Dual Pipe Research Articles

Selective Condensation Reaction of Phenols and Hydroxybenzyl Alcohol Using Micromixers Based on Collision of Fluid Segments

In the production of bisphenol F, fast mixing and feed operation with a high flow rate ratio of two reactant fluids are crucial for improvement of product selectivity and productivity. To contribute to these issues, we have developed two micromixers, the K-M mixer and the dual pipe mixer. In the K-M mixer, reactant fluids are divided into fluid segments and, then, the segments collide at a single point, where shear is applied to enhance mixing performance. In the dual pipe mixer, one reactant fluid flows in the inner tube and the other fluid flows from the outer tube into the inner tube through the holes pierced on the inner tube wall. By this geometry, the second reactant fluid is divided into several segments, which penetrate into the first reactant fluid. These two mixers realize high mixing performance and can be operated under a high flow rate ratio of two reactant fluids.

Production of titania nanoparticles by using a new microreactor assembled with same axle dual pipe

The validity of utilizing microspace for nanoparticles production was investigated by using a newly proposed microdevice. The proposed reactor consists of same axle dual pipes, and this assembly gives a microspace by an annular laminar flow of two immiscible liquids. We tried to produce titania particles by supplying tetraisopropoxide (TTIP) solutes to the inner tube and isopropanol/water mixture to the outer tube. Mono-modal spherical particles of titania with narrow size distribution were successfully produced without precipitation of the particles at the wall. It was also found that the particle size was possible to control in the range from 40 to 150 nm only by changing the diameter of the inner tube at a low TTIP concentration. Thus, the proposed concept was confirmed to be valid for the production of nanoparticles.

Operation of dual drinking and non-potable water networks in Paris: advantages and constraints

Paris is one of the very few cities in the world equipped with a dual network system: the drinking water network is duplicated by a totally independent non-potable water network which possesses its own means of production, storage and distribution pipes. In this second network there circulates untreated water characterized by pressure lower than that observed in the drinking water network. The fact that the constraints governing non-potable water are less than for drinking water is reflected in lower margins in relation to comparative production and storage capacity. Non-potable water in Paris has existed for two centuries; it is very inexpensive and its use in large quantities forms part of the landscape to which Parisians are accustomed. 98% of non-potable water consumption are restricted to the uses of water linked to urban concentration for the comfort or safety of town dwellers: hydrants, fountains, street cleaning, watering of public gardens, flushing of the sewers etc. Therefore, the main consumer being the city of Paris, the operation of the non-potable water network differs in many ways from that applied to the drinking water network. The economic context, the technical implications and the ecological repercussions of the use of non-potable water provide an alternative solution to the exclusive use of drinking water which seems to be efficient and attractive. This exceptional situation does not only offer advantages especially when one analyses the consequences for the network of waste water or the cost of maintaining a dual pipe network.

Numerical and Experimental Study of Offshore Pipeline Stability in Trench

Offshore pipelines are to be stabilized against external loading caused mainly by wave and currents. When pipelines are placed in a trench, the forces acting on them are reduced considerably. To investigate the stability in various trench sections, the flow over the pipeline is numerically simulated and compared with experimental results obtained from particle image velocimetry measurement. This paper consists of two parts: single pipe and dual pipe in various trench sections. Each part compares numerical results with experimental results, which include mean flow pattern, drag-force coefficient, and lift-force coefficient. For a single pipe, Smagainsky's eddy viscosity model combined with a truncated deductive model is applied to represent the stress field in a quadrilateral structured grid system. In the numerical simulation for dual pipes, the Navier-Stokes equation and elliptic mesh generation method are used. The stability of various trench conditions is addressed in terms of mean amplitudes of oscillating lift and drag and reduction factors for each case. The results can be effectively applied to pipeline design.