An experimental investigation which seeks the fundamental relationship between the interfacial condensation rate and the parameters which control it when the liquid side is turbulent is discussed. The scaling laws for free-surface condensation are discussed for this case. It is argued that the condensation of cryogenic liquids can, in principle, be simulated in experiments using steam and water. Data are presented for the condensation rate in terms of the dimensionless scaling parameters which involve the fluid properties and the liquid-side turbulence velocity and length scales

Helmick, M. R.

Khoo, B. C.

Sonin, A. A.

English

NASA Technical Reports Server

Vapor Condcna8tion on 8 Turbulent Liquid Interfrce’ 
M. R. Helmick, B. C. Khoo and A. A. Sonin** 
*) I 
. A  
I a* Department of Mech8nic81 Engineering I ’  I 
htf8888ChU8Ctt8 Inrtitute of Technology I,),,/’ ‘7 J * 
Cambridge, MA. 02139 i -  
ABSTXWX 
The ra t e  at which vapor condanses onto a subcooled liquid is 
controlled by latent heat transport from the interface into 
the bulk of the liquid. Turbulence on the liquid side is 
particularly effective in maximizing this transport. This 
paper describes an experimental investigation which seeks 
the fundamental relationship between the interfacial 
condensation r a t e  and the parameters which control i t  when 
the liquid side is turbulent. The scaling laws for f r e e -  
surface condensation a r e  discussed for this case, and i t  is 
argued that the condensation of cryogenic liquids such as 
hydrogen can in principle b e  simulated with ruitable 
experiments using s t e a m  and w a t e r .  Data a r e  presented for 
the condensation r a t e  in terms of the dimenaionlers scaling 
parameters which involve the fluid properties and the 
liquid-side turbulence velocity and length scales, and the 
application of the data is discussed. I t  is pointed out 
that the steam-water condensation process becomes unstable 
when the liquid-ride turbulence intensity exceeds a 
threshold value. Above the threshold, very short, high- 
intensity bursts of condensation occur intermittently. Our 
scaling laws do not apply to these bursts, and i t  is not 
known whether they can occur with typical cryogenic fluids, 
though we present some arguments for why they should be l e s s  
likely to be t r i g g e r e d  in cryogens. 
* 
Presented at the Cryogenic Fluid Management Technology 
Workshop, April 28-30, 1987, NASA Lewis Research Center, 
Cleveland, Ohio. 
Enquiries should be addressed to Prof. Ain A. Sonin, Room 
* *  
-3-256-, MIT, Cambridge, MA 02139. Telephone (617)  253- 
2 2 4 7 .  
Thie Research is sponsored by the NASA Lewis RGsearch Center 
under Grant NAG 3-731. 
30 1 
https://ntrs.nasa.gov/search.jsp?R=19880006557 2020-03-20T07:48:36+00:00Z
ek . 
302 

Exampk 
304 
ORIGINAL PAGE IS 
QE POOR QUALITY 
TABLE 1 :  h4AJOR CONCEPTUAI. hDDELS FOR 
TRANSPORT ACROSS SURFACE 
-~ 
ASSUMPTIONS I
MODEL 
1 .  Large-eddy m o d e l  
(Forteacue & 
Pearron, 1967 
a 
a 
I I 
I I 
2. Small (Kolmogorov) 
eddy m o d e l  
(Lsmont & Scott, 
1970) 
a 
I I 
1 I 
3. Vircoua inner layer 
m o d e l  ( r e e  text) a 
4 .  H e n s t o c k  & H a n r a t t y  
(1979) a v2/v3A 
5. Levici. (1962) a 
1 A/v I 6. Kirhinevrky (1955) 
CONDENSATION 
STANTON NO. 
stc - v - 1 ( a / r ) " 2  
Stc- cs ZPr' Re -r 4 
Stc - C6 
- 
D - liquid thermal diffurivity Sc I V/D Schmitt number 
v - r.m.8. turbulent 
fluctuating velocity R e  E v A / U  Eddy Reynolds number 
U *  - shcur ve1oci:y 
, cond. S t a n t o n  N o .  mc hfg of turbulent eddies stc - A - integral length scale 
V . liquid kinematic vircosity pc ATv 
p - liquid denrity 
0 - rurface tension 2 3 ( U  Ohaesorge no. P 2 . -  - 
305 c, to c6: constants 
Scaling parameterr for steady vapor c o ~ d e n a a t i o n  of rubcooled 
llquld: rome cornparlions between hydrogen and water. 
v: 
p. abrolute pressure 
TI, raturation temperature 
Tb, bulk liquid temperature 
-: 
Prb, bulk llquid Prandtl 
Pr,, liquid raturatlon 
c AT/h 
number 
Prandtl number 
P f g  
H2 
2 . 5  bar 
( 3 5  psis) 
2 4K 
2 0 . 3 - 2 4  K 
1.3 
1.3 
0-0. I 
1.01 bar 
1 O O O C  
2 0 - 8 5 O C  
2 - 7  
1.8 
0-0.1s 
€I20 
3 . 1 9  bar 
135OC 
8 0 -  135 '  
1 . 3 - 2 . 2  
1 . 3  
0 - 0 . 1 1  
4 . 4 6  bar 
147OC 
20-93OC 
2 -7  
1 . 2  
0 . 1 - 0 . 2 5  
Nomcnclatura: Subscriatl: 
c .. bulk llquld specific heat a t  8 : a t  aaturation temperature 
AT - liquid rubcooling 
f g  
P constant pressure b : at bulk liquid temperature 
h - latent heat of condensation 
306 ORIGINAL PAGE IS 
OF POOR QUALITY 
SYSTEM DIA. 
D -  
NOZZLE DIA. 
d- 
Tin - I 
t STEAMOUT 
IN 
1 
.- 
I 
2 
VOL. FLOW 0 
DRAIN 
COOLER 
Test cell 
307 
- 0.0s t- 
OKGINAL PAGE IS 
POOR QUALITY 
I.U:i I I I I ? ~ ~ ~  rements o f  horfzontal and vertical rms veloclty 
fluctuations in the damped layer near the interface. 
shown i s  the correlation o f  Sonfn e t .  a l .  for large distances 
below the interface. 
Also  
0.015 T 
ORIGINAL PAGE IS 
&).E POOR QUALIW 
r 
c 
b . 
% 
822 
2.2 
2-8 
2-7 
veri0 ble 
5 
0 
7- -1 
Visua l  o b s e r v a t i o n s  o f  a thermal  s t r a t i f i c a t i o n  a t  the  
i n t e r f a c e  a t  low t u r b u l e n c e  i n t e n s i t i e s .  
Exper f rn t r l  corrdJtlocrr 
v' 0.3 m/s 
ATmub 60' C 
H 0.13 I) 
OFJGINtaL PAGE IS 
GF BOOR QUALITY 
A pmtrum h l r t o y  durlng a condenrrtlm 
burst. 
310 
0.3 
0.2 
n 
(I) 
\ 
E 
Y 
-v) w 
0.  I 
1 I I I 
O A  oa 
0 
0 
A 
0 
0 
A -  O * 0 . 0 3 8 m ,  z/0=3.15 
0 - 0=0 .152m,  r / D = 3 . l 7  
0 - 080.152m. r/0*3.67 
30 40 5 0  60 7 0  80 
AT ( K )  
31 1 
CONDITIONS PRIOR TO AND 
Sttadt!stateuburst 
c o n d e n s a t i o n  mass flux 
v a p o r  m o m e n t u m  flux 
0 
DURING CONDENSATION BURSTS AT AT "70 C .  
c o n d e n s a t i o n  h e a t  flux into w a t e r  
t h e r m a l  l a y e r  thicknires 
thrcshard ( v '  6 = 0 . 1 5  m/s) 
c. - 0 . 1 8  kg/mLs 
- 0.42 MV/m 3 0.006 H20 mc/Ps team 9, 
6 - 0.1 mm 
2 
2 
average c o n d e n s a t i o n  mass flux m H 20 kg/m s 
average v a p o r  m o m e n t u m  flux 
a v e r a g e  c o n d e n s a t i o n  heat flux into w a t e r  
d u r a  t ion At N 6 ms 
final 
' 9  E= 68 mm H20 
m c / ~ s t , a m  2 
N 4 5  W/rn 9, 
thickness of l a y e r  h e a t e d  by burat b g ^ . 2 m n  
JHaior Conclusiong 
1. Condensation rate quantified i n  terms of 
Fluid properties 
Liquid-side turbulence characteristic v ' ,  A 
2. Turbulence characteristics v ' ,  d can in principle be 
obtained fran turbulence model (e.g. k-t: model) 
3. High intensity condensation bursts identified at high 
turbulence intensities in steam/water system. 
No basic theory; not clear whether bursts will occur i n  
cryogenic fluids. 
312 
SPEAKER: A. A. SONIN/MASSACHUSETTS INSTITUTE OF TECHNOLOGY 
John R. Schuster/General Dynamics Space Systems: 
It looks as though in your model that you have ignored what takes place in the 
vapor. Is the mass transfer process through the vapor to the liquid-vapor 
interface dominated by diffusion or by convection? 
Sonin: 
In this case, the vapor is basically considered to be still. There is no forced 
convection on the vapor side; there is just feeding of the vapor as it slowly 
moves towards the interface. Since it is just pure vapor on the vapor side it 
doesn’t go through anything, and there is no other gas to diffuse through. 
Sc hus ter: 
I understand that. It’s self diffusion, yet the transport mechanism has got to be 
either molecular diffusion or convection. 
Sonin: 
It is pure convection. You have an interface and the vapor is just in bulk 
motion toward the interface and it disappears at the interface and turns to 
liquid. It moves through nothing, and not even relative to itself. There is some 
turbulence which is associated with it, but, basically, the controlling factor is 
the latent heat transport from the interface. The huge latent heat deposit at 
the interface has to be taken down into the bulk of the liquid, and that controls 
the condensation rate. 
David Daney/National Bureau of Standards: 
I may have observed this same type of condensation burst instability with 
superfluid helium during rapid pressurization of dewars and in transfer lines 
where a banging, crashing, and pinging noise is heard. 
Sonin: 
That sounds very interesting. I would like to talk with you about that 
afterwards. This is quite an audible instability; it is like a little crack or a snap 
when it occurs. What we observe when we inject steam into liquid is a sudden 
burst on the interface, and there is also a snap. I think it is the same thing 
that occurs in nuclear systems, a so called chugging, when you inject vapor into 
liquid and there is a sudden condensation phenomena. 
Robert Hendricks/Lewis Research Center: 
The model that you have is quite similar to Thomas’s replacement model, but you 
didn’t mention it, or maybe you didn’t even use it. 
Sonin: 
I know of Thomas’s work. 
31 3 
Hendric ks: 
Ok, I think it is pretty good. To follow up on the other question; kinetic 
theory is still applicable here. I don’t know how you can say that the vapor 
just slowly moves down; I think that is something you better take a look at. 
You should consider the fact that you do not have uniform condensation over 
the surface. If you did, you wouldn’t have any turbulent eddies underneath the 
surface. You have cellular patterns underneath the surface. You are assuming 
that things are quiescent and they are not. 
Sonin: 
Where do you want me to start answering your questions at this point? 
Hendricks: 
You can start any place you want to, but you are going to have a tough time 
explaining that the surface is uniform when it is not. 
Sonin: 
We do not assume that the surface is uniform, nor, by the way, do I have a 
theory for this. The curve that I presented was purely empirical not theoretical. 
The surface is turbulent; the turbulence is imposed from the liquid side. The 
vapor does what it wants to arrive and condense onto the surface at the various 
points and times consistent with what goes on in the liquid as it removes the 
latent heat. I make no assumption about everything being absolutely static, but 
what I am saying is that it is the liquid side conditions which control the 
condensation rates; that is all that is coiicluded in this model. This modelling is 
an empirical modeling and not a theoretical one. Kinetic theory, of course, is 
always valid. I am familiar with kinetic theory, having taught it, but it has 
nothing to do with what happens at the liquid side. On the steam side, the 
steam is slowly drifting down to neet  the interface and will condense there. 
Hendricks: 
I guess I would disagree with you there because kinetic theory is pretty 
explicate in that region, and it does predict the necessary condensation 
coefficients. You do have accommodation coefficients, you do have surface 
tension effects, you haven’t considered damping in the surface due to surface 
tension, and I don’t understand why you used the K-Epsilon model when a zero- 
order Prandtl model might be equally applicable. Why go to a two equation 
model for something which you don’t know anything about? 
Sonin: 
The two equation model is not used foitanything other than for a better idea to 
calibrate the system. It is not being used at all to characterize what happens at 
the interface. In fact, it can’t be used because you can’t really apply the 
boundary conditions for the K-Epsilon niodel at the free surface. There is no 
turbulence model for the free surface; what I am saying is that it is a useful 
crutch to predict what the turbulence is near the free surface, and you can 
apply this correlation to understand what the condensation rate is at the surface 
based on what the flow conditions are near it.  
31 4 
Hendricks: 
Sounds to me that like you used the Prandtl model anyhow. 
Sonin: 
I haven? used the Prandtl model at all. 
Hendricks: 
It didn’t sound to me like you used the K-Epsilon model in your description. 
Sonin: 
I didn’t really describe what I did. If you want to talk about this later, I’d be 
perfectly happy to describe what we did theoretically, but we have no theory 
that applies to the condensation rate. As far as the kinetic theory is concerned, 
the only thing the kinetic theory does, as far as predicting the condensation 
rate, is to deal with the case when it is vaporside controlled, and it gives you 
an idea, for example, what, if any, Delta-T exists between the saturation 
temperature and the liquid temperature at the interface; it has nothing to do 
with the this problem. 
Hendricks: 
What is your guess as to how much you have to increase the surface area to 
account for the fact that you have a non-uniform surface, essentially due to the 
turbulence below? 
Sonin: 
The turbulence intensities were moderate for the tests presented. You could 
look at the surface and you could say the surface area is perturbed very little 
due to the turbulence. You could crank up the turbulence until you had big 
waves on the liquid surface, but  that  is not the conditions we looked at. The 
surface area did not change except when instability occurred. In that case, with 
the onset of the instability, the surface was more wavy, there was a higher 
degree of turbulence, and then the burst instability caused a roughing of the 
surface on a small, submilimeter scale. That also increased the surface area. 
That changed the whole process of condensation. Under the conditions we were 
looking at, with the exception of burst instabilities, the surface area was well 
characterized. 
v 
31 5 


Vapor condensation on a turbulent liquid interface

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