A creep life assessment method for boiler pipes using small punch creep test

The small punch creep (SPC) test is considered as a highly useful method for creep life assessment for high temperature plant components. SPC uses miniature-sized specimens and does not cause any serious sampling damages, and its assessment accuracy is at a high level. However, in applying the SPC test to the residual creep life assessment of the boiler in service, there are some issues to be studied. In order to apply SPC test to the residual creep life assessment of the 2.25Cr–1Mo steel boiler pipe, the relationship between uniaxial creep stress and the SPC test load has been studied.     

高温流化床的流化特性及结焦非流化行为

在 8 0 mm× 30 mm和 80 mm× 10 mm石英流化床中 ,以低温粘结的高密度聚乙烯和聚丙烯 ,高温粘结的玻璃珠为实验物料 ,研究了高温流化床的流化特性及高温下物料结焦产生的非流化行为。结果表明 ,在本文实验条件下 ,Geldart A、B类高温表面粘结物料 ,床层温度小于其最小粘结温度时 ,床层温度增大 ,颗粒的最小流化速度减小 ;Geldart D类高温表面粘结物料的最小流化速度随温度增加而增大。得出了不同温度下颗粒最小流化速度预测式。床层温度大于最小粘结温度时 ,流化床需在较高的表观气速下才能保持流化 ,床层温度愈高床层流化所需的表观气速越大。研究同时发现 ,颗粒物料的粒径减小 ,流化颗粒的最小粘结温度减小。     

Effects of heparin and its 6-O-and 2-O-desulfated derivatives with low anticoagulant activity on proliferation of human neural stem/progenitor cells

Heparin binds various growth factors and activates them to interact with high-affinity cell surface receptors; a specific array of sulfate groups in the heparin backbone structure is very important for this interaction. In the present study, we evaluated the effects of two novel heparin derivatives, 6-O-desulfated heparin (6-DSH) and 2-O-desulfated heparin (2-DSH), on blood coagulation and the proliferation of human neural stem/progenitor cells (NSPCs). 6-DSH showed lower anticoagulant activity than intact heparin or 2-DSH, as measured by the activated partial thromboplastin time and thrombin time. In the presence of FGF-2, 6-DSH and 2-DSH promoted approximately the same rate of proliferation of human NSPCs, without noticeably changing the expression of nestin. The mitotic effects of 6-DSH and 2-DSH on human NSPCs were different from their effects on mouse hematopoietic stem cells and fibroblasts. These findings indicate that 6-DSH and 2-DSH have the same ability to promote the growth of human NSPCs as intact heparin. Our results suggest that these two novel heparin derivates, especially 6-DSH, could be used in clinical applications for ex vivo human NSPC culture, as a lower-risk growth co-adjuvant than intact heparin.     

Optimizing the design of large-scale ground-coupled heat pump systems using groundwater and heat transport modeling

In order to predict the long-term performance of large-scale ground-coupled heat pump (GCHP) systems, it is necessary to take into consideration well-to-well interference, especially in the presence of groundwater flow. A mass and heat transport model was developed to simulate the behavior of this type of system in the Akita Plain, northern Japan. The model was used to investigate different operational schemes and to maximize the heat extraction rate from the GCHP system.     

3D computation of hydrogen-fueled combustion around turbine blade-effect of arrangement of injector holes-

Recently,a number of environmental problems caused from fossil fuel combustion have been focused on.Inaddition,with the eventual depletion of fossil energy resources,hydrogen gas is expected to be an alternativeenergy resource in the near future.It is characterized by high energy per unit weight,high reaction rate,widerange of flammability and the low emission property.On the other hand,many researches have been underway inseveral countries to improve a propulsion system for an advanced aircraft.The system is required to have higherpower,lighter weight and lower emissions than existing ones.In such a future propulsion system,hydrogen gaswould be one of the promising fuels for realizing the requirements.Considering these backgrounds,our group hasproposed a new cycle concept for hydrogen-fueled aircraft propulsion system.In the present study,we perform 3dimensional computations of turbulent flow fields with hydrogen-fueled combustion around a turbine blade.Themain objective is to clarify the influence of arrangement of hydrogen injector holes.Changing the chordwise andspanwise spacings of the holes,the 3 dimensional nature of the flow and thermal fields is numerically studied.     

Optimization of magnesium hydroxide composite material mixed with expanded graphite and calcium chloride for chemical heat pumps

A composite chemical heat storage material (EMC) comprising a mixture of expanded graphite (EG), magnesium hydroxide (Mg(OH)₂), and calcium chloride (CaCl₂) was developed as a magnesium oxide/water chemical heat pump reactant. The optimization of a mixing weight ratio between the Mg(OH)₂ content of EMC and EMC itself was discussed from the viewpoints of both heat storage capacity and reactivity by considering the reaction rate constants from a kinetic analysis. It was confirmed that the dehydration reactivity of EMC increased as the mixing weight ratio decreased; however, the heat capacity of the EMC unit mass decreased. A multiplied factor consisting of the multiplied value dehydration rate constant and mixing weight ratio was introduced. It was suggested that a weight ratio of approximately 0.80 was the optimized value when the mixing molar ratio between CaCl₂ and Mg(OH)₂ was 0.10. Dehydration of EMC with an optimized mixing weight ratio and dehydration of pure Mg(OH)₂ were conducted under various temperatures to compare the reaction rate constants of each material. From this study, it was demonstrated that EMC performed better on dehydration than pure Mg(OH)₂.     

Experiments on bubble behavior in a horizontal narrow divergent passage

This paper investigates a bubble, placed so that it bridges the cross section of a horizontal narrow divergent passage under Earth gravity (1-G). In a narrow passage, inertial forces are known to be small in comparison with viscous forces. Gravitational force is not dominant in bubble behavior in a horizontal narrow passage under the 1-G condition. In this sense, the bubble behavior in the passage is similar to that under a low-gravity condition. Understanding bubble behavior is important in relation to separating a gas from a two-phase gas-liquid flow and controlling a gas-liquid interface under low-gravity conditions. Thus, a single bubble is placed under the 1-G condition. The bubble geometry and its behavior are studied experimentally for gap sizes ranging from 0.5 mm to 2 mm and divergent angles from 1° to 5° using ethyl alcohol as the working fluid. The following results were obtained: (1) the bubble was found to move to the greater cross-sectional area; (2) the gas-liquid interface geometry in a top view can be expressed as a contact circle model that takes the maximum radius in the passage; and (3) the effects of gap size and the projected bubble area on bubble behavior are clarified. © 1998 Scripta Technica, Heat Trans Jpn Res, 27(6): 447–461, 1998     

Dynamic mechanical properties and morphology of styrene-divinylbenzene copolymer/poly(vinyl chloride) systems. (II). Effect of polymerization temperature

Effect of polymerization temperature on the phase-separated structure of the composite materials [P(St-DVB)/PVC systems] prepared by copolymerization of styrene (St) and divinylbenzene (DVB) in the presence of fine poly(vinyl chloride) (PVC) powder was studied by electron microscopy and dynamic mechanical test. P(St-DVB)/PVC systems have the two-phase nature with a styrene-divinylbenzene copolymer as the continuous phase [P(St-DVB) phase) and a PSt/PVC composite as the dispersed phase (PSt-PVC phase), in which PSt penetrates into the PVC domain. The crosslinking density of the P(St-DVB) phase is larger than that estimated from the recipe in the feed, suggesting that there exists a difference of the diffusion constants of styrene and divinylbenzene into the PVC particles on the paste formation and the polymerization process. The changes of the phase-separated structure of P(St-DVB)/PVC systems polymerized at various temperatures are also explained on the basis of the difference between the diffusion behavior of styrene and that of divinylbenzene into fine PVC particles at these temperatures.