Condensation heat transfer on tubes in actual flue gas

In order to improve boiler efficiency, latent heat recovery from flue gas is a very important concept. Condensation heat transfer on horizontal stainless‐steel tubes was investigated experimentally by using an actual flue gas from a natural gas boiler. The experiment was conducted at different air ratios of the flue gas and a wide range of tube wall temperatures. The condensation pattern was similar to a dropwise condensation near the dew point. By decreasing the wall temperature, the wall region covered with a thin liquid film increased. The heat and mass transfer behavior was well predicted with the analogy correlation at the high‐wall‐temperature region. At the low‐wall‐temperature region, the total heat transfer was higher than that predicted by the analogy correlation. © 2001 Scripta Technica, Heat Trans Asian Res, 30(2): 139–151, 2001     

Experimental study of improved HAWT performance in simulated natural wind by an active controlled multi-fan wind tunnel

The effects of turbulent intensity and vortex scale of simulated natural wind on performance of a horizontal axis wind turbine (HAWT) are mainly investigated in this paper.In particular,the unsteadiness and turbulence of wind in Japan are stronger than ones in Europe and North America in general.Hence,Japanese engineers should take account of the velocity unsteadiness of natural wind at installed opden-air location to design a higher performance wind turbine.Using the originally designed five wind turbines on the basis of NACA and MEL blades,the dependencies of the wind frequency and vortex scale of the simulated natural wind are presented.As the results,the power coefficient of the newly designed MEL3-type rotor in the simulated natural wind is 130％ larger than one in steady wind.     

Double Elimination Protocol for Convenient Synthesis of Dihalodiphenylacetylenes: Versatile Building Blocks for Tailor‐Made Phenylene‐Ethynylenes

Dihalodiphenylacetylenes are conveniently synthesized by a double elimination reaction of β‐substituted sulfones which are readily obtained from halogen‐substituted benzyl sulfone and benzaldehyde derivatives. Halogens can be incorporated at any desired positions in the diphenylacetylene skeleton simply by choosing the substitution position of the halogen on the aromatic rings of the starting compounds. The diphenylacetylenes with different halogen substituents thus obtained undergo sequential carbon‐carbon bond formations due to the different reactivities of the halogens. Thus, various moieties can be incorporated on the diphenylacetylene skeleton at whichever positions so that a variety of tailor‐made phenylene‐ethynylenes with regulated structure and composition could be designed.     

Development of inelastic constitutive model for austenitic stainless steel for design use

To prevent creep-fatigue failure or excessive deformation in high-temperature components of fast reactor plants, accurate estimation of inelastic deformation is essential. In performing inelastic analysis, employment of constitutive models, which can precisely reproduce inelastic deformation of the material is of critical importance. The authors have been engaged in the development of inelastic constitutive model for the use in structural design assessment of liquid metal-cooled fast reactor plants. Various improvements were made on the nonlinear hardening model proposed by Ohno and Wang, placing an emphasis on capability to simulate inelastic deformation behavior of austenitic stainless steels, under regular or irregular cyclic loading possibly with temperature variation and hold time. It was demonstrated that the model can simulate the inelastic deformation behavior under various loading conditions with a sufficient accuracy.     

Comparison of stress intensity factor solutions for cylinders with axial and circumferential cracks

Numerous stress intensity factor solutions have been proposed so far depending on the objects of evaluation including the variations of structures, cracks, and applied loads. In applying the flaw evaluation methodology to components of nuclear power plants, the use of reliable stress intensity factor solutions is essential. In this study, cracked cylinders were focused on as one of the typical configurations in actual plants. Existing stress intensity factor solutions for cracked cylinders were reviewed, and the accuracy of these solutions was investigated thorough the comparison with each other. Specific solutions were then recommended for cylindrical structures. Approximate expressions were newly derived for axially through-wall cracked cylinder subjected to linear stress distribution and for circumferentially through-wall cracked cylinder subjected to bending to realize simple evaluation of stress intensity factor. Considering that the cylindrical structures are often replaced with flat plates in the evaluation of actual components, the propriety of the replacement was also studied.     

A mini-scale mass production and separation system for secretory heterologous proteins by perfusion culture of recombinant Pichia pastoris using a shaken ceramic membrane flask

The perfusion culture technique using a shaken ceramic membrane flask (SCM flask) was applied to the production of a secretory heterologous protein. A recombinant methylotrophic yeast strain, Pichia pastoris, was cultured aerobically on a reciprocal shaker using an SCM flask. High-level production of human serum albumin (HSA) was attempted by increasing both the cell concentration and the expression level of the recombinant gene. In the two-stage culture method, the cell concentration was first raised to 17 g/l by feeding glycerol, after which the expression of HSA was induced by feeding methanol. However, the concentration of HSA in the effluent filtrate was as low as 0.15 g/l, while the cell concentration continued to increase. In contrast, HSA was effectively produced by feeding methanol from an early stage of the culture. In this case, the HSA concentration reached 0.24 and 0.46 g/l, respectively, using the growth-associated production method without and with aeration into the head space of the SCM flask. The results showed that supplying sufficient oxygen together with the growth-associated induction method are effective for obtaining high-level expression of the methanol-inducible recombinant gene of P. pastoris. An HSA concentration in the filtrate of 1.5 g/l was finally achieved when the cell concentration was increased to 53 g/l by supplying oxygen-enriched gas to the SCM flask. The yield and productivity of HSA reached 2.6-fold and 10-fold those obtained in an ordinary fed-batch culture using a shake flask, and these levels were readily achieved by continuous replenishment of the culture supernatant. The achievements made in this study should contribute to the development of a handy bioreactor system for mini-scale mass production of target proteins with separation at high purity.     

Structure development in silica‐filled polyacrylate rubber composites during mixing

The structure of bound rubber in the composites from fumed silica (A200, Nippon Aerosil Co., Japan) and polyethylacrylate rubber (PEA) was studied as a function of mixing temperature. The fraction of bound rubber in the composites increased gradually with increasing the mixing temperature from 80 to 120°C, followed by saturation above 120°C. High‐resolution solid‐state NMR results revealed that there was no chemical bonding between silanol groups and PEA molecules. Scanning electron microscope and optical microscope observation of the composites indicated that, with increasing mixing temperature, the size of agglomerates formed by silica particles decreased. Further, the molecular weight retention of PEA dropped abruptly above 120°C. Dynamic viscoelastic measurements of the composites suggest that the development of network structure in the composites was greatly affected by the mixing temperature. Based on these data, structure development in composites is discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2529–2538, 1999