1.
 The Study on Model Simulation and Experiment for Mass Transferin Bubble Mode Absorber of Ammonia and Water
  

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(2001

The Study on Model Simulation and Experiment for Mass Transfer in Bubble Mode Absorber of Ammonia and Water

Jae-Cheol Lee, Ki-Bong Lee, Byung-Hee Chun, Chan-Ho Lee, Jong-Joo Ha and Sung-Hyun Kim^†

Department of Chemical Engineering, Korea University, Seoul 136-701, Korea (Received 16 August 2001; accepted 13 December 2001)



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Abstract−An absorber is a major component in the absorption refrigeration systems and its performance greatly affects the overall system performance. In this study, both the numerical and experimental analyses on the absorption process of bubble mode absorber were performed. Gas was injected into the bottom of absorber at constant solution flow rate. Region of gas absorption was estimated by both the numerical and experimental analyses. Higher flow rate of gas makes the region of gas absorption increases. As the temperature and concentration of input solution decrease, the region of gas absorption goes down.

In addition, the absorption performance on the countercurrent was superior to that of cocurrent flow. Mathematical model equa- tions were derived from material balance for gas and liquid phase based on the negligible mass transfer of water from liquid to gas phase. Comparison of model simulation and experimental results shows similar values. This means that this numerical model can be applied for design of bubble mode absorber.

Key words: Absorption Process, Absorption Heat Pump, Ammonia-Water, Bubble Mode, Heat and Mass Transfer

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†To whom correspondence should be addressed.

E-mail: kimsh@korea.ac.kr

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Fig. 1. The stages of ammonia absorption process.

K 5 kgùf/cm² )Kyf+ vc (n)Kh2IPump5 &7 5 6>?µ, on/off ,$, metering ,$ …] 1/4 in F-.F Ž  ú/ Swagelok5 &7 56>?). 6s6 flow meter ú/ Krohne 5 signal converterk, =˂ýÂ6 flow meter ™6I 20 L/

min 0x Hi-Tec5 $c EF6 MFCk 56>?). ab= D 

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zY±T).

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” =Ë ‚Æ7 ®h(1-9 L/min);2E#3 bš>?). K¾ % ÂÃ

3 §•” =Ë 6s7 3 w 4àn#3 %% ¡

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= [ K`ë _ÂE ”6 Åxë _ ·>Œ abd7 Ý>

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;>?µ, ‚ý 6sI] 3 w »w7 ڔ= [ D

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;Fm 56& ab=3 ·lÂÃ ¦ D ÂÃ ¢Ok [ Table 1 2/>?).

Fig. 2. The theoretical schematic of numerical analysis.

Fig. 3. Experimental absorption system

1. Absorber 18. Cartridge heater

2. Manometer 19. Data aquisition system

3. NH₃ bomb 10. Solution tank

4. Sampling port 11. Solution pump

5. Thermocouple 12. Flow meter

6. Valve 13. Neutralization tank

7. Venting

Fig. 4. Schematic of bubble mode absorber.

 40 2 2002 4

4.   

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[ D v83 R9V ß ÓK ab= ­] 3 cm, 6s

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=Ë ab= >Å3 x2V ‚I ‚ý& L E2>?).

¦ D ] i%bk ný>µ ;š¨ b ¥ ;FmKÍ bœ5

¼; i%b 56> ¿ Âà 2>?). c (11)-(14)3 ; Ú b (<K ´K ¯– ab= C©, 6s ²©E ®hö ¯–

ŒU E ®bE ‚= ë=&y ®hV). „5‹ =ƒ }

­ ®h ¯– ab= ´K(Z), 6s ‚I(m), 6s ²©(X), a b= C©(T) ™>Œ Wú„v2c (11)-(14)k ö> y › ¡k 2/>?).

Fig. 5 ­K 3 cm ab= >Å$3 6sK 28%, 288 K

‚ý&µ Ó] >Å$ 0.3 cm ?/êF „Hë3 §•” =ËE

‚ý ¾ ab= ´K ™V 6s C©, ²© ®hk zY@ L K). abd V ab= ± C©®h 6s ²© ®h©k 

# é`ab»¼7 A Ú b (). =ËE 1 L/min(Reo=552) „ 5 — c (2)k Õ= =ƒ Ì= 56>?µ ab»¼] % 10 cm K>»¼Kµ 5 L/min(Reo=2760) — 40 cm, 9 L/min(Reo=4968.15)

 — 70 cm K> »¼3 é` ab‹). Fig. 6] 6s C

©E 283 K ‚ý — 5 ¡K). 288 K¾ ¢ ab»¼ K BC DÒ7 ; Ú b (). abW] C© EFV öbKµ a b=3 abd7 ‰ GH7 b ( i%‰E Iö7 Œn ¡K=© >). Fig. 7] =Ë sË ‚ývw7 }™

V ¡K). 6s ‚ý²© C© 28%, 283 KK). Fig. 73 ; Ú b (<K 3 ¢ w — lxÂÃ3 ab»¼ ´K E 15 cm EIKz DÒ7 Ú b ().

4-2. & '(

%% D Âà ¯– ab»¼ 4 =ƒ ³Ž »¼7 È>=

[>Œ ²©, C© 4 ÀÁ7 2>?). Fig. 8] 288 K §•” = Ë §•” 30% 6sK ab= >Å$ ný&y 3 k ¾

 ´K ¯° ²© ®hk Œ"). EF ný ‚ÆK ´” bª,

²© ¤E _¼K #' K¾ ´KE ¤E¨bª, 6s ²©© ¤E V). KUV wq] ²©’ ”•– C©›Jf3© zYzµ, %

´K) œ‹ ú8(manometer)  2‹ ÀÁ ™V Ô K8 ÖS>Œ › ab»¼ =ƒ ³Ž ´Kk ñ¨ b (). 30%

Table 1. Comparison experimental operation conditions with those of typical absorber for heat pump system

Experiment in this study Typical absorber

Pressure 1 bar 0.5-4 bar

Temperature 295-310 K 300-340 K

Re._sol. 530 500-100

Re._gas 500-3,000 500-1,500

Fig. 5. Numerical simulation of cocurrent system 1(at input solution’s temperature=288 K).

Fig. 6. Numerical simulation of cocurrent system 2(at input solution’s temperature=283 K).

6s 9 L/min §•” =Ëk ný> — =Ë ab´Kk

% 70 cm ¨ b (T).

wD 3© ¡ 3 — KE, L] EF ‚Æ

3 20 cm KÑ ²©E Ý x2>', ´] EF ‚Æ3 ab

= >Å$3 ab& ¿' M] EF :K ¤E>Œ IV ab

= ´KE ¤EV). ’“ ”•– ný6s ²©E ´7bª ³Ž E

F ´K ¤E> N7 zY@). 3D  ¢ D  ÔK8 k ž>Œ3© › ab»¼7 È^+ Ú b (Tµ =ƒ ³Ž ´K ÛV A OP¨ b (T). Fig. 93 † b (<K 288 K 30% 6 s 9 L/min §•” EFk ný> — 60 cmK> »¼3 abE ™$„ xyM7 Ú b (). Fig. 10] 6s ²©k 20%

>Œ =Ë }™vw ný;Q w D  ¡K). Fig. 9 ¢ O>Œ † ¾ È^+ =Ë ab´KE JyŸ N7 Ȩ b ().

ný 6sK 20% — 30% 6sx ¾ ¢ =ËnýIK 9 L/min

 — ™ 25 cm EIK Jyæ).

¦ D 7 ž>Œ WÀ, WC ÂÃ3 §•” ab= 2a bRKk ¨ b (Tµ, 6s =Ë nývw ¯–, §•

” 6s ný²© ¯– ab´K ®hE EFö7 Ú b ().

4-3.    )*

Fig. 11] 3 ­ ný 6s C©k 288 K >?7 ¾ a b=3 ²© „ƒ ™V 5¡ D œk ¢OV LK). Fig.

12 w ­ 283 K 6sK ný ¾ 5¡ D œk

¢OV LK). 5 ¡ D D  ` (7 b (  …

¢STq7 ¨ b ¥“, Fig. 11-123 † b (<K ab= 9 Ë3 xyz' ( wqKz é` ab´K …] D ¡  5¡E ”n ; xœ>' (Ò7 Ú b (). ÛV abE xyˆ Ñ Fig. 7. Numerical simulation of countercurrent system(at input solu-

tion’s temperature=283 K).

Fig. 8. The effect of gas flow rate on temperature profile(cocurrent).

Fig. 9. Effect of gas flow rate on concentration profile(countercurrent 1).

Fig. 10. Effect of gas flow rate on temperature profile (countercurrent 2).

 40 2 2002 4

 ©> Ö ²© (y3© ¢UV ¡k zY±' (). ›U z 3 ¡ ¢ w ¡E 5¡ D œ ¢O?7 E V L zYˆ). › K‚ 5¡E
S V ˆ…

 ¢STq ™V »w7 GV LKÍ 3 ¢ W™

5W‹). ÛV w ­ ¡3 5¡ ¢ ab»¼K Ì

 zYˆ L] =Ë „5_3 „5ÀÁK (y W ¢ =ƒE X° Æ© Wá>= ¾K). ›Uz 5¡ Y"qK D 

¡k ž>Œ È&Tµ KUV D 7 ž>Œ '( Ȩ b ¥

i%b »wKz, 'C Û 'À ÂÃ3 ab= Ýl ÛV x2

?7 Y[ Š3 5k ž>Œ ¨ b (Ò7 úV).

5.  

§•” =Ë ab ™V b 5 D  ¢Ok ž>Œ

)Ò Ó] ¡¹7 ÇT).

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¼K Zyzµ, ný6s ²©, C©E L7bª, ÛV ný6s n ý=Ë vwK 3 wk K[ ¾ „5& =Ë ab»¼K J yæ). 3 cm ­ ab=k žV D 3 WC, WÀ3 ™

70 cm 2© ab´KE Iö7 Ú b ().

(2) rI  ™V  9] ì;>µ §•” =Ë Åvw ab2 2V ÿ D  ¡ › wq ¡í (y xœk K' (y ¦ ÿ Y"q 6E¸qK £¤&T).

(3) ¦ ÿ7 ž>Œ D  W>= yà! 'C, 'ÀÂÃ

3 D ab27 E¸>µ, D abc def 6 E¸

V ab= · u6 E¸>).

 

¦ ^_ ‚®\2^_]8(V/ŽÅ ERC) ^_  bš&Tµ K ^K F5Ÿ_•).



1
Lee, K. B.: “Study of the Absorber for Ammonia-Water Absorprtion Heat Pump,” Ph. MA. Thesis, Korea University, Seoul, Korea(2001).

2. Lee, K. B., Chun, B. H., Lee, J. C., Park, C. J. and Kim, S. H.:

Experimental Heat Transfer, in press(2001).

3. Kang, Y., Lim, W. M. and Kim, S. D.: HWAHAK KONGHAK, 25, 460(1987).

4. Lee, K. B., Chun, B. H., Lee, J. C., Park, C. J. and Kim, S. H.: HWA- HAK KONGHAK, in press(2001).

5. Sujatha, K. S., Mani, A. and Srinivasa Murthy, S.: International Commu- nity Heat Mass Transfer, 26, 975(1999).

6. Herbine, G. S. and Perez-Blanco, H.: ASHRAE Transactions, 101, 1324 (1995).

7. Sujatha, K. S., Mani, A. and Srinivasa Murthy, S.: Heat and Mass Transfer, 32, 255(1997).

8. Merrill, T. L. and Perez-Blanco, H.: International Journal of Heat and Mass Tranfer, 40, 589(1997).

9. McCabe, W. L., Smith, J. C. and Harriott, P.: “Unit Operations of Chemical Engineering,” McGraw-Hill, Singapore, 115(1993).

10. Seader, J. D. and Ernest, J. H.: “Separation Process Principles,” Wiley, New York, 123(1998).

11. Treybal, R. E.: “Mass-transfer Operations,” McGraw-Hill, New York 139(1980).

12. Reid, R. C., Prausnitz, J. M. and Poling, B. E.: “The Properties of Gases and Liquids,” McGraw-Hill, Singapore(1986).

13. Perry, R. H. and Green, D. W.: “Perry’s Chemical Engineers’ hand- book,” 6th ed., McGraw-Hill International Editions, Japan(1984).

14. Korean Thermophysical Properties Data Bank of Thermodynamics and Properties Lab. of Korea University.

Fig. 11. Comparison between simulation and experimental data 1(input solution 288 K, cocurrent).

Fig. 12. Comparison between simulation and experimental data 2(input solution 283 K, countercurrent).