TABLE OF CONTENTS SI units are noted in [ ]
Three modes of heat transfer are conduction, convection, and radiation.
It is a mode of heat transfer across a medium caused by temperature difference. A steady state conduction of heat is given by Fourier's law:
| (7-1) |  |
where
| q k | = | heat transferred by conduction in the x direction, Btu/h[W], |
| k | = | thermal conductivity of material, Btu.ft/h.ft 2. F[W/m.K], |
| A | = | area perpendicular to the direction of heat flow, ft 2[m 2] |
| (dT/dx) | = | temperature gradient in the x direction, F/ft[K/m] |
Flat single plate
| (7-2) |  |
where X is the plate thickness, ft[m], and R k = X/kA is the thermal resistance, h. F/Btu[K/W].
Composite Flat Walls
The rate of heat transfer through a series of flat plates forming a composite wall is given by:
| (7-3) |  |
where T 0 > T 1 > ...>T n, R kn = resistance of nth plate = X n/(k nA n), and R kt = total resistance = (R k1 + R k2 +...+ R kn)
Cylindrical Pipe
| (7-4) |  |
where L = length of pipe, ft[m]; T i = temperature at the inside wall, F[K];
T o = temperature at the outside wall, oF[K]; r o, r i = outside, inside radii of pipe, both in the same unit, R k = ln(r o/r i)/(2 ?kL),h. F/Btu[K/W]. The heat transfer through...
