A two-part experimental investigation is reported on the effects of transverse square rib roughening on fluid flow and heat transfer in channels with uniform and non-uniform boundary conditions. The first part of the experimental programme consisted of providing detailed measurements of mean and basic turbulent characteristics of fully developed, flow in two rectangular ducts of aspect ratios 1.63 and 3.0. In each duct only one wall was roughened. In channels having low aspect ratios secondary flows play an important part in momentum transfer, and an interpretation of their effect on the measured Reynolds shear stress distribution has been attempted. In the second part of the experimental programme mean velocity and temperature profiles, friction factors and Stanton numbers were measured in an internally roughened pipe and annuli composed of a rough inner rod and either a smooth or a rough outer pipe. Heating was always applied on the outer surface. In all the geometries the mean velocities near the rough walls were found to be represented by logarithmic straight lines. The gradients of these lines were independent of Reynolds number but differed for various geometries. The mean temperature profiles, measured in the rough pipe and the fully rough annulus, showed that these could also be represented by logarithmic straight lines, but the slopes of these profiles were markedly different from those of the velocity profiles. These results cast considerable doubt on the validity of the 'universal law of the wall' and Nikuradse's drag law for ribbed surfaces, as well as on the correctness of applying Dipprey and Sabersky's heat-momentum analogy to such surfaces. Finally, the various transformation methods proposed for the interpretation of measured pressure drop and heat transfer in channels with mixed rough and smooth surfaces have been analysed. A new simple transformation method has been proposed for the overall pressure drop results.

A survey and evaluation of some models of turbulence for isothermal turbulent flows is made. Models such as mixing length, one-equation, two-equations and three-equations are solved with the aid of a high speed computer for annular turbulent flows. The results are compared with each other and with experiment and the significance is discussed. The three equation model (three transport equations plus the mean velocity equation) emerges as the most accurate and capable of the widest application: one set of constants only is sufficient to solve a number of turbulent flows. Also, this model does not require the prescription of any arbitrary length scale. A study of the effect of varying the constants in the three-equation model shows that the velocity and shear stress profiles are insensitive to the variation of the constants. A variation of up to 50%, in the value of the constants produces, at most, less than 2% variation in the velocity and shear stress profiles. Only the turbulence energy distribution shows some sensitivity. The position of maximum velocity for smooth annuli with different radius ratios, as well as friction factors for a number of wall conditions are calculated with the three-equation model. The comparison between predictions and experimental data shows a fairly good agreement. Starting from this three-equation model, an extended model, capable of predicting turbulent, two-dimensional, incompressible thermal boundary layers is developed. Three more equations are incorporated in the isothermal model, namely, (1) mean temperature equation (T), (2) convective heat flux equation (uyT') and (3) equation for the intensity of temperature fluctuation (1/2T'2). Appropriate approximations are introduced and the new model of parabolic differential equations is solved simultaneously with the equations for the isothermal flow. The new five-equations model (five transport equations plus mean velocity and mean temperature equations) is applied to a number of real flows, with and without the presence of walls. Both rough and smooth walls are considered. Generally, good agreement is obtained when predicted results are compared with the available experimental data.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999. / Includes bibliographical references (leaves 84-86). / by Haiyang Liu. / S.M.

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 2006. / Includes bibliographical references (p. 63). / The Sulfur-Iodine Cycle for the thermochemical production of hydrogen offers many benefits to traditional methods of hydrogen production. As opposed to steam methane reforming - the most prevalent method of hydrogen production today - there are no carbon dioxide emissions. Compared to other methods of hydrogen production, the efficiency of the cycle is excellent. Due to the high temperatures necessary for the cycle, which are generally greater than 8500C, several of the Generation IV nuclear reactor concepts are attractive thermal energy sources. However, the high temperature and corrosive reaction conditions of the cycle, involving reactions including the decomposition of H2SO4 at 400-9000C, present formidable corrosion challenges. The conversion of sulfuric acid to sulfur dioxide was the focus of this study. The alloying of structural materials to platinum has been proposed as a solution to this problem. A catalytic loop to test the materials was constructed. Sulfuric acid was pumped over the material at 903+20C. The sulfur dioxide production of the catalyst was measured as a means of quantifying the efficiency of the system as a function of temperature. / (cont.) The maximum possible production of the material was calculated by using a mass balance. A gas chromatograph was used to calculate the actual production of sulfur dioxide. The results of the experiment show that an molecular conversion efficiency of 10% is attained when operating at 900C while using 800H + 5%Pt as a catalyst. The research confirms the catalytic activity of the material. / by Kevin Miu. / S.B.

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Thesis (M. S.)--Texas A&M University, 2005. / "Major Subject: Nuclear Engineering" Title from author supplied metadata (automated record created on Sep. 15, 2006.) Vita. Abstract. Includes bibliographical references.

Thesis (M. S.)--Texas A&M University, 2006. / "Major Subject: Nuclear Engineering" Title from author supplied metadata (automated record created on Feb. 23, 2007.) Vita. Abstract. Includes bibliographical references.

Thesis (M. S.)--Texas A&M University, 2006. / "Major Subject: Nuclear Engineering" Title from author supplied metadata (automated record created on Feb. 23, 2007.) Vita. Abstract. Includes bibliographical references.

Thesis (M. S.)--Texas A&M University, 2006. / "Major Subject: Nuclear Engineering" Title from author supplied metadata (automated record created on Feb. 23, 2007.) Vita. Abstract. Includes bibliographical references.

Thesis (M. S.)--Texas A&M University, 2006. / "Major Subject: Nuclear Engineering" Title from author supplied metadata (automated record created on Feb. 23, 2007.) Vita. Abstract. Includes bibliographical references.