Thesis (Ph. D.)--University of Adelaide, School of Mechanical Engineering, 2005. / Title from t.p. of source document (viewed Apr. 2, 2007). "September 30, 2005." Includes bibliographical references (leaves 251-263). Also available in print version.

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A numerical analysis of the performance of compact pin-fin array heat exchangers was carried out using water and JP-4 fuel as the working fluids. Three different configurations were used with hydraulic diameters ranging from 0.137 to 0.777 mm, and volumetric area densities varying between 4.5 and 14.5 mm2/mm3. Numerical simulations were carried out to determine the performance of each heat exchanger over a series of Reynolds numbers in both the laminar and turbulent flow regimes. It was found that very large heat transfer coefficients (in the kW/m2K range) can be achieved compared to air for the same footprint. In addition, the simulations were used to predict the Reynolds number range for transition from laminar to turbulent flow which was found to vary depending on the compactness of the heat exchanger configuration. As a final point, this study also investigated the effects of boiling of the liquid within the heat exchanger on its performance. It was found that despite improved heat transfer rates due to latent heat removal, vapor formation and resulting fluid expansion effects could result in undesirable flow patterns at low Reynolds numbers. The results from this study would be useful in the design of micro-scale heat exchangers for applications in the micro-electronic and gas turbine industries. / US Navy (USN) author.

Approved for public release, distribution unlimited / An investigation of vortex shedding downstream of a cascade of compressor stator blades, at off-design inlet-flow angles of 35, 33 and 31 degrees and Reynolds numbers, based on chord length, of 625,000, 750,000 and 800,000 is reported. The objective of the study was to characterize the flow and vortex shedding through blade surface pressure measurements and hot-wire anemometry. Vortex shedding was determined to be a leading edge phenomenon as periodic shedding was only detected on the pressure side of the wake. The relationship between vortex shedding frequency and Reynolds number was nearly linear. The vortex shedding frequency at three incidence angles was observed to be quite similar at lower Reynolds number (i.e. 450,000 and below) but developed into a larger scatter at higher Reynolds number. Similarly, the Strouhal numbers were observed to be fairly consistent (0.22 to 0.24) at low Reynolds number and more scattered (0.18 to 0.25) with increasing Reynolds number. The result obtained was comparable to the experimental results obtained by Roshko[Ref. 14], for vortex shedding behind a circular cylinder. / Major, Republic of Singapore Air Force

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When the paper web and press felt enter a nip in the press section of a paper machine, both the paper web and felt are compressed. Water is forced from the paper sheet into the press felt due to a hydrodynamic pressure gradient between the sheet and felt. Water not only flows through the felt in the transversal z-direction, but also flows through the felt in the machine and cross-machine directions. On the exit side of the nip, the pressure imposed on the sheet-felt system by the rolls begins to decrease. Both the paper web and press felt begin to expand, and a vacuum is created in the web and felt. The vacuum in the web is stronger than that in the felt, and thus water and air tend to flow from the felt back into the sheet, causing rewet. Three mechanisms that contribute to rewet have been proposed: 1) film splitting between the paper web and press felt, 2) capillary forces in the web drawing water from the felt into the web, and 3) the pressure differential between the web and felt during expansion. The objective of this project was to design and test under flow conditions similar to those in a press nip a smart water receiver to be used in the press section of a paper machine. In this manner, the feasibility of such a water receiver was to be determined. The purpose of this water receiver is to accept water that is pressed from the paper web in a nip and prevent the return of this water to the paper web upon exit from the nip. Thus, the smart water receiver allows flow through the felt in the positive z-direction of the felt (away from the paper web) and not in the negative z-direction (towards the paper web). The smart water receiver concept utilizes a layer of micro-check valves incorporated into the press felt to perform in the desired manner. A mathematical model and lab-scale prototype were created in order to predict the behavior of such a design in the press nip.