Research and development of liquid hydrogen (LH2) temperature monitoring system for marine applications

Monitoring the temperature in liquid hydrogen (LH₂) storage tanks on ships is important for the safety of maritime navigation. In addition, accurate temperature measurement is also required for commercial transactions. Temperature and pressure define the density of liquid hydrogen, which is directly linked to trading interests. In this study, we developed and tested a liquid hydrogen temperature monitoring system that uses platinum resistance sensors with a nominal electrical resistance of approximately 1000 Ω at room temperature, PT-1000, for marine applications. The temperature measurements were carried out using a newly developed temperature monitoring system under different pressure conditions. The measured values are compared with a calibrated reference PT-1000 resistance thermometer. We confirm a measurement accuracy of ±50 mK in a pressure range of 0.1 MPa–0.5 MPa.     

Practical Continuous‐Flow Controlled/Living Anionic Polymerization

A continuous‐flow reaction system was developed, allowing flow conditions of the entire system to be maintained at a predetermined constant level, which is one of the most significant factors for successful industrial application. Controlled/living anionic polymerization was selected as a model reaction since the characteristics of its polymer products, molecular weights, and molecular weight distributions are highly susceptible to changes in the relative flow rates of a monomer and initiator solutions. In flow microreactors, controlled/living anionic polymerization of styrene in tetrahydrofuran (THF)/hexane initiated by THF‐diluted n‐butyllithium (n‐BuLi) was examined. Poly(styrenes) of larger molecule sizes such as Mn > 15 000 were successfully synthesized. After continuous operation for four hours, ca. 0.5 kg of the polymer was readily produced with narrow molecular weight distribution, demonstrating the applicability of this continuous‐flow system for controlled/living anionic polymerization on considerably large scale with a view to its industrial usage in the future.     

Effects of V content on hydrogen storage properties of V–Ti–Cr alloys with high desorption pressure

Hydrogen storage is one of the most important issues to realize hydrogen society especially for on-board usage. Recently, high-pressure metal hydride (MH) tank attracts many attentions due to its high volumetric hydrogen storage density and relatively easy heat management. To emphasize its merits, further improvements of properties of MH, such as capacity, hydrogen desorption capability at low temperature and durability, are required. In this paper, V–Ti–Cr alloys of V-rich compositions were investigated with perspective of increasing of hydrogen desorption pressure and durability. In both of 60at%V–Ti–Cr and 80at%V–Ti–Cr alloys, good relationship between hydrogen desorption pressure and Ti content was observed. In comparing with 60at%V–Ti–Cr alloys, 80at%V–Ti–Cr alloys showed good durability. It is quite notable that relationship between limitation line (upper substitution limit of Ti by Cr without degradation of hydrogen capacity) and desorption pressure for V–Ti–Cr ternary system with V-rich composition is clarified. And also, it is revealed that in the case of V–Ti–Cr ternary system, not only Ti/Cr ratio but also V content is important factor to obtain alloys with high hydrogen desorption pressure. 75at%V–5at%Ti–Cr as-cast sample showed good durability, hydrogen desorption capability at low temperature and relatively high effective hydrogen capacity simultaneously.     

Power characteristics of unsteadily forward–reverse rotating impellers in an unbaffled aerated agitated vessel

Power characteristics of an unbaffled aerated agitated vessel with unsteadily forward‐reverse rotating impellers, ie a new type of gas–liquid agitator named ‘AJITER’, treating viscous Newtonian liquids were studied experimentally. Measurements were first made on the agitation torque, ie the torque on the drive shaft on which forward–reverse rotating impellers with four delta‐type blades were attached, and the data obtained were analyzed by fitting them to an equation consisting of two terms with respect to the resistance of the fluid, one due to viscous drag and the other due to added moment of inertia. The effects of operating conditions and physical properties of liquids on the drag and added moment of inertia coefficients were then evaluated, and empirical relationships which estimate values of these coefficients, useful to predict the unsteady behavior and magnitude of agitation torque, were presented. Furthermore, equations were developed for estimating the average and maximum power consumptions as a function of the drag and added moment of inertia coefficients. Prediction of respective power levels in AJITER by these equations was also discussed. © 2001 Society of Chemical Industry     

Required limiting impedance and capacity of fault current limiter installed in customer system with synchronous generator

We investigated the required limiting impedance and capacity of a fault current limiter (FCL) installed at an incoming feeder of a customer system with a synchronous generator in a utility distribution system. It was assumed that two types of FCL were installed, i.e. a resistive type (R‐type) FCL and an inductive type (L‐type) FCL. A fault current out of the customer system and a voltage in the customer system were calculated following a three‐phase, short‐circuit fault occurrence. It was found that the required type of FCL and the required limiting impedance depended on the rated capacity of the generator in order to obtain the suppression of the fault current under 0.1 kA_S and to maintain of customer voltage between 85 and 100% of the nominal voltage (6.6 kV). The capacity of FCL consisting of the smallest limiting impedance is discussed. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Fatigue threshold and low-rate crack propagation properties for structural steels in 3 Pct sodium chloride aqueous solution

The fatigue threshold and low-rate crack propagation properties for a carbon steel, two high-strength steels, and two stainless steels were investigated in a 3 pct sodium chloride aqueous solution at frequencies between 0.03 and 30 Hz. Tests were conducted in a manner designed to avoid crack closure. Under freely corroding conditions, the effective values of the threshold stress intensity factor range, ΔK_th,eff, were lower than in air for all of the steels. In particular, the ΔK_th,eff values for the carbon and high-strength steels were almost equal to the theoretical ΔKth value of about 1 MPa m^1/2 calculated on the basis of the dislocation emission from the crack tip. At a given ΔK level higher than the threshold, the fatigue crack propagation rates accelerated with decreasing frequency for all of the steels. Under cathodic protection, the threshold and fatigue crack propagation properties were coincident with those in air regardless of material and frequency. The observed fatigue crack propagation behavior in a 3 pct NaCl solution was closely related to the corrosion reaction of the bare surface formed at the crack tip during each loading cycle.