Heat Transfer of Low GWP Refrigerants...Two very low GWP molecules have been developed HFO-1234yf...
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HEAT TRANSFER OF LOW GWP HEAT TRANSFER OF LOW GWP REFRIGERANTS REFRIGERANTS PRESENTED BY: ANKIT SETHI PRESENTED BY: ANKIT SETHI
Transcript of Heat Transfer of Low GWP Refrigerants...Two very low GWP molecules have been developed HFO-1234yf...
HEAT TRANSFER OF LOW GWP HEAT TRANSFER OF LOW GWP
REFRIGERANTSREFRIGERANTS
PRESENTED BY: ANKIT SETHIPRESENTED BY: ANKIT SETHI
CONTENTSCONTENTS
• Introduction
• Evaporation Heat Transfer
• Condensation heat Transfer
• Evaporation and Condensation Pressure Drop
• Introduction to LGWP R410A Replacements
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• Introduction to LGWP R410A Replacements
• System results for LGWP R410A Replacements
• Applicability of correlations to LGWP refrigerants
• Conclusions
HFO-1234yf
IntroductionIntroduction� Used data from NISTIRs 5144 (evaporation), 6095 (condensation)
and 6333 (pressure drop) database of experimental data for micro-
fin tubes
� Data includes both condensation and evaporation for single fluids
(R22, R32, R134a,R125), azeotropic mixtures (R410A, R502,
R507A) and zeotropic mixtures (R407C, R32/R125 and
R32/R134a)
� Refprop 9.0 properties used for all calculations
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� Various heat transfer and pressure drop correlations were
evaluated
� Two very low GWP molecules have been developed HFO-1234yf
and HFO-1234ze
� These molecules are components of our blends (L-41) to replace
R410A which were tested in a 3 ton heat pump
� System data was used to analyze the relative heat transfer and
pressure drop performance of the new refrigerants
HFO-1234ze(E)
Evaporation Heat TransferEvaporation Heat Transfer
Different correlations were evaluated and two were selected
1. Thome et al. 1997- Annular flow in Microfin tubes
� Approach based on new flow map (modified form of Steiner (1993) flow map)
�Overall heat transfer coefficient has contributions from nucleate and covective
� Asymptotic approach for convective and nucleate boiling (Cooper 1984)
� Enhancement factor were included to account for microfin tubes
2. Cavallini et al. 1999 –Annular flow for Microfin tubes
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2. Cavallini et al. 1999 –Annular flow for Microfin tubes
�Overall heat transfer sum of convective and nucleate boiling contributions
� Nucleate boiling (Cooper 1984)- Suppression factor and enhancement factor
� Area enhancement factor applied to smooth tube for convective coefficient
� Accounted for surface tension effects and vapor shear
Evaporation Heat Transfer CoefficientEvaporation Heat Transfer Coefficient--Pure FluidsPure Fluids
THOMECAVALLINI
10
20
30
40
50
De
va
tio
n (
%)
R22 R32 R134a
10
20
30
40
50
De
va
tio
n (
%)
R22 R32 R134a
0
10
20
30
40
50
De
va
tio
n (
%)
R22 R32 R134a
0
10
20
30
40
50
De
va
tio
n (
%)
R22 R32 R134a
5
-50
-40
-30
-20
-10
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
De
va
tio
n (
%)
xref
-50
-40
-30
-20
-10
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
De
va
tio
n (
%)
xref
-50
-40
-30
-20
-10
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1D
ev
ati
on
(%
)xref
-50
-40
-30
-20
-10
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1D
ev
ati
on
(%
)xref
� Cavallini’s correlation was found to be more consistent for this experimental data
Evaporation Heat Transfer CoefficientEvaporation Heat Transfer Coefficient-- ZeotropicZeotropic MixturesMixtures
THOMECAVALLINI
0
10
20
30
40
50
De
va
tio
n (
%)
R407C R32/R125 R32/R134a
0
10
20
30
40
50
De
va
tio
n (
%)
R407C R32/R125 R32/R134a
0
10
20
30
40
50
De
va
tio
n (
%)
R407C R32/R125 R32/R134a
0
10
20
30
40
50
De
va
tio
n (
%)
R407C R32/R125 R32/R134a
6
� Cavallini’s correlation was found to be more consistent for this experimental data
� Cavallini’s correlaton was used for further analysis
-50
-40
-30
-20
-10
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
De
va
tio
n (
%)
xref
-50
-40
-30
-20
-10
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
De
va
tio
n (
%)
xref
-50
-40
-30
-20
-10
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
De
va
tio
n (
%)
xref
-50
-40
-30
-20
-10
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
De
va
tio
n (
%)
xref
CONDENSATION HEAT TRANSFERCONDENSATION HEAT TRANSFER
Different correlations were evaluated and three were selected
1. Cavallini et al. 1993,1995- Microfin and Cross grooved tubes
� Correlation has form of forced convective equation
� Area enhancement factors were used
� Vapor shear and Surface tension effects were included
2. Koyama et al. 1998- Microfin tubes with pure fluids
� Total heat transfer coefficient has contributions from forced convective
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� Total heat transfer coefficient has contributions from forced convective
condensation and natural convective condensation
� Modified correlation for smooth tube by including area enlargement ratio
� Did not account for surface tension effects
3. Cavallini et al. 2009- Microfins tubes pure fluids and near azeotropes
� Total heat transfer coefficient contribution from annular and stratified
wavy flows (asymptotic form exponent 3)
� Surface tension effects were not considered
� Validated against very large experimental database
Condensation Heat Transfer CoefficientCondensation Heat Transfer Coefficient
CAVALLINI-1993,1995 CAVALLINI-2009 KOYAMA
-100
-50
0
50
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R32 R125 R134a
-100
-50
0
50
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R32 R125 R134a
-100
-50
0
50
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R32 R125 R134a
-100
-50
0
50
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R32 R125 R134a
-100
-50
0
50
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R32 R125 R134a
-100
-50
0
50
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R32 R125 R134a
8
-100
-50
0
50
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R410A
-100
-50
0
50
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R410A
-100
-50
0
50
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R410A
-100
-50
0
50
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R410A
-100
-50
0
50
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R410A
-100
-50
0
50
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R410A
� Cavallini’s 2009 correlation was found to be more consistent than the earlier correlation
� Cavillini 2009 was chosen for further analysis since it was validated for a large experimental
data set
Pressure Drop EvaluationPressure Drop Evaluation--Pure FluidsPure Fluids
CHOI CAVALLINI
-100-80-60-40-20
020406080
100
0 0.2 0.4 0.6 0.8 1
De
viat
ion
(%)
xref
R22 R32 R125 R134a
-100-80-60-40-20
020406080
100
0 0.2 0.4 0.6 0.8 1
De
viat
ion
(%)
xref
R22 R32 R125 R134a
-100-80-60-40-20
020406080
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
Xref
R22 R32 R125 R134a
-100-80-60-40-20
020406080
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
Xref
R22 R32 R125 R134a
EVAPORATION
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� Choi et al. 1999- Modified Pierre (1964) for evaporation and condensation
� Choi’s correlation has a lower spread for condensation
CONDENSATION
-100-80-60-40-20
020406080
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R22 R32 R125 R134a
-100-80-60-40-20
020406080
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R22 R32 R125 R134a
-100-80-60-40-20
020406080
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R22 R32 R125 R134a
-100-80-60-40-20
020406080
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R22 R32 R125 R134a
Pressure Drop EvaluationPressure Drop Evaluation-- Refrigerants BlendsRefrigerants Blends
CHOI CAVALLINI
EVAPORATION
-100-80
-60-40-20
020
406080
100
0 0.1 0.2 0.3 0.4 0.5 0.6
De
via
tio
n (
%)
xref
R407C R410A R32/R134a
-100-80
-60-40-20
020
406080
100
0 0.1 0.2 0.3 0.4 0.5 0.6
De
via
tio
n (
%)
xref
R407C R410A R32/R134a
R410A R502 R507AR410A R502 R507A
-100-80-60-40-20
020406080
100
0 0.1 0.2 0.3 0.4 0.5 0.6
De
via
tio
n (
%)
xref
R407C R410A R32/R134a
-100-80-60-40-20
020406080
100
0 0.1 0.2 0.3 0.4 0.5 0.6
De
via
tio
n (
%)
xref
R407C R410A R32/R134a
R410A R502 R507AR410A R502 R507A
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CONDENSATION
� Choi’s prediction for condensation show a lower spread
� Choi’s corrleation was selected for further analysis
-100-80-60-40-20
020406080
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R410A R502 R507A
-100-80-60-40-20
020406080
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R410A R502 R507A
-100-80-60-40-20
020406080
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R410A R502 R507A
-100-80-60-40-20
020406080
100
0 0.2 0.4 0.6 0.8 1
De
via
tio
n (
%)
xref
R410A R502 R507A
LGWP R410A ReplacementsLGWP R410A Replacements
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LGWP R410A ReplacementsLGWP R410A Replacements
Test System (R410A 13 SEER 3Test System (R410A 13 SEER 3--Ton) and Operating ConditionsTon) and Operating Conditions
Tests Conditions according to AHRI Std 210
�All tests performed under near drop-in conditions (original equipment)
�An EEV was used for superheat control
�Charge optimization performed for AHRI test H1 condition
Test
Cooling ModeIndoor Room Outdoor Room
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DB(F) WB(F) DB(F) WB(F)
A 80 67 95 75
B 80 67 82 65
C 80 57 82 65
MOC 80 67 115 75
Test Indoor Room Outdoor Room
DB(F) WB(F) DB(F) WB(F)
H1 70 60 47 43
H2 70 60 35 33
H3 70 60 17 15
Test Indoor Room Outdoor Room
Heating Mode
Experimental ResultsExperimental Results--L41L41
Capacity
Capacity
Capacity
Capacity
Efficiency
Efficiency
Efficiency
Efficiency
Mass Flow
Mass Flow
Mass Flow
Mass Flow
60%
70%
80%
90%
100%
110%
% of R410A
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� Modified L-41: Reduced R-32 content to reduce discharge temperatures enabling use of current compressor technology in all climates.
� At AHRI MOC conditions discharge temperature is 24 F higher than R410A compared to 41F for R32
� Formulated to reduce flammability (BV < 4) and maintain GWP below R-32.
� A slightly larger displacement compressor (~10%) used to recover capacity but maintaining efficiency
� Lower mass velocities due to lower flow rates indicate further improvements in heat exchanger design may be possible
Mass Flow
Mass Flow
Mass Flow
Mass Flow
30%
40%
50%
AHRI B AHRI A AHRI H1 AHRI H3
Evaporating and Condensing TemperaturesEvaporating and Condensing Temperatures
410A, 115
410A, 134
L41, 118
L41, 138
L41, 109
410A, 52
80
100
120
140
160Condensing and Evaporating Temperature (Deg. F)
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� Drop-in testing results show similar evaporating temperatures
� Condensing temperatures slightly higher indicating scope of improvement in heat exchanger design. However performance is not affected.
� This indicates good heat transfer properties since mass velocities ~ 75-80% of R410A
410A, 103
410A, 115
410A, 134
410A, 105
L41, 106
L41, 118
L41, 138
L41, 109
410A, 48
410A, 50
410A, 52
410A, 32L41, 50
L41, 51
L41, 52
L41, 35
20
40
60
AHRI B AHRI A AHRI MOC AHRI H1
Condensing and Evaporating Temperature (Deg. F)
Pressure Drop in Heat ExchangersPressure Drop in Heat Exchangers
R410A
L41
3.0
4.0
5.0
6.0
Drop of Dew Temperature (Deg.F)
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� Drop of saturation temperature good measure of penalties in the system
� Lower drop of saturation temperature in heat exchangers. Further improvement in heat exchanger design to improve heat transfer is possible
R410A
R410A
R410A
L41
L41
L41
R410A
R410A
R410A
L41
L41
L41
0.0
1.0
2.0
AHRI B AHRI A AHRI H1
Drop of Dew Temperature (Deg.F)
EVAPORATOR EVAPORATORCONDENSER CONDENSER EVAPORATOR CONDENSER
Evaporation Heat Transfer and Pressure DropEvaporation Heat Transfer and Pressure Drop
0 100 200 300 400 500
2
3
4
5
6
7
8
2
3
4
5
6
7
8
Ev
ap
ora
tio
n A
ve
rag
e P
ress
ure
Dro
p (
kP
a/m
)
L41 R407C R410A R22 L41 Expt.
Pressure Drop Model- Choi et al. (1999)
Evaporation Temperature- 283.15 K (50 F)
Tube Diameter- 7.4 mm (microfin)
0 100 200 300 400 500
2
3
4
5
6
7
8
2
3
4
5
6
7
8
Ev
ap
ora
tio
n A
ve
rag
e P
ress
ure
Dro
p (
kP
a/m
)
L41 R407C R410A R22 L41 Expt.
Pressure Drop Model- Choi et al. (1999)
Evaporation Temperature- 283.15 K (50 F)
Tube Diameter- 7.4 mm (microfin)
0 100 200 300 400 500
4000
6000
8000
10000
12000
14000
4000
6000
8000
10000
12000
14000
Av
era
ge
Ev
ap
ora
tio
n H
TC
(W
/m2.K
)
L41 R22 R407C R410A L41 Exp.
Heat Transfer Model- Cavallini et al. (1999)
Evaporation Temperature- 283.15 K (50 F)
Tube Diameter- 7.4 mm (microfin)
0 100 200 300 400 500
4000
6000
8000
10000
12000
14000
4000
6000
8000
10000
12000
14000
Av
era
ge
Ev
ap
ora
tio
n H
TC
(W
/m2.K
)
L41 R22 R407C R410A L41 Exp.
Heat Transfer Model- Cavallini et al. (1999)
Evaporation Temperature- 283.15 K (50 F)
Tube Diameter- 7.4 mm (microfin)
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� Cavallini’s correlation predicts heat transfer coefficients for L41 in between R22 and R407C
� Detailed system performance data was used to estimate the average heat transfer coefficient
� Extracted total heat exchanger duty and used LMTD approach to calculate heat transfer coefficient
� The uncertainty is heat transfer coefficient is estimated to be ± 30%
� Further research is necessary to understand the heat transfer characteristics of new fluids
� The pressure drop predictions seem reasonable since system pressure drop would be expected to be higher due to additional resistances
0
1
2
0
1
2
0 100 200 300 400 500
Ev
ap
ora
tio
n A
ve
rag
e P
ress
ure
Dro
p (
kP
a/m
)
Mass Flux (kg/m2.s)
0
1
2
0
1
2
0 100 200 300 400 500
Ev
ap
ora
tio
n A
ve
rag
e P
ress
ure
Dro
p (
kP
a/m
)
Mass Flux (kg/m2.s)
0
2000
4000
0
2000
4000
0 100 200 300 400 500
Av
era
ge
Ev
ap
ora
tio
n H
TC
(W
/m
Mass Flux (kg/m2.s)
0
2000
4000
0
2000
4000
0 100 200 300 400 500
Av
era
ge
Ev
ap
ora
tio
n H
TC
(W
/m
Mass Flux (kg/m2.s)
Condensation Heat Transfer and Pressure DropCondensation Heat Transfer and Pressure Drop
0 100 200 300 400 500
1
1.5
2
2.5
1
1.5
2
2.5
Av
era
ge
Co
nd
en
sati
on
Pre
ssu
re D
rop
(k
Pa
/m)
L41 R410A R407C R22 L41 Expt.
Pressure Drop Model- Choiet al. (1999)
Condensation Temperature- 319.30K (115 F)
Tube Diameter- 8.9 mm (microfin)
0 100 200 300 400 500
1
1.5
2
2.5
1
1.5
2
2.5
Av
era
ge
Co
nd
en
sati
on
Pre
ssu
re D
rop
(k
Pa
/m)
L41 R410A R407C R22 L41 Expt.
Pressure Drop Model- Choiet al. (1999)
Condensation Temperature- 319.30K (115 F)
Tube Diameter- 8.9 mm (microfin)
0 100 200 300 400 500
3000
4000
5000
6000
7000
8000
9000
3000
4000
5000
6000
7000
8000
9000
Av
era
ge
Co
nd
en
sati
on
HT
C (
W/m
2.K
)
L41 R22 R407C R410A L41 Exp.
Heat Transfer Model- Cavallini et al. (2009)
Condensation Temperature- 319.30K (115 F)
Tube Diameter- 8.9 mm (microfin)
0 100 200 300 400 500
3000
4000
5000
6000
7000
8000
9000
3000
4000
5000
6000
7000
8000
9000
Av
era
ge
Co
nd
en
sati
on
HT
C (
W/m
2.K
)
L41 R22 R407C R410A L41 Exp.
Heat Transfer Model- Cavallini et al. (2009)
Condensation Temperature- 319.30K (115 F)
Tube Diameter- 8.9 mm (microfin)
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� Cavallini’s correlation predicts heat transfer coefficients similar to R22 and R410A
� Further investigation of heat transfer coefficients is necessary
� The pressure drop data seems reasonable since system pressure drop would be expected to be higher due to additional resistances
0
0.5
0
0.5
0 100 200 300 400 500
Av
era
ge
Co
nd
en
sati
on
Pre
ssu
re D
rop
(k
Pa
/m)
Mass Flux (kg/m2.s)
0
0.5
0
0.5
0 100 200 300 400 500
Av
era
ge
Co
nd
en
sati
on
Pre
ssu
re D
rop
(k
Pa
/m)
Mass Flux (kg/m2.s)
0
1000
2000
0
1000
2000
0 100 200 300 400 500
Av
era
ge
Co
nd
en
sati
on
HT
C (
W/m
Mass Flux (kg/m2.s)
0
1000
2000
0
1000
2000
0 100 200 300 400 500
Av
era
ge
Co
nd
en
sati
on
HT
C (
W/m
Mass Flux (kg/m2.s)
CONCLUSIONSCONCLUSIONS
� Under the test conditions studied, the new LGWP blends provide good
system performance with minor system modification
� Improvements in heat exchanger design may further improve system
performance with LGWP blends
� In these studies, the new blends seemed to have good heat transfer
properties and presented a lower pressure drop in the heat exchangers
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properties and presented a lower pressure drop in the heat exchangers
� Further research is necessary to understand the heat transfer and
pressure drop properties of the new LGWP refrigerants
THANK YOUQUESTIONS?
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QUESTIONS?
