Heat transfer and flow fluid in thermal equipment is a concerned and basic topic in thermal area. The main objective of this thesis is tocultivate basic skills of analyzing athermal problemand selecting an appropriate methodto solve itaccording to the background.In the following context, basic modes of heat transfer and classification of heat exchangers will be presented and Navier-Stoke equation for incompressible fluids will be introduced. In the next chapter, a problem of composed wall will be solved using analytical and numerical method. Before solving the problem, discretization equation for one-dimension steady conduction is deduced.Later, convection-diffusion equation is developed and a new convection problem of an isotherm tube is studied. In this case, step-by-step method is used to obtain final results.Last chapter is about heat exchangers. Methodologies to solve design and predict problem of heat exchangers are introduced: F-factor method and e-NTU method. The next step is to apply them into some problem: a simple co-current flow HX and a simple counter flow HX. Both analytical and numerical method are used to verify each other. Finally, an advanced double tube is studied