safety review draft

8/8/2019 Safety Review Draft

1/19

MUCOOL TEST AREA

LH2 ABSORBER CRYO-SYSTEM

PRELIMINARY DESIGN

DRAFT

to support the BD/cryo Internal review

to be completed with more detail for the final design

Christine Darve

Fermilab / Beams Division / Cryogenic Department / E&D Group

Content

Overview ..............................................................................................................................................1

1 Hydrogen inventory ............................................................................................................................5

2 LH2 cryo-system components ............................................................................................................ 52.1 LabG magnet ................................................................................................................................5

2.2 Vacuum vessel ............................................................................................................................. 6

2.3 Thermal shield ............................................................................................................................. 62.4 LH2 absorber ............................................................................................................................... 7

2.5 Piping system ...............................................................................................................................8

2.6 LH2 pump .................................................................................................................................... 82.6.1 Impeller assembly .................................................................................................................9

2.6.2 AC motor .............................................................................................................................. 9

2.7 Supporting system ........................................................................................................................9

3 Heat loads calculation .......................................................................................................................104 Heat exchange system design ........................................................................................................... 11

5 Thermo Hydraulic system .................................................................................................................12

5.1 Pressure drop determination and LH2 pump requirement ......................................................... 125.2 Forced flow, temperature and pressure drops in the LH2 absorber ...........................................14

6 Pressure relief valves ........................................................................................................................ 15

6.1 LH2 loop ................................................................................................................................... 15

6.2 Vacuum vessel .......................................................................................................................... 157 LH2 pump test ...................................................................................................................................16

8 Conclusion ........................................................................................................................................ 16

Overview

MTA LH2 Absorber Cryo-system preliminary design 1


2/19

A Mucool Test Area (MTA) is being developed at Fermilab to run components of a cooling cell

together under a high power beam test. A description of the Muon Collider and Neutrino Factory

purpose is detailed in reference [1]. MTA will house the Mucool LH2 absorber system. MTAenclosure will house a string of magnets, RF cavities and a liquid hydrogen (LH2) absorber housed

in a vacuum vessel, which fits the bore of a 5 T superconducting solenoid magnet.

The design of the LH2 absorber cryo-system is the charge of the BD cryogenic department. Thisdesign has been introduced in reference [2]. It is composed of a hydrogen cryo-system and helium

refrigeration provided by an onsite cryoplant. Helium refrigeration can provide up to 500 W of

cooling capacity at 14 K. The hydrogen cryo-system is distributed between a gas shed and anexperimental hall. Figure 1 shows the process and instrumentation diagram of the LH2 absorber

cryo-system. The LH2 is subcooled at 17 K and 0.12 MPa within a structurally safe vacuum vessel.

The main requirement for the Mucool LH2 absorber cryo-system is to keep the densityfluctuation of LH2 in the LH2 absorber lower than 2.5%, without boiling LH2 and while absorbing

up to 500 W of beam power and static heat load.

The Mucool LH2 absorber cryo-system can be compared to other experiments using LH2, like

the E158 hydrogen target system under test at Stanford Linear Accelerator Center (SLAC) [3] and

the SAMPLE experiment at Bates [4]. Although these three experiments have different physicsgoals, the test facilities house a similar cryo-system and have to satisfy similar safety requirements.

Operating parameters like LH2 capacity, flow rate, pressure and temperature are the main differencesfor such experiments.

This note summarizes the calculations for the development of the LH2 absorber cryo-system at

MTA. The design of this cryo-system is in compliance with the guidelines issued from previous LH2experiments at Fermilab [5]. An overview on the project and the main issues are available at

http://www-bdnew.fnal.gov/cryo-darve/mu_cool/mu_cool_HP.htm

http://www-bdnew.fnal.gov/cryo-darve/mu_cool/linac.htmhttp://www-bdnew.fnal.gov/cryo-darve/mu_cool/linac.htm


3/19

Figure 1: Process and Instrumentation Diagram of the LH2 absorber cryo-system



4/19

Figure 2 shows the conceptual design of the LH2 absorber cryo-system cryostat. Figure 3 shows the

3D solid model of the cryostat. The cryostat is composed of:

- LH2 loop- Stainless Steel vacuum vessel

- Two Al2090 or Al 6061T6 vacuum vessel windows

- Aluminum thermal shield actively cooled by N2 + Multi Layer Insulation (MLI)- G10 Supporting systems

- Supply and return pipes for the LH2

- Supply and return pipes for the He- Supply and return pipes for the LN2

- Pumping system

- Pressure safety relief valves

- Instrumentation and electrical connectors.

Figure 2: Conceptual design of the LH2 absorber cryo-system cryostat

Figure 3: 3D solid model of the cryostat



5/19

The LH2 loop is composed of:

- LH2 Absorber (2 windows + 1 manifold)

- LH2 pump- H2/He heat exchanger

- LH2 buffer

- Piping system- Pressure safety relief valves

- Instrumentation (TT, PT, Heaters..) and valves (safety, controlled..)

All components are reviewed in the following chapters.

1 Hydrogen inventory

The volume of the LH2 cryoloop is about 25 liters, which corresponds to 18 x 10 3 STP liters of

gaseous H2. We intend to use three gas cylinder of hydrogen size T (each 2400 psia, 261 SCF). Thebottles are stored in the gas shed. For the nominal operation, the LH2 cryo-system is filled with LH2

pressurized at 17.6 psia (1.2 atm).We can attach up to three open gas cylinders to the system at any one time, normal operations

specify that one bottle be open at a time [3].

2 LH2 cryo-system components

2.1 LabG magnet

Figure 4 shows the Lab-G 5 T superconducting solenoid magnet layout. The LH2 absorber

cryo-system is installed in its bore. This magnet was build and used at Livermore then it was shipped

to Fermilab for the study of 800 MHz RF cavity. One 800 MHz RF cavity will be implemented in

the MTA string.

Figure 4: Lab-G magnet layout



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2.2 Vacuum vessel

The vacuum vessel must satisfy the requirement of the Vacuum Vessel section (section5033) of the Fermilab ES&H Manual. The vacuum vessel is fabricated from 304 stainless steel.

ASME code shows that the maximum stress allowed for 304 is 20,000 psi and the allowable

temperature range at the allowable stress is 20 to +500F (Section II, Part D, Table1A). Section 5031of the Fermilab ES&H Manual requires derating of the allowable stress to 80% of the allowed value

in cases where the vessel is either fabricated in house or is not code-sampled. This reduces the

allowed stress in pressure vessel calculations to 16,000 psi.

The mechanical load on the vacuum vessel consists of the gravity load of internal componentsand vacuum vessel itself and the internal vacuum load. The weight of the vacuum vessel is estimated

to 500 lbs.The vacuum load is equivalent to one atmosphere external pressure.

Figure 2 illustrates in the conceptual design of the cryostat. The cryostat is mainly composedof two cylinders welded together and supported to the LabG magnet. A Stainless Steel IPS16, Sh 10

is used as for the first cylinder installed in the 44 cm magnet bore. The second cylinder is located

outside of the magnet bore and is made out ofIPS48, Sh 10. Two stainless steel plates Sc10 close

the vacuum vessel volume. Annex 1 shows the detail of the calculation for the sizing of the vacuumvessel thickness. The choice of IPS16 Schedule 10 (wall thickness of 0.188) meets the requirements

so is the IPS48 Sc10.

A 10 IPS venting line is welded to the side of the vacuum vessel for 1) routing the gas in caseof failure outside of the experimental hall and 2) increasing the volume of the vacuum vessel. The

pressure relief system is composed of three 2 diameter parallel plates designed at Fermilab and

located at the extremity of the venting line venting. The parallel plats open just above atmosphericpressure. The system is redundant. The total volume of the vacuum vessel needs to be 52 times

larger than the hydrogen cryo-loop capacity in order to withstand the expansion of the saturated LH 2if a rupture of the system should occur. Therefore the vacuum vessel volume is 1300 liters.

2.3 Thermal shield

The vacuum vessel thermal shield consists of an Aluminum circular shield, cooled by N2flowing into two lateral pipes. The two aluminum IPS cooling pipes are thermally connected to

the thermal shield by a series of 6 long welds every 12.A wrap of 30 layers of MLI surrounds the thermal shield. The thermal shield is made of a 1.5

mm thick sheet of Aluminum bended into a cylinder shape and closed at its edges by G10 supports.

The G10 supports permit to avoid a close loop of metallic material perpendicular to the magneticfield of the solenoid magnet and to reduce the forces applied in case of quench of the Lab-G magnet.

Figure 5 shows the dimensions and clearance in between the different components inside of

the magnet bore.

http://www-esh.fnal.gov/FESHM/5000/5033.htmlhttp://www-esh.fnal.gov/FESHM/5000/5033.htmlhttp://www-esh.fnal.gov/FESHM/5000/5031.htmlhttp://www-esh.fnal.gov/FESHM/5000/5033.htmlhttp://www-esh.fnal.gov/FESHM/5000/5033.htmlhttp://www-esh.fnal.gov/FESHM/5000/5031.html


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Figure 5: Dimensions and clearance in between the different components inside of the magnet bore.

2.4 LH2 absorber

17 K-LH2 circulates in a close loop to remove the power deposed in the LH2 absorber volume

by the beam and to the heat exchanger. Figure 6 illustrates the LH2 absorber design. The LH2

absorber is composed of two thin aluminum windows and an aluminum manifold. Doubled Indiumsealing are used. Nozzles in the manifold permit to direct the LH2 flow towards the window

surfaces. A forced flow is created to remove the energy deposed by keeping a temperature difference

less than 1 K and preventing any boiling. The piping design permits to maintain a temperaturedifference in LH2 less than 1 K over the low-pressure side of the heat exchanger. The LH2 absorber

manifold design and the thin windows design are not the focus of this note.

Figure 6: LH2 absorber design


VVaaccuuuumm vveesssseell SSSS,, OODD 1166 ,, SShh 1100SS

LLaabb--GG MMaaggnneett

G10 Support,3x1x 4.3

TThheerrmmaall sshhiieelldd AAll

AAbbssoorrbbeerr AAll

Fixatio

Support,Contact surf:3x 0.5x 4.3

ID 44 cm

ID 15.624

1.5 cm ML

0.77 cm

ID 13.75

G10 Support,2x0.75x1.5

0.15 cm


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2.5 Piping system

The piping system is composed of stainless steel IPS1 and IPS2, Sc5. Figure 7 shows thetransition between the inlet and outlet pipes of the aluminum LH2 absorber and the stainless steel

piping. Some bimetallic junctions, Tevenet Clerjounie, are used at the interface with LH2 absorber

piping.The main requirement for the piping design is to limit the pressure across the LH2 pump. The

piping system is designed so that the choice of elbows, reducers and transitions parts minimizes the

pressure drop in the system. Chapter 5.1 describes the pressure drop calculations.

Figure 7: Connection between the LH2 absorber and the cryo-system piping

2.6 LH2 pump

The LH2 pump was designed and built by Caltech as a spare pump for the SAMPLEexperiment [4]. It is half of the diameter and capacity of the one used in E158. Figure 8 shows the

design of the pump.

During operation, a mechanical pump circulates hydrogen in a close loop at a flow rate up to0.55 kg/s (volume flow rate of appreciatively 7900 cm3/s). The circulating pump is immersed in the

liquid and controlled by a 2 HP AC motor which sit in a room temperature nitrogen environment

outside the vacuum chamber.

The pump impellers are connected to a stainless steel housing and a shaft permits to drive thepump via motor located outside of the cryostat at room temperature. Foam installed around the shaft

between the pump impellers and the AC motor limits the heat leak to the 17 K cryo-system.

Figure 8: Pump design



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2.6.1 Impeller assembly

The LH2 pump is composed two impeller blades and three stators. Two cones located beforeand after the pump permit to reduce the impedance of the flow. Figure 9 shows the impellers of the

pump without the two cones. The material used for the impellers, cones and stator is Aluminum

6061 T6.

Figure 9: Impellers view

2.6.2 AC motor

The 2 HP motor used is a typical AC motor used for the wet engine Tevatron. The motor

environment is purged by gaseous nitrogen, which also served as a coolant. The motor is enclosed in

a can, which is connected to the cryostat vacuum vessel using Oring and vacuum flanges. This

intrinsically safe system was preferred to the purchase of an explosion proof motor.A backing pump permits to keep a low vacuum in the shaft space between the LH2 pump and

the motor in order to 1) reduce the risk of H2 leak to the atmosphere, 2) reduce the conductionthough residual gas and 3) prevent the leakage of N2 to the LH2 cryoloop where it could freeze.

The 2HP motor will dissipate up to 1500 W of power, which will be taken away by a loop of

gas nitrogen at room temperature and 5 psig. The estimated mass flow of nitrogen is 140 g/s for an

admissible temperature difference of 10 K. A lower mass flow can be used if different temperatureranges are chosen.

2.7 Supporting system

The supporting system is composed of G10 material spiders to assure the supporting of thevacuum vessel, thermal shield and absorber. The supporting system minimizes the thermal contact in

between two surfaces at different temperatures. Figure 5 shows the clearance in between the

different parts to support.The supporting system of the vacuum vessel in the magnet bore withstands the 500 lbs vacuum

vessel. The fixation of the vacuum vessel to the Lab-G prevents the vacuum vessel to move during

quench. The gap available to install this supporting system is 34 mm.



10/19

The supporting system in between the vacuum vessel and the thermal shield is sized to

withstand the 70 lbs-thermal shield and to limit the heat load to the thermal shield. Figure 10 shows

the conceptual design of the thermal shield supporting system. It is composed of 3 blocks of G10screwed to a stainless steel band located at two different sections.

The supporting system in between the thermal shield and the absorber is sized to withstand the

50 lbs LH2 absorber + liquid hydrogen capacity and limit the heat load to the LH2 absorber.

Figure 10: Conceptual design of the supporting system.

3 Heat loads calculation

The dimensions shown on Figure 1 are used for the heat load calculations. Temperature,

pressure, geometrical dimensions, material and fluid properties are parameters of the calculations.

The insulating vacuum is estimated to 10-4

Pa. Two temperature levels are taken into account for therefrigeration power calculation: 77 K-thermal shield and 17 K-LH2 cryoloop.

The heat load to 77 K thermal shield is due to infrared radiation and conduction thoughsupporting system. Since MLI is used, radiation and conduction into residual gas need to be

estimated. The thermal conditions are similar in the LHC magnet cryostat; therefore our

calculation takes into account results of measurements performed on the LHC main magnetcryostat at CERN, [6]. Equation (1) relates the contribution of radiation and residual gas

conduction to the heat load from room temperature to the 80 K cryostat thermal shield.

( )

+

=

4422

2 tsvtsv

TTb

TT

aAQ (1)

where a=4.7 10-6 W/m2/K2 and b= 1.25 10-10 W/m2/K4.

Tv and Tts are the temperatures of the vacuum vessel (300 K) and the thermal shield (~80 K)respectively. The heat load calculated from the ambient to the cryostat thermal shield is 2.8

Watt (if we would consider no MLI wrap it would be 64.3 Watt).



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The static heat load to the 17 K cryoloop is composed of the heat load due to:

o The infrared radiation from the two vacuum vessel windows and from the thermal

shield.

o Conduction thought the G10 system

o The LH2 pump shaft and motor [3].

The heat load due to radiation is calculated from the Stefan-Boltzmann law ( =5.67 10-

8W/m2/K4):

( )44cwTTSeQ = (2)

With, e the emissivity and S the surface of the emitting object.

The calculations of the heat load due to conduction though G10-support arestraightforward, therefore not detailed here. More detailed on the calculated can be found in

[1]. A safety factor of two is used to size the refrigeration capacity of the LH2 cryoloop.

Table 1 summarizes the static heat loads to the refrigeration system.

Table 1 Static heat loads calculated for the current conceptual design

80 K 17 K

67 6

Superinsulation 1.5 0.2

Cryostat windows - 17

LH2 pump - 50

Total 68.5 73.2

Heat load (W)

Mechanical Supports

4 Heat exchange system design

The heat budget for the MuCool test facility is 150 W from the beam, 100 W from the pumpand 50 W from the heat leak to the absorber. Taking into account a margin, the heat exchanger is

sized for a cooling capacity of 500 W at 17 K or 1 kW at 20 K.

In order to remove 500 W, 63 g/s of LH2 at 0.12 MPa and 27 g/s of helium at 0.2 MPa are

needed. The difference of temperature across the heat exchanger is 1 K, the pressure drop in thehelium side is 4.3 psi and 10-3 psi in LH2 loop. The heat transfer coefficient is 0.1 W/cm2-K. Note

that the helium flow for LH2 is much smaller than the one mentioned in chapter 5.Annex 2 shows the detail calculation for the case of 500 W to remove with a differentialtemperature in the LH2 equal to 1K.

Based on this condition the proposed co-current heat exchanger is a helical copper tube housed

in a 6 ID, 20 long stainless steel outer shell. The length of the copper tube is 260 . The coppertube inner diameter is 0.623 its wall thickness is 0.032. The heat transfer surface is 0.472 m2.

http://www-bdnew.fnal.gov/cryo-darve/mu_cool/linac/calculation/HX_sizing_500_0_555.pdfhttp://www-bdnew.fnal.gov/cryo-darve/mu_cool/linac/calculation/HX_sizing_500_0_555.pdf


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LH2 capacity in the heat exchanger was reduced by inserting a 2 rod of aluminum in the

central section of the coil. This HX will also permit to extract up to 1kW at 20K with a large

temperature difference.

Figure 11: Conceptual design of the heater exchanger and terminology.

The heat exchanger system is completed by a heater system. The heater system will be

controlled in order to keep a constant powers distributed between the beam power and the system

static heat load. This power absorbed by the LH2 cryoloop must be equal to the constantrefrigeration power of the helium refrigeration loop.

Two electrical heaters are mounted in the vacuum side of the heat exchanger outer shell. The

heat is transmitted though the stainless steel heat exchanger outer shell. In order to be in compliance

with the safety requirement and to be intrinsically safe, the electrical heater isenclosed in a leak tightvessel. The electrical heaters are constantly purged and cooled by a loop of gaseous N2. This system

consists in seal electrical connectors, protected wires and Mica foils.

5 Thermo Hydraulic system

5.1 Pressure drop determination and LH2 pump requirement

The pressure drop in the LH2 loop is driven by the admissible pressure difference across the

LH2 pump. The SAMPLE LH2 pump performance was measured and we use these characteristics to

size our system. Figure 12 illustrates the correlation between the mass-flow, the pump speed and thepressure drop measured across the SAMPLE LH2 pump. The pump speed was used at SAMPLE to

determine the mass flow.



13/19

Characteristics of the current LH2 pump

0

5

10

15

20

25

30

35

40

45

0 200 400 600 800

Mass-flow (g/s)

Pumpspeed(Hz

)

0.0

0.1

0.2

0.3

0.4

0.50.6

0.7

0.8

PressureDrop(ps

id)

Figure 12: Pressure drop available versus mass flow

Figure 13 shows the distribution of the pressure drops in the system, with emphasize on the critical

components. The main pressure drop is located at the nozzles of the LH2 absorber.

Figure 13: Distribution of the pressure drop in the system

The pressure drop in the system is 0.177 psig whereas the maximum pressure drop affordableacross the LH2 pump is 0.500 psig. Annex 3 shows the detailed calculation for the pressure drop in

the LH2 loop with 550 g/s, which is the maximum mass flow available at 1.2 bar. These calculationsare performed for a nozzle diameter of 0.6.


1

5

8

.

1

5 1

6

0

.

7

3

.

8

1

.

8

2

.1


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5.2 Forced flow, temperature and pressure drops in the LH2 absorber

The main requirement is to maintain a difference of temperature in the LH2 absorber volume,smaller then 1 K, using sub-cooled hydrogen at 17 K and 0.12 MPa (17.6 psi). This condition

prevents LH2 to boil and the density fluctuation to be more than +/-2.5 % during operation. The

liquefaction point of the hydrogen at normal pressure is 20.27 K. Figure 14 illustrates the densitychange versus temperature of LH2. We can conclude that a temperature difference of 4 K would still

permit to keep a density change lower than 5 %. Using a conservative approach, we decided to

restrict our studies to 1 K of temperature difference.

Based on this temperature criteria, we determine the flow velocity at the nozzle correspondingto a difference of temperature smaller than 1K. This flow velocity is directly related to the requested

mass-flow.

Correlation bwt density change and temperature

change

-5

-4

-3

-2

-1

0

1

2

3

4

5

14 16 18 20

Temperature of LH2 (K)

D

ensitychange/dens.

LH2@1

7

(%)

Figure14: Density change versus the temperature of LH2 (K).

A Finite Element Analysis is being developed in collaboration with Oxford to determine the

requirements to cool the LH2 absorber using forced flow. These FEA calculations together with the

calculations of the acceptable pressure drops in the cryo-system underline that the design of the LH2

manifold is critical.

A number of the FEA existing thermal / fluid interactive models have been run and are beingclosely examined for accuracy and consistency. The FEA program allows the steady state

temperature run to be performed on the fluid model based on its "terminated" flow velocity. Thismeans that if one runs the fluid model at, say, 4m/s, it will store all its velocity profile at the end of

the fluid run when the flow reaches 4m/s. Using the recorded velocities when the fluid run stopped,

it then calculates the local HTC values at various parts of the Window. This information is thenstored in a file to allow steady state thermal run based on this information. These calculations permit

to gain the temperature distribution in the LH2 absorber volume.



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Figure 5 shows..

Figure 15: Distribution of the temperature in the LH2 absorber for a 150 W beam power distributed

on the 11 cm diameter window.

A possible change of the manifold nozzle dimensions, number and orientation would permit to

get the maximum allowable pressure drop in the system equal to 0.37 psi. This solution would

permit to have a velocity of 4 m/s at the nozzle, a turbulent regime and a mass flow of 450 g/s

permissible by the current LH2 pump. The solution is still critical for the expected pressure drop andwe currently work on this issue.

6 Pressure relief valves

6.1 LH2 loop

The MuCool test facility at Fermilab has a volume of 25 liters of LH2 sub cooled at 17 K and

pressure 1.2 atm (0.101325 MPa=17.63psi). The total weight of LH2 at 17 K is 487 grams. The total

wetted surface area of the LH2 loop, A, is 0.947 m^2 (10.197 ft^2). The surface of the containmentvessel is 1.378 m^2, its volume is 151 liter.

In case of vacuum failure of the LH2 loop, the surrounding gas will warm the LH2 loop. The

liquid hydrogen will start to boil and the pressure inside the loop will be built up. Annex 4shows the

calculation of the pressure relief valve. Two Anderson Greenwood type valves, serie G, section0.503 in^2 are capable of accommodating the flow rate required in the case of a pressure rise.

6.2 Vacuum vessel

The total surface of the containment vessel is 1.378 m^8, its volume is 151 liter. The wetted areaof the containment vessel that would be in contact with the LH2 after a window rupture is 4370

cm^2. The mass flow of LH2 corresponding to the boil-off is 200 g/s. Annex 5 shows that three

http://www-bdnew.fnal.gov/cryo-darve/mu_cool/linac/calculation/PRV_LH2loop.pdfhttp://www-bdnew.fnal.gov/cryo-darve/mu_cool/linac/calculation/PRV_LH2loop.pdfhttp://www-bdnew.fnal.gov/cryo-darve/mu_cool/linac/calculation/VVreliefvalve_API.pdfhttp://www-bdnew.fnal.gov/cryo-darve/mu_cool/linac/calculation/PRV_LH2loop.pdfhttp://www-bdnew.fnal.gov/cryo-darve/mu_cool/linac/calculation/VVreliefvalve_API.pdf


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parallel plate of diameter 2 are capable of accommodating the flow rate required in the case of a

window rupture.

7 LH2 pump test

In regard to the cryostat set-up, the LH2 pump motor shaft can only be vertical and the motor

mounted in the top of the cryostat. This installation of the LH2 pump corresponds to a configurationwhere LH2 flows from top to bottom of the LH2 absorber volume. A more natural and more

effective heat exchange path for the heat is from bottom to up of the LH2 absorber volume.

Therefore the LH2 pump must work in reverse mode.In order to check that the pump could run in both directions, a test was performed using water

[7]. The pump circulates water is in a close loop from a vessel filled with water. A heater was

implemented in order to measure the influence of the density. Instrumentations permit to measurethe mass-flow, pressure, and temperature. The speed and the intensity of the motor are registered.

Figure 15 shows the schematic of the set-up.

Figure 15: Schematic of the water pump test.

The first conclusion was to observed that the performance of the pump running in the reverses

mode is only 5 % less than in the forward mode. A sleep velocity of 5 % was also measured. The

results are detailed reference [7]. .

8 Conclusion

This note summarizes the different engineering issues of the MTA LH2 absorber cryo-system.

The cryo-system has been design to be in compliance with several codes (ES&H Fermilab, NEC,LH2 target guidelines).

References



17/19

1. Rajendran R. et al., Status of Neutrino Factory and Muon Collider Research and Development and future Plans,FNAL-Pub-02/149-E, Batavia, Illinois, USA (2001)

2. C. Darve, D. Allspach, E. Black, M.A. Cummings, C. Johnstone, D Kaplan., A. Klebaner, A. Martinez, B. Norris,

M. Popovic, Cryogenic design for a liquid hydrogen absorber system, presented at ICEC19, 2002 Grenoble

3. R. Carr, J. Gao, E. Jones, R.D. McKeown, R. Boyce and J. G. Weisend II, E158 Liquid Hydrogen Target

Preliminary design, SLAC Internal report E158-1014. E.J. Beise et al., A high power liquid hydrogen target for parity violation experiments, Research instruments &

methods in physics research (1996), 383-391

5. Del Allspach et al. Guidelines for the Design, Fabrication, Testing, Installation and Operation of LH2 Targets 20

May 19976. C. Darve et al, Thermal performance measurements for a 10 meter LHC dipole prototype (Cryostat Thermal Model

2), CERN, LHC-Project-Note-112, November 1997.7. Water pump test, internal report

8.

Annexes

Annex 1: Vacuum vessel thickness calculationAnnex 2: Calculation of the heat exchanger

Annex 3 shows the detailed calculation for the pressure drop in the LH2 loop with 550 g/s

Annex 4: Calculation of the LH2 loop pressure reliefAnnex 5: Calculation of the vacuum vessel pressure relief

The pressure along the flow path was calculated using the valve characteristic (Cv) and the tube

diameter was determined regarding the admissible pressure drop and mass-flow of the system during

the cooldown.

Issues:LH2 buffer

Freezing N2 where pumping

Heater and reaction time constant

If too much Dp or too less He flow, than increase DT. In LH2Oxford and Meson mH2 and mHe not consistent and not accessiblke..



18/19

Annex 1: Vacuum vessel thickness calculation

Shell as a vacuum vessel (governing equations (UG-28(c))

Method 1:

=

t

Do

BPa

3

4

Method 2:

=

t

Do

AEPa

3

2

Shell as a pressure vessel (governing equations (UG-27(c))

Circumferential stress:

PSE

PRct

6.0)(

=

Longitudinal stress:

PSE

PRlt

4.02)(

+

=

Variable Value Units Descriptions and references

Do 17in Vacuum vessel OD

L (total) 27in Total shell length

n 2 Number of stiffening supports

L 16 Distance between stiffeners

t 0.5in Vacuum vessel thickness

E 2.76E+07psi Young's Modulus

L/Do 0.941176471

Do/t 34

A 0.00045 Subpart 3, Section II, Part D, Figure G

B 6500 Subpart 3, Section II, Part D, Figure CS-1

Pa (method 1) 254.9019608psi Calculated maximum allowable external working pressure

Pa (method 2) 243.15psi Calculated maximum allowable external working pressure

Variable Value Units Descriptions and references

P 25psid Internal design pressureR 8in Shell inside radius

S 16000psi Subpart 1, Section II, Part D, Table 1A, derated to 80% of allowed

E 0.65 Weld joint efficiency (Table UW-12)

t 0.019258546in Minimum shell thickness when sizing for circonferential stress

t(l) 9.61E-03in Minimum shell thickness when sizing for longitudinal stress

t 0.019258546in Minimum thickness

Annex 4: Calculation of the LH2 loop pressure relief



19/19

The heat transfer rate to the target loop per unit area, q is:

q= U(Tg-TL)

U : heat transfer coefficient,

Tg : temperature of the gas outside the LH2 loopTL : temperature of the liquid inside the LH2 loop

U is related to the film boiling LH2 in the inner loop wall, conduction of heat through the

LH2 loop wall and convection heat transfer from the surrounding gas to the LH2 loop outside wall.

The heat flux,q , is q=3500BTU/hr-ft^2 = 1.1E4 W/m^2 [Ref.:Cryogenic system, from Baron, 2 nd

edition p404]. Hence the total heat transfer rate is

Q=qA=10.457 kWatt

Plus, we took into account a conservative 500 Watt of beam power,Q =10.957 kWatt.

The difference of enthalpy between 17 K and 22.21 K at 25 psia is 208.72 BTU/hr-ft^2

88,890 Joule/kg. Thus the LH2 boil off rate in term of mass ism= Q/hv=22.8 g/s

And the boil off time is :t = M/m=487g/22.8 g/s = 21.36 sec

For a vent system consisting of a 10 m (33ft) 2 OD pipe, the hydrogen gas mass flow ratefor the sonic flow (max flow), is:

Mdotsonic= 325.7 g/s

For Hydrogen gas mass flow of 325.7 g/s, the pressure drop along the venting pipe calculated

for 25 psig average pressure and average temperature with:

If T1=17K and T2=300K then P= 15.38 psi,If T1=17K and T2= 50K, P = 2.56 psi

MTA LH2 Ab b C t li i d i 19

safety review draft

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