1. J. Direito - M. Battistin – 28 th May 2010EN/CV/DC J. Direito, M. Battistin (EN/CV/DC) 28 th May 2010 Detector Cooling Project III Thermosiphon Workshop - Thermosiphon solution for Alice SPD cooling system

2. J. Direito - M. Battistin – 28 th May 2010EN/CV/DC Why we are talking about modifications The actual Cooling Plant could need to be refurbished: –Increasing leak rates could not be compatible with the volume of the present condenser. –It has been the first evaporative plant built in EN/CV/DC… we have learnt since… –The original plant has been modified several times (Sub Cooling HX, Filters, Redundant Pumps and Compressors). This lead to a higher probability of occurrence of leaks. Access to some components is very difficult. The plant became less reliable. Low reliability of the Pumps: –Some Cavitation problems while restarting the plant and when switching between the pumps. –The graphite impellers can pollute the system once they break (filters have been installed to avoid the pollution of the circuit). Maintenance of the compressors: –MTBF = 125days –Long time of the intervention: RP of the fluid, locking the the manifold, Draining the Manifold, replacing the membranes, leak test the manifold (more than 1 day). 2 This system is not critical now, but it could become it…

3. J. Direito - M. Battistin – 28 th May 2010EN/CV/DC Overview of the present plant and Thermodynamic Cycle (P-h diagram) Chilled Water PT Return Manifold (Gas) PT Supply Manifold (Liq) Return Gas pressure set point of 1.6 to 1.8 bar H=~8m C4F10 3 Supply Liquid pressure set point of 3.5 to 5.5bar

4. J. Direito - M. Battistin – 28 th May 2010EN/CV/DC PT Return Manifold (Gas) PT Supply Manifold (Liq) Return Gas pressure set point of 1.6 to 1.8 bar Supply Liquid pressure set point of 3.5 to 5.5bar SPD Thermosiphon solution Chiller DUMMY LOAD (By – Pass) Height C4F10 Pressure [bar] Enthalpy [kJ/kg] A B C D E F GH A-B: Condensation and sub-cooling B-C: Hydrostatic Pressure difference C-D: Pressure regulation D-E: Detector height E-F: Sub-Cooling F-G: Capillary/Expansion G-H: Evaporation and superheating H-A: Return pressure drop H=~8 m Supply and Return Manifolds would not be modified! 4 A B H E A D C DN25DN32

5. J. Direito - M. Battistin – 28 th May 2010EN/CV/DC SPD Thermosyphon Parameters Condensation Pressure: – Dependent on the evaporation temperature and return pressure drop: P Cond = P evap – P Return P Cond = 1.73 bar (Evap. Temp. 12°C) – 0.015 bar (DN32, 45m) = 1.715 bar (Saturation Temperature of 11.8°C). The TSP un stability requires 5K of difference between condensing gas and sub- cooled liquid (to be verified for C4F10 on mini thermosiphon) –Condenser Liquid Temperature = 11.8 °C – 5 K = 6.8°C –Chilled water could even be enough to run the system Required Height: –The liquid distribution set point id 5.5 bar a today. –The pressure regulator will tune it: we have to assure 6 bar before it P set point SetPoint = P Hydrostatic + P condenser – P supply pipes P hydrostat = P set point – P condenser + P supply pipes P hydrostatic = 6 bar - 1.715 bar + 0.01 bar (DN25, 45m) P hydrostatic required = 4.3 bar (density is 1560 kg/m3 between 5 and 10°C) Minimum Height = 28 m –We have 30.5 m available! 5

6. J. Direito - M. Battistin – 28 th May 2010EN/CV/DC ALICE SPD Thermosyphon main Parameters Total required flow: –Cooling of the Detector 36g/s + 15g/s (by-pass) = 51g/s –Return pipe (45 m) gas pressure drop on DN35 = 15 mbar –Supply pipe (45 m) liquid pressure drop on DC25 = 10 mbar Chiller required power: –5.1 kW at 5°C. –Standard industrial chiller Dummy Load required Power: –1.5 kW: standard construction for EN/CV/DC 6

7. J. Direito - M. Battistin – 28 th May 2010EN/CV/DC Operation Set Points Chiller PID – Sets the Temperature reading the Saturation Temperature (from the pressure transmitter). Pressure regulator – Sets the supply pressure. Three Way Valve on the Chiller Circuit – Sets a minimum ΔT between the Saturation temperature and the liquid temperature (This set point is fixed at 5K). Dummy Load PID – Sets the gas return temperature (Fixed Value of 20°C). 7

8. J. Direito - M. Battistin – 28 th May 2010EN/CV/DC Civil Engineering Integration 8

9. J. Direito - M. Battistin – 28 th May 2010EN/CV/DC Cost Estimation ThermosyphonHypothetic Refurbishment ComponentPrice estimation [kCHF] Condenser/Tan k 10 Chiller (7kW @ 0°C) 3.5 Dummy Load2 Pressure Regulator 1.5 Piping25 Manpower8 TOTAL50 ComponentPrice estimation [kCHF] Condenser/Tan k 10 New Rack5 Piping10 Manpower10 TOTAL35 9

10. J. Direito - M. Battistin – 28 th May 2010EN/CV/DC Conclusions The Thermosyphon solution is perfect for the ALICE SPD –All physical parameters fits –A drastic reduction of maintenance activity –An increased reliability for the future years It can be tested by connecting it to the supply and return manifolds. –The present plant could remain as back up during the commissioning phase. We can test the C4F10 solution on the mini thermosiphon installation. The implementation could be compatible with the 2011 technical shutdown. 10