Heat flow takes place when there is a temperature gradient in a system. Hence it becomes necessary to study heat transfer as well as temperature distribution in various systems. Analysis of heat transfer for example is the first step in the design of heat exchangers, boilers, heaters, refrigerators and radiators. Further modern electric and electronic equipment require efficient dissipation of hea ......

In chapter 2 while deriving the equation, the thermal conductivity k, was assumed as constant. This assumption is justified for materials involving only small temperature differences across them. However, it is seen that in practice, the thermal conductivity of most materials depends on temperature. Hence it becomes necessary to include in the analysis and derivations, the variation of thermal con ......

The addition of insulation on plane wall surface will not affect the surface area of heat transfer, but for pipes and spherical surfaces, the addition of insulation thickness increases the outside surface of heat transfer. Due to this increase in surface area, heat transfer rate increases.

The heat transfer from a heated surface to the ambient is given by the relation q = hA (T). In this relation “h” is heat transfer coefficient. T is the temperature difference, A is surface area of heat transfer. To increase the value of q, h may be increased or surface area may be increased.

An important application of fin theory is in estimation of error in temperature measurement by a thermometer in flowing fluids. The thermometer is placed in a small pocket of length L and diameter d and thickness . This pocket is usually welded radially or obliquely into another tube through which the fluid whose temperature T to be determined is flowing.

Convection heat transfer occurs by the movement of fluid particles. If the motion of fluid particles occurs by the variation of density of fluid due to temperature, then the heat transfer process is called free or natural convection.

The lumped parameter analysis presumes that a solid possesses infinitely large thermal conductivity. Internal conduction resistance is then so small that heat flow to and from the solid is controlled primarily by the convective resistance. Temperature gradients are negligible within the sold.

The mechanism of heat transfer in natural convection involves the motion of fluid particles past a solid boundary which is a result of the density differences resulting from the energy exchange. As a result the heat transfer coefficients will vary with geometry of a system.

In this chapter, the method of computing heat transfer rates in forced convection problems related to both external and internal flows will be discussed. First force convection concerning flow over external surfaces such as flat plate, cylinders, spheres and flow across tube banks will be considered. Further problems concerning internal flow such as flow in pipes will be considered.

Heat exchanger is a device or equipment used to transfer heat from one fluid to another which are at different temperatures. Heat exchangers are widely used in many industrial applications where heat has to be transferred from one flowing fluid to another through a solid barrier separating them.

The heat transfer processes discussed in the earlier chapters were restricted to homogeneous single phase systems. However in engineering practice, the processes involving a phase change, like boiling and condensation are also important. Boilers and condensers are essential components of modern thermal power plants and so are the evaporators and condensers in a vapour compression refrigeration cyc ......

When a system contains one or more compounds whose concentrations vary from point, to point there is a natural tendency for mass to be transferred minimizing the concentration difference with in the system. The transport of one constituent from a region of higher concentration to that of lower concentration is called Mass Transfer. Mass may be transferred by molecular diffusion as a result of driv ......

Thermal radiation is the energy emitted by matter that is at finite temperature. The emission may occur not only from solid surfaces, but also from liquids and gases. The emission may be attributed to changes in electron configurations of the constituent atoms or molecules. The radiation energy is transported by electromagnetic waves or alternately photons.

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