This thesis numerically studied mass transfer during fully confined liquid jet impingement on a rotating target disk of finite thickness and radius. The study involved laminar flow with jet Reynolds numbers from 650 to 1500. The nozzle to plate distance ratio was in the range of 0.5 to 2.0, the Schmidt number ranged from 1720 to 2513, and rotational speed was up to 325 rpm. In addition, the jet impingement to a stationary disk was also simulated for the purpose of comparison. The electrochemical fluid used was an electrolyte containing 0.005moles per liter potassium ferricyanide (K3(Fe(CN6)), 0.02moles per liter ferrocyanide (FeCN6?4), and 0.5moles per liter potassium carbonate (K2CO3). The rate of mass transfer of this electrolyte was compared to Sodium Hydroxide (NaOH) and Hydrochloric acid (HCl) electrochemical solutions. The material of the rotating disk was made of 99.98% nickel and 0.02% of chromium, cobalt and aluminum. The rate of mass transfer was also examined for different geometrical shapes of conical, convex, and concave confinement plates over a spinning disk. The results obtained are found to be in agreement with previous experimental and numerical studies. The study of heat transfer involved a microchannel for a composite channel of trapezoidal cross-section fabricated by etching a silicon wafer and bonding it with a slab of gadolinium. Gadolinium is a magnetic material that exhibits high temperature rise during adiabatic magnetization around its transition temperature of 295K. Heat was generated in the substrate by the application of magnetic field. Water, ammonia, and FC-77 were studied as the possible working fluids. Thorough investigation for velocity and temperature distribution was performed by varying channel aspect ratio, Reynolds number, and the magnetic field. The thickness of gadolinium slab, spacing between channels in the heat exchanger, and fluid flow rate were varied. To check the validity of simulation, the results were compared with existing results for single material channels. Results showed that Nusselt number is larger near the inlet and decreases downstream. Also, an increase in Reynolds number increases the total Nusselt number of the system.

This thesis consists of two different research problems. In the first one, the heat transfer characteristic of wavy fin assembly with dehumidification is carried out. In general, fin tube heat exchangers are employed in a wide variety of engineering applications, such as cooling coils for air conditioning, air pre-heaters in power plants and for heat dissipation from engine coolants in automobile radiators. In these heat exchangers, a heat transfer fluid such as water, oil, or refrigerant, flows through a parallel tube bank, while a second heat transfer fluid, such as air, is directed across the tubes. Since the principal resistance is much greater on the air side than on the tube side, enhanced surfaces in the form of wavy fins are used in air-cooled heat exchangers to improve the overall heat transfer performance. In heating, ventilation, and air conditioning systems (HVAC), the air stream is cooled and dehumidified as it passes through the cooling coils, circulating the refrigerant. Heat and mass transfer take place when the coil surface temperature in most cooling coils is below the dew point temperature of the air being cooled. This thesis presents a simplified analysis of combined heat and mass transfer in wavy-finned cooling coils by considering condensing water film resistance for a fully wet fin in dehumidifier coil operation during air condition. The effects of variation of the cold fluid temperature (-5˚C - 5˚C), air side temperature (25˚C - 35˚C), and relative humidity (50% - 70%) on the dimensionless temperature distribution and the augmentation factor are investigated and compared with those under dry conditions. In addition, comparison of the wavy fin with straight radial or rectangular fin under the same conditions were investigated and the results show that the wavy fin has better heat dissipation because of the greater area. The results demonstrate that the overall fin efficiency is dependent on the relative humidity of the surrounding air and the total surface area of the fin. In addition, the findings of the present work are in good agreement with experimental data. The second problem investigated is the heat transfer analysis of confined liquid jet impingement on various surfaces. The objective of this computational study is to characterize the convective heat transfer of a confined liquid jet impinging on a curved surface of a solid body, while the body is being supplied with a uniform heat flux at its opposite flat surface. Both convex and concave configurations of the curved surface are investigated. The confinement plate has the same shape as the curved surface. Calculations were done for various solid materials, namely copper, aluminum, Constantan, and silicon; at two-dimensional jet. For this research, Reynolds numbers ranging from 750 to 2000 for various nozzle widths channel spacing, radii of curvature, and base thicknesses of the solid body, were used. Results are presented in terms of dimensionless solid-fluid interface temperature, heat transfer coefficient, and local and average Nusselt numbers. The increments of Reynolds numbers increase local Nusselt numbers over the entire solid-fluid interface. Decreasing the nozzle width, channel spacing, plate thickness or curved surface radius of curvature all enhanced the local Nusselt number. Results show that a convex surface is more effective compared to a flat or concave surface. Numerical simulation results are validated by comparing them with experimental data for flat and concave surfaces.