CO Cooling Systems

Advantages of the CO2 refrigeration As a refrigerant CO2 has excellent thermodynamic properties, in terms of good heat-transfer inside an evaporator. CO2 is a good detergent / solvent. It dissolves grease and cleans the inside of the systems where it is used. Using CO2 as a fluid gives a relatively simple system. The main difference is that the pipes and components used are refrigeration components. On the other hand the pipe sizes are considerably smaller which means a low mass cooling system inside the particle detectors.

Lower energy consumption Reduced carbon footprint Smaller pipes Less insulation

Smaller pumps More economical operation Lower installation costs

Work Package 13“Detectors and Data Acquisition”

An evaporative bi-phase cooling system based on CO2 has been chosen as the best option to extract the heat produced by the read-out electronics in the CBM Silicon Tracking System. In the framework of the EU-FP7 project CRISP, the system TRACI (Transportable Refrigeration Apparatus for CO2 Investigation), developed at NIKHEF/CERN to provide support to the ATLAS and LHCb experiments, is being upgraded at GSI from 100 W to 1 kW cooling power. This system TRACI-XL will be used as a testing device for the CBM application.

The I-2PACL principle (Integrated 2 Phase Accumulator Controlled Loop) was created as simplification of the 2PACL systems by using the CO2 line to condensate the gas inside the accumulator instead of using a branched line derived from the condensing unit. This concept is under patent since Friday September 9th, 2011. Therefore the control is reduced to one cartridge heater controlled by PLC Siemens Simatic S7-1200. The size of the control unit is decreased and it allows a wider range of possible operating temperatures from -30 ⁰C up to room temperature.

I-2PACL concept applied to TRACI-XL

Bitzer 2DC-3.F1Y Varispeed:• at 30 Hz; Q0 = 0,55 kW, T0 =-45◦ C,Tsuction = -30◦ C, Tc = +35◦ C, Tsub = 3 K, R404a.• at 87 Hz; Q0 = 1.59 kW, T0 = -45◦ C,Tsuction = -30◦ C, Tc = +35◦ C, Tsub = 3 K, R404a.

The return line (8-1) contains a bi-phase mixture which is liquefied by the condensing unit named previously below the operating temperature. By controlling the pressure inside an accumulator the evaporation temperature can be fixed. This vessel contains two-phase CO2 in contact.

TRACI-XL Development

The heat generated in the read-out electronics is absorbed and extracted by the evaporator capillaries inside the thermal box (5-6).

Discharge pressures LEWA pump: Pd,min=22 bar Pd,max=79 bar Pmin=P1=20.9 bar Pmax=P2=82.95 bar Pt ≈ theoretical or work pressure. Residual pressure admitted ±5% (by now)P1 = Pt1 - ( 5/100 ) Pt∙ 2 = 20.9P2 = Pt2 + ( 5/100 ) Pt∙ 1 = 82.95Dampener should be able to work within this rangePlunger: ø=25mm L=15 mm dV=7363.11 mm3

If V1 = V0 – v, and v = 0.1 V∙ 0 (1)We have V1 = 0.9 V∙ 0 (2) and also V2 =V1- dv (3)Therefore P0=0.9xP1 = 18.81 bar (4)Finally from (1) (2) (3) and (4) we will obtain:P0 V∙ 0=P2 V∙ 2 ; 0.9P1 V∙ 0=P2 (V1-dv) =P2 (0.9V0-dv) from the underlined equalities we have the final formula

Ambient or circuit temperature can change the charging gas value at 20⁰C (take note that for a 10⁰C of temperature variation the gas pressure will change approx. a 3%)This volume has to be equal to ”V2” from the formula P2/P0 = V0/V2 then:( V0 / 13.67) = ( 82.95/ 18.81 ) → V0 = 60.28 cm3

1. Accumulator2. Flow meter3. LEWA Pump (Remote head)4. LEWA Pump (Flange motor)5. Heat Exchanger 6. Fire Rod (heater)7. Control System Box8. Condensing Unit Platform9. Compressor 2DC-3.F1Y Varispeed10.Vacuum Pump

--- CO2 (R744)Line--- Rest of the System

1

4

2

5

3

6

7

8

9

10

Pulsation Dampener Calculation

-45⁰

C

-40⁰

C

-30⁰C

TRACI-XL: The Test Cooling System for the CBM Silicon Tracking System J. Sánchez1, J.M. Heuser1, C. J. Schmidt1, A. Lymanets2, H. R. Schmidt2 P. Petagna3, B. Verlaat3 and L. Zwalinski3

1GSI, Darmstadt, Germany; 2Eberhard Karls University, Tübingen, Germany; 3CERN, Geneva, Switzerland