Slide 1

Report
THE LOOP HEAT PIPE
FOR AMS-02
Stefano Zinna
Marco Marengo
LSRM, Faculty of Engineering, University of
Bergamo, viale Marconi 5, 24044 Dalmine,
Italy
Inside ANTASME
OBTAINED RESULTS
8.1 The LHP for AMS is built and
run for orbital conditions
8.2 The ground LHP for AMS is
built and stationary results
are compared with LHP model
in microgravity
8.3 The construction of the
thermal chamber in China is
delayed (cancelled)
8.4 A simplified model of the LHP
is carried out in order to be
implemented in
multidisciplinary codes
9.3 The LHP model has been run
by including the FEM results
about valve
INDEX
1.
2.
3.
Simulation of the LHP prototype in the
thermal chamber (ground test)
(deliverable 8.2)
Definition of data input and output
structures for future implementation
in general multidisciplinary codes
(deliverable 8.4)
Implementation of the FEM data in the
SINDA/FLUINT network scheme
(deliverable 9.3)
Deliverable - 8.2
Simulation of the LHP prototype in the thermal chamber
(ground test)
Ground LHP results


TCC
The ground propylene LHP
has been implemeted: The
model has different correlation
for pressure drop and
condensation in the twophase part (condenser)
The reservoir temperature
(TCC) and subcooling
temperature (TS) are
compared with microgravity
model
TS
CONDENSER
254
252


Stationary mode is run with
power from 30 W to 90 W
The 1G results have
temperature lower than mG
while the power is increasing
The temperature difference is
about 2° for 90W
250
248
246
TCC (mG)
244
242
T [K]

TS (mG)
240
238
TCC (G)
236
TS (G)
234
232
230
228
226
224
30
40
50
60
Q [W]
70
80
90
m-G/1G PRESSURE DROP
m-G

Bubbly/Slug flow: McAdam’s formulation for homogeneous flow

The annular regime: Lockhart-Martinelli correlation
(Zhao L. Rezkallah K.S., 1995. Pressure drop in gas-liquid flow at microgravity
conditions. Int. J. Multiphase Flow 21, 837-849)
1G

The predicted pressure drops is based on the Muller-Steinhagen and Heck
correlation (John R. Thome, Wolverine Engineering Data Book III, 2006)
The factors A and B are the frictional pressure gradients for all the flow
liquid and all the flow vapour
1G Model SLIP FLOW

The Tabular connector
device allows users to
specify flow rate versus head
(or pressure drop)
relationships in tabular (array)
formats

The gravitational forces are
independent of the velocity
while the friction and the
acceleration forces are
function of the square of the
flow rate

These coefficient are
inserted in the equation for
the fluid path while the
vapour path is set in order to
satisfy the slip flow model
chosen
m-G/1G pressure drop differences

The Clausius–Clapeyron correlation is used to calculate the temperature
difference in the two-phase part of the condenser
Q [W]

MICROGRAVITY
NORMAL GRAVITY
DT
DP (Pa)
DT
DP (Pa)
30
0.008
69.3
0.012
97.2
60
0.076
701.7
0.095
874
90
0.16
1815.7
0.16
1791
THE TEMPERATURE DIFFERENCE IS WEAKLY RELATED TO THE
PRESSURE DROP
m-G/1G CONDENSATION
m-G
The condensation heat transfer coefficient for two-phase flow is based on Shah’s
correlation (Po-Ya Abel Chuang, An improved steady-state model of loop heat
pipes on experimental and theoretical analyses. 2003, Phd Thesis)

1G
The correlation is based on Dobson and Chato method. (Soliman transition
criterion) (John R. Thome, Wolverine Engineering Data Book III, 2006)


The annular correlation:

The stratified-wavy correlation:
GRAVITY FLOW PATTERN

The Soliman transition criterion
for predicting the transition from
annular flow to stratified-wavy
flow was used
350

The G is always lower than 500:
G (30W)=9.3; G (60W)=18.7; G
(90W)=28
300
225
240
255
270
285
300
315
ANNULAR
250

The transition from stratified to
annular is with quality between
0.6 and 0.8 depending on the
temperature
Froude
200
K
K
K
K
K
K
K
150
100
50
transition
STRATIFIED
0
0,0
0,2
0,4
0,6
X
0,8
1,0
m-G/1G condensation differences
TRANSITION
225 K
285 K
315 K
8,0
7,5

7,0
6,5
Q
6,0
90 W
5,5
5,0

4,5

4,0
3,5
3,0
2,5
30 W
2,0
1,5
0,0
0,2
0,4
0,6
0,8
Stratified-wavy Dobson &
Chato heat transfer compared
with Shah heat transfer
High quality
The heat transfer coefficient
difference is higher with higher
power incoming the
evaporator
1,0
X
TRANSITION
9
225 K
285 K
315 K
8
7

6
5
4
3

2

1
0,1
0,2
0,3
0,4
0,5
0,6
X
0,7
0,8
0,9
1,0
Annular Dobson & Chato heat
transfer compared with Shah
heat transfer
Low quality
The heat transfer for D&C is
always higher
CONCLUSIONS

The gravity model temperatures are lower than
the microgravity model and the difference is
increasing while the power incoming in the
evaporator is increasing
 The pressure drop has a negligible
influence on the temperature drop in the
two-phase condenser
 Wider two-phase lenght for high power
 Higher difference in the heat transfer for
high power
Deliverable - 8.4
Definition of data input and uotput structures for future
implementation in general multidisciplinary codes
ANALYTICAL MODEL
(Evaporator balance)
•To test the SINDA/FLUINT results
and to understand which are the
most important parameters that
influence the LHP in order to set the
input/output structures
•The heat absorbed from the cryoocooler crosses from the evaporator
wall to the solid wick and it is shared
between Fluid wick and Reservoir:
•The pressure in the end of the liquid
line is close to the saturation pressure
& the liquid flow rate depends on the
power and the evaporation enthalpy
at saturation temperature (Tsat):
UW
Gback
ANALYTICAL MODEL
(Radiator balance)
•The temperature changes depends
only on the axial conductances with
the evaporator wall and can be
considered negligible while the
pressure drop has a small influence
on the enthalpy:
•The power rejected from the
radiator (Qout) is due to the
radiation towards the external
environmental
ALGEBRAIC SYSTEM
•The algebraic system has now 5
parameters: UWB, QCRYO, Qflux, Grad,
Tsink:
300
280
T [K]
260
240
220
200
•The results are shown in the graphic
for the steady state operating
temperature: (a) Qflux=70 [W],
Uwb=25/3 (b) Qflux=0 [W], Uwb
=25/3 (c ) Qflux=70 [W], Uwb=25/6.
For all the cases the radiative
conductance Grad is 5.010-9 [W/T^4]
and the Tsink is 170K.
180
Tsink
0
20
40
60
80
100 120 140 160 180 200 220 240 260
Q [W]
CONDENSER TEMPERATURE

The initial part of the pipe is
near the end. The high
temperature of the incoming
two-phase fluid causes a
important heat transfer to the
outgoing fluid, the TS increases
and consequently the TCC is
higher.

Another heat flux is exchanged
between two parts of the same
condenser in the middle of the
radiator and leads to the first
maximum in figure.
Input/output structures

Where Lo is a system operator, t is
time, x(t) is the state of the system,
u(t) is its input, w(t) is some external
or internal disturbance, and l is a
parameter that defines the system.
Each one of these quantities belongs
to a suitable set or vector space and
there are a large number of
possibilities

y: the steady state operating
temperature and subcooling
temperature; u: the power coming in
the evaporator; w: the boundary
conditions (the external fluxes in the
radiator, the radiative conductance
and the sink temperature for the
radiator); l : the ratio between the
conductance inside the wick and the
conductance from the wick to the
reservoir, and the radiator area.
INPUT
OUTPUT
SYSTEM
BOUNDARY
CONCLUSIONS


An analytical model is carried out in order to
achieve a simplified model: good
approximation of the SINDA results for high
power
The input/output structures are defined: the
solver Lo could be by the analytical model
(Lo-> an algebraic operator ) or the sinda
model
SINDA
ANALYTICAL MODEL
Deliverable - 9.3
Implementation of the FEM data in the SINDA/FLUINT
network scheme
LHP-VALVE

Temperature requirements:
Q
Min. turn-on and operational
temperature of the Cryocooler
263K
Max. operational temperature of
the Cryo-cooler
313K
WORST CONDITIONS
(Coldest environment, nominal
working (2LHP), minimum
power (61W)) :
226K< TCRYO <230K
TCRYO
EVAPORATOR
VALVE

CRYOCOOLER
TCC
OPEN
CLOSE
MODE
MODE
L
H
RADIATOR
P
TRAD
EXTERNAL AMBIENT
Implementation of the FEM data



The information about the valve come
from FEM ANALYSIS (Speetjens M. &
Rindt, C. 2006 Numerical analysis of
the bypass valve in aloop heat pipe,
INTERREG IIIC MATEO-ANTASME
Deliverable 9.2. )
The solver is only sinda (NO analytical
model)
The pressure drop :
VALVE
SINDA
1 set point
264

OPEN MODE:
TCRYO<263
CLOSE MODE:
TCRYO>263
262
TCRYO
TRCC
260
258
T [K]

256
254
252
250
8000

The temperature in
the cryo react
quickly to the open
mode
The temperature in
the cryo reachs
262.7
9000
9500
10000
time [s]
280
TCRYO
TCC
R
260
TRAD
T [K]

8500
240
220
200
5000
10000
15000
time [s]
20000
25000
2 set point


OPEN MODE:
TCRYO<263
CLOSE MODE:
TCRYO>265
Valve between the
open and the close
mode:
263<TCRYO<265
264
TCRYO
TR
262
CC
260
T [K]

266
258
256
254
252
8000
8500
280

The temperature
requirements are
satisfied
The temperature is
2° higher than 1 set
point
9500
10000
TCRYO
TCC
260
TRAD
T [K]

9000
time [s]
240
220
200
5000
10000
time [s]
15000
CONCLUSIONS


The FEM data are inserted in the sinda
model and two cases are run depending
on 1/2 set points
There is a little inertia between the
compensation chamber and the cryo


a higher set point should be chosen
2 set point should be definied

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