Gas-liquid flows with heat transfer play an important role in many natural and industrial processes such as combustion, petroleum refining. In particular, the heat transfer enhancement caused by air bubble motion is of practical interest in many industrial applications ranging from boiling solar collectors to nuclear reactors. A bubble sliding over a heated obstacle increases heat transfer by displacing liquid, particularly in the wake region behind the bubble. This, in turn, increases heat transfer from the hot surface, by continuously bringing cooler liquid into contact with the hot surface and removing hot liquid from the surface. However, despite its industrial relevance, many important hydrodynamics and heat transfer phenomena associated with bubble flow, such as bubble formation, bubble coalescence, bubble breakup and bubble wake effect on heat transfer are still poorly understood. The primary objective of this research is to develop a numerical tool to simulate multi-fluid flow problems and assess its suitability to study the enhancement effect of an ellipsoidal air bubble on heat transfer from a heated flat plate immersed in water, and the resulting flow patterns. The Volume-of-Fluid (VOF) method is adopted to model the multi-fluid interface dynamics, where the interface is tracked and advected by Young’s Piecewise Linear Interface Construction (PLIC) Method. The mass, momentum, and energy conservation equations are solved on a fixed (Eulerian) Staggered Cartesian grid using the Finite Volume formulation of Semi-Implicit Pressure Linked Equation (SIMPLE) method along with Krylov subspace and iterative multigrid solvers. In order to consider wall adhesion effects, while simulating a sliding bubble over an obstacle, the static contact angle model is adopted. iv Numerous single-and multi-fluid flow problems have been computed and the results have been compared against published experimental, analytical and computational information. For single phase fluid flow, the code has been validated with the benchmark lid driven cavity problem, and for single phase heat transfer, buoyancy driven flow of air with the Boussinesq approximation has been studied. However, convective heat transfer in water cannot be modelled using the Boussinesq approximation, so a variable thermal property model has been included and validated against published experimental results. For multi-fluid flow, the code has been validated against published experimental results of rising air bubbles of different diameters. The problem considered is that of sliding bubbles over inclined heated and non heated flat plates. The rising and sliding bubble shapes and velocity plots are presented and discussed to study the fluid flow behavior, and to study the dependance of timeresolved surface temperature distribution on bubble dynamics are produced. In order to investigate the suitability of a two-fluid flow model when the fluid interface is in contact with a surface, simulations are carried out with three contact angles and assessments of contact angle effects on bubble dynamics and on wall surface temperature are made. The effects of plate inclination on heat transfer characteristics are also highlighted. Results are analysed and discussed in order to gain an understanding of the relationship between bubble wake interaction and heat transfer performance. It is found that the rising velocity of an air bubble sliding along the inclined plate increases monotonously as the inclination angle increases towards the vertical and that bubbles lift off from the surface with larger plate inclination angles. It is also shown that the bubble moving through the liquid phase strongly influences the heat transfer rates occurring between the hot surface and the liquid phase. The most significant effect is enhanced convection due to an increase in fluid agitation caused by bubble motion as the bubble acts as a bluff body, displacing the liquid and disrupting the thermal boundary layer at the hot surface and significantly promoting fluid mixing. Comparison with experimental results is made in spite of the two dimensional limitation of the computational model. This is justified by the fact that the primary objective of the study is to assess the suitability of the numerical modelling methods adopted to v represent the main mechanisms affecting the dynamics behaviour of the sliding bubbles. It is observed that the predicted temperature drop is more in the computations than in the experiments. This can be explained by the fact that, in the computations, the calculations are carried out using a 2D model which cannot account for lateral mixing as the bubble slides in the boundary layer. Conduction from the third direction might be effecting the experimental observations. This brings heat from the surrounding region of the plate surface in that direction. This effect can not be considered in the 2D computational model and this is a limitation of the present model. However, it gives an insight into the underlying mechanism of mixing and vortex-shedding that are responsible for increases in the heat transfer from the surface and has qualitative agreement with the experimental results. It is worth mentioning here that it is difficult to gain a good insight into processes taking place in the thermal boundary layer and how the bubble interacts with it through experiments. Computational results, on the other hand, help to understand the mechanisms that are responsible for temperature reduction.