TABLE OF CONTENTS Basic concepts of heat transfer are reviewed in this chapter and applied primarily to heat exchangers, which are equipment for the transfer of heat between two fluids through a separating wall. Heat transfer also is a key process in other specialized equipment, some of which are treated in the next and other chapters. The three recognized modes of heat transfer are by conduction, convection, and radiation, and may occur simultaneously in some equipment
In a solid wall such as Figure 8.1(a), the variation of temperature with time and position is represented by the one-dimensional Fourier equation
| (8.1) |  |
For the most part, only the steady state condition will be of concern here, in which the case the partial integral of Eq. (8.1) becomes
| (8.2) |  |
assuming the thermal conductivity k to be independent of temperature. Furthermore, when both k and A are independent of position,
| (8.3) |  |
in the notation of Figure 8.1(a).
Equation (8.3) is the basic form into which more complex situations often are cast. For example,
| (8.4) |  |
when the area is variable and
| (8.5) |  |
in certain kinds of heat exchangers with variable temperature difference.
Thermal conductivity is a...
