Development of small scale cooling systems at AT-ECR (Compact Cooling System, developments at CERN Cryolab) (Compact Cooling System, developments at CERN Cryolab) Friedrich Haug and Jihao WU Friedrich Haug and Jihao WU Contributions by Contributions by Hugo Pereira and Phillip Santos
Context: TOTEM Roman Pots Cooling � Demand in 2004 by TOTEM collaboration to develop and provide a system for the Silicon-Detectors cooling at 120 K. � Specific conditions: Remote (Large distance from CMS intersection up to 220 m) Radiation environment (Radiation hard equipment) High intensity and high luminosity beams Reliability system Close to maintenance free
Our Approach Innovative system largely based on 1) Passive heat transfer (Heat pipes) 2) Highly reliable cryo-coolers (Pulse tube refrigerator) g )
Technology � Development of Cryo-coolers (pulse tube type) yp ) � Development of Cryogenic Heat Pipes � Development of Cryogenic Loop Heat Development of Cryogenic Loop Heat Pipes � Thermal Models for TOTEM Roman Pots � Thermo-mechanical Simulations � Peltier Elements
Location of Totem Roman Pot Stations
Cooling system principle for a RP station Cooling system principle for a RP station Cooling Principle -The dissipated heat load in C Central Cryostat with Pulse t l C t t ith P l H Heat Pipes t Pi 6 Roman Pots is extracted 6 R P t i t t d by two-phase flow in heat Tube Refrigerator (PTR) pipes and transferred to a central cryostat. -A Pulse Tube Refrigerator g provides the cooling power Characteristics: -In large part passive system -Small amounts of working Small amounts of working fluids in hermetically closed pipes (Safety for beam vacuum) -Radiation hard QRL Transfer Line for Helium compressor to drive the Pulse LHC collider magnets Tube Refrigerator (will be placed at non-radiation area)
Lay-out of CMS area, TOTEM Compressor location CMS detector hall CMS Helium refrigerator Technical side cavern Location of compressor Pi Pipe runs to remote Pulse Tube t t P l T b Refrigerators in LHC tunnel at up to 220 m.
Laboratory prototypes Laboratory prototypes y p y p yp yp � Design, fabrication and testing and of Pulse tube refrigerators � Heat pipes development � Development of thermal-mechanical RP model
Configurations of single-stage PTRs Features of pulse tube refrigerator U coaxial inline –No vibration –Long life Long life –Close to maintenance free –Eco-friendly (an ideal gas (helium) as the working fluid) working fluid) –Oscillating pressure wave –Thermodynamic cycle (compression/expansion) without (compression/expansion) without mechanical expander (no piston) GM type Stirling type Pulse tube refrigerators (PTRs) were becoming the most actively investigated area of small scale cryogenic refrigeration.
Development, fabrication and testing of PTR Development, fabrication and testing of PTR Coaxial Type U Type Coaxial Type Coaxial Type PTR on permanent loan from KEK Cryogenics Dep. 60 80 100 120 140 160 180 100 100 90 90 90W@165K New U type PTR 80 80 64K, 90W@165K (Japanese PTR) @ ( p ) 70 Actual performance (Japanese PTR) 70 g power(W) 60 Comp 1.83MPa@3kW. 60 50 50 40 40 Cooling 30 30 20 20 10 10 63.09K 0 0 64K 64K 83.77K -10 -10 Highly compact, lowest T 30K 60 80 100 120 140 160 180 Temperature(K)
j6 Development of heat pipes Development of heat pipes SInerted type wick structure Grooved type wick structure Mesh type wick structure
Slide 11 j6 A heat pipe is a heat transfer mechanism that can transport large quantities of heat with a very small difference in temperature between the hotter and colder interfaces. Inside a heat pipe, at the hot interface a fluid turns to vapour and the gas naturally flows and condenses on the cold interface. The liquid falls or is moved by capillary action back to the hot interface to evaporate again and repeat the cycle. jwu, 9/13/2007
Development of heat pipes Development of heat pipes PTR Miniature heat pipe Purpose of test station Purpose of test station � Optimal charging mass of working fluid � Maximum heat transfer rate
Development of heat pipes Development of heat pipes— p p p p p p integration in thermal model -”Big” heat pipe -Thermal connecter -Two “miniature” heat pipes charged with Xenon -Copper piece welding to “miniature” heat pipe
Development of a RP thermal model Development of a RP thermal model Thermal model Designed for investigation on g g thermo-mechanics analysis The model use heat pipes to conduct the dissipated heat load p to a pulse tube refrigerator
Thermal model details 03 02 01 This model uses 12 copper frames as mechanical support for the 10 PCB cards and for heat conduction t f th 10 PCB d d f h t d ti On frames and cards, they are equipped with temperature sensors, strain gauges and heaters
Test facility for a RP Thermal Model Test facility for a RP Thermal Model - Pulse Tube Refrigerator (PTR) - Heat Pipes heat transfer system - Thermal Model At this condition, the thermal model simulates an horizontal RP The facility integrated in vacuum envelope
Conclusions � Design principle validated � Design principle validated � Development of pulse tube refrigerator to the stage of laboratory application stage of laboratory application � Development of cryogenic heat pipes to the stage of laboratory application stage of laboratory application � Development of cryogenic loop heat pipes in progress progress � Investigations with Peltier elements in progress
Circuit of the Evaporative Cooling System In the initial operation phase In the initial operation phase with low beam intensity, the cooling of the detectors is done with an adapted evaporative system at 250 K system at 250 K. Main components Compressor, Condenser Pump of the cooling plant, The liquid inlet and the vapour back pressure regulators p g Capillary Functionality Cold load (e.g. the detector structures ) Superheated coolant vapor compressed by compressor The fluid is delivered in liquid phase at room temperature from the condenser The fluid expands through the capillaries and then remains in saturation conditions (boiling) in the detector structure The fluid expands through the capillaries and then remains in saturation conditions (boiling) in the detector structure The residual liquid is evaporated by means of an heater which also raises the temperature of the vapor Reaches the compressor in superheated vapor state
Loop heat pipe Condenser Liquid Line Compensation Chamber Q Q Q Evaporator Main advantage of loop heat pipes Main advantage of loop heat pipes Vapor Line •Being able to provide reliable operation over long distance g •The ability to operate against gravity. Evaporator : ∅ 16mm x 30mm. Improved design for higher performance, BACK much highly compact structure in progress
j5 Peltier elements investigation BACK between 295 (K) Temperature gradient 285 285 hot and cold side 275 265 255 245 T 0.14 0.56 24.8 40 57.6 78.4 97.7 DC power (W) One stage Peltier element Peltier effect P lti ff t Two stage Peltier elements Peltier element plus PTR Peltier element plus heat pipe (heat sink cryocooler) (heat sink ambient water)
jwu, 9/13/2007 Slide 20 j5
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