19
| Specifying the MH Humidifier / Air Cooler
Specifying for Air Cooling
Direct Air Cooling
Direct air cooling is normally used to cool the makeup air in an air handling system because
trying to cool return air which has a high RH due to previously being cooled is not very effective.
The easiest way to determine the maximum cooling which can be achieved is to calculate the
maximum effectiveness of the MH and then use a psychrometric chart to determine end
conditions. Since the maximum cooling will always be achieved with the 12 in. (30 cm) media it
is normally used. The maximum cooling that can be achieved is;
Max. Cooling = (outdoor dry bulb– outdoor Wet bulb) x Max effectiveness
Example Direct Cooling
Compare the maximum cooling of 12 in. (30 cm) and 8 in. (20 cm) thick media, Los Angeles
California, Air volume = 50,000 cfm, Duct size = 10 x 10 ft. (Figure 15)
Figure 15: Direct Cooling, Los Angeles
1
Calculate the Air Velocity
V= 50,000 cfm / (10 ft x 10 ft) = 500 fpm
2
Determine the maximum effectiveness - Use Figure 12: Maximum MH Effectiveness vs Air
Velocity along with the calculated velocity to determine maximum effectiveness of each
media.
12 in. (30 cm) Media =
94%
8 in. (20 cm) Media =
84%
3
Determine the supply air conditions
ASHRAE cooling design conditions in Los Angeles California are DryBulb (DB) = 88.9 ºF,
Wet Bulb (WB) = 61.6 ºF.
40 42 44 46
48 50 52 54
56 58 60 62
64 66 68
70 72 74 76
78 80 82 84
86 88 90 92
94 96 98 100 102 104 106 108 110
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
Dry Bulb Temperature, F Pressure= 29.921 inHg
º
H
u
m
id
ity
R
a
ti
o
,
lb
/k
lb
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56 BTU/lb(d.a)
58
10% RH
20%
RH
30%
RH
40%
RH
50
%
RH
60
%
RH
70
%
R
H
80
%
RH
90
%
R
H
88.9
66
61.6 63
84%
100%
94%
10
0%
R
H
Sa
t
a
ur
te
d
Summary of Contents for MH Series
Page 45: ...MH Installation Requirements 42 ...
Page 46: ...43 Warranty ...
