Research On2K Superfluid Helium Refrigeration System For Realizing Ultrahigh Vacuum

This article studies the design and the related research of the2K superfluid heliumrefrigeration system for realizing the ultrahigh vacuum. This paper studies around thethermal cycle scheme, thermal performance optimization and major equipmemt designand optimization of the cryogenic system.This article introduces the physical properties of the helium-I, makes the thermalproperties of the curve and the relevant curve fitting of the computational formular andprovides property basis for2K superfluid helium cryogenic system process simulationcalculation and the negative pressure heat exchanger design calculation.This article provides the calculation method of2K superfluid cryogenic systemheat load and confirms the2K superfluid cryogenic system heat load. This paper putsforward the four saturation of superfluid helium cryogenic system process for realizingthe ultrahigh vacuum. Applying the Aspen HYSYS software to make the numericalsimulation, this paper provides the major thermal parameters such as temperature,pressure and mass flow. Analyzing and comparing the simulation results of the fourprocesses, this paper confirms the2K superfluid helium cryogenic system process ofthis paper.This article applies drawing the2K superfluid helium refrigeration system flowchart. By counterbalancing the mass balance and the enthalpy balance of each module inthe flow process chart, make simulations and confirm the streams of the physical stateparameters and the physical properties, thus drawing the2K superfluid heliumrefrigeration system temperature-entropy graph and the heat exchanger’s heat flow withtemperature graph.This article makes the optimization design of the high pressure helium subcoolerstructure in the superfluid helium cryogenic system. In the condition of the givenworking medium entrance parameters and export parameters, this article studies thelength of the different diameter parameters and provides the tendency of the walltemperature with the subcooler length. This article preliminarily determines the highpressure helium subcooler structure size.This article chooses the hampson heat exchanger according to the designrequirements of the superfluid helium negative heat exchanger. This article confirms thetwo types of the hampson smooth pipe heat exchanger and the hampson finned tubeheat exchanger design method and makes the structural parameters design of the twokinds of hampson heat exchangers. Through calculation and comparison of theparameters, this article makes the proposal of applying the hampson finned tube heat exchanger as the superfluid helium negative pressure heat exchanger.