(Thai)Investigation on Characteristics of Ejector Refrigeration Using CFD

7/25/2019 (Thai)Investigation on Characteristics of Ejector Refrigeration Using CFD

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. 33 6(639 - 654) - 2549KKUEngineering Journal Vol.33No.6 (639654) November December2006

*

1)1)Masud Behnia2)1)3)1)..2)Dean of Postgraduate Study, University of Sydney, Sydney, NSW, Australia

3).Email: [email protected]

(ejector refrigeration)

(compressor) Computational Fluid Dynamics (CFD)FLUENTCPM CMA 120oC-140oC5oC-15oC CFD (effective area) (axis symmetric) 3 (3D)

:, , Computational Fluid Dynamics (CFD)

*1 2549 28 2549


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Investigation on Characteristics

of Ejector Refrigeration Using CFD*

Wirapan Seehanam1)Kulachate Pianthong1) Masud Behnia2)Thanarath Sriveerakul1)

and Satha Aphornratana3)

1) Department of Mechanical Engineering, Faculty of Engineering, Ubon Ratchatany University.

2) Dean of Postgraduate Study, University of Sydney, Sydney, NSW, Australia.3) Department of Mechanical Engineering, Sirinhorn International Institute of Technology, Tammasat

University.

ABSTRACT

Ejector refrigeration system is usually designed to utilize the low-grade energy for driving the cycle.

It also has a low maintenance cost, because it operates without compressor. Mainly, the ejector performancedirectly affects the refrigerating performance. Therefore, an investigation on characteristics and an efficient

design of the ejector areimportant to improve the ejector refrigeration system. In this study, ComputationalFluid Dynamics (CFD) code (FLUENT) is employed to predict the flow phenomena and performance of

CPM and CMA steam ejector. The ejector refrigeration system, using water as the working fluid, is operatedat 120oC-140oC of boiler and 5oC-15oC of evaporator temperature. CFD can predict the ejector performance,very well and reveals the effect of operating conditions on an effective area which is directly related to its

performance. Besides, it is found that the flow pattern doses not depend much on suction zone because theresults of axis symmetric and 3D simulation are similar. This investigation aids to understand the ejector

characteristics and provide the information for designing ejector to suited the optimum condition.

Keywords : Ejector, Ejector refrigeration, Computational Fluid Dynamics(CFD)

*Original manucript submitted: June 1, 2006 and Final manucript received: September 28, 2006


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2 Entrainment ratio, Em (1) CriticalBack Pressure (CBP)

Entrainment ratiom

mass flow rate of secondary flowE =

mass flow rate of primary flow (1)

2 constantpressure mixing (CPM)constant mixing area (CMA)(2.7) CMA mR CBP CPM mR CBP (Computational FluidDynamics : CFD)

2(a) constant-pressure mixing ejector (b) constant-area mixing ejector

Keenan (Keenan, J.H. et al.,1942 andKeenan, J.H. et al.,1950) 1

(a) Constant Pressure Mixing (CPM)

(b) Constant Mixing Area (CMA)


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643

(constant capacityeffect) Munday J.T. (Munday, J.T. et al.,1997) (soniccondition)(choking ) (effective area) 3

CFD

3

CFD Riffat, S.B. (Riffat, S.B. et al., 2001) (methanol) Rusly, E. (Rusly, E. et al.,2002 and Rusly, E. etal.,2005)2 real gas model Seehanam, W. (Seehanam, W.et al.,2005) Rusly, E. (Constant Rate of Momentum Changes ,CRMC) CMA CPMCFD

Secondary fluid

Secondary fluid

Primary fluid

Effective area

Jet-core


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644 Masud Behnia

42 1)(primary nozzle) 2) 4 (secondary inlet) ,(mixingchamber), (throat) (diffuser)

FLUENT(Chunnanond, K et al., 2004) (axis symmetry) 48,0004 k realizable (Near-walltreatment)(standard near wall function) couple-implicit pressure inlet pressureoutlet(energy equation) 3hexahedral5,000,0005 3

(ideal gases) (2)

opP

0

opP P

RT

+

= (2)

+ -

4CFD

ThroatMixing chamber Diffuser

NXP

Nozzle


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53D CFD

2 3

3 CPM 6 ( nozzle) 1 mbar (fluctuation) shock train shock train

3

0 50 100 150 200 250 300 350 400 4500

10

20

30

40

50

Staticpressure(mbar)

Position along ejector (mm)

CPM ejector, Boiler 130oC Evaporator 10

oC Condenser 40 mbar

2D 3D

62 () 3


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CFD

CFD Chunnanond, K. (Chunnanord, K. et al.,2005)CFD 7 Em CBP 10%6% CFD 7

20 30 40 50 60 70

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Em

Condenser pressure(mbar)

Evaporator 10oC Boiler

Exp: 120oC 130

oC 140

oC

CFD: 120oC 130

oC 140

oC

20 30 40 50 60 70

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Em


Boiler 130oC Evaporator

Exp: 15oC 10

oC 5

oC

CFD: 15oC 10

oC 5

oC

(a) (b)

7CFD (a) (b)

CPM CMA

Em CBP


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EmCBP EmCBP CMA (Em) CPM CMA CPM8 Em

8(a)

8(b)

0 10 20 30 40 50 60 700.0

0.1

0.2

0.3

0.4

0.50.6

0.7

0.8

Em


Evaporator 10oC and Boiler

CMA 120oC CMA 130

oC CMA 140

oC

CPM 120oC CPM 130

oC CPM 140

oC

0 10 20 30 40 50 60 70

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Em


Boiler 130oC and Evaporatror

CMA 5oC CMA 10

oC CMA 15

oC

CPM 5oC CPM 10

oC CPM 15

oC

(a) (b)

8

(a)(b)

NXP

(NXP) 9 (Nozzle Exit Position, NXP) (Maximumentrainment ratio, Max.Em)


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648 Masud Behnia

Em NXP CFD

-15 -10 -5 0 5 10

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8Max.Em

NXP

Evaporator 10oC Boiler

CMA 120oC CMA 130

oC CMA 140

oC

CPM 120oC CPM 130

oC CPM 140

oC

-15 -10 -5 0 5 10

0.0

0.1

0.2

0.3

0.4

0.50.6

0.7

0.8

Max.Em

NXP

Boiler 130oC Evaporator

CMA 5oC CMA 10

oC CMA 15

oC

CPM 5oC CPM 10

oC CPM 15

oC

(a) (b)

9(a)

(b)

Throat

(TL) NXP = 0 mm = 125 mm4 CPM CMA

20 30 40 50 60

0.0

0.1

0.2

0.3

0.4

0.5

0.6

CMA Ejector Boiler 130oC and Evaporator 10

oC

Throat lenght,TL-125 (mm) 40 80 95

120 160 180 200 220

Em

Condenser pressure (mbar)20 30 40 50 60

0.0

0.1

0.2

0.3

0.4

0.5

0.6

Em


CPM Ejector Boiler 130oC and Evaporator 10

oC

Throat lenght,TL(mm) 10 40 70

95 130 160 190 220

(a) (b)

10 throat (a)CMA(b) CPM


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10 TL TL CBP 10(a) CMATL-125 CBP 95-120 mm. 10(b)TL 130mm. CPM CBP TL CBP11 12 TL Max.EmTL EmTL

0 50 100 150 200

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Max.Em

Throat length(mm)

Evaporator 10oC Condenser 20 mbar Boiler

CMA 120oC CMA 130

oC CMA 140

oC

CPM 120oC CPM 130

oC CPM 140

oC

0 50 100 150 200

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Max.Em

Throat length(mm)

Boiler 130oC Condenser 20 mbar Evaporator

CMA 5oC CMA 10

oC CMA 15

oC

CPM 5oC CPM 10

oC CPM 15

oC

(a) (b)

11 TL Em

(a)(b)

CFD CFD

CFD


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123

12 3 (Mach number)X Y 130oC , 10oC30 mbar

choking

() 3

( on design conditions) Em (backpressure) CBP (off design condition)


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13 (path line) CMA (reverseflow) (Em)

13

throat CFD

CFD

(3) CFD CFD 14 15 jet-core

(a) (b) (c)

14jet- core (a) 120oC, (b) 130oC (c) 140oC


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(a) (b) (c)

15jet-core (a) 5oC, (b) 10oC (c) 15oC

14 jet-core 140oC(14(c) 120 oC 8 (a) 15 jet-core

8 (b)

14

15

(a) (b) (c)

(d) (e) (f)

16jet core (a) 20 mbar , (b) 25 mbar , (c) 30 mbar, (d) 35 mbar(CBP), (e) 38 mbar (f) 40 mbar


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(back pressure) 16 CBP Em CBP Em

( CBP ) CBP

Em

(layer) 2 1 CPM CMA

Em 2 TL 10 11 TL Em

3 CFD CFD CFD


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Chunnanond, K. 2005. A study of steam ejector refrigeration cycle, parameters affecting

performance of ejector. Ph.D. Thesis, Sirindhorn International Institute of TechnologyUniversity Thailand

Chunnanond. K. and Aphornratana, S. 2004. An experimental investigatation of a streamejector refrigerator: the analysis of the pressure profile along the ejector. Applied

Thermal and Energy. 24:311-322.Keenan, J.H. and Neumann, E.P. 1942. A simple air ejector. Transactions of the ASME.

Journal of Mechanics.64:75-81.Keenan , J.H., Neumann, E.P. and Lustwerk. 1950. An investigation of ejector design by

analysis and experimentTransactions of the ASME. Journal of Mechanics. 72 : 299-309.

Munday, J.T. and Bagster, D.F. 1997 . A new theory applied to steam jet refrigeration.Industrial and Engineering Chemistry Process Design and Development.16(4) : 442-449.

Riffat, S.B. and Omer, S.A. 2001. CFD modeling and experimental investigation of an ejectorrefrigeration system using methanol as the working fluid. International Journal ofEnergy Research. 25:115 -128.

Rusly, E., Lu Aye., Charters, W.W.S., Ooi, A. and Pianthong, K. 2002. Ejector CFDmodelling with real gas model Proceedings of the 16th Annual conference of

Mechanical Engineering Network Thailand, Phuket, Thailand : Paper TF 136.Seehanam, W., Sahumin, K.,Pianthong, K. and Behnia, M. 2005. Prediction of flow

characteristic and performance of steam ejector in refrigeration cycle using CFD.Proceedings of the 8th Asian Symposium on Visualization, Chiangmai, Thailand :

Paper 10.

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(Thai)Investigation on Characteristics of Ejector Refrigeration Using CFD

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