Split_00051 - Vroom = 141 ft 3 DA = dry air 8.70 mDA = ha =...

8-51
8.70
V
m
h
room
3
DA
3 o
3
m
o
m
a
m 2
m
m 2 m
ft . DA = dry air.
=
ft lb - mol R
0.7302 ft atm
lb DA
lb - mol
atm
550 R
lb DA
lb H O
lb DA
lb H O / lb DA
=
⋅
⋅
=
= =
141
140
29
1
101
0 205
101
0 0203
.
.
.
.
From the psychrometric chart, F,
h T F V ft / lb DA
T F H Btu / lb
db
o
a
r wb
o 3
m
dew point
o
m
T h = =
= = =
= = − ≅
90 0 0903
67% 805 14 3
77 3 44 0 011 439
.
.
±
.
.
±
. . .
8.71
T
T
h
r
db
ab
C
C
He wins
= °
= °
⇒ =
35
27
55%
8.72 a. T T
h h
T
r a
wb
db dew point
Fig. 8.4-1
2
C, C
kg H O kg dry air
C
= ° = ° ⇒
= =
= °
40 20
33%, 0 0148
255
.
.
b. Mass of dry air: m
da
= = ×
−
2.00 L 1 m 1 kg dry air
10 L 0.92 m
kg dry air
3
3 3
2 2 10
3
.
↑
from Fig. 8.4-1
Mass of water:
2.2 10 kg dry air 0.0148 kg H O 10 g
1 kg dry air 1 kg
g H O
2
3
2
×
=
− 3
0 033 .
c.
±
. . . H 40 78 0 0 65 77 4 ° ≈ − = C, 33% relative humidity kJ kg dry air kJ kg dry air
b g b g
±
. H 20 57 5 ° ≈ C, saturated