The physical properties of materials for the fluid domains, properties including density, viscosity, thermal conductivity and specific heat capacity are required for the calculation purposes. The physical properties can be assumed as dependent or independent of temperature. When there is a large temperature difference between the fluid and the surface the assumption of constant thermo-physical fluid properties may cause some errors, because in reality the thermo-physical properties of the most of the fluids vary with temperature. It is also important to note that the Prandtl number of liquids also varies with temperature, similar to that of viscosity. These property variations, of course, will affect the velocity and the temperature profile of fluid in the tube. the thermo-physical properties of working fluids are assumed as temperature dependent throughout this paper. There is working fluids used in this review paper. Keywords: therm , phys , Hagen, wall
