Introduction to Loop Heat Pipes p p Jentung Ku g NASA/ Goddard - - PowerPoint PPT Presentation

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https://ntrs.nasa.gov/search.jsp?R=20150018090 2018-05-15T17:56:28+00:00Z Introduction to Loop Heat Pipes p p Jentung Ku g NASA/ Goddard Space Flight Center GSF C 2015 Introduction to LHP - Ku 2015 TFAWS Outline From Heat Pipe to

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SLIDE 1

Introduction to Loop Heat Pipes p p

Jentung Ku g NASA/ Goddard Space Flight Center

GSF C· 2015

Introduction to LHP - Ku 2015 TFAWS

https://ntrs.nasa.gov/search.jsp?R=20150018090 2018-05-15T17:56:28+00:00Z

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SLIDE 2

Outline

  • From Heat Pipe to Loop Heat Pipe (and Capillary Pumped

Loop)

  • LHP Operating Principles

LHP Operating Principles

  • LHP Components Sizing and Fluid Inventory
  • LHP Operating Temperature Control
  • LHP Start-up
  • LHP Shutdown
  • LHP Analytical Modeling
  • LHP Analytical Modeling
  • Recent LHP Technology Developments

Introduction to LHP - Ku 2015 TFAWS 2

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SLIDE 3

From Heat Pipe to Loop Heat Pipe From Heat Pipe to Loop Heat Pipe and Capillary Pumped Loop

Introduction to LHP - Ku 2015 TFAWS 3

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SLIDE 4

Heat Pipes - Heat Transport Limit

  • For proper heat pipe operation, the

total pressure drop must not exceed its capillary pressure head . Ptot ≤ Pcap,max Ptot = Pvap+ Pliq + Pg

Liquid Flow Heat Sink Heat Source wall L e L a L c

Pcap,max =  cos/Rp

  • Heat Transport Limit

– (QL)max = QmaxLeff – Leff = 0.5 Le + La + 0.5 Lc

wall Liquid Flow Evaporator Condenser Adiabatic S ti Vapor Flow

Vapor Vapor

eff e a c

– (QL)max measured in watt-inches

  • r watt-meters
  • Capillary pressure head:

P 1/ R

Section Section Section

Liquid Pressure Drop Pressure Capillary Pressure Vapor Pressure Drop Liquid Li id

Pcap  1/ Rp

  • Liquid pressure drop:

Pliq  1/ Rp

2

A ti l di i t f

Le La Lc Liquid No Gravity Force Adverse Gravity Force

  • An optimal pore radius exists for

maximum heat transport.

  • Limited heat transport capability
  • Limited pumping head against gravity

Introduction to LHP - Ku 2015 TFAWS 4 Distance b) Vapor and liquid pressure distributions

p p g g g y

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SLIDE 5

Evaporator Wick Heat In

Constant Conductance Capillary Pumped Loop

S Vapor Out Heat Out Liquid In Vapor Subcooling Liquid Leg Condenser Duct Heat Out High Velocity Vapor Plus Liquid Wall Fil Vapor

Bubble

Liquid “Slug” Film Flow Forces Predominate Surface Tension Forces Predominate

  • Wicks are present only in the evaporator, and wick pores can be made small.
  • Smooth tubes are used for rest of the loop, and can be separately sized to

reduce pressure drops.

Introduction to LHP - Ku 2015 TFAWS

  • Vapor and liquid flow in the same direction instead of countercurrent flows.
  • Operating temperature varies with heat load and/or sink temperature.

5

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SLIDE 6

Variable Conductance Capillary Pumped Loop

Reservoir Evaporator Liquid Line Vapor Line

  • The reservoir stores excess liquid and controls the loop operating

Condenser

The reservoir stores excess liquid and controls the loop operating temperature.

  • The operating temperature can be tightly controlled with small heater

power.

  • The loop can be easily modified or expanded with reservoir re-sizing.
  • Pre-conditioning is required for start-up.
  • Evaporator cannot tolerate vapor presence, may be prone to deprime

Introduction to LHP - Ku 2015 TFAWS 6

during start-up.

  • Polyethylene wick with pore sizes ~ 20 µm
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SLIDE 7

Capillary Two-Phase Thermal Devices

Heat In Reservoir Evaporator ne Evaporator Reservoir Heat In Liquid Line Vapor Line Condenser/Subcooler Vapor Lin Liquid Line Heat In/Out Condenser Line Heat Out Wick Structure Container Wall QOUT QIN Liquid Flow Vapor Flow Condensation Evaporization Introduction to LHP - Ku 2015 TFAWS 7 q

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SLIDE 8

CPL and LHP Flight Applications – NASA Spacecraft

TERRA 6 CP HST/SM - 3B; 1 CPL Launched Feb 2002 TERRA, 6 CPLs Launched Dec 1999

AURA, 5 LHPs Launched July 2004

Introduction to LHP - Ku 2015 TFAWS 8

ICESat, 2 LHPs

Launched Jan 2003 SWIFT, 2 LHPs Launched Nov 2004

GOES N-Q, 5 LHPs each Launched 2006

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SLIDE 9

CPL and LHP Flight Applications – NASA Spacecraft

SWOT, 4 LHPs To be launched GOES R-U, 4 LHPs each To be launched ICESat-2, 1 LHP To be launched

  • LHPs are also used on many DOD spacecraft and commercial

satellites.

Introduction to LHP - Ku 2015 TFAWS 9

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SLIDE 10

Introduction to Loop Heat Pipes

Introduction to LHP - Ku 2015 TFAWS 10

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SLIDE 11

Schematic of an LHP

Primary wick Arteries Compensation Chamber Evaporator Bayonet A Primary wick Secondary wick Secondary wick Bayonet Vapor Grooves Vapor line Vapor grooves Liquid line A y

Section A-A

Condenser

  • Main design features

− The reservoir (compensation chamber or CC) forms an integral part of the evaporator assembly integral part of the evaporator assembly. − A primary wick with fine pore sizes provides the pumping force. A secondar ick connects the CC and e aporator

Introduction to LHP - Ku 2015 TFAWS

− A secondary wick connects the CC and evaporator, providing liquid supply.

11

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SLIDE 12

Main Characteristics of LHP

Heat In Vapor Line uid Line Evaporator Heat In/Out Reservoir Heat In Condenser/Subcooler V Liqu Heat Out

  • High pumping capability

– Metal wicks with ~ 1 micron pores – 35 kPa pressure head with ammonia (~ 4 meters in one-G)

Heat Out

p ( )

  • Robust operation

– Vapor tolerant: secondary wick provides liquid from CC to evaporator

  • Reservoir is plumbed in line with the flow circulation.

– Operating temperature depends on heat load, sink temperature, and surrounding temperature. – External power is required for temperature control. Limited growth potential

Introduction to LHP - Ku 2015 TFAWS

– Limited growth potential

  • Single evaporator most common

12

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SLIDE 13
  • The total pressure drop in the loop is the sum of viscous pressure drops in LHP

LHP Operating Principles – Pressure Balance

The total pressure drop in the loop is the sum of viscous pressure drops in LHP components, plus any pressure drop due to body forces: Ptot = Pgroove + Pvap + Pcond + Pliq + Pwick + Pg (1)

  • The capillary pressure rise across the wick meniscus:

Pcap = 2 cos /R (2)

  • The maximum capillary pressure rise that the wick can sustain:
  • The maximum capillary pressure rise that the wick can sustain:

Pcap, max = 2 cos /rp (3) rp= radius of the largest pore in the wick

p

g p

  • The meniscus will adjust it radius of curvature so that the capillary pressure rise

matches the total pressure drop which is a function of the operating condition: P P (4) Pcap = Ptot (4)

  • The following relation must be satisfied at all times for proper LHP operation:

Ptot  Pcap max (5)

Introduction to LHP - Ku 2015 TFAWS

Ptot  Pcap, max (5)

13

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SLIDE 14

Pressure Profile in Gravity-Neutral LHP Operation

Capillary Force Driven

P1

Vapor Channel Primary Wick Secondary Wick Bayonet 2 6

1

P2 P3 P4 P5 P6 sure

Reservoir Evaporator 1 7

  

Press P

Vapor Line Liquid Line Condenser

Location P7

7 (Liquid) (Liquid) 3 5 4

  • Evaporator core is considered part of reservoir.
  • P6 is the reservoir saturation pressure.
  • All other pressures are governed by P6

  Introduction to LHP - Ku 2015 TFAWS

p g y

6

  • All pressure drops are viscous pressure drops.

14

1 wick wick (Vapor) (Vapor)

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SLIDE 15

Thermodynamic Constraints in LHP Operation (1)

  • For the working fluid in a saturation state there is a one-to-one
  • For the working fluid in a saturation state, there is a one-to-one

correspondence between the saturation temperature and the saturation pressure.

  • There are three LHP elements where the working fluid exists in

a two-phase state, i.e. evaporator, condenser and reservoir.

  • There is a thermodynamic constraint between any two of the

above-mentioned three elements, i.e. the pressure drop and the temperature drop between any two elements are temperature drop between any two elements are thermodynamically linked. E.G. PE – Pcc = (dP/dT) (TE – Tcc)

  • The derivative dP/dT can be related to physical properties of

the working fluid by the Clausius-Clapeyron equation:

Introduction to LHP - Ku 2015 TFAWS

dP/dT = / (Tcc v)

15

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SLIDE 16

Thermodynamic Constraints in LHP Operation (2)

Vapor Channel Primary Wick Secondary Wick Bayonet 2 6

Saturation Curve Reservoir Evaporator Li id 1 7

  

ressure P4 P1 P6

  

6 1 4 Vapor Line Liquid Line Condenser 3 5 Pr T4 T1 Vapor Liquid T6

PE – Pcond = (dP/dT) (TE – Tcond)

3 5 4 Temperature

Pcond – Pcc = (dP/dT) (Tcond – Tcc) PE – Pcc = (dP/dT) (TE – Tcc)

Introduction to LHP - Ku 2015 TFAWS 16

  • Gravity affects the pressure drop, and hence the temperature difference.
slide-17
SLIDE 17

LHP Operating Principles – Energy Balance

Reservoir e Evaporator Reservoir

QIN m Qsub Q

Condenser/Subcooler Vapor Line Liquid Line

QRA Qleak QLA QC,2Φ QC,1Φ m

) , , (

, 2 , , wall c c

  • ut

c

T L m f T

 

T D L m T f T 

L E IN

Q Q Q  

 

CC E CC E L

T T G Q  

,

 

amb LL LL

  • ut

c IN

T D L m T f T , , , ,

,

 

IN CC P sub

T T C m Q  

 m QE 

) ( 2

, 2 , 2 , 2 , wall c CC c c c c

T T h L D m Q   

  

 

Introduction to LHP - Ku 2015 TFAWS 17

  

RA sub leak

Q Q Q

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SLIDE 18

Simplified LHP Thermal Network

Reservoir Heat In Condenser/Subcooler Vapor Line Liquid Line Evaporator Heat In/Out

amb

T

Q

e

Q

 cc e

Q ,

Heat Out

,

l l

T h m

cc cc

T h m, , e T e h m

a cc

Q ,

e

Q

Compensation Chamber Evaporator

l l

q T

cc cc

q 1  e q h m h m

a v

Q ,

amb

T

amb

T

 a l

Q , 1

, 

v sat v v

q T T h m ,  

c sat c c

q T T h m

, 

sc sc sc

q T h m

Inactive Condenser (Subcooler) Active Condenser

Introduction to LHP - Ku 2015 TFAWS

sink

T

s c

Q , 

sink

T

s sc

Q ,

Vapor Line Liquid Line

18

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SLIDE 19

LHP Reservoir Sizing and Fluid Inventory

  • The fluid inventory must satisfy

the following relation under the cold start-up/operation ( > 0):

  • r Line

d Line Evaporator Heat In/Out Reservoir Heat In

M = l,c (Vloop +  Vcc )+ v,c (1- )Vcc Vloop = Loop volume excluding CC

Condenser/Subcooler Vapo Liquid Heat Out

  • The fluid inventory must also satisfy the following relation under the

hot operating condition ( > 0): M = l h [Vliq +Vpw +Vsw +(1-) Vcc] + v h (Vgr + Vvap +Vcon +  Vcc ) M l,h [Vliq Vpw Vsw (1 ) Vcc] v,h (Vgr Vvap Vcon  Vcc )

  • The values of  and , selected at the designer’s discretion, determine

Vcc and M.

cc

  • The loop must contain all liquid volume at the maximum non-operating

temperature:

Introduction to LHP - Ku 2015 TFAWS

M  l, max (Vloop + Vcc)

19

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SLIDE 20

ICESat-2 ATLAS LHP Charge Analysis 15% Fill in Cold Case 15% Fill in Cold Case

  • Charge to maintain 15% CC fill fraction in the cold case startup conditions
  • LHP requires 193.4 grams of ammonia

Volume Cold Start-up Non-Operating Case Operating Hot Case liquid liquid vapor liquid liquid vapor liquid liquid vapor fraction temp dens dens mass fraction temp dens dens mass fraction temp dens dens mass in3 cc in3 cc K gm/cc gm/cc gms K gm/cc gm/cc gms K gm/cc gm/cc gms Evaporator (vapor) 0.43 7.1 0.4 7.1 1.00 268

0.65 0.0029

4.6 1.00 333

0.54 0.0213

3.8 0.00 313

0.57 0.0126

0.1 Evaporator (liquid) 4 67 76 5 4 7 76 5 1 00 268

0 65 0 0029

49 5 1 00 333

0 54 0 0213

41 1 1 00 313

0 57 0 0126

43 6 Evaporator (liquid) 4.67 76.5 4.7 76.5 1.00 268

0.65 0.0029

49.5 1.00 333

0.54 0.0213

41.1 1.00 313

0.57 0.0126

43.6 Liquid Core 0.69 11.2 0.7 11.2 1.00 268

0.65 0.0029

7.3 1.00 333

0.54 0.0213

6.0 1.00 313

0.57 0.0126

6.4 Vapor transport line 1.28 21.0 1.3 21.0 1.00 233

0.69 0.0007

14.0 1.00 333

0.54 0.0213

11.3 0.00 313

0.57 0.0126

0.3 Condenser 4.92 80.6 4.9 80.6 1.00 233

0.69 0.0007

55.4 1.00 333

0.54 0.0213

43.3 0.12 313

0.57 0.0126

6.2 Liquid Transport Line 2.00 32.8 2.0 32.8 1.00 233

0.69 0.0007

21.9 1.00 333

0.54 0.0213

17.6 1.00 313

0.57 0.0126

18.7 Hydro-accumulator Wicks Liquid 0.24 3.9 0.2 3.9 1.00 268

0.65 0.0029

2.5 1.00 333

0.54 0.0213

2.1 1.00 313

0.57 0.0126

2.2 Hydro-accumulator Free Volume 23.50 385.1 23.5 385.1 0.15 268

0.65 0.0029

38.3 0.302 333

0.54 0.0213

68.2 0.518 313

0.57 0.0126 116.0

TOTAL 37 72 618 27 37 7 618 3 193 4 193 4 193 4

– 15% required reservoir liquid fraction at cold startup (β = 0.15) – Design has 70% void volume in hot non-operational (processing) case at 60C

TOTAL 37.72 618.27 37.7 618.3 193.4 193.4 193.4

g p (p g) – 51.8% max fill at hot operating condition (α = 0.482)

Typical values:   0.15 ( 0.85 liquid fraction)

Introduction to LHP - Ku 2015 TFAWS

  0.15 (0.15 liquid fraction)

20

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SLIDE 21

LHP Operating Temperature

  • The LHP operating temperature is governed by the CC saturation

The LHP operating temperature is governed by the CC saturation temperature.

  • The CC temperature is a function of

– Evaporator power Evaporator power – Condenser sink temperature – Ambient temperature – Evaporator/CC assembly design Evaporator/CC assembly design

  • As the operating condition changes, the CC temperature will change

during the transient, but eventually reaches a new steady temperature.

emperature T1 T2

1 2 5

  • r Line

Evaporator Reservoir

QIN m QRA

CC Te T3 T5

3 5

Condenser/Subcooler Vapo Liquid Line

m

Introduction to LHP - Ku 2015 TFAWS

Net Evaporator Power Q2 Q3 Q5

QC,2Φ QSC

21

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SLIDE 22

LHP Operating Temperature

No Active Control of CC Temperature

e T1 1

Line Evaporator Reservoir QIN m QRA

CC Temperature T2 T5 1 2 5

Condenser/Subcooler Vapor L Liquid Line Q Q m

  • Qsub

Qleak CC, Tcc

C T3 Q2 Q3 Q5 3

QC,2Φ QC,1Φ

Qleak – Qsub = 0

Net Evaporator Power

  • For a well insulated CC, Tcc is determined by energy balance between

heat leak and liquid subcooling.

Introduction to LHP - Ku 2015 TFAWS

  • Tcc changes with the evaporator power, condenser sink temperature,

and ambient temperature.

22

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SLIDE 23

Effect of Sink Temperature on CC Temperature - Theory

rature CC Temper T2min T1min Net Evaporator Power Q2 Q1

1min

Introduction to LHP - Ku 2015 TFAWS

Net Evaporator Power

23

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SLIDE 24

Ground Test Results of Thermacore miniLHP at Various Sink Temperatures

Operating Temperature vs Power (New Chiller, Evaporator above Condenser by 0.25") 330 310 320 (K)

Heater on large TM (Tsink = 293K) Heater on large TM(Tsink = 273K) Heater on large TM(Tsink = 253K) Heater on Evap.(Tsink = 293K) Heater on Evap.(Tsink = 273K)

300 310 ting Temperature

Heater on Evap.(Tsink = 253K)

280 290 Operat 270 20 40 60 80 100 120 Power (W) Introduction to LHP - Ku 2015 TFAWS 24

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SLIDE 25

LHP Operating Temperature

CC Temperature Controlled at Tset

ature Natural Operating Temperature Natural Operating Temperature

Q Q Qcc

CC Tempera Fixed Operating Temperature Tset Tset

  • Qsub

Qleak CC, Tcc ≡ Tset

C li Q Q Heating Required

Qcc = Qsub - Qleak Qleak - Qsub + Qcc = 0

  • CC is cold biased, and electrical heaters are commonly used to maintain Tcc at Tset.

O ll th l d t d

Power Input Cooling Req’d QLow QHigh

Qcc Qsub Qleak

  • Overall thermal conductance decreases.
  • Qcc varies with Qsc, which in turns varies with evaporator power, condenser sink

temperature, ambient temperature and number of coupling blocks.

  • Qcc can be large under certain operating conditions.

Introduction to LHP - Ku 2015 TFAWS

  • Electrical heaters can only provide heating, not cooling, to CC.

25

slide-26
SLIDE 26

LHP Temperature Control Methods

  • All methods involve cold-biasing the CC and use external heat

source to maintain CC temperature – Electric heater on CC only (Aura TES, GOES-R GLM) y ( , ) – Electric heater on CC and coupling blocks placed between vapor and liquid lines (ICESat GLAS) – Electric heater on CC and VCHP connecting the evaporator Electric heater on CC and VCHP connecting the evaporator and liquid line (Swift BAT) – Pressure regulator on the vapor line with a bypass to liquid line (AMS) line (AMS) – TEC on CC with thermal strap connecting to the evaporator (heating and active cooling) – no electric heater (ST8) Heat exchanger and separate subcooler (GOES R ABI – Heat exchanger and separate subcooler (GOES-R ABI, ICESat-2 ATLAS)

Introduction to LHP - Ku 2015 TFAWS 26

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SLIDE 27

LHP Operating Temperature Control

Electric Heater on CC

Reservoir Heat In QCC

Q Q Qcc

Vapor Line Liquid Line Evaporator Heat In/Out

  • Qsub

Qleak CC, Tcc ≡ Tset

Condenser/Subcooler L Heat Out

Qcc = Qsub - Qleak Qleak - Qsub + Qcc = 0

  • The electrical heater attached to the CC provides the necessary

Qcc Qsub Qleak control heater power to the CC.

  • Advantages: simplicity, direct heating
  • Disadvantage: required control heater power could be large.

Introduction to LHP - Ku 2015 TFAWS 27

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SLIDE 28

EOS-Aura Tropospheric Emission Spectrometer (TES) Instrument Loop Heat Pipe Layout

SIGNAL CHAIN/ LASER HEAD ASSEMBLY LHP EVAPORATOR MECHANICAL COOLER B LHP EVAPORATOR MECHANICAL COOLER A LHP EVAPORATOR IEM LHP EVAPORATOR MECHANICAL COOLER ELECTRONICS LHP EVAPORATOR

Introduction to LHP - Ku 2015 TFAWS

EVAPORATOR

28

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SLIDE 29
  • CCHPs and LHPs manage equipment

Tropospheric Emission Spectrometer (TES)

CCHPs and LHPs manage equipment power dissipation from:

  • 2 Mechanical Cooler Compressors
  • Cooler electronics
  • Signal Chain and Laser Head

l t i g electronics

  • Integrated Electronics Module (IEM)

Cooler Electronics B Instrument Electronics Module

Introduction to LHP - Ku 2015 TFAWS 29

Cooler Electronics A

slide-30
SLIDE 30

EOS-Aura TES Components Thermal Performance

Introduction to LHP - Ku 2015 TFAWS 30

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SLIDE 31

LHP Operating Temperature Control

Use Coupling Blocks

Vapor Line QE QCC

Q Q Qcc

Liquid Line Evaporator Reservoir Coupling Blocks

  • Qsub

Qleak CC, Tcc ≡ Tset

Condenser

Qcc = Qsub - Qleak Qleak - Qsub + Qcc = 0

  • The coupling blocks serve as a heat exchanger which transfers heat from

the vapor line to the liquid line.

QSub Q

C

Qcc Qsub Qleak

– Re-distribution of LHP internal heat

  • The reduction of liquid subcooling, Qsub, leads to reduced Qcc.
  • The contact area of coupling blocks is determined by the LHP hot
  • perational condition; the CC heater is then sized to accommodate the

Introduction to LHP - Ku 2015 TFAWS

  • perational condition; the CC heater is then sized to accommodate the

worst subcooling condition.

31

slide-32
SLIDE 32

LHP Operating Temperature Control

Use Coupling Blocks

Vapor Line QE QCC

ture Natural Operating Temperature Natural Operating Temperature

Liquid Line Evaporator Reservoir Coupling Blocks

CC Temperat Fixed Operating Temperature Tset Tset

Condenser Q Q

Heating Required

  • Advantages

– Easy to implement

QSC Q

C

Power Input Cooling Req’d QLow QHigh

– Efficient in reducing CC control heater power

  • Disadvantages

– Increases the natural operating temperature at low and high powers

Introduction to LHP - Ku 2015 TFAWS

– May add difficulty to low power start-up – May still require high CC control heater power under the cold condition.

32

slide-33
SLIDE 33

LHPs on ICESat

  • GLAS has high powered lasers to measure
  • GLAS has high powered lasers to measure

polar ice thickness

  • First known application of a two-phase loop

to a laser

  • 2 LHPs; Laser altimeter and power
  • 2 LHPs; Laser altimeter and power

electronics – Propylene LHPs

  • Launched January, 2003

B th LHP f ll t d

  • Both LHPs successfully turned on
  • Very tight temperature control ~ 0.2 oC

Radiator High Power Lasers Radiator Loop Heat Pipe

Introduction to LHP - Ku 2015 TFAWS 33

slide-34
SLIDE 34

Coupling Blocks on ICESat GLAS LHPs

  • There are eight coupling blocks between the vapor and liquid lines

for each LHP.

– Liquid subcooling is reduced by about one half.

  • The ICESat spacecraft was launched in January 2003.
  • Both LHPs have been working very well.

Introduction to LHP - Ku 2015 TFAWS

g y

34

slide-35
SLIDE 35

GLAS Laser Temperatures

  • LLHP active control is finer than can be measured in the laser

GLAS CLHP Transient Data 02/20/03 (Laser Turn-on Turn off warmup heaters all

  • LLHP active control is finer than can be measured in the laser

telemetry when the LHP is at full 110 W of power

GLAS CLHP Transient Data 02/20/03 (Laser Turn-on, Turn off warmup heaters, all components powered)

20 30 10 0:00.8 5:01.8 0:04.8 5:06.8 0:08.8 5:09.8 0:12.8 5:13.8 0:16.8 5:17.8 0:20.8 5:24.8 0:25.8 5:28.8 0:29.8 5:33.8 0:35.8 5:38.8 0:41.8 5:42.8 0:45.8 5:47.8 0:49.8 5:50.8 0:53.8 5:54.8 0:57.8 5:58.8 1:01.8 6:03.8 1:05.8 6:06.8 1:09.8 6:10.8 1:13.8 6:14.8 ure (°C)

  • 30
  • 20
  • 10

2003/051-15:00 2003/051-15:15 2003/051-15:30 2003/051-15:45 2003/051-16:00 2003/051-16:15 2003/051-16:30 2003/051-16:45 2003/051-17:00 2003/051-17:15 2003/051-17:30 2003/051-17:45 2003/051-18:00 2003/051-18:15 2003/051-18:30 2003/051-18:45 2003/051-19:00 2003/051-19:15 2003/051-19:30 2003/051-19:45 2003/051-20:00 2003/051-20:15 2003/051-20:30 2003/051-20:45 2003/051-21:00 2003/051-21:15 2003/051-21:30 2003/051-21:45 2003/051-22:0 2003/051-22:16 2003/051-22:3 2003/051-22:46 2003/051-23:0 2003/051-23:16 2003/051-23:3 2003/051-23:46 Temperatu

  • 50
  • 40

Time (s)

Introduction to LHP - Ku 2015 TFAWS

TGLLHP2LLCCT TGLLHP2RADT TGLLHP2VLT TGLLHP2EVAPT

35

slide-36
SLIDE 36

LHP Operating Temperature Control Use VCHP to Couple Evaporator and Liquid Line

QE Evaporator Reservoir QCC

Q Q Qcc

Vapor Line Liquid Line VCHP

  • Qsub

Qleak CC, Tcc ≡ Tset

Condenser Liquid Line

Qcc = Qsub - Qleak Qleak - Qsub + Qcc = 0

  • The VCHP transmits heat from the evaporator to the liquid line when the

t li id i t ld d i th t f li id b li Q

QSC Q

C

Qcc Qsub Qleak

return liquid is too cold, reducing the amount of liquid subcooling, Qsub. – The required CC control heater power Qcc is reduced.

  • The VCHP is shut down when more subcooling is needed.

Introduction to LHP - Ku 2015 TFAWS 36

slide-37
SLIDE 37

LHP Operating Temperature Control

Use VCHP to Couple Evaporator and Liquid Line

ature Natural Operating Temperature Natural Operating Temperature

QE Evaporator Reservoir QCC

CC Tempera Fixed Operating Temperature Tset Tset

Vapor Line Liquid Line VCHP

Q Q Heating Required

Condenser

  • Advantage

– Active control of heating the liquid line versus passive heating when

Power Input Cooling Req’d QLow QHigh

QSC Q

C

g q p g compared to the coupling blocks

  • Disadvantages

– Needs a VCHP, which may not be ground testable. N d dditi l t l d i f th VCHP

Introduction to LHP - Ku 2015 TFAWS

– Needs an additional control device for the VCHP. – VCHP reservoir requires cold biasing.

37

slide-38
SLIDE 38

LHPs on SWIFT BAT

  • Burst Alert Telescope, a gamma ray detector array, is one of three

p , g y y, instruments on Swift .

  • Launched: November 20 , 2004
  • Detector array has 8 CCHPs for isothermalization and transfer of 253 W

to dual, redundant, LHPs located on each side.

Shield

LHP 2 Condenser

Detector Array Shield

LHP 1 C d Liquid Line 2 Liquid Line 1

LHP Array

LHP 1 Condenser Vapor Line 2 Compensation Chamber 2 Vapor Line 1

LHP evaporator

Compensation Chamber 1 LHP 1 Evaporator LHP 2 Evaporator V Li 1

Introduction to LHP - Ku 2015 TFAWS

Compensation Chamber Radiator For both loops

p Liquid Line 1 Liquid Line 2 Vapor Line 2 Vapor Line 1

38

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SLIDE 39

Swift BAT LHP Evaporator Assembly

Titanium bracket support of hydro-accumulator G-10 washers for thermal isolation pp y Saddle soldered to VCHP Aluminum clamps for VCHP CCHPs attached to evaporator saddle with Eccobond G-10 washers for th l i l ti Saddle attached to evaporator pump with Eccobond thermal isolation Heat exchanger swaged over VCHP condenser

Introduction to LHP - Ku 2015 TFAWS 39

Titanium support bracket for VCHP reservoir

slide-40
SLIDE 40

BAT Flight Data Both LHPs Day 013 (1/13/2005) Nominal Operation

Loop 0 CC Loop 0 Evap (A1) Loop 0 Vapor @ Cond Loop 0 Lower Cond Loop 0 Cond Outlet DAP Loop 1 Evap (B1) Loop 1 Vapor @ Cond Loop 1 Lower Cond Loop 1 Cond Outlet 10 20 p p ( ) p p @ p p

  • 10

rature (C)

  • 30
  • 20

Temper

  • 50
  • 40

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

  • Temperature fluctuations of detectors < 0.4 0C
  • Frequent spacecraft slews have no noticeable effect on LHP operation.

UTC Time (Hr:min)

Introduction to LHP - Ku 2015 TFAWS

  • Flight results verify satisfactory operation of dual LHPs for tight temperature control.

40

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SLIDE 41

LHP Operating Temperature Control

Use Heat Exchanger and Separate Subcooler

Vapor Line QE Evaporator Reservoir QCC

Qcc

id Line Heat Exchanger

  • Qsub

Qleak CC, Tcc ≡ Tset

Condenser Liqui Subcooler

Qcc = Qsub - Qleak Qleak - Qsub + Qcc = 0

  • The subcooler is separated from the condenser.

Th li id li i l d ith th li th h h t h h

Qc Q

sub

Qcc Qsub Qleak

  • The liquid line is coupled with the vapor line through a heat exchanger, where

liquid is allowed to vaporize. The liquid line then enters the subcooler.

  • With proper sizing, the heat exchanger will take away most of the subcooling, and

the subcooler will provide slightly subcooled liquid to the CC

Introduction to LHP - Ku 2015 TFAWS

the subcooler will provide slightly subcooled liquid to the CC.

  • Results of TV testing of ABI LHPs indicate that the design meets the LHP

temperature control and CC control heater power requirements.

41

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SLIDE 42

LHP Operating Temperature

Use Heat Exchanger and Separate Subcooler

ature Natural Operating Temperature Natural Operating Temperature

Vapor Line QE Evaporator Reservoir QCC

CC Tempera Fixed Operating Temperature Tset Tset

uid Line Heat Exchanger

Q Q Heating Required

Condenser Liqu Subcooler

  • Advantages

– The natural operating temperature will be closer to Tset for heat loads

Power Input Cooling Req’d QLow QHigh

Q

C

Qsub

p g p

set

between QLow and QHigh.

– The CC control heat power is reduced significantly.

  • Disadvantages

– Needs a separate subcooler

Introduction to LHP - Ku 2015 TFAWS

Needs a separate subcooler. – Needs a longer liquid line, which imposes a higher frictional pressure drop.

42

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SLIDE 43

GOES-R ABI Radiator/LHP Assembly System Architecture

Evaporator Assemblies (2) Transport Lines Heat Exchangers (2) S b l R i Sub-cooler Region (Condenser-like lines embedded in Panel) Transport Lines

Introduction to LHP - Ku 2015 TFAWS 43

slide-44
SLIDE 44

LHP Operating Temperature Control

Use Pressure Regulator and Vapor Bypass

QE Evaporato r Reservoir QCC

Qcc

Line quid Line Q Pressure Regulator Vapor Bypass

  • Qsub

Qleak CC, Tcc ≡ Tset

Condenser Vapor L Liq Vapor Bypass

Qcc = Qsub - Qleak Qleak - Qsub + Qcc = 0

  • The pressure regulator and vapor bypass valve allow some vapor to

flow to the reservoir when needed.

Q

C

Q

sub

Qcc Qsub Qleak

– Re-distribution of LHP internal heat

  • The required reservoir control heater power Qcc is reduced.
  • Several variations of this approach.

Introduction to LHP - Ku 2015 TFAWS

– Passive: no heater for bypass valve. A single set point temperature. – Active: bypass valve is controlled by an external heater.

44

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SLIDE 45

LHP Operating Temperature Control

Use Pressure Regulator and Vapor Bypass

QE Evaporator Reservoir QCC

Qcc

Line quid Line Q Pressure Regulator Vapor Bypass

  • Qsub

Qleak CC, Tcc ≡ Tset

Condenser Vapor L Liq Vapor Bypass

Qcc = Qsub - Qleak Qleak - Qsub + Qcc = 0

  • The pressure regulator and vapor bypass valve allow some vapor to

flow to the reservoir when needed.

Q

C

Q

sub

Qcc Qsub Qleak

– Re-distribution of LHP internal heat

  • The required reservoir control heater power Qcc is reduced.
  • Several variations of this approach.

Introduction to LHP - Ku 2015 TFAWS

– Passive: no heater for bypass valve. A single set point temperature. – Active: bypass valve is controlled by an external heater.

45

slide-46
SLIDE 46

LHP Operating Temperature

Use Pressure Regulator and Vapor Bypass

rature Natural Operating Temperature Natural Operating Temperature

QE Evaporator Reservoir QCC

CC Temper Fixed Operating Temperature Tset Tset

ine uid Line Q Pressure Regulator

C li Q Q Heating Required

Condenser Vapor L Liqu Vapor Bypass

  • Advantages

Power Input Cooling Req’d QLow QHigh

Q

C

Q

sub

g

– Requires very little CC control heater power.

  • Disadvantages

– More complex design.

Introduction to LHP - Ku 2015 TFAWS

– Calculation of flow rate through bypass valve is complex. – Additional heater and controller for the pressure regulator

46

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SLIDE 47

LHP Operating Temperature Control

Use Pressure Regulator and Vapor Bypass

  • Passive bypass valve

– Yamal 2000 spacecraft, launched in 2003 Payload temperature was controlled within 2K – Payload temperature was controlled within 2K.

  • Active bypass valve

– TerraSAR satellite – Ground tests demonstrated temperature control within  0.5K for heat load of 5W to 15W and condenser sink temperature between 233K and 308K. – TerraSAR was launched in 2007. Thermal control system was functioning successfully.

Introduction to LHP - Ku 2015 TFAWS 47

slide-48
SLIDE 48

LHP Operating Temperature Use TEC

Thermal Strap TEC QE

ure Natural Operating Temperature Natural Operating Temperature

Condenser Vapor Line Liquid Line Evaporator Reservoir

CC Temperatu Fixed Operating Temperature Tset Tset

Condenser Q Qc

Heating Required

  • Advantages

– Can be used to heat or cool the CC

QSC Qc

Power Input Cooling Req’d QLow QHigh

Can be used to heat or cool the CC – Changing the voltage polarity changes the mode of operation – Very efficient

  • Disadvantages

M l d i

Introduction to LHP - Ku 2015 TFAWS

– More complex design – Additional mass

48

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SLIDE 49

Schematic of ST 8 MLHP Use TECs and Coupling Blocks for CC Temperature Control

Heat In Thermoelectric Converter Radiator 1 Heat O t Instrument Simulator 1 Heat In Heat In Thermoelectric Converter Radiator 1 Heat O t Instrument Simulator 1 Evaporator 1 CC 1 Condenser 1 Radiator 1 Out Evaporator 1 CC 1 Condenser 1 Radiator 1 Out Vapor Line Liquid Line Coupling Block Flow Regulator Vapor Line Liquid Line Coupling Block Flow Regulator CC 2 Liquid Line Heat In Instrument Simulator 2 CC 2 Liquid Line Heat In Heat In Instrument Simulator 2 Evaporator 2 CC 2 Thermoelectric Converter Heat Condenser 2 Radiator 2 Evaporator 2 CC 2 Thermoelectric Converter Heat Condenser 2 Radiator 2 Condenser 2 Radiator 2

Introduction to LHP - Ku 2015 TFAWS

Converter Out Converter Out

49

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SLIDE 50

Loop Operating Temperature Control Using TECs

Power and Sink Cycle Tests

CETDP T C l T /2 /200 CETDP Temperature Control Test 5/25/2005

310 25 30

E1 (2) E2 (4)

290 300 RE (K) 15 20 W)

C2 Sink (62) CC1 (42) CC2 (46)

270 280 TEMPERATUR 5 10 POWER (W

C1 Sink (59) TEC1 Power TEC2 Power

260

  • 5

CC1=303K E1/E2 = 75W/0W E1/E2 = 0W/75W E1 /E2 =75W/0W CC1/CC2 =303K CC2=303K CC1/CC2 = 303K CC1=303K

250 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 TIME (HH:MM)

  • 10
  • The loop operating temperature was controlled within ±0.5K by TECs regardless of

changes in evaporator power and/or sink temperature and regardless of which CC was

Introduction to LHP - Ku 2015 TFAWS

changes in evaporator power and/or sink temperature, and regardless of which CC was being controlled.

50

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SLIDE 51

LHP Operating Temperature Control

Use Secondary Evaporator

QCC QE

Qcc

Primary Evaporator Reservoir   E 1 Q m   m 

  • Qsub

Qleak CC, Tcc ≡ Tset

Secondary Evaporator E q   E 2 q m  2 m

Qcc = Qsub - Qleak Qleak - Qsub + Qcc = 0

Condenser/Heat Exchanger 2 1 m m   

Qcc Qsub Qleak

  • The secondary evaporator forms an LHP within an LHP.
  • The secondary loop cools the CC by drawing vapor out of the CC.
  • Degenerates to the regular LHP when the secondary evaporator is not

h t d

Introduction to LHP - Ku 2015 TFAWS 51

heated.

slide-52
SLIDE 52

LHP Operating Temperature Control

Use Secondary Evaporator

ature Natural Operating Temperature Natural Operating Temperature

QCC QE

CC Tempera Fixed Operating Temperature Tset Tset

Primary Evaporator Reservoir   E 1 Q m   2 m 

Heating Required

Secondary Evaporator E q   E 2 q m 

  • Advantages

– Active cooling of the CC – can quickly reprime the loop

Power Input Cooling Req’d QLow QHigh

Condenser/Heat Exchanger 2 1 m m   

– Active cooling of the CC – can quickly reprime the loop – Especially useful for cryogenic LHP for start-up and parasitic heat control

  • Disadvantages

Introduction to LHP - Ku 2015 TFAWS

– Needs an additional evaporator and transport lines – Still needs CC control heater

52

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SLIDE 53

NASA H2-CLHP POWER CYCLING

60.0 70.0

Date: 07/20/01 Note: TV chamber shroud was cooled by LN2

6.0 7.0 50.0

K)

5.0

s)

2nd Pump Power 30.0 40.0

T emperature (K

Primary Pump (TC2) 2nd Pump (TC13) 2nd Condenser (TC15) 3.0 4.0

Power (Watts

1st Pump CC (TC11) 10 0 20.0 1 0 2.0 10.0 14:30 15:00 15:30 16:00 16:30 17:00 17:30 18:00 18:30 Cold Finger (TC20) 0.0 1.0 0.0 Primary Pump Power 19:00 19:30 20:00 20:30 Introduction to LHP - Ku 2015 TFAWS 53

Time

slide-54
SLIDE 54

LHP Start-up

  • LHP Start-up is a complex phenomenon.
  • The primary wick must be wetted prior to start-up.
  • The loop start-up behavior depends on initial conditions inside the

evaporator. f f – Vapor grooves on the outer surface of the primary wick

  • Liquid filled: superheat is required for nucleate boiling
  • Vapor presence: instant evaporation

– Liquid core on the inner surface of the primary wick

  • Liquid filled: low heat leak
  • Vapor presence: high heat leak
  • A minimum power is required for start-up under certain conditions.

Introduction to LHP - Ku 2015 TFAWS 54

slide-55
SLIDE 55

Four Start-up Scenarios for LHP

  • Vapor grooves

– Liquid filled: superheat is

Temperature Te Tcc Start up Tamb Temperature Te Tamb

superheat is required for nucleate boiling – Vapor presence:

Time Start-up Time Tcc Start-up

p p instant evaporation

  • Liquid core

(a) Situation 1 (c) Situation 3

– Liquid filled: low heat leak – Vapor presence: hi h h t l k

Temperature Te T Start-up Tamb Temperature Te Tcc Tamb St t

high heat leak

Time Tcc Time Start-up

Introduction to LHP - Ku 2015 TFAWS 55 (b) Situation 2 (d) Situation 4

slide-56
SLIDE 56

Vapor Presence in Vapor Grooves

  • Situation 1

– Vapor presence in vapor grooves – Core is liquid flooded; low heat leak

Temperature Te Tcc Start up Tamb

q – Instant liquid vaporization in grooves – Smooth start-up with no or small temperature overshoot during start-up

Time Start-up

transient

  • Situation 2

(a) Situation 1

– Vapor presence in vapor grooves – Vapor presence in core; high heat leak – Instant liquid vaporization in grooves

Temperature Te Tcc Start-up Tamb

– Smooth start-up with possible large temperature overshoot during start-up transient

Time

Introduction to LHP - Ku 2015 TFAWS (b) Situation 2 56

slide-57
SLIDE 57

Worst Case Start-up –Situation 4

Sit ti 4

  • Situation 4

– Vapor grooves are flooded with liquid; superheat is required for nucleate boiling

Temperature Te Tamb

boiling – Core contains vapor; high heat leak – The CC temperature rises along with the evaporator temperature

Time

e

Tcc Start-up

p p – The required superheat may never be

  • btained before the maximum allowable

temperature is reached.

(d) Situation 4

CC T

rature

CC T

rature

Evap Loop does not start

Temper

Evap Loop starts

Temper Introduction to LHP - Ku 2015 TFAWS

Time Time Time Time

Desired Actual

57

slide-58
SLIDE 58

Situation 3 – Choosing Between Two Evils

  • Situation 3

– Vapor grooves are flooded with liquid; superheat is required for nucleate boiling

Temperature Te Tamb

boiling – Core is flooded with liquid; low heat leak – The CC temperature remains constant

Time Tcc Start-up

– The CC temperature remains constant

  • r rises slowly while the evaporator

temperature is rising – The required superheat will eventually

(c) Situation 3

y be reached.

  • The current practice for LHP start-up is to

flood the entire loop prior to start-up to t th i k i tt d d t i

CC E T

erature

guarantee the wick is wetted, and sustain the burden of potentially high superheat for nucleate boiling at start-up – “the lesser of the two evils”.

Time Evap Loop starts Time

Tempe Introduction to LHP - Ku 2015 TFAWS

Time Time

Desired and Actual

58

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SLIDE 59

High and Low Power Start-up

  • With high power to the evaporator, liquid in the vapor grooves can

be vaporized quickly regardless of the initial two-phase status in the grooves and the evaporator core. – The required superheat, if any, can be achieved in a short time. – Within the short time, the total heat leak is small.

  • With low power to the evaporator, start-up could be problematic.

– Under situation 4, the required superheat for nucleate boiling may never be achieved. may never be achieved. – After the loop starts, a steady state may not be established within the allowable temperature limit at low powers due to a high heat leak from evaporator to CC if the core contains vapor. high heat leak from evaporator to CC if the core contains vapor.

Introduction to LHP - Ku 2015 TFAWS 59

slide-60
SLIDE 60

I di ti f th i ti f l t t

Some Examples of Start-up Tests

  • Indication of the inception of loop start-up:

– Sudden sharp increase of the vapor line temperature to the CC saturation temperature – Sudden sharp decrease of the liquid line temperature

  • Successful start-up

– The CC temperature approaches a SS – The vapor line temperature approaches a SS (same as or close to the CC temperature) close to the CC temperature) – The evaporator temperature approaches a SS (slightly higher than the CC temperature)

  • Results of some start-up tests under various conditions follow.

Introduction to LHP - Ku 2015 TFAWS 60

slide-61
SLIDE 61

GLAS LHP Breadboard Start-up

(Evaporator core is liquid-filled)

Sit ti 3 t t

12/1/97 GLAS LHP Start-Up 100 watts, No Controlling, Chiller@0°C, Radiator in Horizontal Position

CompCham(TC2) Evaporator(TC10) VapLine(TC22) LiqLine(TC52) Cart1

Situation 3 start-up

295 300

100 120

power

290

ture (ºC)

80

r (W)

evap comp cham

280 285

Temperat

40 60

Power

liq line vap line

270 275 9:15 9:30 9:45 10:00 10:15 10:30

20

vap line Introduction to LHP - Ku 2015 TFAWS

Time(Hours) 61

slide-62
SLIDE 62

GLAS LHP Breadboard Start-up

( Vapor present in evaporator core)

Sit ti 4 t t 100W

GLAS LHP Start-Up 100 watts, No Controlling, Chiller@0°C, Radiator in Vertical Position

C Ch (TC2) E t (TC10) V Li (TC22) Li Li (TC52) C t1

Situation 4 start-up: 100W

300 305

100 120

CompCham(TC2) Evaporator(TC10) VapLine(TC22) LiqLine(TC52) Cart1

power

290 295

re (K)

80 100

W)

evap comp cham

280 285

Temperatur

40 60

Power (W

270 275 9 5 9 7 9 9 10 1 10 3 10 5 10 7 10 9

20

vap line liq line

Introduction to LHP - Ku 2015 TFAWS

9.5 9.7 9.9 10.1 10.3 10.5 10.7 10.9

Time(Hours) 62

slide-63
SLIDE 63

GLAS LHP Breadboard Start-up

( Vapor present in evaporator core)

GLAS LHP Testing

Situation 4 start-up: 20W

26Nov1997 320 25 Evaporator CompCham 300 310 15 20 Evaporator Power CompCham 290 10 LiqLine 270 280 9:00 9:30 10:00 10:30 11:00 11:30 12:00 12:30 5 VapLine

Introduction to LHP - Ku 2015 TFAWS

9:00 9:30 10:00 10:30 11:00 11:30 12:00 12:30 Time

63

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SLIDE 64

Enhancing the Start-up Success

  • A small start-up heater is used to achieve the required superheat for

nucleate boiling in a localized region to generate the first bubble in vapor grooves. After vapor is present in grooves liquid evaporation takes place – After vapor is present in grooves, liquid evaporation takes place instead of nucleate boiling, i.e. superheat is no longer required.

  • Cool the CC using an active means (e.g. TEC).

Evap CC T Loop starts CC T Temperature Evap CC Temperature Time Loop starts Time T Time Loop starts Time Loop starts T

Start-up heater raises the evaporator

Introduction to LHP - Ku 2015 TFAWS

TEC lowers the CC temperature Start up heater raises the evaporator temperature quickly over a small area

64

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SLIDE 65

LHP Shutdown

  • Some instrument operation requires LHP to shutdown for a period of time

Some instrument operation requires LHP to shutdown for a period of time.

  • LHP can continue to pump fluid if the evaporator temperature is higher

than the CC temperature.

  • Requirements for LHP shutdown

Requirements for LHP shutdown – No net heat load to evaporator – CC temperature is higher than evaporator temperature

  • Heating the CC is the only viable method

Heating the CC is the only viable method

  • When the CC temperature is higher than the evaporator temperature, fluid

flow stops. p – Loop will not restart as long as there is no net heat load to evaporator. – Loop may restart if the evaporator continues to receive net heat load and its temperature rises above the CC temperature.

  • To guarantee that the payload stays above its minimum allowable

temperature, the CC temperature control can be set slightly above that value during loop shutdown.

Introduction to LHP - Ku 2015 TFAWS 65

slide-66
SLIDE 66

Analytical Modeling of LHP

  • SINDA/Fluint can be used to model LHP operation.

– CAPIL connector and CAPPMP macro to model wick – Phase suction option to model two-phase heat transfer Phase suction option to model two phase heat transfer – Tedious and time-consuming to build the detailed LHP model – Run time could be an issue

  • Under NASA SBIR and the ST 8 Project, TTH Research Inc. has

developed an LHP model specifically for the simulation LHP

  • peration
  • peration.

Introduction to LHP - Ku 2015 TFAWS 66

slide-67
SLIDE 67

NASA LHP Analytical Model

  • Developed by TTH Research, Inc. under NASA SBIR Project in

2002.

  • The objective was to develop an analytical model to simulate LHP

steady state and transient behaviors – based upon physical laws and verified by test data – efficient and stable solutions – easy to use by thermal analysts (non-experts) – accurate and detailed predictions for LHP researchers (experts) (experts) – Can be used as a stand-alone model for LHP design, or a subroutine to general thermal analyzer (e.g. SINDA/Fluint)

  • Additional funding for modeling the secondary wick was provided

by DOD and the ST8 project in 2005.

Introduction to LHP - Ku 2015 TFAWS 67

slide-68
SLIDE 68

Modeling Approach

  • Derive governing equations for each component and the overall loop
  • Derive governing equations for each component and the overall loop

based on mass, momentum and energy balance. – fluid movement based on pressure difference – improved heat leak model based on test data p – two-phase correlations in condenser – database for fluid properties, wick performance characteristics

  • Model Assumptions

– One dimensional pipe flow – liquid and vapor at one temperature (saturation) inside the reservoir – track liquid level in CC at all times (including gravity effects) N li ibl t f d bl – Negligible amount of non-condensable gases

  • Effects of gravity are included in the model.

Gravity 1 g 0-g

Introduction to LHP - Ku 2015 TFAWS

1-g 0-g

Compensation Chamber Fluid Distribution as a function of Gravity

68

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SLIDE 69

Nodal Map of LHP Analytical Model

Fluid-to-Wall G171-G180 510 505 (Pump #5) CC #5 Wall Fluid-to-Wall G171-G180 510 505 (Pump #5) CC #5 Wall Nodes 371 380 (Wall) Fluid-to-Wall G171-G180 510 505 (Pump #5) CC #5 Wall Fluid-to-Wall G161-G170 Fluid-to-Wall G151-G160 Pump #3 Return Line Pump #4 Return Line Pump #5 Return Line 508 509 503 (Pump #3) 504 (Pump #4) CC #3 Wall CC #4 Wall Fluid-to-Wall G161-G170 Fluid-to-Wall G151-G160 508 509 503 (Pump #3) 504 (Pump #4) CC #3 Wall CC #4 Wall Nodes 1151-1160 (Fluid) Nodes 351 360 (Wall) Nodes 1161-1170 (Fluid) Nodes 361 370 (Wall) Nodes 1171-1180 (Fluid) Node 1308 Node 1309 Node 1310 Node 1303 Node 1304 Node 1305 Fluid-to-Wall G161-G170 Fluid-to-Wall G151-G160 508 509 503 (Pump #3) 504 (Pump #4) CC #3 Wall CC #4 Wall d) l) Fluid-to-Wall G141-G150 Fluid-to-Wall G51-G60 Pump #1 Return Line Pump #2 Return Line Pump #3 Return Line (Fluid in CC #1) (Vapor) 506 507 CC #1 Wall 501 (Pump #1) 502 (Pump #2) CC #2 Wall Fluid-to-Wall G141-G150 Fluid-to-Wall G51-G60 (Fluid in CC #1) (Vapor) 506 507 CC #1 Wall 501 (Pump #1) 502 (Pump #2) CC #2 Wall 20 d) ) Nodes 1051-1060 (Fluid) Nodes 251-260 (Wall) Nodes 1141-1150 (Fluid) Nodes 341 350 (Wall) Node 1306 Node 1307 Node 1308 Node 1301 Node 1302 Node 1303 d) d) l) Fluid-to-Wall G141-G150 Fluid-to-Wall G51-G60 (Fluid in CC #1) (Vapor) 506 507 CC #1 Wall 501 (Pump #1) 502 (Pump #2) CC #2 Wall Nodes 1201- 1220 (Fluid Liquid Line Nodes 231- 250 (Wall Fluid-to-Wall G31-G5 Vapor Line ( ) ( p ) Liquid Line Fluid-to-

  • (

) ( p )

  • Wall G201-G22

luid to Nodes 1031-1050 (Fluid Nodes 401- 420 (Wall) Nodes 1201- 1220 (Fluid Nodes 1201- 1220 (Fluid Nodes 231- 250 (Wall Fluid-to-Wall G31-G5 ( ) ( p ) N Fluid-to-Wall G1-G20 Fluid-to-Wall G61-G80 Condenser #2 Condenser #1 C d #3 Fluid-to-Wall G21-G30 F Fluid-to-Wall G1-G20 Fluid-to-Wall G61-G80 Fluid-to-Wall G21-G30 F Fl Nodes 1001-1020 (Fluid) Nodes 201 220 (Wall) Nodes 1061-1080 (Fluid) Nodes 261 280 (Wall) Nodes 1021

  • 1030 (Fluid)

Nodes 221 230 (Wall) Subcooler N N N Fluid-to-Wall G1-G20 Fluid-to-Wall G61-G80 Fluid-to-Wall G21-G30 F Fluid-to-Wall G1-G20 Fluid-to-Wall G81-G100 Fluid-to-Wall G101-G120 Condenser #3 Condenser #4 Condenser #5 Fluid-to-Wall G81-G100 Fluid-to-Wall G101-G120 ( ) Nodes 1081-1100 (Fluid) Nodes 281 300 (Wall) Nodes 1101-1120 (Fluid) Nodes 301 320 (Wall) Nodes 1121-1140 (Fluid) Fluid-to-Wall G81-G100 Fluid-to-Wall G101-G120

Introduction to LHP - Ku 2015 TFAWS

Fluid-to-Wall G121-G140 Fluid-to-Wall G121-G140 ( ) Nodes 321 340 (Wall) Fluid-to-Wall G121-G140

69

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SLIDE 70

LHP Analytical Model Solution Scheme

Two-Step Predictor-

Corrector

Thermal Analyzer (e.g. SINDA) Thermal Analyzer CALL LHP_IN LHP Data File Thermal Analyzer (e.g. SINDA) CALL LHP

Next Time Step

CALL LHP END

Introduction to LHP - Ku 2015 TFAWS 70

slide-71
SLIDE 71

LHP Analytical Model Input Data

 Vapor Line

  • O.D., wall thickness, length, material

Li id Li  Liquid Line

  • O.D., wall thickness, length, material

 Condensers

  • No. of condensers
  • Condenser 1 O.D., wall thickness, length, material
  • Repeat for Condenser 2 Condenser 3 etc
  • Repeat for Condenser 2, Condenser 3, etc.

 Subcooler

  • O.D., wall thickness, length, material

 Evaporators

  • No. of evaporators
  • Evaporator 1

p

  • Vapor exit line: O.D., wall thickness, length, material
  • Liquid inlet line: O.D., wall thickness, length, material
  • Pump body O.D., length, material
  • Primary wick O.D., I.D., length, material, pore radius,

permeability, porosity, thermal conductivity

  • Bayonet tube: O.D., I.D.
  • Vapor grooves: number of grooves, hydraulic diameter
  • f each groove
  • Reservoir: O.D., I.D., length, material
  • Adverse elevation

S d i k di bilit

  • Secondary wick: pore radius, permeability, cross

sectional area, thermal conductivity, no. of vapor channels, hydraulic diameter of each vapor channel

  • Start-up initial condition (situation 1, 2, 3 or 4)
  • Superheat at start-up
  • Repeat for Evaporator 2 Evaporator 3 etc

Introduction to LHP - Ku 2015 TFAWS

  • Repeat for Evaporator 2, Evaporator 3, etc.

 Gravitational acceleration

 Working fluid 71

slide-72
SLIDE 72

Model Capabilities

  • LHP with up to 5 evaporators and up to 5 condensers
  • Simulation of steady state or transient behavior
  • Database for more than 40 working fluids

Database for more than 40 working fluids

  • Database for wick properties based on empirical test data
  • Default values for input data
  • Gravity effects included
  • A FORTRAN subroutine to be used with any thermal analyzer

(e.g. SINDA, TMG)

Introduction to LHP - Ku 2015 TFAWS 72

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SLIDE 73

Model Limitations

  • The analytical model can predict when system pressure

drop exceeds capillary limit of primary wick. The model cannot simulate loop behavior thereafter. p

lity Vapor “Blow-Through” Bubble Point Probabi

M d l d t t k i t t ff t f i ffi i t

Pore Size

  • Model does not take into account effects of insufficient

liquid in reservoir (undercharged LHP in 1-g)

Introduction to LHP - Ku 2015 TFAWS 73

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SLIDE 74

Recent LHP Technology Developments

  • Miniature LHP

– 6.35 mm diameter evaporator

  • A Single LHP with Multiple Evaporators and Multiple Condensers

C /

  • Hybrid CPL/LHP
  • Cryogenic LHP

– Nitrogen LHP: ~75K-100K – Neon LHP: ~28K-44K – Hydrogen LHP: ~20K-30K – Helium LHP: ~2.7K-4.4K

Introduction to LHP - Ku 2015 TFAWS 74

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SLIDE 75

CEDTP Miniature Loop Heat Pipes

  • Miniature LHPs under NASA

CETDP program.

– Breadboards built by Swales d Th and Thermacore

Condenser Evaporator 60 cm

Liquid Transport Line Vapor Transport Line

Transport Lines CC 9 52mm OD

Evaporator Pump Reservoir Subcooler

Vapor Line 1.59 mm 6.35 mm OD Evaporator CC 9.52mm OD TEC

Counter-flow Condenser

Liquid line 1 59 OD TEC Saddle

Introduction to LHP - Ku 2015 TFAWS

Liquid line 1.59 mm OD

75

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SLIDE 76

Mini LHP for CCQ Flight Experiment

  • Made by Russians

Cylindrical Evaporator inside block for heaters Compensation Chamber

  • Flown for CCQ Flight

Experiment (2012)

Chamber Flat evaporator with integral compensation chamber

Introduction to LHP - Ku 2015 TFAWS 76

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SLIDE 77

ST8 Thermal Loop - LHP Installed on Test Frame

Evap2 Li id li Vapor line Vapor line Evap2 Li id li Vapor line Vapor line CC 2 Liquid line Evap2 CC 2 Liquid line CC 2 Liquid line Evap2 CC 2 Liquid line Evap1 CC 1 C d 2 Evap1 CC 1 Evap1 CC 1 C d 2 Evap1 CC 1 Condenser 1 Condenser 2 Condenser 1 Condenser 2 Condenser/Radiator 2 Condenser/Radiator 1 Condenser/Radiator 2 Condenser/Radiator 1

  • A single LHP with two evaporators and two condensers
  • Miniature LHP

Introduction to LHP - Ku 2015 TFAWS 77

  • Miniature LHP
  • TECs for reservoir temperature control
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SLIDE 78

Cryogenic Loop Heat Pipe (CLHP)

IN

Q

R

Q

IN

T Primary Evaporator Reservoir  

E

1 Q m

OUT

x Line Line asitic Heat Secondary Evaporator 1

IN

q 2 m S d C d Vapor L d Line econdary Fluid Para

The Innovation

2

m 2 1 m m  Primary Condenser Secondary Condenser Liquid S Pressure Reduction “Hot” Reservoir

  • Nitrogen CLHP
  • Hydrogen CLHP

Introduction to LHP - Ku 2015 TFAWS 78

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SLIDE 79

CLHP for Large Area Cryocooling

  • Delivered by TTH

Research in 2007

X X X B2 B5 B7 B1 A1 Evaporator Plate

  • Manufactured by

Thermacore, Inc.

X X X X X B6 A2 B2 B5 B7 B1 B3 X B8 Reservoir Condenser Plate

X

A5

X

A6 X X A3 A4 A8 on 2nd Shroud Bottom Capillary Pump

X

A7 B4 on 2nd Shroud Top

  • CLHP

– all stainless steel construction

  • Evaporator Plate

– copper 10”  48 in2 – capillary pump: 1/4”OD x 1.5”L – wick: 1.2m x 45% porosity – reservoir: 1/4”OD x 2.5”L

  • Condenser Plate

– copper 3” x 5.5” x 1”

Introduction to LHP - Ku 2015 TFAWS

– transport line: 1/16”OD x 63”L

  • Hot reservoir

– 1000 ml (not shown)

79

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SLIDE 80

Other Advanced Topics Not Covered in This Course

  • Temperature Oscillations in LHPs

T t H t i

  • Temperature Hysteresis
  • Effect of Secondary Wick on LHP Transient Operation
  • Start-up and Re-start due to Reservoir Cold Shock
  • Multiple LHPs Serving a Single Components (Swift ABT , GOES-

R ABI, and GOES-R GLM)

  • Gravity Effects

Introduction to LHP - Ku 2015 TFAWS 80

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SLIDE 81

LHP Summary (1 of 3)

K t hi h h t t t f LHP

  • Key to high heat transport of LHP

– Metal wicks with very fine porous wick – High thermal conductivity affects operating temperature K t b t LHP ti

  • Key to robust LHP operation

– Integral evaporator and CC design – Secondary wick connecting CC to evaporator: vapor tolerant K t d t di LHP ti

  • Key to understanding LHP operation

– CC saturation temperature governs the loop operating temperature – CC is plumbed in line with flow circulation CC t t it lf ff t d b ti diti – CC temperature itself affected by operating conditions – Thermodynamic constraints: P is linked to T – CC volume and liquid inventory K d i i CC i

  • Key to determining CC saturation temperature

– Net heat gain must be balanced by subcooling of returning liquid – Ambient temperature affects liquid subcooling

Introduction to LHP - Ku 2015 TFAWS 81

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SLIDE 82

LHP Summary (2 of 3)

  • Heat leak from evaporator to CC affects

Heat leak from evaporator to CC affects – Loop natural operating temperature – Overall system thermal conductance – Temperature hysteresisce – Temperature hysteresisce

  • Heat leak from evaporator to CC is affected by

– Wick thermal conductivity Heat load to the evaporator – Heat load to the evaporator – Two-phase status inside the evaporator core

  • Liquid subcooling is affected by

Heat load to the evaporator – Heat load to the evaporator – Temperature difference between sink and ambient – Parasitic heat gain/loss along the liquid line

  • CC sizing and liquid inventory
  • CC sizing and liquid inventory

– Determined concurrently – Must satisfy cold start-up and hot operating conditions Loop must not become liquid filled at maximum non operating

Introduction to LHP - Ku 2015 TFAWS

– Loop must not become liquid-filled at maximum non-operating temperature.

82

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SLIDE 83

LHP Summary 3 of 3

  • The thermodynamic constraint (P versus T) affects

– Normal operation – Start-up Start up – Operation with presence of body force and/or NCGs – Operation of an LHP with multiple evaporators – Operation of multiple LHPs Operation of multiple LHPs

  • Operating temperature range
  • Never operate LHP near the freezing point except for rare
  • Never operate LHP near the freezing point except for rare

extremely cold start-up transients

  • Never operate LHP near the critical point

Introduction to LHP - Ku 2015 TFAWS 83

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SLIDE 84

Questions? Questions?

Introduction to LHP - Ku 2015 TFAWS 84