(E) 200-400-600-800 7.7 40.1
R290 200-400-600-800 14 41
R32/R1234ze(E)
0.23/0.77
400 13.8 36.7-47.6
R32/R1234ze(E)
0.5/0.5
200-400-600 18 36.3-43.7
Experimental test conditions
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13th International Conference
MULTIPHASE FLOW IN INDUSTRIAL PLANTS 5
R32/R1234ze(E) Mixture
17.7 bar
43.1 °C
35.6 °C
Composition by mass R32/R1234ze(E) 0.5/0.5
T_dew 43.1°C
T_bubble 35.6°C
T_glide 7.5°C
Temperature given at 17.7 bar
Fluid properties calculated with NIST Refprop 9.1 using for the mixing parameters the KW2
model with tuned parameters as recommended by Akasaka (2013)
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13th International Conference
MULTIPHASE FLOW IN INDUSTRIAL PLANTS
Test apparatus
6
DP Test Section
INTERNAL
DIAMETER
di = 0.96 mm
INNER SURFACE
ROUGHNESS
Ra = 1.3 µm
ABIABATIC
TWO-PHASE FLOW
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13th International Conference
MULTIPHASE FLOW IN INDUSTRIAL PLANTS
Test Rig
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PS pre-sector MF mechanical filter PV pressure vessel TV valve CFM Coriolis-effect mass flow meter PV pressure vessel FD filter drier P pressure transducer T thermocouple DP differential pressure transducer
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13th International Conference
MULTIPHASE FLOW IN INDUSTRIAL PLANTS
Experimental technique
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enters as subcooled liquid
enters as superheated vapor
Refrigerant
,
, ,
water water water PS
in MS in PSref
m c Th h
m
, ( , )in PSh f P T
1234, , R zex f P h X
ADIABATIC
,in MS L
V L
h hx
h h
For
PURE FLUIDS
For
MIXTURES
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13th International Conference
MULTIPHASE FLOW IN INDUSTRIAL PLANTS
0,001
0,010
0,100
100 1000 10000 100000
FR
ICT
ION
FA
CT
OR
[ / ]
Re [ / ]
Blasius
Churchill
R290 Liquid
R290 vapor
R32 R1234ze 23/77% liquid
R32 R1234ze 50/50% liquid
R1234ze liquid
R1234ze vapor
Single Phase Friction Factor
Re [/]
Fric
tio
n F
acto
r [/
]
9
22
hD pf
G L
In order to validate the
data acquisition and to
gain a critical insight into
the test section hydraulic
performance
Friction Factor Definition
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13th International Conference
MULTIPHASE FLOW IN INDUSTRIAL PLANTS
Del Col et al. (2013) model
10
The Del Col et al. model (IJHMT, 2013) suggested the following equation to
predict two-phase frictional pressure drop during annular or mist flow (JG >
2.5) in minichannels
If JG < 2.5 the authors proposed to use the same equation, fixing a minimum
value for ϕ2LO equal to 1.
22 2
,
2 LOLO LO
f f LO h L
f Gdp dp
dz dz D
The liquid-only friction factor is evaluated as
RR = 2Ra/Dh
RR is the relative roughness of the tube.
0.2
0.046 0.7
LO LOf Re RR X
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13th International Conference
MULTIPHASE FLOW IN INDUSTRIAL PLANTS
Del Col et al. (2013) model
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0.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
0.022
0 2000 4000 6000 8000 10000
f LO
[/]
ReLO [/]
CAVALLINI ET AL. SMOOTH
CAVALLINI AT AL. ROUGH
PRESENT MODEL
0
0
.2
0
.
.2
2
5
0,
1, 3500
0.0461 , 3500
0.7
0.046 0.7
0.7
0.046 35000.0
46
LO
LO LO
LO
LOLO L
LO
O
LO
if Re Re
X
f Re R
if Re
f Reif Re Re
RR
f RRf R
R X
e
Re+LO 3500
If ReLO is small RR does not affect the pressure losses, so fLO is evaluated as in a smooth
tube. If ReLO increases RR starts to influence the friction factor, the more the bigger is ReLO,
and fLO tends to the one evaluated for rough tubes.
RR = 0.005
comparison with previous model
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13th International Conference
MULTIPHASE FLOW IN INDUSTRIAL PLANTS
0
50
100
150
200
250
300
350
400
0 50 100 150 200 250 300 350 400
(dp
/dz) f
,CA
LC
[kP
a m
-1]
(dp/dz)f,EXP [kPa m-1]
R32/R1234ze 50/50%
R32/R1234ze 23/77%
R290
R1234ze
+20%
-20%
Comparison with the model
(dp/dz)f,EXP [kPa m-1]
(dp/d
z) f
,CA
LC [kP
a m
-1]
Fluid eAB [%] eR [%] σN [%]
R1234ze(E) 8.6 -6.1 7.7
R290 10.3 -8 12
R32/R1234ze(E) 3.8 -1.5 4.8
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13th International Conference
MULTIPHASE FLOW IN INDUSTRIAL PLANTS
Conclusions
For most applications alternatives to high GWP synthetic refrigerants
could be found in natural refrigerants, HFOs or mixtures.
A model to predict frictional pressure drop during two-phase flow in small
diameter channels has been tested against an updated database which
includes different fluids R1234ze(E) (HFO), propane (HC), and a mixture of
R32/R1234ze(E) (mixture of HFC and HFO).
The present two-phase pressure drop database is satisfactorily predicted
by the model, with a total mean absolute deviation equal to 7.6%, a mean
average deviation equal to -5.2% and a standard deviation of 8.2%.
This model is a useful and reliable tool to design compact heat
exchangers using minichannels where the prediction of the two-phase
pressure drop is a crucial issue.
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13th International Conference
MULTIPHASE FLOW IN INDUSTRIAL PLANTS
Thank you
for your attention
http://www.dii.unipd.it/en/sustainable-thermal-energy-technologies
Università degli Studi di Padova
Dipartimento di Ingegneria Industriale
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