D0 Silicon Upgrade: Control Dewar Steady State Thermodynamic Operating Goals
This engineering note documents the thermodynamic operating parameter goals for the steady state operation of the control dewar/solenoid system. Specifically, how the control dewar pressure control valve, PV-3062-H and the magnet flow control valve EVMF are operated to give the lowest possible temperature fluid at the solenoid magnet. The goals are: (1) For PV-3062-H - The process variable is the helium reservoir pressure, minimize the reservoir pressure, provide only enough pressure plus a little margin to ensure leads flow; and (2) For EVMF - The process variable is firstly a manual setpoint of flowrate as read by the flow venturi, FE3253-H, and secondly the reservoir liquid level, minimize the pressure drop thru the solenoid cooling tubes, provide at least enough flow to maintain reservoir level and stable operation of the magnet. The thermodynamic states for the fluid thru the system are shown on the Pressure versus Temperature graph. Lines of constant enthalpy are also shown. State A is shown as two phase liquid entering the inlet of the subcooler. The subcooler subcools the fluid to State B. State B to State C is caused by the pressure drop across EVMF. State C to D is the estimated pressure drop from the outlet of EVMF thru the solenoid cooling tubes and back up to the helium reservoir inlet. To give the coolest fluid in the cooling tubes, the two phase fluid in the reservoir should be at the lowest pressure (and thus temperature). This lowest pressure is limited by the required pressure for leads flow and if this does not dominate, the low pressure side pressure drop thru the refrigerator and suction pressure set point. My guess is the lead flow requirement will dominate. I suggest putting the PV-3062-H set point such that the lead flow control valves operate at about 80% open. The second parameter that will give the coolest fluid in the cooling tubes is a minimized pressure drop thru the cooling tubes. This can be accomplished by providing a minimized flowrate, sufficient only to ensure that the reservoir level is full and some liquid fraction leaves the helium outlet tubing. D-Zero Engineering note, EN-338, 'LHe Flow Regime/Pressure Drop for DO Solenoid at Steady State Conditions' shows that even though the gas fraction increases at lower flowrates, the pressure drop decreases. This goal is ideal, and assumes good cooling at the magnet. Real effects such hot spots or quench experience in the magnet may necessitate a higher flowrate. The current design flow rate from Toshiba is somewhere around 2.5 gls which is very low. Experience with the accuracy of the venturi flowmeter, coil characteristics etc. and some conservativeness will help determine the optimum flowrate. I would venture a guess that it would be a minimum of 5 g/s. The philosophy that I have been taking with transfer line and valve sizing is such that our refrigerator system will have the ability to supply up to at least 20 g/s if required and necessary. Preferably we will be around 5 g/s.
- Research Organization:
- Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- AC02-07CH11359
- OSTI ID:
- 1033295
- Report Number(s):
- FERMILAB-D0-EN-436; TRN: US1200372
- Country of Publication:
- United States
- Language:
- English
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