All fluids have its resistance to relative motion between surfaces and is called Viscosity. This property is about the friction between the particles of a fluid. A fluid that is forced in a tube has the liquid moving faster as it is closer the axis of the tube and slower when farther from it.
3.1.1 Dimensionless Parameters
In analysis of convection heat transfer, it is convenient to convert to non-dimensional the governing equations and combine the variables, which makes the group of dimensionless numbers in order to reduce the number of total variables.
3.1.1.1 Prandtl Number
The Prandtl number is the ratio of the momentum diffusivity or viscous diffusuion rate and thermal diffusivity or thermal diffusion rate expressed as
where is the specific heat, is the thermal diffusivity, is the …show more content…
It is the dimensionless number, which is basically the ratio of the heat flux for convection and for conduction, defined as
where is the convective heat transfer coefficient. A larger Nusselt number represents a more effective convection heat transfer. In natural convection, there are complexities in fluid motion that makes difficult for analytical analysis of relations for heat transfer. However, simple empirical correlations with claimed accuracy for the average Nusselt number is used for heat transfer analysis in natural convection expressed as
where and are the constants depending on the geometry of the surface and flow regime. For value of for laminar flow and turbulent flow are usually equal to and , respectively (Cengel, Y.A. 2007).
3.2 Basic Heat Transfer
Heat is normally absorbed or rejected by a working substance at a constant pressure. The heat transferred without a phase change results in a change of temperature is called sensible heat and can be measured by the
3.1.1 Dimensionless Parameters
In analysis of convection heat transfer, it is convenient to convert to non-dimensional the governing equations and combine the variables, which makes the group of dimensionless numbers in order to reduce the number of total variables.
3.1.1.1 Prandtl Number
The Prandtl number is the ratio of the momentum diffusivity or viscous diffusuion rate and thermal diffusivity or thermal diffusion rate expressed as
where is the specific heat, is the thermal diffusivity, is the …show more content…
It is the dimensionless number, which is basically the ratio of the heat flux for convection and for conduction, defined as
where is the convective heat transfer coefficient. A larger Nusselt number represents a more effective convection heat transfer. In natural convection, there are complexities in fluid motion that makes difficult for analytical analysis of relations for heat transfer. However, simple empirical correlations with claimed accuracy for the average Nusselt number is used for heat transfer analysis in natural convection expressed as
where and are the constants depending on the geometry of the surface and flow regime. For value of for laminar flow and turbulent flow are usually equal to and , respectively (Cengel, Y.A. 2007).
3.2 Basic Heat Transfer
Heat is normally absorbed or rejected by a working substance at a constant pressure. The heat transferred without a phase change results in a change of temperature is called sensible heat and can be measured by the