Mitsubishi Electric Zuba-Dan

7/27/2019 Mitsubishi Electric Zuba-Dan

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Zuba-Dan Inverter

New Mr.SLIM Inverter for colder climate regions

Mitsubishi Electric CorporationShizuoka Works

2007 JSRAE Technology Award



1. Development background

2. Features of Zuba-Dan models

3Flash Injection Cycle & its characteristics4. Improvement on Start-up & Defrost

5. Field Test Result6. Summary

Mr. SLIM Zuba-Dan Inverter models



1. Development Background



<Min. Temp. in January>(average of 1991 to 2000)


-15 to -20oC in Northernpart of Hokkaido.

Around -10oC in Southern

part of Hokkaido and inTohoku region



<in case of Standard Heat Pump air conditioner>

Electric heater assistedindoor unit

0.4

0.6

0.8

1

1.2

-15 -10 -5 0 5 10

Capacity is reduced at lowambient temperature.

Capacity is reduced by defrostoperation which leads to poor comfortability.

Burner assisted indoor unit

Liquid injection Heat Pump

Heating Peformance Curve




Electric Heater assisted A/C

> Low in operation efficiency.

Burner assisted A/C> Periodical servicing is required for burner.> Requires big installation space.> Big amount of the initial investment.

Liquid INJ COMP mounted A/C

> Limited in injection amount(discharge temperature goes down too much)

> Operation efficiency should be improvedduring injection.

Challenges for Heat Pump*Poor performance at low ambient temperature.*Room temperature goes down during defrost.

Slow in starting up.*Not adequate for use in northern part of Hokkaido.

Required functions for A/Cfor cold climate regions

(1)No periodical servicing is required.

(2)Keeps good performance even atlow ambient temperature.

(3)Highly efficient operation at lowambient temperature.

(4)No drop in room temperaturewhile defrosting.

solution: Zuba-Dan

(5)Can be used in all areas

in Hokkaido.







(1)High heating capacity at low ambient temperature

Our ‘Flash Injection cycle’ (patent to be filed) enables to keepthe maximum heating capacity even at -15

oC.

(2)Comfortability

*Improved defrost control:Defrost duration is reduced to one third of the conventional model.

*Quick start-up:Required time to reach the air blowing temperature of 40oC is halved.

(3)Wider operation range <Industry First!>

Heating operation even at -25oC is possible. (conventionally only to -20oC)

> Possible to be used in all areas in Hokkaido.


(4)Easy and quick installation <Industry First!>The ‘Activated carbon filter ’ and the ‘Wide strainer ’ enable the reuse of

existing piping even when the compressor is broken and the refrigerantoil is contaminated.



3. Flash Injection Cycle & its characteristics



*Flash Injection of refrigerant. Refrigerant heat is recovered by HIC circuit.*Power Receiver circuit without inlet accumulator (good in start up / inlet dry control)*3 LEVs optimally control evaporator, condenser and discharge temperature.

: Refrigerant flow in heating mode<Characteristics>

Injection

Compressor

HIC

LEV A LEV BLEV C

Outdoor HEXIndoor HEX

4-way valveOutdoor unit Indoor unit

Power Receiver (Heat recovery typeliquid pool)

A

B

C

D

E

FGH

J

K

3. Zuba-Dan refrigerant circuit<Flash Injection + Power Receiver Circuit>



0.1

1

10

100 150 200 250 300 350 400 450 500Enthalpy[kJ/kg]

P r e s s u r e [ M

P a ]

A

B

K J

IH

GF

E

D C

Heat Exchangeby heat recovery type receiver

Heat Exchangeby HIC

Injected Gas gets drier >>>

Injection amount is increased. (Toprevent discharge SH to decrease.)

Increased

refrigeration

effect

(1)Increased refrigeration effect (improved refrigerant cycle theory)

(2)Quick recovery from defrosting with no accumulator.

(3)Inlet gas super heat >>> to secure compressor high efficiency

(to avoid liquid compression efficiency to be lowered)

3. Zuba-Dan refrigerant circuit<Zuba-Dan refrigeration cycle (Pressure-Enthalpy diagram)>



: refrigerant flow in heating mode

Injection

Compressor

HIC

LEV A LEV BLEV C

4-way valve

Outdoor unit Indoor unit

Power Receiver (heat recoverytype liquid pool)

AB

C

D

EFGH

J

K

0.1

1

10

100 150 200 250 300 350 400 450 500Enthalpy[kJ/kg]

P r e s s u r e [ M P a ]

A

B

K J

IH

GF

E

D C

Heat Exchange

by heat recovery type receiver

Heat exchange by HIC

Increased

refrigeration

effectI n d o or HE X

O u t d o

or HE X

3. Zuba-Dan refrigerant circuit<Flash Injection Cycle>

(1)Increased refrigeration effect(improved refrigerant cycle theory)

(2)Quick recovery from defrosting with no accumulator.

(3)Inlet gas super heat

>>> to secure compressor high efficiency

(to avoid liquid compression efficiency to be lowered)



Flash INJGas INJLiquid INJ

Injection Compressor

Evaporator Condenser Gas/Liquid separator HIC

X=0.2X=0.21.0X=1.0

Discharge temperature increases>>> capacity cannot be increased a lot= not suitable for a/c for cold regions.

3. Zuba-Dan refrigerant circuit<Comparison with conventional injection>



0.1

1

10

100 150 200 250 300 350 400 450 500Enthalpy[kJ/kg]


Pd

Ps

Pinj

Ge

Gi

Qc

Qe

Inside HEX without HIC

Conditions: Ambient-15oC / COMP 120rps / Heating capacity 14kW

COMP input = 7.13kW

Big amount of liquid injection>>> discharge temperature

decreases.Liquid INJ(w/o HIC)

Flash INJInlet gas gets drier

>>> discharge SH

can be secured.

0.1

1

10

100 150 200 250 300 350 400 450 500

Enthalpy[kJ/kg]

P r e s

s u r e [ M P a ]

“ ŕ• ”” M Ś đ Š ·Š íHIC— L‚ čŹ đ Ś ŹFŠ O‹ C-15 Ž A łŹk‹ @‰ ń“ ] ”120rps A ’ g– [” \ — Í14kW

łŹk‹ @“ ü—Í=6.14kW

Qc

Qe

3. Zuba-Dan refrigerant circuit<Comparison of Flash INJ with Liquid INJ (same capacity basis)>

Inside HEX with HIC


COMP input = 6.14kW



0.1

1

10

100 150 200 250 300 350 400 450 500

Enthalpy[kJ/kg]


Pd

Ps

Pinj

Ge

Gi

Qc

Qe

“ ŕ• ”” M Ś đ Š ·Š íHIC – ł‚ µŹ đ Ś ŹFŠ O‹ C-15 Ž A łŹk‹ @‰ ń“ ] ”120rps A ’ g– [” \ — Í14kW

łŹk‹ @“ ü—Í=7.13kW

Liquid INJ(w/o HIC)

Flash INJ

0.1

1

10

100 150 200 250 300 350 400 450 500

Enthalpy[kJ/kg]

P r e s s u

r e [ M P a ]

“ ŕ• ”” M Ś đ Š ·Š íHIC— L‚ čŹ đ Ś ŹFŠ O‹ C-15 Ž A łŹk‹ @‰ ń“ ] ”120rps A ’ g– [” \ — Í14kW

łŹk‹ @“ ü—Í=6.14kW

Qc

Qe

HIC— L‚č HIC– ł‚µ

Ge kg/h 168.4 174.2

Gi kg/h 84.4 137.4“ fŹ o°Ęß°Ë°Ä deg 20 0

łŹk‹ @‰ ń“ ] ” rps 120 120

Qc ‚‹W 14.00 14.00

Qe kW 8.03 7.01

“ ü — Í kW 6.14 7.13

cop | 2.28(116%)1.96(100%)

3. Zuba-Dan refrigerant circuit<Flash Injection circuit>

COMP input = 7.13kW

Inside HEX with HIC


Inside HEX without HICConditions: Ambient-15oC / COMP 120rps / Heating capacity 14kW

with HIC w/o HIC

discharge SH

input

COMP rotation



3.063MPa(50)

0.269MPa(-30)

0.908MPa

Sub cool 10deg

Super heat 10deg

Evaporator refrigerant amount Ge

Injection amount Gi

*Pomer množstiev α=Gi/Ge*HIC temperature efficiency ε ε=(T5-T7)/(T5-Tm)

Tm: Injection refrigerant temp.

T5:HIC inlet liquid temperature

T7:HIC outlet liquid temperature

Equal entropycompression

Condenser refrigerant amount Ge+Gi

3. Zuba-Dan refrigerant circuit<Theoretical characteristics: calculation conditions>



1.00

1.05

1.10

1.15

1.20

1.25

1.30

1.35

0 0.2 0.4 0.6 0.8 1

HIC Temperature Efficiency ε

R a t i o o f H e a t i n g

C O P &

C a p a c i t y

( b a s e c o n d i t i o n

α = ε = 0 )

ratio of COP

ratio of Capacity

As HIC temperature efficiency increases,heating capacity and COP also increase.

3. Zuba-Dan refrigerant circuit<Theoretical characteristics: temperature efficiency influence>



2.6

2.7

2.8

2.9

3

3.1

0 0.2 0.4 0.6 0.8

Injection Ratio α

D i s c h a r g e P r e s s u r e [ M P a ]

0m

1.5m

3m

HIC Length

40

50

60

70

80

90

100

110

120

0 0.2 0.4 0.6 0.8

Injection Ratio α

D i s c h a r g e T e m p e r a t u r e [

]

0m

1.5m

3m

HIC Length

*Discharge pressure increases as Injection ratio increases.It has got no relations with HIC length.

*Discharge temperature decreases as Injection ratio increases.

3. Zuba-Dan refrigerant circuit<Test Result (1)>



100

105

110

115

120

125

130

135

0 0.2 0.4 0.6 0.8

Injection Ratio α

H e a

t i n g C a p a c i t y R a t i o [

]

0m

1.5m

3m

HIC Length

80

85

90

95

100

105

110

0 0.2 0.4 0.6 0.8

Injection Flow Ratio α

H

e a t i n g C O P R a t i o [

] 0m

1.5m

3m

HIC Length

*Heating capacity gets bigger as the HIC length gets longer.

It depends on the Injection ratio as well but not largely.*COP worsens as the Injection ratio gets bigger.125% Heating capacity / 100% COP is realized when injection ratio is 0.4.

3. Zuba-Dan refrigerant circuit<Test Result (2)>



*Heating capacity is improved by 30% even at same COMP rotation speed (at -15oC)

*Heating capacity is almost doubled with increased COMP rotation speed. (at -15oC)

>>>This was impossible before due to the excessive temp.rise of discharge refrigerant.

0

2000

40006000

8000

10000

12000

14000

1600018000

-25 -20 -15 -10 -5 0 5

Outdoor Temp.mŽn

H e a t i n g C a p a c i t y [ W ]

ConventionalRotational Speed 70%

FLASH InjectionRotational Speed 70%

FLASH InjectionRotational Speed 100%

3. Zuba-Dan refrigerant circuit<Heating capacity at low ambient temp. (comparison with conventional model)>



<LEV> <controls on> A: Suction refrigerant Super HeatB: Condenser Sub CoolC: Discharge refrigerant Super Heat

Suction SH

Discharge SHSC

“d Žq –c ’Ł •Ů A

“d Žq –c ’Ł •Ů C

“d Žq –c ’Ł •Ů B

3 conditions (suctionrefrigerant, condenser and evaporator) isoptimally controlled.

3. Zuba-Dan refrigerant circuit<Flash Injection Cycle Control>

LEV B

LEV C

LEV A



0

5

10

15

20

25

30

35

100 200 300 400

INJ LEV Š J“ x[pulse]

S

H , S C [ d e

“ fŹ oSH

SC

‹ z“ üSH

0

5

10

15

20

25

30

35

170 190 210 230

Ź ă’ iLEV Š J“ x[pulse]

S

H , S C [ d e

“ fŹ oSH

SC

‹ z“ üSH

0

5

10

15

20

25

30

35

100 110 120 130 140

‰ ş’ iLEV Š J“ x[pulse]

S

H , S C [ d e

“ fŹ oSH

SC

‹ z“ üSH

SH

Refrigerant distribution is analyzed when each LEV is controlled individually.

SH

SH SH SC

3. Zuba-Dan refrigerant circuit<LEV characteristics>

discharge SHSCsuction SH



Lower LEV opening (pulse) Upper LEV opening (pulse) INJ LEV opening (pulse)

Suction Super Heat control

Sub Cool control Discharge Super Heat control

Only suction SH responds toline shape.

Influence on refrigerantdistribution.

Discharge SH respondsacutely.



<Purpose>

*3 LEVs operates individually towards different control targets.

*Does individual LEV control interfere each other resulting in unstable refrigerant cycle?

*Most stable control constant is chosen.

<Background>

We apply ‘Quality Engineering’ in order to checkwhether the currently chosen ‘control constant combinations’(current control) is appropriate or not.

3. Zuba-Dan refrigerant circuit<Application of Quality Engineering>



10deg

11deg

9deg

SHs

SHs

time

*What is the stability of the refrigerant cycle?<Definition of Basic Function>

Starting from the stable condition, compressor rotation should be increasedfrom 60 to 70rps. If the integrated value of SHs in the next 10 minutes issmall, it means the stability is high.

)119(0

)11(11

)9(9

,600

)( 260 0

12

SHsSHs

SHsSHsSHs

SHsSHsSHsSHs

t

L

L

L

=∆

>−=∆

<−=∆∆

=

∑=

σ

3. Zuba-Dan refrigerant circuit<System Basic Functions>



Pd

Ps

Pm

Pinj

1

2

3

4

56

7

8

9

Ge

Gi

h1

h2

Vst1[cc/r] = Compressor’s suction volumeVst2[cc/r] = Compression room volumeat the end of injection

*Point 1

Inlet refrigerant (density D1) is trapped in Vst1.

*Point 1 >>> 2

Injection refrigerant (condition 9) is poured

into compression roomExisting refrigerant amount increases to D1 (1+α).

*Point 2 >>> 3

Injection port is closed at the compression roomvolume of Vst2. Normal pressure rise process afterward.

By adjusting the discharge SH at point 3 by α, and

by adjusting Pinj to make the density at point 2 gets D2,

Injection pressure can be calculated.

α = G i / G e

3. Zuba-Dan refrigerant circuit<Injection Pressure calculation method>



Pinj is about 2.5 times of Ps.INJ amount (discharge SH) has

just small influence.

0

0.5

1

1.5

2

2.5

3

3.5

0 0.2 0.4 0.6 0.8 1

Ps[MPa(abs)]

[ M P a ( a b s ) ]

Pd

Pinj(SHd20deg)

Pinj(SHd50deg)

0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1

Ps[MPa(abs)]

I N J

α

INJ (SHd20)

INJ (SHd50)

The lower the Ps is, the bigger the INJ ratio α gets.

The smaller the discharge SH is,the bigger the α gets.

Pd: stable, Ps: variation character

3. Zuba-Dan refrigerant circuit<Injection Pressure>

INJ ratio (SHd20)

INJ ratio (SHd50)

Pressure(MPa(abs)) INJ

ratio

α



4. Improvement on Start up & Defrost



<Standard Accumulator circuit>Refrigerant is pooled in the accumulator during

start up and defrosting. As a result, it takeslong time to start up due to insufficient refrigerantcirculation.

Normal start up: Refrigerant within outdoor HEXmoves into the accumulator.

Defrost: surplus refrigerant is pooledin the accumulator.

<Flash Injection cycle>(1)Start up with a bit ‘return in liquid’ condition as there is

no liquid pool on low pressure side.(to secure circulation amount)

(2)Refrigerant pooled in the receiver during defrostis quickly let return to compressor from injection circuit.It contributes to improve start up characteristics.

(3)Refrigerant circulation amount at start up is securedby Injection.

Injection compressor

HIC

4-way valveOutdoor unit

Power receiver

Compressor

4-way valveOutdoor unit

Accumulator

Slowly returnto suction

through oilrecovery hole.

4. Improvement on Start up & Defrost



0

5

10

15

20

25

30

35

40

45

50

0 5 10 15 20 25 30

(min)

(

)

0

1

2

3

4

5

6

7

8

9

10

(

In accumulator cycle, the temperature does not rise rapidly due toinsufficient refrigerant circulation when starting up.

On the other hand in Zuba-Dan, the discharge air temperature can reachhigh level in short time.

4. Improvement on Start up & Defrost<Start up characteristics (at -10oC ambient)>

Zuba-Dan air discharge air temp.

Accumulator cycle air discharge temp

Zuba-Dan low pressure

Accumulator cycle low pressure

Air dischargetemp (oC)

Time (minute)

Low pressure(MPa)



(1)Quicker start up

*Optimal supply of refrigerant by receiver circuit at start up.

*Refrigerant circulation amount is increasedby Flash Injection.

(2)Shorter defrost

*Defrost is shortened by Flash Injection.

(3)Less frequent defrost

*Less frost on HEX with hydrophilic fins.*Estimation control on Frost formation contributes toreduce defrost frequency largely, especially in lowambient temperature (low absolute humidity).

Better comfort is achievedby ‘Flash Injection cycle’ and ‘new Defrost control’.

4. Improvement on Start up & Defrost<Better comfort with better defrost control>



5. Field Test Result



<Tested units and conditions>

*Test Period: From December 2004 to February 2005

*Test Location: At an office building in Asahikawa, Hokkaido

Žş ŠO ‹@ 11.2KwN ‰ XŽş “ŕ ‹@ 5.6KwN ‰ X ~ c C “”z ŠÇ ’· –ń 15‚Ť§ Śä Žd — l ‡@ Š¦ — â ’n § Śä ( ÝĽŢŞ Ľ®Ý— L )

‡A ’Ę Źí § Śä ( ÝĽŢŞ Ľ®Ý–ł )*‡@ ,‡A ‚đ Śđ ŚÝ ‚É ŽŔ Ž{

‘Ş ’č Ť€ –Ú Žş “ŕ ‹z Ťž / Źo ‰· “xŽş “ŕ ‰· “x •Ş •z AŠO ‹C ‰· “x A

— â ”} ‰· “x AŹÁ ”ď “d — Í — Ę

*Test Points

5. FT Result (1): Office building in Asahikawa City

Outdoor unit: 11.2kW class unit

Indoor unit: 2 units of 5.6kW class

Piping length: about 15m

Control specifications: (1)with Injection (control for cold regions)

(2)w/o Injection (normal control)

*(1) & (2) are both realized alternatively.

Test points: *Indoor inlet & outlet temperature

*Indoor temperature distribution, Ambient temperature,

Refrigerant temperature, Energy consumption



Outdoor unit 2 Indoor units




without INJ >>> with INJCapacity increases by about 30%

Heating Capacity & COP

based on the different ambient temperature

Heating CapacityBasic cycle

Heating Capacity

Injection cycle

Heating capacity:(indoor outlet – inlet) x air volume x density x specific heat

0

2

4

6

8

10

1214

16

18

-25 - -15 -10 -5 0

O‹ C‰·“ ( )

î – {» ˛ ¸

’ g – [ ” \ — Í

(

0

2

4

6

8

10

1214

16

18

-25 -20 -15 -10 -5 0

O‹ C‰·“ . ( )

Ę ’ g ’ g – [ ” \ — Í (

cataloguespecifications

Basic cycle Zuba-Dan

Heatingcapacity(kW)

Heatingcapacity(kW)

Ambient temperature (oC) Ambient temperature (oC)




<with Injection>*Indoor outlet temperature

in stable condition>>> more than 50oC

*To reach indoor outlet temperatureof 45oC>>> takes only about 10 minutes

(when unit starts runningat the ambient temp of -15oC andat the indoor room temp of 23oC)

<Shorter start up>about ½ of conventional model

0

10

20

30

40

50

60

0 5 10 15 20 25Timemmin.n

I n d o o r U n i t D i s c h a r g e @ T e m p . m

Ž n Injection Cycle

Normal Cycle

45Ž

5. FT Result (1): Office building in Asahikawa City<Quicker Start up in Heating operation>



-30

-20

-10

0

10

20

30

40

50

60

12:00 14:00 16:00 18:00 20:00 22:00 0:00 2:00 4:00 6:00 8:00 10:00

Timemhourn

T e m p .

m

Ž n

Ž “ŕ Źo ‰· “x Ž “ŕ ‰· “x ŠO ‹C ‰· “x

<data taken between 25 Jan 2004 (noon) and 26 Jan 2005 (noon)>

<ambient temp.: -20oC>(1)continuous operation of more than 150 min.

(2)Defrosting only for about 3 minutes.

(1) (2)

indoor outlet temp.

indoor roomtemp.

ambienttemp.

5. FT Result (1): Office building in Asahikawa City<Defrosting characteristics>



As the ambient temp. decreases (below 0oC), the average heating operation ratio increases.>>> The operation ratio improves more by extending the continuous operation duration

with no frost on the coil.

<Heating operation ratio>

(Heating operation duration – Defrost duration) /(Heating operation duration)

90%

92%

94%

96%

98%

100%

-25 -20 -15 -10 -5 0

î – { TC N ×ŻĽ- ˛ ĽŢŞ¸Ľ® » ˛ ¸

Š O‹ C‰·“ x.( )

‰ ^ “ ] —

operationratio

minimum temperature in a day

Basic cycle Flash Injection cycle

5. FT Result (1): Office building in Asahikawa City<Defrosting characteristics (operation ratio)>



Feb 2006 (wooden building, door is opened frequently)

4HP wall mounted type indoor unitfor about 30m2 room.

5. FT Result (2): Station waiting room (in Niigata pref.)



-10

-5

0

5

10

15

20

25

30

35

40

45

50

0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 0:00

Indoor Temp.

Ambient Temp.

Outlet Temp.

Defrost (5 times in 12 hours)

Room Temp.

lowered by 2oC

during defrost

Exceeds 45oC in 18 min. from start up.(Room temp. at start up was about 8oC)

(

)

From 06.20 am to 18.30 on 12 Feb 2006.Humidity: 60 – 80 %

Much better comfort can be achieved by ‘quicker start up of heatingoperation’ and ‘improved defrost control’.

5. FT Result (2): Station waiting room (in Niigata pref.)

<Measured Data>

Temp.

(o

C)

Hours (o’clock)



6. Summary



(1)Improved Heating Performance*High heating performance & high COP achieved by Flash Injection.*Operation range extended down to -25oC.

(2)Better Comfort*Start up and Recovery from defrost are improved very much

by Injection together with Receiver circuit.*Defrosting frequency at below 0oC ambient is reduced to about 1/3.

(3)Exsisting piping can be reusedeven though the compressor was broken down.

*Since its launch in July 2005, Zuba-Dan has beenhighly appreciated in cold regions such as in Hokkaido.

*Zuba-Dan technology has also been adopted toour City Multi (VRF) since December 2006.

6. Summary: Following functions are realized as the A/C for cold regions



For which application do you need ZubaDAN?

Can you use Zuba Dan Air to Air without cooling function?

How do you calculate the cooling and heating capacity

What do you expect from ZubaDan?

ZubaDan

Which price is accaptable in comparison to Power Inverter?5% 10% 20% 30% 40% 50 %



Thank you very much!

Documents

Mitsubishi Electric Zuba-Dan