Status of the Marco chiller and Marco capacity analyses Bart Verlaat, Lukas Zwalinski, Maciej Osterga, Jan Godlewski MPI Munich,1 March

Marco chiller Marco will be equipped with a R404a chiller with a 2-stage compressor. A 2 stage compressor approach is chosen as experiment to meet the low temperature requirements of Atlas IBL -50°C). 2-stage chiller features: –Water-cooled condenser –Back-pressure regulator to avoid CO 2 freezing (<-55°C) –Variable speed compressor and a hot-gas bypass over accumulator for capacity control. 2

What is the real capacity of Marco? Marco started with a capacity goal of 1kW, but made modular for an easy capacity upgrade. Later Marco was seen as a perfect prototype for Atlas IBL. IBL requires low temperatures: –Chiller selection is according to IBL specs, smallest in range was chosen. Chiller was funded from Atlas research budget. –Now Marco has an over capacity in the chiller So what is the real capacity of Marco? 3

Capacity depending on: Chiller: Determines the cooling capacity as function of the lowest temperature. At high temperatures more capacity is available. CO2 system: –The pump (flow) determines the cooling capacity on the CO2 side. –The tubes sizes must be sufficient to accommodate the flow Pressure drop = efficiency loss => higher CO 2 temperatures Pressure drop can result in reduced CO2 flow => Capacity loss –Heat exchangers must sufficient to exchange the heat. Smaller HX cause higher CO2 temperatures. Let see what the status is of the current Marco………… 4

Marco Pump Performance 5 Mass flow (g/s) Pressure head (bar) Performance curves of a Gather gear pump Model: #1M- J/12-11/X-SS/S/Q/K200/DLC/HTD at -50°C Mass flow meter limit Safe working limit By-pass flow setting

Marco’s tube capacities 6 Estimate: 2m pipe in Marco: 0.1 bar / 17g/s (3kW) & -40°C Estimate: 5m pipe in Marco: g/s (3kW) & -40°C 17 g/s is the limit for Marco (Flow meter) Marco is expected to have a maximum capacity of 3kW wrt to pumps and pipes.

Marco’s heat exchange capacity 7 Current heat exchangers have a capacity of 1kW, upgrading Marco is relatively easy as the HX’s are connected with VCR’s

Marco 2-stage chiller capacity 8 Minimum load (Hot gas by pass) Marco max heat load The chiller is able to absorb the 3kW heat load at CO 2 liquid temperatures of <-50°C. This is sufficient sub cooling for a 2-phase temperature of -40°C. Sufficient for IBL (1.5kW detector + estimated 1kW environmental heat leak) Back-pressure regulator

Chiller schematic 9

2 stage chiller cycle kg/h39.7 kg/h 19.6 kg/h Back-pressure regulator limit 1 st stage 2 nd stage -70°C -60°C -50°C -40°C -30°C -20°C -10°C 0°C 10°C 20°C 30°C 90°C Evaporator Condenser Intercooler

Chiller part numbers 11

Chiller ready for delivery. 12 The chiller ready for shipment to CERN where it will be tested stand-alone.

Marco chiller design 13

Marco chiller 14 Electronics box 2-stage compressor Back pressure regulator Condenser Liquid receiver Suction line accumulator Inter cooler

15 CO 2 condenser Accumulator Marco chiller connections

Marco overview 16

Marco dimensions after chiller integration 17

Chiller frame 18

Marco chiller production 19

Chiller electronics pages of things I don’t understand….. Frequency controller Carel Valve drivers Back- pressure regulator driver Chiller is a self controlling unit. Only interfaces of set-points to PLC