Flow Sizing the Cryosystem Valves

摘要

The liquid argon dewar and the three cryostats which contain the modules of the D-Zero detector are cooled and maintained at a low pressure equilibrium by the use of liquid nitrogen cooling loops. The dewar has one vacuum jacketed valve at the inlet of the cooling loop and one at the outlet. Each cryostat has two inlet valves, one for the cooldown loops and one for the operating loops. in addition to an outlet valve. The flow rate of the liquid nitrogen, and hence the valve sizes and corresponding flow coefficients (Cv), is deter mined by the required cooling rate of each system. The large variance between the cooling rate required -for cooldown and that required for operation, and the high control resolution required, makes the selection of a valve seat and plug difficult. The liquid valve coefficient calculations do not specifically consider the size affect of gas generated within the valve by adiabatic pressure drop.