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Helium   refrigerators  and Helium   refrigerators  and

Helium refrigerators and - PowerPoint Presentation

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Helium refrigerators and - PPT Presentation

liquefiers Outline Air Liquide range of cryogenic plants at 45K and below Few thermodynamical concepts Refrigerators and Liquefiers main equipments Helium refrigerators and ID: 781475

cryogenic helium plants heat helium cryogenic heat plants temperature main cold components oil liquid power liquefiers refrigerators range thermal

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Slide1

Helium refrigerators and liquefiers

Slide2

OutlineAir Liquide range of

cryogenic plants at 4.5K and belowFew

thermodynamical conceptsRefrigerators and Liquefiers

main equipments

Slide3

Helium refrigerators and Liquefiers

Why to use helium

refrigerators and liquefiers ?Supraconductivity

(magnets, fusion, light sources,…)Industrial

market

(

gas

transportation,…)

Cavities for particles linear accelerators (2K)Cold neutron sources (20K)Space activities

Why

?

Slide4

Air Liquide range of cryogenic plants

Standard

Liquefiers

Standard

liquefiers

range

from

15 L/

hr to 650 L/hrFully automatic operation

Slide5

Air Liquide range of cryogenic plants

Standard

Refrigerators

Standard

refrigerators

range

from

100W to 1000 W @ 4.5K

Fully automatic operation

Slide6

Air Liquide range of cryogenic plants

Specific

refrigerators

and

liquefiers

Specific

customized

liquefiers and refrigerators above650 L/hr and 1000 W @ 4.5KExample: SCL2 - Korea

- 4.2 kW @

2K - ~4 MW of

installed

power

4.2 kW @2K CB

3.6m

20m

Slide7

Air Liquide range of cryogenic plants

Specific

refrigerators

and

liquefiers

Specific

customized

liquefiers and refrigerators above650 L/hr and 1000 W @ 4.5KExample: ITER

-

France – 3 x 25

kW @

4.5K

with

pulses

operation

~24 MW of

installed

power

110

kWeq

. @ 4.5K

40

kWeq

. @ 4.5K

Loads

variation of 65% in 30 min.

Slide8

Few thermodynamical concepts

General

principle

Power injection

which

will

be

transformed

into

cold

Recovery

of not

used

power

Transfer of power to a

colder

temperature

level

Heat

load

cooling

Insulation

against

heat

inleaks

Slide9

Helium properties

Problem: during expansion in a valve, helium warms

-up above ~40KA valve can be

used to cool-down helium only below ~40K.

Above

~40K,

energy

needs

to be extracted with turbinesHelium

particular

properties

Slide10

Few thermodynamical concepts

General

principle

Turbines are

used

to

extract

energy

Increasing

the

number

of turbines

steps

increases

the

efficiency

Slide11

Few thermodynamical concepts

TS

Diagram

A simple

brayton

cycle

Slide12

Cryogenic plants main components

Global

view

Slide13

Cryogenic plants main components

Global

view

Slide14

Cryogenic plants main components

Standard

Liquefier

process

scheme

Slide15

Cryogenic plants main components

Helium

screw

compressors

Main Characteristics

:

Oil lubricated

screw

compressorHigh pressure up to 25 barSpecial oil is used to avoid contamination of cryogenic circuitsVariable Frequency Drive (VFD) can be used to reduce electric power when capacity reduction is requiredVolumetric compressors: mass flow m

a

P

in

/T

in

Power:

P

id

= m.

R.T

in

.Ln

(P

out

/P

in)

Yield ~ 50%

Slide16

Cryogenic plants main components

Helium

screw

compressors

Ideal adiabatic compression of helium to 15 bar would lead to a temperature of 585°C.

Oil is used to keep compressor outlet temperature around 80°C.

To compress 1 g/s of helium to 15 bar, ~40 g/s of oil is required to limit temperature increase to 80°C

20% of

cooling

8

0% of

cooling

Slide17

Cryogenic plants main components

Helium

screw

compressors

Helium "standard" Compressors

Up to 100 g/s and 300 kW

Specific compressors skids

Above 300 kW and when number of machines decreases reliability and generates too much maintenance

Slide18

Cryogenic plants main components

Oil

Removal System (ORS)

Oil Removal System (ORS) is used to remove traces of oil in helium

Coalescing cartridges remove oil aerosols (liquid droplets of µm size)

Charcoal

adsorber

remove oil vapours

ORS efficiency is crucial to avoid cryogenic heat exchangers clogging and turbines damage

Slide19

Cryogenic plants main components

Oil

Removal System (ORS)

Oil Removal System (ORS) is used to remove traces of oil in helium

Coalescing cartridges remove oil aerosols (liquid droplets of µm size)

Charcoal

adsorber

remove oil vapours

ORS efficiency is crucial to avoid cryogenic heat exchangers clogging and turbines damage

Slide20

Cryogenic plants main components

Helium

Buffers

Characteristics

:

3

bar abs <

P

operation

< 13 barAt room temperatureVolume: from 5 m3 (for HELIAL SL) to 400 m3

(large

cryoplants

)

Gaseous helium storage is necessary to manage helium inventory during cool-down or warm-up.

Slide21

Cryogenic plants main components

Plate fin

heat

exchangers

Brazed aluminium plate fin heat exchangers are used in cold boxes to transfer heat from low pressure circuits to high pressure circuits.

High

compacity

=> limit the size of vacuum vessels

Design with multi-streams

Sensibles

to thermal stresses

Helium

flow

Picture

from

Fives Cryo

Slide22

Cryogenic plants main components

Turbines

Turbines are used to cool down helium (extract power from the gas)

High speed turbines (up to 4 000 Hz) based on static gas bearings

Large range of power: from 200 W to 200 kW

Efficiency between 70 and 85%

High reliability : MTBF > 100 000 hrs

Slide23

Cryogenic plants main components

Turbines

Power extracted proportional to mass flow rate

High

pressure

flow

Kinetic

energy

production

on

fixed

Inlet

Guide Vanes

And flow calibration

mechanical

energy

transmission

through

the

shaft

Journal and

thrust

gas

Bearing

for

shaft

guidance

Fluid

enthalpy

extraction by

centripetal

turbine

impeller

Centrifugal

compressor

driven

by turbine

mechanical

energy

Slide24

Cryogenic plants main components

Turbines

A complete management of the production chain : from design up to test

Slide25

Cryogenic plants main components

Adsorbers

Adsorbers

are used at ~80K and ~20K to remove small traces of impurities

Molecular sieve or activated charcoal traps

air impurities in the ppm range

1 single

adsorber

: stop of the plant for

regeneration

or 2

adsorbers

operating in push-pull

for regeneration on-line

Slide26

Cryogenic plants main components

Insulation

system

A vacuum vessel is used to install all cryogenic component

Multilayer Insulation (MLI) is used to stop radiations

Vacuum pumps are used to stop convection (vacuum < 10

-5

mbar)

Material with low conductivity and long thermal path are used to reduce conduction

Slide27

Cryogenic plants main componentsHigh

efficiency cryomachines manufactured

by AL-aT since 80's with

new developments in 2009Technology

based

on

magnetic

bearings

for high

reliability (MTBF > 100 000 hrs)More than 40 cryomachines

produced

since

new

developments

with

flow rates

from

10 g/s up to 220 g/s

Cold

Compressors

Slide28

Helium properties

Risk of Anoxia

A light

gas

Helium

Nitrogen

Gas

density

(1

bar, 300K)

0.16 kg/m3

1.12 kg/m3

Boiling

temperature

(1

bar)

4.2 K

77.3 K

Liquid density at saturation (1 bar)

125 kg/m3

809 kg/m3

Vapor density at saturation (1 bar)

16.6 kg/m3

4.6 kg/m3

Cp

5.2 J/(g.K)

1.0 J/(

g.K

)

Latent heat (1 bar)

20.7 J/g

199

J/g

Sensible

heat

(

liq

-> 300K)

1543 J/g

234

J/g

x 178

x 720

x 780

x 7.5

x 74

x 1.2

Slide29

Few thermodynamical concepts

Refrigerator

vs.

liquefier

Power

is

necessary

at cold

temperature

Continuous

power

is

necessary

between

ambiant

temperature

and cold

temperature

Cold production

Cold production

Refrigerator

Liquefier

Slide30

30

Liquefaction

:

To

liquefy

helium

, extraction of specific heat

from

ambient

temperature

to 4.4K

is

necessary

,

then

extraction

from

latent

heat

is

necessary

to

liquefy

the

gas

.

COLD

BOX

300 K

1573 J/g

GHe

L He

4.4 K

10 J/g

31 J/g

Energy to extract =

1563

J/g

Refrigeration vs. Liquefaction

Large turbines are

required

to

produce

the cold

required

in all the

temperature

range

Slide31

31

Réfrigeration at 4.5K:

 Extraction of latent heat

at cold temperature

COLD

BOX

LHe

4.4 K

LHe

4.4 K

Re-liquefaction

Cold

vapours

returns

Energy to extract

=

21

J/g@4.4K

Refrigeration vs. Liquefaction

Large

heat

exchangers

are

required

to

transfer

energy

from

vapour

returns

to

helium

supply

Slide32

Helium properties

Particular

properties

Slide33

Helium properties

Liquid Helium:1 g/s of Helium

 ~20 W @ 4.4K 1 g/s of Helium

 ~30 L/hr

Gaseous

Helium

:

1 g/s of

Helium  ~20 Nm3/hrCp = 5.2 J/(g.K)

Keep

in

mind

!

20 W of

heat

inleak

at 4.4K vaporises 30L/

hr

of

liquid

helium

20 W of

heat

inleak

warm up 1g/s of ~4K

Slide34

34

Specific power or Carnot efficiency

Ideally, 70W at 300K are

necessary to produce 1W

at 4.2K

.

In

practical

,

between 250 and 400 W are necessary to produce 1 W at 4.2K. The larger the installation, the higher the efficiency.

Slide35

Summary

Standard helium liquefiers available

from 15L/hr to 650 L/hr

Standard helium refrigerators

available

from

100W to 1000 W @ 4.5K

Specific customized plants for helium liquefiers larger than 650 L/hr and refrigerators larger than 1000 W @ 4.5K

Several

references

at 1.8K or 2.0K

with

state of the art cold

compressor

technology

.

Helium

refrigerators

and

liquefiers

Slide36

End of the presentation

Slide37

Back-up slides

Slide38

QuizzA

liquid helium dewar is

full of liquid helium. What

would be the pressure in the dewar if all the

liquid

vaporizes

up to ambiant

temperature ? A 1000L liquid helium dewar has 10W of heat inleaks. What is the autonomy of the dewar ?

A thermal

shield

requires

1g/s of

helium

at 35K. The

cryogenic

line to the thermal

shield

has 20W of

heat

inleaks

.

What

will

be the temperature at the thermal shield

inlet after the cryogenic

line ?

Questions

Slide39

QuizzA

liquid helium dewar is

full of liquid helium. What

would be the pressure in the dewar if all the

liquid

vaporizes

up to ambiant

temperature ? 125/0.16 ~780 bar A 1000L liquid helium dewar has 10W of heat inleaks. What is the autonomy of the

dewar

?

10W = 0.5 g/s = 15 L/

hr

Autonomy

= 1000/15 ~ 67

hrs

A thermal

shield

requires

1g/s of

helium

at 35K. The

cryogenic

line to the thermal

shield has 20W of heat

inleaks. What will

be the temperature at the thermal shield

inlet after the cryogenic

line ?Q = m.Cp

.ΔT => Δ

T = 20/5.2 ~ 4K => Temperature

inlet = 39K

Answers

Slide40

Thermodynamical concepts

The LATENT HEAT (Lv) is the quantity of

heat absorbed or released by a fluid

undergoing a change of state, such as ice

changing

to water or water to

steam, at constant

temperature

and pressure.

Also called heat of transformation.Applied to vaporisation, condensation, melting, solidification etc..For pure component, the process is isothermalExamples:Water : Liq to Gas @ 373K : 2300 kJ/kgWater : Solid to Liq

@ 273K : 330

kJ/kg

LN2

to GN2 at 77K : 200

kJ/kg

LHe

to

Ghe

at 4.2K : 20.7 kJ/kg

The SPECIFIC HEAT (Cp)

is

the

quantity

of

heat

necessary

to warm-up 1 g from

1 K.Examples:Water : 4.18 kJ/kg.K-1

Nitrogen : 1 kJ/kg.K-1Helium

: 5.2 kJ/kg.K-1

Latent

heat

Slide41

41

Remark

:

Radiation

is

driven

by the warm

temperature

whatever the cold temperature.

T

c

= 80K, T

f

= 4K

80

4

= 4.09 x 10

7

4

4

= 256

(T

c

4

-T

f

4

) = 4.09 x 107

Thermal shields

can

thus allow

to decrease radiation

heat at 4K by a factor of 200. (

4W sur les Gardner !)

Thermal

Shields

utility:

limit

the radiation

heat

loads

Stefan-Boltzmann

law

:

Q

= kA x (

T

w

4

-T

c

4

)

Un simple calcul :

T

w

= 300K,

T

c

= 4K

T

w

= 300K,

T

c

= 80K

300

4

= 8.10 x 10

9

300

4

= 8.1 x 10

9

4

4

= 256 80

4

= 4.09 x 10

7

(

T

w

4

-T

c

4

) =

8.10 x 10

9

(

T

w

4

-T

c

4

) =

8.06 x 10

9

Slide42

Helium properties

But not

so

particular

During an isenthalpic expansion in a valve, does helium cool down or warm-up ?