In recent years, the study of fluid flow with nanoparticles in base fluids has attracted the attention of several researchers due to its various applications to science and engineering problems. Recent investigations on convective heat transfer in nanofluids indicate that the suspended nanoparticles markedly change the transport properties and thereby the heat transfer characteristics. Convection in saturated porous media with nanofluids is also an area of growing interest. In this thesis, we study the effects of radiation on the heat and mass transfer characteristics of nanofluid flows over solid surfaces. In Chapter 2, an investigation is made into the effects of radiation on mixed convection over a wedge embedded in a saturated porous medium with nanofluids, while in Chapter 3 results are presented for the effects of radiation on convection heat transfer about a cone embedded in a saturated porous medium with nanofluids. The resulting governing equations are non-dimensionalized and transformed into a non-similar form and then solved by Keller box method. A comparison is made with the available results in the literature, and the results are found to be in very good agreement. The numerical results for the velocity, temperature, volume fraction, the local Nusselt number and the Sherwood number are presented graphically. The salient features of the results are analyzed and discussed for several sets of values of the pertinent parameters. Also, the effects of the Rosseland diffusion and the Brownian motion are discussed.

Two existing evaporation two-phase heat transfer models are validated using 526 experimental data points for pure refrigerants and refrigerant mixtures. The Kido et al. (1995) model fails to predict pure refrigerant data sets except their R22 experimental data set. The Cavallini et al. (1999) model successfully predicts the available R22 data sets; however, the model over-predicts the R12 and the R134a data sets. In addition, the Cavallini et al. (1999) mixture model fails to predict the available 155 refrigerant mixture data points. The proposed modified model, based on the Cavallini et al. (1999) model, successfully predicts the experimental data for pure refrigerant and for refrigerant mixtures.

The Turbulent Heat Transfer Test Facility (THTTF) has been refurbished and the data acquisition system upgraded. The THTTF is now controlled by a LabView 4.1 program which replaces the old program in BASIC. Heat transfer data acquired using this new program is presented as Stanton number distributions. The new data set is compared to previously reported data obtained with this facility and other wellepted published data. This project has successfully qualified the THTTF for zero-pressure gradient, isothermal wall temperature, incompressible boundary-layer flow over smooth flat plates without transpiration. The THTTF is now set to accommodate modifications which will facilitate heat transfer investigations with high freestream turbulence.

The last few decades have seen a significant development of complex heat transfer enhancement geometries such as a helicallyinned tube. The arising problem is that as the fins become more complex, so does the prediction of their performance. In addition to discussing existing prediction tools, this dissertation demonstrates the successful use of artificial neural networks as a correlating method for experimentally- measured heat transfer and friction data of helicallyinned tubes.

A precise prediction of the heat loads in metal materials in contact with the hot gas is an increasingly demanding problem in the design phase of the complex cooling schemes in the modern turbine engines. The coupled calculation of the fluid flow and the heat transfer is a promising approach as heat transfer coefficients are not necessary in the calculation and the heat transfer itself is part of the calculation and can be derived from local heat fluxes. Therefore, it is useful to incorporate an appropriate scheme for directly coupled heat transfer computations (conjugate heat transfer), capable of handling complex geometries into the existing Computational fluid dynamics (CFD) codes. The intent of the present work is to add the conjugate heat transfer solving capability to an existing flow solver. The coupled approach is achieved by maintaining a continuous local heat flux and a common temperature at the points along the fluid-solid interface. At every iteration, the temperature which is directly calculated via the equality of the local heat fluxes passing the fluid-solid contacting cell faces serves as the thermal boundary condition on the interfaces, instead of traditional isothermal/adiabatic thermal boundary conditions. In the solid domain, simplified energy equation is solved using the discretization and computational methods which have been used in the flow by introducing an effective equation of state. The connectivity is built for the points at the fluid-solid interfaces in order to communicate the thermal conditions with each other. Validation of the developed conjugate capability has been investigated. Computed results have been compared with theoretical or experimental results for laminar flat plate, high pressure guide vane, cooled plate, and effusion-cooled plate. All results obtained thus far compare rather favorably with theoretical or experimental results.

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