Page 128 - Industrial Ventilation Design Guidebook

90 CHAPTER 4 PHYSICAL FUNDAMENTALS

FIGURE 4.13 Determination lines for the state of air when 6 M - 0 odl4 °C. M - determination line
for wet bulb temperature, £ = constant enthalpy, A adiabatic humidification line.

The enthalpy of humid air responding to the point 14 °C on the satura-
tion curve is

b kad = 1.0016 • 14 + 0.01009 • (1.85 • 14 + 2501) = 39.58 kj/kg .

The humidity at the temperature of 25 °C corresponding to this enthalpy is
determined from the equation

39.58 = 1.006 • 25+ *(1.85-25+ 2501),
and so x = 0.00567.
Comparing this value with the (a) and (b) point results of Example 7, we
discover that the line of constant enthalpy lies between the determination line
of wet bulb temperature and the adiabatic humidification line. The nearer the
Lewis number is to 1, the nearer the wet bulb temperature is to the adiabatic
humidification temperature.
In practical calculations the Mollier diagram's constant enthalpy line can
be used as the auxiliary line for the wet bulb temperature line to a satisfactory