This thesis research investigates the adhesion mechanisms of protein molecules to surfaces of biomaterials. New understanding in such adhesion mechanisms will lead to materials design and surface engineering in order to extend the lifespan of implants. The present research evaluates and analyzes the adhesive strength of proteins on pure High Density Polyethylene (HDPE), Single Wall Carbon Nanotube (SWCNT) enhanced HDPE composites, Ti-C:H coating and Ti6Al4V alloys (grade 2). The adhesive strength was studied through fluid shear stress and the interactions between the fluid and material surfaces. The adhesive strength of protein molecules was measured through the critical shear strength that resulted through the fluid shear stress. The effects of surface and material properties, such as roughness, topography, contact angle, surface conductivity, and concentration of carbon nanotubes on adhesion were analyzed. Research results showed that the surface roughness dominated the adhesion. Protein was sensitive to micro-scale surface roughness and especially favored the nano-porous surface feature. Results indicated that the unpurified SWCNTs influenced crystallization of HDPE and resulted in a nano-porous structure, which enhanced the adhesion of the protein onto a surface. Titanium hydrocarbon coating on silicon substrate also had a porous topography which enhanced its adhesion with protein, making it superior to Ti6Al4V.

Traditionally Shell-and-tube heat exchangers are designed using correlation based approaches like Kern method and Bell-Delaware method. With the advances in Computational Fluid Dynamics (CFD) software, it is now possible to design small heat exchangers using CFD. In this thesis, shell-and-tube heat exchangers are modeled and numerically analyzed using a commercial finite volume package. The modeled heat exchangers are relatively small, have single shell and tube passes. The leakage effects are not taken into account in the design process. Therefore, there is no leakage from baffle orifices and no gap between baffles and the shell. This study is focused on shell side flow phenomena. First, only shell side is modeled and shell side heat transfer and flow characteristics are analyzed with a series of CFD simulations. Various turbulence models are tried for the first and second order discretization schemes using different mesh densities. CFD predictions of the shell side pressure drop and the heat transfer coefficient are obtained and compared with correlation based method results. After selecting the best modeling approach, the sensitivity of the results to the flow rate, the baffle spacing and baffle cut height are investigated. Then, a simple double pipe heat exchanger is modeled. For the double pipe heat exchanger, both the shell (annulus) side and the tube side are modeled. Last, analyses are performed for a full shell-and-tube heat exchanger model. For that last model, a small laminar educational heat exchanger setup is used. The results are compared with the available experimental results obtained from the setup. Overall, it is observed that the flow and temperature fields obtained from CFD simulations can provide valuable information about the parts of the heat exchanger design that need improvement. The correlation based approaches may indicate the existence of a weakness in design, but CFD simulations can also pin point the source and the location of the weakness.

Zeolites are microporous hydrated aluminosilicate crystals containing alkali and/or alkali earth metal cations in their frameworks. Due to their molecular size pores, they can separate molecules according to their size and shape. Zeolites are mostly used in ion exchange, adsorption processes and catalytic applications. The hydrophilic/hydrophobic character of zeolites also makes them favorable materials for adsorption based separations. Recently the potential of zeolite/ceramic composite membranes have been shown in the separation of liquid and gas mixtures. Self-supported zeolite membranes with asymmetric structure can be an alternative to the composite zeolite membranes. Because asymmetric structure may eliminate the problems originated from the differences in thermal expansion coefficients of zeolites and ceramics. In this study tubular zeolite A membranes were prepared on binderless zeolite A supports. The supports were perepared by hydrothermal conversion of amorphous aluminosilicate tubes into zeolite A. The amorphous aluminosilicate powder, which was obtained by filtering the homogenous hydrogel with a composition of 2.5Na2O:1Al2O3:1.7SiO2:150H2O, was mixed with an organic binder (HEC-Hydroxyethyl Cellulose) and water to obtain the paste. The paste was then extruded through a home-made extruder into bars and tubes. These extrudates were dried at room temperature for 24 hours, calcined at 600oC for 2 hours to remove organic binder and finally synthesized at 80oC for 72 hours in hydrothermal conditions to convert amorphous aluminosilicate to zeolite. The effect of composition of the synthesis solution on the crystallinity and morphology of zeolite A tubes and bars were investigated. The crystallization field of zeolite A bars has been established and shown on a ternary phase diagram. Tubes were mechanically stable, typically had a crystallinity over 90% and a macroporosity of 35%. The tubes were composed of highly intergrown crystals of zeolite A. The average particle size was 3.5 &micro / m. The asymmetric membranes were synthesized by growing zeolite A films on binderless zeolite A supports with a geometry of disk, bar and tube. Continuous zeolite A films can only be obtained when the supports were saturated with water prior to synthesis. The film thicknesses were approximately 5 &micro / m on disks and approximately 10 &micro / m on tubes. A method was proposed to prepare self-supported tubular zeolite A membranes in this study.

The performance of outlets under constant head is investigated in this study. Behavior of single outlet is analyzed / subsequently effect of multiple outlets on a single outlet is examined. Parameters taken into account are constant head of water, orifice shape, orifice length, number of open outlets and discharge. The outlet type, which is examined, can be classified as a short tube orifice. Two different orifice diameters and tube lengths are used. Outlets had the diameter, 6.00 and 10.35mm. The ratio of orifice length to diameter (l/d) was 5 and 8. Number of outlets is 5, which are opened in several combinations. A dimensional analysis shows that discharge coefficient, Cd is a function of diameter-length ratio and the Reynolds Number. In this study, high Reynolds Number (2300&lt / Re&lt / 18600) range is examined and the results are compared with the available data in the literature. Furthermore, performance of the group outlets is investigated.

Based on the well-known theoretical studies related to the film condensation inside vertical tubes, a known temperature distribution is prescribed as boundary condition at the inner surface of the tube wall. But, in reality, there is a thermal interaction between the condensate fluid and conduction through the wall where the temperature variation along the inner surface of the tube wall is unknown and this unknown temperature profile should be determined by taking account of this interaction. In other words, the heat conduction equation for the tube wall and the energy equation for the condensate fluid flow should be coupled and solved simultaneously. Therefore, this type of problem is named &ldquo / conjugate condensation heat transfer problem&rdquo / . Subject to the conjugate condensation heat transfer problem in the industrial applications, there are two different fluid flows separated by a tube where the vapor flowing inside the tube condensates whereas the other one is heated and it flows externally in the counter current direction in the annular passages. Because of its fundamental and practical importance, in this doctoral thesis, the studies are focused on the analytical and numerical investigation of conjugate heat transfer due to the steam condensation inside vertical tubes which is cooled externally by a fluid flowing in the counter current direction. The unknown wall temperatures of the condenser tube, condensate liquid layer inside the tube and the turbulent coolant flow outside the tube are coupled. A computer code, named ZEC, containing condensation conjugate heat transfer model is developed in FORTRAN 90 Language. This code and the models it contains are assessed against the various experimental databases. The predictions of the code ZEC are found to reasonably agree with the experimental results over a wide range of conditions. Therefore, this developed code, ZEC, may be used for the preliminary design of in-tube condensers and for the performance evaluation of such condensers in operation.

Orifices are essential devices for measurement and control of flow. It is important to define the flow field and understand the flow characteristics behind an orifice for the sake of reliability measures in many hydraulic engineering applications. Since analytical and experimental solutions are restricted, a numerical solution is obtained using volume of fluid (VOF) method with the CFD solver, FLUENT, for sharp crested orifices, orifice tubes and slots. The results are compared to the available data in the literature / also a large spectrum of data collection has been achieved.

The objective of this study uses the plasticity theory of the slab method and the numerical analysis of the finite difference method to construct a mathematical model. And a computer program will be developed to evaluate the quality of the tubes formed by hydraulic expansion. Considering sticking and sliding modes, a mathematical model is proposed to predict the forming pressure needed to hydroform a circular tube into square and rectangular cross-sections and the thickness distribution of the product. In the sticking friction mode, it is assumed that the elements after contact with the die do not move or slide. Whereas, in the sliding friction mode, the element in contact with the die will continue to deform with the stress variation in the subsequent forming process. A series of FE simulations on tube expansion by a commercial FE code¡§DEFORM¡¨have been carried out. In addition, the experiment employing aluminum alloy AA 6063 that has been annealed to proceed the hydraulic expansion experiment. The comparisons between analysis and the result of forming pressure, corner radius and thickness distribution by experiment are verified the validity of this mathematical model. The effects of the forming parameters such as the die geometry, the material property of the tube, friction coefficient between the die and tube, etc., upon the expansion results, such as the forming pressure, corner radius, the tube contact distance with the die, thickness distribution after expansion, etc., are systematically discussed.

The present study considers steady laminar two-dimensional incompressible flow over both in-line and staggered flat tube bundles used in heat exchanger applications. The effects of various independent parameters, such as Reynolds number (Re), Prandtl number (Pr), length ratio (L/Da), and height ratio (H/Da), on the pressure drop and heat transfer were studied. A finite volume based FORTRAN code was developed to solve the governing equations. The scalar and velocity variables were stored at staggered grid locations. Scalar variables (pressure and temperature) and all thermophysical properties were stored at the main grid location and velocities were stored at the control volume faces. The solution to a one-dimensional convection diffusion equation was represented by the power law. The locations of grid points were generated by the algebraic grid generation technique. The curvilinear velocity and pressure fields were linked by the Semi-Implicit Method for Pressure Linked Equations (SIMPLE) algorithm. The line-by-line method, which is a combination of the Tri-Diagonal Matrix Algorithm (TDMA) and the Gauss-Seidel procedure, was used to solve the resulting set of discretization equations. The result of the study established that the flow is observed to attain a periodically fully developed profile downstream of the fourth module. The strength increases and the size of the recirculation gets larger as the Reynolds number increases. As the height ratio increases, the strength and size of the recirculation decreases because the flow has enough space to expand through the tube passages. The increase in length ratio does not significantly impact the strength and size of the recirculation. The non-dimesionalized pressure drop monotonically decreased with an increase in the Reynolds number. In general, the module average Nusselt number increases with an increase in the Reynolds number. The results at Pr = 7.0 indicate a significant increase in the computed module average Nusselt number when compared to those for Pr = 0.7. The overall performance of in-line configuration for lower height ratio (H/Da = 2) and higher length ratio (L/Da = 6) is preferable since it provides higher heat transfer rate for all Reynolds numbers except for the lowest Re value of 25. As expected the staggered configurations perform better than the in-line configuration from the heat transfer point of view.

In this thesis, mechanical and electronic properties of a (4,4) SiC nanotube under different tensile strain were investigated by density functional theory (DFT) calculation. The HOMO-LUMO gap of nanotube will significantly decrease linearly with the increase of axial strain. Two different slopes are found before and after an 11% strain in the profile of HOMO-LUMO gap versus strain. The partial density of states, bond order and electronic deformation density were discussed for demonstrating the strain effect on the electronic properties of SiC nanotube under axial strain. The adsorption mechanism of CO on SiC nanotubes with different axial strains as well as the charge distributions after the adsorption were also discussed.

Pulse tube refrigerators (PTR) are robust, rugged cryocoolers that do not have a moving component at their cold ends. They are often employed for cryogenic cooling of high performance electronics in space applications where reliability is paramount. Miniaturizing these refrigerators has been a subject of intense research interest because of the benefits of minimal size and weight for airborne operation and because miniature coolers would be an enabling technology for other applications. Despite much effort, the extent of possible PTR miniaturization is still uncertain. To partially remedy this, an investigation of the miniaturization of pulse tube refrigerators has been undertaken using several numerical modeling techniques. In support of these models, experiments were performed to determine directional hydrodynamic parameters characteristic of stacked screens of #635 stainless steel and #325 phosphor bronze wire mesh, two fine-mesh porous materials suitable for use in the regenerator and heat exchanger components of miniature PTRs. Complete system level and pulse tube component level CFD models incorporating these parameters were then employed to quantitatively estimate the effects of several phenomena expected to impact the performance of miniature PTRs. These included the presence of preferential flow paths in an annular region near the regenerator wall and increased viscous and thermal boundary layer thicknesses relative to the pulse tube diameter. The effects of tapering or chamfering the junctions between components of dissimilar diameters were also investigated. The results of these models were subsequently applied to produce successively smaller micro-scale PTR models having total volumes as small as 0.141 cc for which sufficient net cooling was predicted to make operation at cryogenic temperatures feasible. The results of this investigation provide design criteria for miniaturized PTRs and establish the feasibility of their operation at frequencies up to 1000 Hz with dimensions roughly an order of magnitude smaller than those that have recently been demonstrated, provided that challenges related to their regenerator fillers and compressors can be addressed.