Fluids worked example

Thermally driven convective instabilities in fluid flow, and, more specifically, Rayleigh-B6nard instabilities are favorite working examples in the area of low-dimensional dynamics of distributed systems (see (14 and references therein). By appropriately choosing the cell dimensions (aspect ratio) we can either drive the system to temporal chaos while keeping it spatially coherent, or, alternatively, produce complex spatial patterns. 

Exposures to hydraulic fluids occur mainly in workers using hydraulic equipment and in people who work on cars or tractors that use the fluids. Most people are exposed when fluids spill or leak on the skin, when the fluid is changed, or when the fluid reservoirs are filled. Low levels of hydraulic fluids may occur in the air near machines that use them. Understanding environmental levels of hydraulic fluids is very difficult because the ingredients in hydraulic fluids are used in many products other than hydraulic fluids. For example, mineral oil is an ingredient in both motor oil and mineral oil hydraulic fluids. In the environment, mineral oil from both sources would appear to be the same. Polyalphaolefin hydraulic fluids have chemical components and potential applications similar to mineral oil hydraulic fluids. 

There are many standard texts of fluid flow, e.g. Coulson Richardson,1 Kay and Neddermann2 and Massey.3 Perry4,5 is also a useful reference source of methods and data. Schaschke6 presents a large number of useful worked examples in fluid mechanics. In many recent texts, fluid mechanics or momentum transfer has been treated in parallel with the two other transport or transfer processes, heat and mass transfer. The classic text here is Bird, Stewart and Lightfoot.7... 

C. Schaschke, Fluid Mechanics Worked Examples for Engineers, IChemE, Rugby, 1998. 

Comparison between Co-Current-Flow and Counter-Current-Flow Heat Exchangers. The worked examples reported below will demonstrate the different efficiencies of the two heat exchanger configurations in terms of the heat transfer area required in both cases for the same U. Let us consider two fluids between which heat is being... 

The application of supercritical fluids, for example SCCO2, as an environmentally acceptable replacement for conventional solvents, is well documented in the industry. Based on the work of Zosel, the decaffeination of coffee and tea using SCCO2 was the first industrial use of this technology [1]. The advantages of supercritical fluids are not only useful in separation techniques, for example supercritical fluid extraction (SFE) or supercritical chromatography (SFC), their application as process solvents is well recognized [2, 3]. 

It should be noted that the only valid application of dropwise condensation is for steam condensers, since nonwetting substances are not available for most other working fluids. For example, no dropwise condensation promoters have been found for refrigerants (i.e., no dropwise condensation promoters seem to be Freon-phobic ) [46]. The enhancement of dropwise condensation, beyond inducing the process by selection of an effective, durable promoter, is fruitless, since the heat transfer coefficients are already so high. 

A worked example using this method is given by Hewitt et al. [13]. The Correlation ofKatto and Ohne [310] for Critical Heat Flux in Upward Flow in Vertical Tubes. The Katto and Ohne correlation is based on data for a wide variety of fluids and is not (like the Bowring [293] correlation) restricted to water, and there is no need to use the scaling procedure in this case to calculate the critical heat flux. The Katto and Ohne correlation is expressed generally in the form ... 

The other extreme of slurry behavior in a horizontal pipe, heterogeneous flow, is characterized by a pronounced variation in the local solids concentration with position in the pipe. The particle settling velocity in this case is high. This implies that the density of the solid particles is higher than the working fluid, for example, sand-water slurry... 

Rectifier - An electrical device for converting alternating current to direct current. The chamber in a cooling device where water is separated from the working fluid (for example ammonia). 

Energy relationships within fluids are composed of both potential and kinetic energy terms (Section 2.4). The potential energy of a fluid is related to the height of a fluid relative to some datum, and also to the pressure exerted either by or on the fluid. As examples of these, consider the height of sap within the tallest Sequoia tree. In order to raise the sap to this height above the roots, work must be done to the fluid. The taller the tree, the more work that must be done. The potential energy of the sap at the top of the tree would be available to perform mechanical work if it could be harnessed. 

---