Page 24 - Packed bed columns for absorption, desorption, rectification and direct heat transfer
P. 24
19
The total difference between the quantity of entering and outgoing heat
is
d{w xp) [ d(w yp | g(w z
= c pit {
dx dy dz
dt dt dt)
dy dz
From the equation of continuity (18) in case of a steady state flow, it
can be written
d(pwj 8(pw y)
_
a. a. dz * '
m dy
From Eqs. (52) and (53) it follows:
dt dt
d v^p— labc.dy.dz (54)
Q =
dx
In case of a steady state process the quantity of heat in the hypothetical
parallelepiped remains constant and thus the heat according to Eq. (54) is equal
to the heat transferred by conduction through its walls. According to Eq. (35)
written for a steady state process:
dy dz
From Eqs. (54) and (55) after simple transformations it follows:
