1. CHAPTER
13
Gas – Vapor Mixtures
and Air-Conditioning

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FIGURE 13-1
The Cp of air can
be assumed to be
constant at 1.005
kJ/(kg · °C) in the
temperature
range - 10 to 50°C
with an error
under 0.2 percent.
13-1

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FIGURE 13-2
At temperatures below
50°C, the h = constant
lines coincide with
the T = constant lines in
the superheated vapor
region of water.
13-2

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FIGURE 13-4
For saturated air, the
vapor pressure is equal to
the saturation pressure of
water.
13-3

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FIGURE 13-5
Specific humidity is
the actual amount of
water vapor in 1 kg
of dry air, whereas
relative humidity is
the ratio of the
actual amount of
moisture in the air
to the maximum
amount of moisture
air can hold at that
temperature.
13-4

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FIGURE 13-6
The enthalpy of
moist (atmospheric)
air is expressed per
unit mass of dry air,
not per unit mass of
moist air.
13-5

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FIGURE 13-8
Constant-pressure
cooling of moist air
and the dew-point
temperature on the
T-s diagram of
water.
13-6

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FIGURE 13-11
The adiabatic
saturation process
and its represen-
tation on a T-s
diagram of water.
13-7

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FIGURE 13-12
A simple arrangement
to measure the wet-
bulb temperature.
13-8

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FIGURE 13-14
Schematic for a
psychrometric chart.
13-9

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FIGURE 13-15
For saturated air,
the dry-bulb, wet-
bulb, and dew-point
temperatures are
identical.
13-10

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FIGURE 13-20
Various air-
conditioning
processes.
13-11

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FIGURE 13-21
During simple
heating, specific
humidity remains
constant, but
relative humidity
decreases.
13-12

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FIGURE 13-22
During simple
cooling, specific
humidity remains
constant, but
relative humidity
increases.
13-13

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FIGURE 13-23
Heating the
humidification.
13-14

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FIGURE 13-24
Schematic and
psychrometric chart
for Example 13–5.
13-15

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FIGURE 13-25
Schematic and
psychrometric chart
for Example 13–6.
13-16

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FIGURE 13-27
Evaporative cooling.
13-17

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FIGURE 13-29
When two airstreams at
states 1 and 2 are mixed
adiabatically, the state of
the mixture lies on the
straight line connecting
the two states.
13-18

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FIGURE 13-31
An induced-draft
counterflow cooling
tower.
13-19

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FIGURE 13-33
A spray pond.
Photo credit: Yunus Çengel
13-20