Test plan for the PX15 thermosiphon (TSP )

1. Test plan for the PX15 thermosiphon (TSP ) D. Giugni Thermosiphon Review III, May 28th 2010 Thermosiphon Review III, May 2010

2. General The PX15 thermosiphon is a 2kW cooling system at -40C evaporation temperature that follows the mini-thermosiphon plant covered so far in other talks. The audience might be triggered by some questions that naturally come up listening the previous talks. I would like to try to list and to answer some of them: • Why 2kW size? • Can the mixtures (C3F8/C2F6) be explored? • Why do we need a wider PX15 installation after the mini-thermosiphon test? • What about the testing plan? Thermosiphon Review III, May 2010

3. Why 2kW power size • These type of systems require a minimum flow. There are few parameters to play with to reduce it: • DT between the vapour and the liquid phases in the condenser. • Insulation of the feeding lines to minimize the heat pick up. •  ~13 g/s is the minimum for the mini-TSP. Assuming a similar minimum flow rate for the SX15 TSP: Pmin=DHEF =416 [W]; This is the minimum cooling power available at the best estimate (up to now) flow rate Mini-TSP minimum flow Flow [g/s] DP [bar] Time [min]

4. Why 2kW power size (2) • The minimum flow rate is difficult to predict and it has big uncertainness scaling up the plant. Needs to take into account a “generous” safety factor. • The cooling power drives the flow rate: • This sets the pipe sizes (marginal cost) • The main cost is on the chiller: Better to design the piping for a larger cooling power and eventually run the plant with a less powerful chiller. • Needs to foresee to test detector structures in parallel: Pixel and SCT Ppixel_loop = 220W PSCT_loop= 504W 2kW is a reasonable cooling power for the test plant Thermosiphon Review III, May 2010

5. Mixtures • The PX15 TSP is compatible with the full range of C3F8/C2F6 mixtures. • The most volatile component [C2F6] has a pressure of ~40bar at 30C. • This is the maximum pressure that can built up in the plant in case the whole installation thermalizes during an hot summer day with the pure C2F6 The pressure rate of the plant is PN40. Thermosiphon Review III, May 2010

6. Why do we need a wider PX15 installation • To measure the time constants of the full scale system: • Cool-down speed: time required to go down to the nominal temperature (start from warm). • Develop fast recovery procedures from accidental stop (re-start from cold: recovery from a “flow stop” event). • Tune up the control to deal the variable load. When the flow rate requested by the detector changes following the number of the operational loops, the control has to divert part of the flow to the dummy load to guarantee the minimum flow rate below which the system stops. • Demonstrate to reach all the thermodynamic parameters required to run SCT and Pixel loops: 13bara @ +20C on the detector feeding lines and the evaporation temperature of -40C. Thermosiphon Review III, May 2010

7. Testing Plan I would disentangle the testing plant over two different sets: • Plant oriented tests • Detector oriented tests Thermosiphon Review III, May 2010

8. Plant oriented tests (1) • Initial start up (procedure 1) Test on the filling and first start up • Start-up from cold stop The goal is to simulate the cold stop situation and restart the flow • Liquid recovery Test the procedure for recovering the fluid in the main tank • Start-up from warm stop, (procedure 2) Validate the cool down procedure • Regulations • Heater regulation in the test section • Evaporator performance in the by-pass • By-pass regulation and flow control in the loop • Temperature control in the loop • Reliability • Short run: 24h • Long run: ~ month(s) Thermosiphon Review III, May 2010

9. Plant oriented tests (2) • Effect of the leaks and degassing procedure An air leak will be induced and the effect on the condensation temperature will be measured. Afterwards, the degassing system will be tested. • Failure modes • Power cut: Induced power cut and follow up of the evolution of the plant • Mixed water cut: simulated failure of the mixed water system • Chiller break down Simulated failure of the chiller • Instrumentation failure Thermosiphon Review III, May 2010

10. Detector oriented tests The aim is to connect to the plant a full Pixel and SCT loop in the test section in USA15. • Pixel Pixel has still available some local structures partially loaded with silicon heaters and thermal sensors that can easily be connected to the TSP. A full loop that includes a bi-stave, a HeX, a capillary and exhausts is rather easy to set up. • SCT As far as I know the only detector structure available is now in SR1. A wide testing plan has been set up for mixtures (C3F8/C2F6) with an ad hoc compressor based plan in SR1. I strongly suggest to evaluate to build a second test setup dedicated to the TSP in order to fully validate this system for the actual detector. Thermosiphon Review III, May 2010

11. Some relevant considerations • SCT is suffering from a relevant pressure drop along the exhaust (main contribution is from the HeX). • The limit on the evaporation temperature is actually set by the minimum sucking pressure of the compressors (800 mbara, nominal 1 bara). Since the anomalous Pdrop in the HeX is added to the compressor sucking pressure, the evaporation temperature is far from being -27C at the beginning of the boiling channel. This may lead to approach thermal run away effects with the integrated dose in the sensor. • Now, the cause of the problem cannot be addressed here since it would require to change the HeX in the detector. Two are the possible way out: • Reduce the sucking pressure: with C3F8 in TSP marginally doable • Mixtures: to test Thermosiphon Review III, May 2010

12. Conclusions • The PX15 TSP will provide within 2010 all the relevant operation parameters required to design (in 2011) the TSP big one. • The testing plan outlined should be able to detect the major failure modes and indicate the backup procedures. This turns out to be fundamental since we are convinced that many of the problems we are encountering now with the actual plant are due to : • Partial or missing qualification. • Coordination between the “detector” and “plant” designers. ... it looks like we are doing better now. Thermosiphon Review III, May 2010