混合工质变浓度热泵系统的研究-CERN.PPTVIP

(Silicon) Particle Detectors and Cooling (Silicon) Particle detectors have specific needs for thermal control: Many distributed heat sources over large volumes. Serial evaporators Low temperature gradients between these sources. Low pressure drop, constant heat transfer coefficients Permanent cooling (0oC, With or without heat load) Irradiated detectors will get damaged when becoming warm Low mass inside detectors Light weight evaporators, low volume, = mini-channels Low structural impact Small diameter tubing, wiggly structure Radiation resistant cooling fluid Typical temperature distribution of a heated tube Property Comparison (1) Property comparison (2) Example of and Atlas upgrade stave Heat transfer and dry-out of CO2 in the VTCS evaporator (1mm ID tube) Cooling Fluid Choice:Facts, advantages and disadvantages When looking to the presented data CO2 seems the most promising candidate for detector cooling. Small diameter tubing Isothermal behavior (Low dT) Although CO2 has relative high heat transfer coefficients, the possible small diameters (=small heat exchange surface), need special attention. CO2 is easy to use especially for testing, it is cheap and allowed to vent into the atmosphere. High system pressure not a problem in small tubes. CO2 can not be liquid in atmospheric conditions, a leak is in general not problematic. It produces snow as in a fire extinguisher How to get the ideal 2-phase flow in the detector? The 2-Phase Accumulator Controlled Loop(2PACL) 2PACL principle ideal for detector cooling: Low vapor quality for serial evaporators. No local evaporator control, evaporator is passive in detector. No maintenance in hostile area No actuators in radiation zone. LHCb Detector Overview The LHCb-VELO Thermal Control System (LHCb-VTCS)A 2-Phase Accumulator Controlled Loop LHCb-VTCS Overview A 2-Phase Accumulator Controlled Loop VTCS 2PACL Operation VTCS Evaporator performance(Stability and response to heat-load changes) VTCS Transfe