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R290 RAC

李廷勋/Li Tingxun Litx@hotmail.com

November 2019, Brasilia, Brazil


Contents • Performance

• Design • Safety

• Q&A November 2019, Brasilia, Brazil


Performance

November 2019, Brasilia, Brazil


• A lot of papers have been published to compare performance of alternative refrigerants with R22 or R410A. • The comparisons are almost performed within two separate groups, R22 and R410A series. • Most of the papers consider only cooling but not heating

November 2019, Brasilia, Brazil


Conditions for theoretical analysis Atmosphere/℃

27

35

46

52

55

Atmosphere/℃

7

2

-5

-10

-15

Evaporating/℃

11

12

13

15

15

Evaporating/℃

3

-1

-8

-13

-17

Condensing/℃

37

44

54

60

63

Condensing/℃

43

36

33

30

28

Subcooled/℃

9

8

7

7

7

Subcooled/℃

15

12

7

6

5

Superheat/℃

5

6

7

8

8

Superheat/℃

2

2

1

1

1

November 2019, Brasilia, Brazil


Theretical Performance

Cooling

Heating November 2019, Brasilia, Brazil


Design

November 2019, Brasilia, Brazil


Component

Normal Working Electrical Parameters

Working and Construction Feature

Terminal (except using screw fastening with anti-loosening 220V/380V,AC function,

Screw fixed type:Using screws to fix and making deformation turn into pressure.

PCB(control board)

220V-240V,AC/DC

By the integration of ac and dc to output and control

Capacitor(including “connecting” part)

220V-450V,AC

Relay( 220V-240V,AC including“connecting”part) Contactor( 220V-240V,AC including“connecting”part) Motor (Except the motor without 220V-240V,AC/DC brush or plastic-coating motor )

Quick plug type: Using quick plug without anti-loosening device.

Running with motor or compressor,voltage is high when running, fixed frequency air-conditioner frequently starts

Thermal fuse link( 220V-240V,AC including“connecting”part) Four-way valve 220V-240V,AC Transformer 220V-250V,AC Motor-compressor( excluding external electrical AC/DC parts)

NO No , if the board is empty NO

By starting up and shutting down to control the motor, to make it frequently starts

YES if not solid state type

By starting up and shutting down to control the motor, to make it frequently starts

YES

plastic-coating type:coil and motor are plastic-coating metallic shell :no-sealing

Fuse link(overcurrent)( 220V-240V,3.5-10A It is generally sorted into glass tube type and ceramic tube type used for circuit protection including“connecting”part) Electric heating thermostat (including thermal protector 220V-240V,AC )( including“connecting”part)

Whether Could Be the Source of Ignition or not

Thermostat which could be adjusted or fixed, During normal working period, by circuit opening or closing automatically to make it sure that the components are kept in a suitable limited values.

YES as the motor has brushes we may recommend induction motor a) NO for ceramic type b) yes for glass type if they operate in the event of a leak c) No, generally. YES

During abnormal working period,this device works by automatically cutting off the circuit No unless it operates in or reducing the current to limit the components temperature, according to its structure, user the event of a leak cannot change the setting value By magnetic flux controlling mechanical valve. Motor coil is plastic-coating. Possibly No Safety isolating transformer and switching mode power supply transformer NO Motor-compressor is composed of the mechanical structure and motor, compressor and NO motor are both sealed in a sealing shell without external shaft seal. The motor operates in the refrigerant which could be used with


Approach 1: use of explosion -proof components to ensure that there are no ignition sources in R-290 unit to avoid possibility of fire even flammable refrigerant leaks. Approach 2: adding protection measures to make sure that the concentration of the flammable refrigerant around the potential ignition sources is less than LFL (or 25%LFL refer to the standards).

November 2019, Brasilia, Brazil


Heat Exchanger • There is no need to change the tube diameter and thickness for heat exchangers • The heat exchangers need to be optimized especially for condenser in outdoor unit where most of the refrigerant is always in liquid form which constitute a major part of total mass of refrigerant.

9.52 7.94 7.00 5.00

4.00

• Small tube diameter heat exchanger or Microchannel heat exchanger is useful

November 2019, Brasilia, Brazil


Mechanic Structure

• The indoor unit mechanical structure theoretically does not need changes • The outdoor unit for flammable refrigerants can be the same as of R22 units • Develop a new structure to avoid accumulation of leaked flammable refrigerant and speedy dispersement of refrigerant to reduce the potential fire risk.

November 2019, Brasilia, Brazil


Electric heater

• Electric heater might be used for heat pump • Resistance heater or PTC heater are mostly used in ACs. • For the safety reason, the hot surface temperature needs to be controlled • It is recommended to use ceramic PTC heaters AC with flammable refrigerants.

November 2019, Brasilia, Brazil


Compressor • No need to change in the design pressure except matching in volumetric capacity of the compressor which may be lower by 10% to 15%. • The electrical/ electronic components like overload protector, relay etc need to be replaced by spark-free components. •

The connectors need to be upgraded to reduce the potential fire risk by short circuit. Uncovering metals with electric should be avoided as possible. Increased creepage distance is necessary and a unitary electric connector is always helpful.

• In order to reduce refrigerant charge quantity the compressor, mechanical parts need to be optimized and improve efficiency.

November 2019, Brasilia, Brazil


Printed Circuit Board (PCB) • Most of the parts on the PCB of R-290 AC remain the same as in the case of R-22 units. • Components which are the potential ignition sources must be replaced with Explosion-Proof components . For example, the glass fuse should be changed to ceramic fuse . The capacitance protection class should be upgraded. • There is no need to make such changes if an enclosed envelope is designed for the PCB

November 2019, Brasilia, Brazil


Connecting tubes • All connecting tubes exposed to outside need to be protected. • The use of polyurethane or polythene insulation material is recommended for protection

of the tube if its thickness is enough. • Although, the use of screw connector was not allowed in the 4th edition IEC 60335-2-40, it has been allowed in the newest 5th edition of the standard.

November 2019, Brasilia, Brazil


Lubricant Oil

• Lubricant oil is not only for lubrication but also for sealing of the compressor moving parts. • Reducing the refrigerant mass absolved in the oil is an effective way to reduce the total refrigerant charge mass. • The oil for R22 or R410A are not recommended to be used directly for R290.

• It is recommended use either mineral oil with higher viscosity than used in HCFC-22 unit or polyol ester oil with higher viscosity than used in R-410A.

November 2019, Brasilia, Brazil


Package

• No specific requirements for package in the standards for flammable refrigerants units. •

It is recommended for packaging of outer door unit, use anti-static plastic envelope for the safety in case there is leak during transportation.

• In addition, leak detection is needed before installation to ensure that the refrigerant has not been leaked during transportation.

November 2019, Brasilia, Brazil


Label •

Flammable sign and refer to the document sign are needed both in indoor and outdoor units.

•

Flammable label should be permanent but not erased or removed easily

Indoor unit labels of R290 AC in China

Outdoor unit labels of R290 AC in China November 2019, Brasilia, Brazil


Contactor

There might be a spark from the contactor, it is recommended either use an explosive- -proof Otherwise, it should be installed in an explosive proof sealed box

November 2019, Brasilia, Brazil


Safety

November 2019, Brasilia, Brazil


=

R290 is flammable

AC is flammable AC is ignited

=

=

AC with R290 is flammable

AC must be ignited

Explosion


The Fire Triangle 

u

Oxidizers – – –

Fuels: –

Liquids Gases Solids

Liquids v

Solids v

v

Sparks flames static electricity heat

plastics, wood dust, fibers, metal particles

Gases v

Ignition sources

gasoline, acetone, ether, pentane

v v v

Acetylene propane carbon Monoxide hydrogen November 2019, Brasilia, Brazil


 500 million HC fridge/freezers, ignition frequency about 1×10-8 per year

HC refrigerator annual market (World)

 HC fridge/freezers are Safe enough

HC refrigerator current market (China)

 Is AC with R290 safe if the risk is same with HC fridge?

HC air conditioner current stock (World) Air Conditioner annual market (China) 0.1

1 10 100 Millions of units

November 2019, Brasilia, Brazil


Criteria Frequency of ignition (y-1)

Ignition events per million per 10 y

“Acceptable” risk to public

Refrigerator

Air cond

< 1×10-5

6×10-8

5×10-10

100

0.6

0.005

Daniel Colbourne,Comparative quantitative risk analysis (QRA) of domestic refrigerator and room air conditioner using R290, CHEAA INTERNATIONAL WORKSHOP FOR IMPLEMENTING HPMP OF RAC SECTOR,2011,Hangzhou,China

November 2019, Brasilia, Brazil


A series risk assessment of R290 RAC have been finished by institutes and companies in China

November 2019, Brasilia, Brazil


Leak tests â&#x20AC;&#x201C; Indoor refrigerant concentration profile â&#x20AC;&#x201C; Highest concentration and location

November 2019, Brasilia, Brazil


•Lab(4.8m×3.6m×2.4m) •in Tianjin Fire fighting Research Institute

•Lab(5.4m×4.4m×2.6m) •in Tianjin Fire fighting Research Institute November 2019, Brasilia, Brazil


November 2019, Brasilia, Brazil


The flammable range of a release of R-290 is only located within the close locality of the indoor unit, implying that only sources of ignition present in the immediate vicinity of the indoor unit have the possibility to ignite a leak of refrigerant.


No

Compressor on

Leaking rate fast

Leaking point

off

slow

101

102

103

104

105

106

107

108

201

202

203

204

indoor

connector

Fan speed High

off

        

 

 

 


November 2019, Brasilia, Brazil


泄漏点正下方(0.5m)浓度 The R290 concentration underneath the leaking point 120

B2

Concentration(LFL%)

Leaking 80

A1 A4 A7 B8

60

A2 A5 A8 B5

A3 A6 A9 B2

40 20 0 0

100

200

300

Leaking

Flambale

400

500

Time(s)

A (Leaking fast and RAC fan off)

600

700

Concentration(LFL%)

100

B2

100

Flambale A1 A4 A7 B8

80 60

A2 A5 A8 B5

A3 A6 A9 B2

40 20 0 500

1000

1500

2000

2500

Time(s)

B (Leaking slowly and RAC fan with low speed)

It is found that the B2’s concentration will get combustible no matter the RAC fan is on or off. November 2019, Brasilia, Brazil


Summaries â&#x20AC;˘

â&#x20AC;˘

The indoor R290 concentration would not be flammable except the part space just under the leak point The R290 will diffuse quickly and the indoor concentration become homorganic after the leak stop

November 2019, Brasilia, Brazil


Different charge mass with different airflow rate

50

40 30 Floor Middle Roof

20 10 0 200

700

1200 Time(s)

350g-fan off (Theoretically 14.9%)

700g-1000rpm (Theoretically 29.9%)

70

1200

60

1000

50

800

40

600

30 Floor Middle Roof

20 10 0

400

Mass(g)

Concentration(LFL%)

60

800 700 600 500 400 300 200 100 0

Concentration(LFL%) Mass(g)

70

200 0

100

600

1100 Time(s)

1000g-1400rpm (Theoretically 42.6%)

November 2019, Brasilia, Brazil


• Airflow can affect the refrigerant diffusion greatly for R290. • Larger leaked mass rate needs higher airflow rate for example, 175g/min needs 369m3/h airflow • With airflow, the concentration can mix well

November 2019, Brasilia, Brazil


700g-214m3/h

700g-369m3/h

November 2019, Brasilia, Brazil


50s

250s

November 2019, Brasilia, Brazil


Leak time=50s

Leak time=100s

Leak time=150s

Leak time=200s

November 2019, Brasilia, Brazil


Ignition tests â&#x20AC;&#x201C; Flammability with different location ignition source â&#x20AC;&#x201C; Risk of ignition or explosion if possible

November 2019, Brasilia, Brazil


Indoor unit ignition tests

Output Voltage: 2500V

Diffuser ignition energy:20J

Ignition frequency:14 times/s

November 2019, Brasilia, Brazil


Leak time

Location of ignition

Result

1

240s

h=50cm

NO propagation

2

180s

h=50cm

NO propagation

3

190s

h=8cm

NO propagation

4

185s

h=0cm

NO propagation

192s

h=160cm

6

427s

h=50cm

NO propagation

7

196s

h=30cm

NO propagation

8

190s

h=30cm

NO propagation

9

246s

h=30cm

NO propagation

415s

h=30cm

NO propagation

11

240s

h=160cm

NO propagation

12

210s

h=160cm

NO propagation

No

5

10

Leak point

Pipe connector

Evaporator

Propagation lasts for 1-2 seconds and within 1-2 meters

November 2019, Brasilia, Brazil


No fire propagation

With fire propagation

Video of ignition tests November 2019, Brasilia, Brazil


热流计冷却水串联 布置,此处为进口

摄像头

窗 室 内 机

T6

T1、H1

T4、H4

T2、H2

T5、H5

热流计冷却 水出口

T1—T6为热电偶 H1—H5为热流计

T3、H3

热电偶、热流 计线束出口

摄像头

Temperatures when the indoor unit was fired November 2019, Brasilia, Brazil


热流计冷却水串联 布置,此处为进口

3kw/m^2 located 1m from the unit

摄像头

窗 室 内 机

T6

T1、H1

T4、H4

T2、H2

T5、H5

热流计冷却 水出口

T1—T6为热电偶 H1—H5为热流计

T3、H3

热电偶、热流 计线束出口

摄像头

Heat flux when the indoor unit was fired

November 2019, Brasilia, Brazil


6.5Kp,1m from the RAC unit

热流计冷却水串联 布置,此处为进口

摄像头

窗 室 内 机

T6

P1

T1、H1

P2

P3

P4 T4、H4

T2、H2

T5、H5

1m 热流计冷却 水出口

T1—T6为热电偶 H1—H5为热流计

T3、H3

热电偶、热流 计线束出口

摄像头

Measured pressure when the indoor unit was ignited and propagation was happened November 2019, Brasilia, Brazil


Propagation test inside the RAC unit(video) November 2019, Brasilia, Brazil


Pressure

Time

November 2019, Brasilia, Brazil


Conclusions  Hard to ignite the R290 AC indoor unit  When the RAC is fired, the maxim heat flux is about 3kW/m2  The highest temperature is about 200 ℃  The biggest overpressure is about 6Kpa even there is fire propagation

 No explosion, the most dangerous is the smoke November 2019, Brasilia, Brazil


Test of combustion of RAC

November 2019, Brasilia, Brazil


Heat flux

Heat

November 2019, Brasilia, Brazil


R22

R290

No refrigerant

Maximum Heat flux(kW)

1001

976

479

Total heat(MJ)

102

132

116

November 2019, Brasilia, Brazil


Conclusions  Similar maximum heat flux for R290 and R22  Similar total heat for R22,R290 and no refrigerant  The most heat is from RAC itself

November 2019, Brasilia, Brazil


Risk of Ignition of outdoor unit

November 2019, Brasilia, Brazil


Conclusions  Hard to ignite the R290 AC outdoor unit  Only when keep igniting inside the outdoor unit, it can be fired  No damage to the nearby RAC

November 2019, Brasilia, Brazil


Thank for your attention TINGXUN LI Sun Yat sen University Phoneï¼&#x161;+86 135-3350-9330 E-mail: Litx@Hotmail.com

Profile for Protocolo de Montreal - Brasil

4-Estudo de caso Conversão de Ar Condicionado para R-290 - Tingxun Li  

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