Minimization of Problems while Creating Two-Phase Flowmeters for Cryogenics and Their Features: Part II. Diagnostics of Hydrogen and LNG Flows

The ways to create two-phase hydrogen flowmeters in the range of mass or volume flow rates from approximately 0.2 to 2.5 kg/s or from ~10 to ~130 m³/h, counting by liquid, and flowmeters for liquefied natural gas (LNG) from ~5 to ~210 kg/s or from ~50 to ~2100 m³/h are offered. The principle of operation of flowmeters is based on a combination of void-fraction RF-sensors with a uniform electric field inside sensitive elements with different sensitivities to determine the average density of a two-phase mixture and conical narrowing devices to find the average flow velocity. The expediency of using gamma densitometers for two-phase LNG flowmeters at relatively large diameters DN ≥ 250 is shown. It is proposed how to minimize the problems inherent in such two-phase flowmeters taking the experience of creating analogues for helium into account. The differences between the approaches for the implementation of systems for hydrogen and LNG compared to analogues for two-phase helium due to the significant difference in their properties are considered. Specific technical solutions of two-phase hydrogen and LNG flowmeters with horizontal flow-through cryostats are presented, which are operable in the range of void fractions from 0 to ~0.9 with a relatively small total hydraulic resistance of the flowmeter path. The features of RF-sensor calibrations at different temperatures of cryogens are noted. Some disadvantages of previous approaches to determining the LNG flowrates are shown and the uncertainties of finding the flowrates of two-phase hydrogen and LNG flows are estimated.