Transcript R32 Rich Mixtures

Use of Hydrocarbons in
Refrigeration and
Air-Conditioning Systems
Center for Environmental Energy
Engineering (CEEE)
University of Maryland
Yunho Hwang
1
Outline

Regulation Update:
Especially EU’s response

Properties of HCs

Performance of HC Systems

Design Guide of HC Systems
Alternative Refrigerant Seminar: Hydrocarbons, 2003
2
Response to Climate Change



The international community recognized the climate
change as one of the greatest environmental and
economic challenges facing humanity.
The UN Framework Convention on Climate Change was
adapted in 1992 to achieve stabilization of greenhouse
gas (GHG) concentrations in the atmosphere at a level
which prevents dangerous anthropogenic interference
with the climate system.
The Kyoto Protocol was adapted in 1997, which requires
industrialized countries to reduce their collective
emissions of greenhouse gases by 5.2% below their
1990 levels for the period 2008 to 2012.
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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EU’s Response to Climate Change

In 2001 the European Climate Change Program reported:




Fluorinated gas emissions in 1995 were around 65 million tones
of CO2 equivalent (2% of total GHG emissions in the EC).
Emissions will increase to around 98 million tones of CO2
equivalent by 2010 (2-4% of total GHG emissions in the EC).
The EC and the Member States have all ratified the
Kyoto Protocol in 2002.
Under the Kyoto Protocol the EC is committed to reduce
its emissions by 8%, an overall reduction of 336 million
tones of CO2 equivalent.
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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EU’s Response to Climate Change




In August 2003 Commission of the EC proposed
“Regulation on certain fluorinated greenhouse gases.”
The proposal is expected to reduce projected emissions
of fluorinated gases by 23 million tones of CO2
equivalent by 2010.
Highlights of the proposal are:
Article 3: improve the containment of fluorinated gases.



Duty to prevent and minimize leakage
Mandatory inspections for leakage (3 kg or more: once/year, 30 kg or
more: 4/year, 300 kg or more: monthly)
Leakage detection systems: All owners of systems containing 300
kilograms or more of fluorinated gas are required to install leak
detection systems.
Maintenance of records

Alternative Refrigerant Seminar: Hydrocarbons, 2003
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EU’s Response to Climate Change

Article 4: recovery


Fluorinated gases must be recovered for recycling, reclamation
or destruction from the cooling circuits of all refrigeration, airconditioning and heat pump equipment. Unused fluorinated gas
contained in refillable containers must also be recovered. The
recovery of fluorinated gases from all other products and
equipment shall be done if it is technically feasible and costeffective to do so.
Article 5: training and certification programs

Member States will be required to establish programs to provide
for the training and certification of personnel involved in
making inspections for leakage, and for those involved in the
recovery, recycling, reclamation and destruction of fluorinated
gases.
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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EU’s Response to Climate Change

Article 6: reporting


Data on the production, importation, export, recycling and
destruction of fluorinated gases above one ton per year must be
submitted to the Commission annually.
Article 7: control of use


The initial charging of the air-conditioning system of any
passenger vehicle and light commercial vehicle placed on the
market after 1 January 2009 should use a refrigerant with a GWP
of 150 or less.
This is to prevent such vehicles being placed on the market
during the phase-out period with an empty air-conditioning
system which could then be charged with R134a or any other
fluorinated refrigerant gas with a GWP above 150.
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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EU’s Response to Climate Change

Articles 9 and 10: air-conditioning systems in new cars

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A/C systems containing fluorinated gases with a GWP higher
than 150 (ex: R134a) for any new passenger cars and light
commercial vehicles are subject to a maximum leakage rate.
The leakage rate shall not exceed 40 g and 50g per year for
single and dual evaporator systems, respectively.
Phase out of A/C systems in new passenger cars and light
commercial vehicles using R134a begins January 1, 2009 and
ends December 31, 2013.
In 2009 only 80% of a predetermined quota of passenger cars
and light commercial vehicles can be placed on the market with
A/C systems containing R134a. This level is reduced over the
following years to 60%, 40%, 20% and 10% and in 2014 no A/C
systems in new passenger cars and light commercial vehicles
will contain R134a.
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Global Warming Consideration


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Regulations on High GWP Substances

EU will impose more strict control

Low GWP substances (GWP < 150) are wanted
Two HFCs (R32 & R152a) are attractive.

R32: 7% higher COP, 18% lower TEWI than R410A (Yajima, 2000)

R152a: 2-17% higher COP than R134a (Andersen, 2002)
Natural refrigerants have minimal GWP.

HCs based refrigerators: EU (1992) & Japan (2002)

HC heat pumps: Germany, Austria, Sweden, Netherlands (1997)

CO2 water heaters: EU & Japan (2002)
GWP (100 years; Calm, 1998)
R404A
R410A
R134a
R32
R152a
R290
CO2
3,700
1,730
1,300
650
140
20
1
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Leakage of R134a from Vehicle A/C
R134a emissions
Low
High
Assumptions
Regular emissions occurring 0.96
during normal operation
0.96
53 g / year
Irregular emissions resulting 0.29
from accidents, defects etc.
0.36
16/20 g / year in “low” and
“high” cases
Emissions during servicing
0.26
0.52
100/200 g / service in
“low” and “high” cases
Emissions at end of-life
0.14
0.35
20/50% of lost of the
charge at the end of life in
the “low” and “high” cases
Total vehicle lifetime leakage 1.70
(ton of CO2 equiv.)
2.24
Vehicle life: 14 years
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Leakage from Vehicle A/C
Case
No. of Exposures to Vehicle
Occupants in the U.S.
Sudden medium leak
( > 5000 ppm)
Sudden large leak
122 (4.5%)
Sudden medium leak after
recharge
Leak caused by collision
673 (24.8%)
2 (0.1%)
1,913 (70.6%)
No. of vehicles w A/C in the U.S. (automobiles & light truck): 150 million
No. of exposure to Service Technicians are three orders of magnitude higher than the
no. of exposure to vehicle occupants.
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Flammability Consideration

HFC mixtures are current alternatives.

R410A, R407C (R22 alt.) & R404A (R502 alt.): non-flammable

R32, R143a & R152a: slightly flammable
R143a
R32
66%
60%
R410A
flammable
flammable
25°C
100°C
58%
55%
51.5%
R404A
33%
R407C
nonflammable
36% 60°C
33% 100°C
nonflammable
R125
R134a R125
Alternative Refrigerant Seminar: Hydrocarbons, 2003
R134a
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Flammability Consideration

ASHRAE Safety Classification
no identified toxicity
at concentrations
<= 400 ppm
Higher
flammability
A3
(R170,R290,
R600,R600a)
evidence of
toxicity
below 400 ppm
B3
(R-1140)
LFL <= 0.10 kg/m3
or
DHcomb >= 19 MJ/kg
LFL > 0.10 kg/m3
and
DHcomb < 19 MJ/kg
Lower
flammability
A2
(R32,R143a, R152a)
B2
(NH3)
No flame
propagation
A1
(R22, R125, R134a,
R410A, R404A, CO2)
B1
(R-123)
Lower toxicity
Higher toxicity
[Reference] ASHRAE Standard 34-1992
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Risk Analysis of HCs

‘Accepted’ in-use risk (UK)
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Ignition risk of R290:



fire from gas cookers 8.7x10-4
fire from washing machine 1.6x10-4
fire from refrigerators 1.1x10-5
fire from gas central heating 4.0x10-5
fire from television 2.7x10-5
4.7x10-11 (normal use), 2.2x10-8 (service)
Based on 1 kg R290 in 48m2 office operating 12 hrs/day
All are higher than flammable refrigerant ignition
risk
Source: Calor gas, Purdue Conference, 2002
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Regulations on HCs
Region Automobile A/C
Refrigeration & Air-conditioning
USA
SNAP (CAA Sec.612)
HCs cannot be used.
SAE (J 639)
The refrigerant should be
non-flammable.
UL (250)
HCs can be applied for small refrigerators up to 50 g.
ASHRAE (Standard 15)
The max. amount of refrigerant released into the
occupied space is restricted (less than 1/5 of LFL)
EU
EN (378)
HCs cannot be used in direct cooling and heating systems
BS (4434)
Highly flammable refrigerant can be used under the following conditions.
Sealed system, Charge less than 1.5 kg
 The max. amount of refrigerant released into the space should be less than 1/5 of LFL.

DIN (7003) & NPR (7600)
Limited amounts of HC charge may be permitted within the living space
Japan
JIS (8620)
The refrigerant should be
non-flammable.
None
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Characteristics of Hydrocarbons






Environmentally benign (zero ODP, zero GWP)
Possibly higher cycle efficiency
Non toxic
Miscible and compatible with mineral oil
Lower discharge temperature
Reduced refrigerant charge
 Flammable
 Need higher safety standards and designs (secondary
loop, sealed electric parts)
 Lower volumetric capacity
 Need larger displacement compressors
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Properties: Vapor Pressure
10.00
Pressure [MPa]
10A
R-4
2
R-2
07C
R-4
90
R-2
1.00
34a
R-1
0.10
0.01
-4.5
-4.0
-3.5
-3.0
-2.5
-1/T x 1000 [K]
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Density Ratio & Specific Heat Ratio (R290/R22)
Properties: Density & Specific Heat
3.0
2.5
2.0
Liquid Density Ratio
Vapor Density Ratio
Liquid Specific Heat Ratio
Vapor Specific Heat Ratio
1.5
1.0
0.5
0.0
-40
-20
0
20
40
60
80
Temperature [°C]
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Thermal Conductivity Ratio & Viscosity Ratio
(R290/R22)
Properties: Thermal Conductivity & Viscosity
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
Liquid Thermal Conductivity Ratio
Liquid Viscosity Ratio
0.2
Vapor Thermal Conductivity Ratio
Vapor Viscosity Ratio
0.0
-40
-20
0
20
40
60
80
Temperature [°C]
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Properties: Single-phase HTC
Heat Transfer Coefficient Ratio (R290/R22)
1.50
1.45
1.40
1.35
1.30
1.25
1.20
1.15
1.10
1.05
Liquid HTC Ratio
Vapor HTC Ratio
1.00
-40
-20
0
20
40
60
80
Temperature [°C]
for 1kW cooling capacity, 8.5mm id tube, mass flow rate of R290 is about 60% of R22
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Properties: Single-phase Pressure Drop
Pressure Drop Ratio (R290/R22)
0.80
0.75
0.70
0.65
0.60
0.55
Liquid Pressure Drop Ratio
Vapor Pressure Drop Ratio
0.50
-40
-20
0
20
40
60
80
Temperature [°C]
for 1kW cooling capacity, 8.5mm id tube, 1m length, mass flow rate of R290 is about 60% of R22
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Properties: Pressure vs. Sat. Temperature
Saturation Temperature [°C]
80
60
40
20
0
-20
R22 Saturation Temperature
R290 Saturation Temperature
-40
0
1000
2000
3000
4000
Pressure [kPa]
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Cycles in P-h Diagram
10.0
Pressure [MPa]
R22 Cycle
R290 Cycle
1.0
0.1
0
100
200
300
Enthalpy [kJ/kg]
Alternative Refrigerant Seminar: Hydrocarbons, 2003
400
500
600
23
Cycles in T-s Diagram
120
R22 Cycle
R290 Cycle
100
Temperature [°C]
80
60
40
20
0
-20
-40
0
0.5
1
Entropy [kJ/kgK]
Alternative Refrigerant Seminar: Hydrocarbons, 2003
1.5
2
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Performance of HCs: Refrigerator

CEEE experimental results (1995)



Test Unit: 566 liter, automatic defrost, top mount
refrigerator/freezer
Freezer/food compartments temps: -15.6/3.3 °C
Energy consumption of R290/R600 is 7% less than that of R12
Parameter
Energy consumption
[kW/day]
On-time ratio
[%]
Charge
[g]
R12
2.46
46
240
R290/R600 (70/30)
2.29
33
70
Ratio (compared to R12)
0.93
0.72
0.29

Americold (1994)

Energy consumption of R600a is 2% less than that of R12
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Performance of HCs: Unitary A/C

CEEE experimental results (2002)
 Test Unit: 3 RT Unitary Heat Pump
 Charge: R22 4.0 kg, R290 1.9 kg
 Steady State Performance of R290
(ASHRAE A, B, 47S, 17L)
 3 ~ 6% lower capacity; -3 ~ +2% variation in COP
 Cyclic Performance of R290
 Unmatched superheat: 16% lower cyclic degradation
 Same superheat: 5% lower degradation
 Seasonal Energy Efficiency of R290
 Unmatched superheat: 2% lower SEER
 Same superheat: 7% lower SEER
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Performance of HCs: Unitary A/C
CEEE: 11% larger compressor displacement volume
Test Conditions
(baseline R22)
Cooling A Cooling B
Heating 47
Heating 17
Capacity Ratio
0.96
0.97
0.94
0.97
COP Ratio
0.97
0.98
0.99
1.02
Discharge Temp.
Reduction [K]
15.1
13.0
11.7
18.2
AREP: 18% larger compressor displacement volume
Test Conditions
(baseline R-22)
Cooling A Cooling B
Heating 47
Heating 17
Capacity Ratio
1.09
1.08
1.04
1.09
COP Ratio
1.06
1.03
1.00
0.98
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Performance of HCs:
Commercial Refrigeration

CEEE experimental results (2003)
 Test Unit: 5 HP unit cooler with condensing
unit, 21% larger comp. displacement volume
 Charge: R404A 5.0 kg, R290 1.9 kg
 Full Load Performance of R290
(1.6/35 °C indoor/outdoor air temperatures)
 1% higher COP for matched capacity
 Part Load Performance of R290
(1.6/18.5 °C indoor/outdoor air temperatures)
 3% lower capacity, 1% higher COP
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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R-290 Design Challenges


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
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Refrigerant: thermophysical properties &
impurities
Compressor: displacement volume selection
TXV: degree of superheating
Suction line pressure drop
Cycle options:



Suctionline heat exchanger (SLHX)
Secondary loop (SL)
Safety
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Temperature Profiles along the Cycle
80
ASHRAE B Conditions
Temperature [°C]
70
1.
2.
3.
4.
5.
6.
60
50
R22
Compressor Discharge
Condenser Inlet
Condenser Outlet
Evaporator Inlet
Evaporator Outlet
Compressor Suction
R290
40
30
20
10
0
0
1
2
3
4
5
6
7
Position
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Compressor Temperatures in Cyclic Mode
70
ASHARE D Conditions
60
Temperature [°C]
R22 discharge
50
R290 discharge
40
30
R22 suction
20
R290 suction
10
0
0
20
40
60
80
100
Time [min]
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Impurities of Propane
Composition by Mass [%]
Grade
Propane
C 3H 8
Isobutane
C4H10
Butane
C4H10
Ethane
C 2H 6
Research (RG)
99.99
nil
nil
nil
Instrument (IG)
99.53
0.40
0.07
0.01
Chemically Pure (CPG)
98.98
0.77
0.20
0.03
nil: less than 0.01%
•
•
•
•
•
Properties between 0.6 to 2 MPa
Saturated liquid temperature: less than 0.2 K
Saturated vapor temperature: 0.2 to 0.3 K higher (IG), 0.5 K higher (CPG)
Saturation enthalpies & densities: within 0.1% variation
Refrigerant-side capacity: within 0.5% variation
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Effects of Impurities on
Saturation Temperature
Saturated Liquid
Temperature [°C]
Pressure
[MPa]
Saturated Vapor
Temperature [°C]
Temperature
Glide [K]
Pure
IG
CPG
Pure
IG
CPG
IG
CPG
0.6
7.9
7.9
8.0
7.9
8.2
8.4
0.2
0.5
0.8
18.3
18.4
18.4
18.3
18.6
18.8
0.2
0.4
1.0
26.9
27.0
27.0
26.9
27.2
27.5
0.2
0.4
1.2
34.4
34.4
34.5
34.4
34.6
34.9
0.2
0.4
1.4
41.0
41.0
41.1
41.0
41.2
41.5
0.2
0.4
1.6
46.9
47.0
47.0
46.9
47.1
47.4
0.2
0.3
1.8
52.3
52.4
52.5
52.3
52.5
52.8
0.1
0.3
2.0
57.3
57.4
57.4
57.3
57.5
57.8
0.1
0.3
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Compressor Sizing: Volumetric Capacity
Volumetric Capacity Ratio of R290/R22
1.00
0.98
0.96
0.94
0.92
0.90
0.88
0.86
0.84
0.82
0.80
-40
-20
0
20
40
60
80
Temperature [°C]
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Superheating Control by TXV
Saturation Pressure
1000
R22
R22, 5K SH
900
R290
Pressure [kPa]
R290, 5K SH
800
700
Fspring
Fspring
Sensor
Pbulb
600
Psuction
5K
External Equalizer
Fspring
5K
500
Outlet
3K
400
270
275
280
285
290
295
300
Temperature [K]
Inlet
Force Balance:
Pbulb x Adia = Psuction x Adia + Fspring
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Superheating Control by TXV

Superheating matching
-




same hardware
same temperature increase
same amount of heat
Mass flow rate of R290: 60% of R22
Specific heat of R290: 2.4 times of R22
R290 needs 43% more energy to make
the same degree of superheating.
R290 causes 70% of degree of superheating for
the same amount of energy.
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Suction Line Pressure Drop
R22-Comp. I (~1.1K)
Suction Line Pressure Drop [kPa]
25
R290-Comp. I (~0.8K)
R290-Comp. II (~1K)
R290-same S/H (~1K)
20
15
10
5
0
ASHRAE A
Alternative Refrigerant Seminar: Hydrocarbons, 2003
ASHRAE B
ASHRAE C
37
Cycle Options

Cycle was modeled for the following options:




R22 & R290 Basic cycles
R290 cycle with SLHX
R290 cycle with secondary loop (SL)
R290 cycle with SLHX + secondary loop
Option
R290,
Base
R290,
SLHX
R290,
SL
R290,
SLHX+SL
Capacity Ratio
0.99
1.07
0.82
0.91
COP Ratio
0.99
1.06
0.84
0.92
Same compressor efficiency, 11% lager R290 compressor, same indoor coil temp for SL
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Safety

State-of-the-art technology
Hermetic compressor operating in hermetically sealed
systems
 Using brazed joints
 Brazed heat exchangers to minimize charge
 Avoid the use of suction accumulator
 Isolation of electrical components in air-tight
 Using sealed control devices and spark proof switches
 Leak detection system

Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Conclusions


New regulation in EU: Regulation of HFC-134a from 2009
Performance of HCs in single loop systems:



Slightly better in low temperature applications
Comparable in high temperature application within 6% variation
Design challenges:

Thermophysical properties of HCs:







Good: high specific heat, low viscosity, high latent heat
Poor: low volumetric capacity
Impurities: The purity should be higher than 99%.
Compressor selection: needs about 10-20 % larger displacement
TXV: needs to set to lower degree of superheating
Suction line pressure drop should be considered in tube sizing
Cycle options:


Suctionline heat exchanger (SLHX): improve 6-7%
Secondary loop (SL): worsen 16-17%
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Conclusions-Continued




Additional safety measures are required.
HCs are immediate options for applications
with small charge less than 50g.
HCs garners more attention due to climate
changes.
Increase of natural refrigerants use is
expected in
EU > Japan > USA
Alternative Refrigerant Seminar: Hydrocarbons, 2003
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Gas Price
Grade
Butane Iso-Butane Propane
Ethane
R22
R407C
1.43
9.78
Research
(99.9%)
n/a
n/a
25.84
80.67
Instrument
(99.5%)
10.12
6.13
9.38
11.98
C.P.
(99.0%)
8.50
8.75
7.88
15.21
Natural
(96.0%)
-
-
3.92
-



Price checked January 2003
HCs: from Air Products, Cylinder rental free for 30 days, $0.2/day
R22, R407C: from DuPont local dealer, include cylinder price
Alternative Refrigerant Seminar: Hydrocarbons, 2003

Unit: $/lb
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