# Presentation: 947334

## He II HEAT EXCHANGER TEST UNIT FOR THE LHC INNER TRIPLET  Ch. Darve1, E. Blanco2, Y. Huang1, T. Nicol1, T. Peterson1 and Rob van Weelderen21 Fermi National Accelerator Laboratory, Batavia, IL, 60510, USA2 CERN, European Organization for Particle Physics, Geneva, 1211, CH

## Headlines

*** ******Overview on the LHC IR inner triplet ***
*** ******IT-HXTU test description and purpose ***
*** ******Thermal measurements under investigation ***
*** ******Results and discussion***
*** ******Consequences on the inner triplet***

## Overview on the LHC IR inner triplet

- Eight inner triplets located @ the Interaction Regions.
- C-08C-03 LHC Interaction Region Quadrupole
- Cryostat Design
_**Concerns**_:
- Large dynamic heat loads @ 1.9 K
- Require a large Heat Exchanger tube

- Qnom=60.1W
- Qult= 95.1W

- Qnom=212.9W
- Qult= 472.8W

- Qnom=61.1W
- Qult= 97.5W

- Qnom=212.9W
- Qult= 472.8W

## From the LHC IR inner triplet to the IT-HXTU

** ****Four similar modules (7 m x ø 0.8 m) to simulate the IT cooling scheme.**
** ****Magnet simulators (resistive heaters)**
** ****Full He II capacity (~800 l)**

**200 W**

**Heat transfer**

**Inner triplet**

**IT-HXTU**

**1.4 %**

## View of the IT-HXTU

***View of the IT-HXTU***

- support

**Side view of one of the four identical modules**

**The feedbox without the thermal shield **
**and vacuum vessel**

## View of the IT-HXTU

- Heat exchanger tube

- Shield cooling pipes

- Sat He II supply

- Magnet simulator pipe

- Pressurized He II  circuit

***View of the IT-HXTU***

- Connecting pipes

## View of the IT-HXTU

## Purpose of the IT-HXTU

**Validation of the the inner triplet cooling scheme by checking **
**the max. temperature rise in the stagnant and pressurized He II. **
**Validation of theoretical estimation of the heat transfer in Pressurized He II.**
**Measurement of the heat exchanger tube wetted area.**
**Development of the Nonlinear Model-Based Predictive Control.**
**C-02B-03 Nonlinear Advanced Control of the LHC Inner Triplet Heat Exchanger Test Unit**** **

## The IT Heat Exchanger tube

- Stainless steel flange

- Corrugated tube

## Process and Instrumentation Diagram

- accumulator

- Connecting pipes

- The heaters provide the heat load
- The JT valve controlled the saturated He II flow
- The thermal equilibrium is dictated by the evolution of the dry-out point and the overflow in the accumulator

## Instrumentation

**Temperature sensors implemented in the pressurized He II bath**

-  Error of +/-5 mK on the temperature measurements.
-  Stainless steel tubes to route the wires.

## Acquisition and Control system 

-  Instrumentation (temperature sensor, pressure transducers, mass-flowmeter, controlled valves...)
-  An industrial PLC acquires and controlled the sensors and valves.
-  Profibus fieldbus routes the information to the acquisition system.
-  PCVue32 is the software used for the graphic interface, control and acquisition.
-  Ethernet network permits us to acquire and supervise the equipment

## Heat transfer in superfluid helium

- If T=1.85 K to 1.95 K @ 1 bar
- then 1/f(T) = 1200 W3/cm5K for m=3

_*Gorter-Mellink equation:*_

- Heat flux (W/cm2)

- Heat flux through the superfluid into the system

- For estimating the temperature difference in regions with distributed heat input, we can use:

- with 1/f(T) = thermal conductivity of He II

## Heat transfer and Kapitza Effect

- Rth=2.Rkapitza+Rcu=(1/Tpres3)+****

- Rth=(Tpres-Tsat)/Qelec

- Rkapitza

***Determination of the Kapitza resistance:***
***Small scale Heat Exchanger test @ FNAL***

## Heat transfer and Kapitza Effect

**OFHC- @ IT-HXTU**

- Bronze (95%Cu-5% Sn)

- OFHC+ HCl

## Installation & Commissioning of the IT-HXTU

**1. Measurement of the heat exchanger tube deflection :< 8 mm**
**2. Installation on the supports (1.4%)**
**3. Connecting the 4 modules **
**4. Pressure test: 2.5 bar abs**
**5. Leak check: 10****-8**** mbar l/s (@120 mbar)**
**6. Mechanical calibration of the controlled valves**
_**At cryogenic temperatures**_
**Time constants for the thermal equilibrium: 4-6 hours**
**LHe velocity measurements:10 cm/s**
**Controlled valves, JT valve: PID parameters**
**Recalibration of thermometers**
**Calibration of the turbine mass-flow meter**
**Calibration of the JT opening**
**Static heat load measurements**

## Determination of the static heat loads

- The static heat load was measured using the enthalpy balance between the JTvalve and the accumulator

## Nominal condition

**Total integrated heat load to Inner Triplet : **
**Nominal Condition = 211 watt**

## Nominal condition

## IT-HXTU Ultimate condition Q= 315 W

## Comparison with calculation

## DT vs.  heat load - Tsat ~ 1.90 K  ~21 mbar

**0**

**5**

**10**

**15**

**20**

**25**

**30**

**35**

**40**

**45**

**50**

**4.0**

**4.5**

**5.0**

**5.5**

**6.0**

**6.5**

**7.0**

**7.5**

**8.0**

**8.5**

**9.0**

**Power applied (W/m)**

**T-Tsat (mK)**

**HX side @ connecting pipe**

**HX side @ middle of the module**

**Magnet side @ connecting pipe**

**Magnet simulator pipe @ middle**

## DT vs.  heat load - Tsat ~ 2.00 K  ~32 mbar

***DT vs.  heat load - T*****sat ~ 2.00 K  ~32 mbar**

**HX side @ connecting pipe**

**HX side @ middle of the module**

**Magnet side @ connecting pipe**

**Magnet simulator pipe @ middle**

## Prediction for LHC high luminosity conditions

- Magnet simulator side

- HX side

## Conclusions

** ****More than 50 heat load configurations were measured**
**http://www-bdcryo.fnal.gov/darve/heat_exchanger/instrumentation.html**
** ****The temperature rise at nominal LHC luminosity conditions **
**will not exceed 50 mK.**
**Validation of the theoretical model.**
** ****The wetted area of the heat exchanger tube is about 22 %.**
**Need to increase of the connecting pipe diameter in order to reduce the temperature rise resulting from the possible LHC ultimate luminosity conditions.**

## Acknowledgement

**This work was supported by the US Department of Energy. **
**We would like to thank the LHC/ACR, LHC/ECR, LHC/CRI groups and in particular the support of R. Losserand-Madoux, A. Bezaguet, E. Fernandez, C. Masure, **
**	****B. Vullierme, L. Herblin, S. Pelletier, JB Bart, B. Beauquis, D. Tobias, M. Gautier, C. Berthelier and R. Vuillermet.**