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CHAPTER 4
Characteristics
3. How to Obtain Efficiency from Characteristic Curves
How to read characteristic curve
Recovery efficiency
5
4
Static pressure outside unit
At 50 Hz, equivalent to 60 Hz at dotted line
Obtaining the efficiency when supply air and exhaust air volumes differ
The efficiency obtained from the intake side air volume in each characteristic curve can be corrected with the air volume ratio
in the chart on the right.
If the intake side and exhaust side duct lengths differ greatly or if a differential air volume is required, obtain the intake side
efficiency from the chart on the right.
Efficiency obtained
with air volume on
supply side from
characteristic curve
44
Recovery
Static pressure
efficiency
outside unit
Exhaust air volume
Air volume ratio =
Supply air volume
Supply side efficiency
after correction
Enthalpy recovery efficiency
(heating)
Enthalpy recovery efficiency
(cooling)
1
Total static pressure loss (or total straight pipe equivalent length)
Static pressure loss related parts
(straight pipe equivalent length total)
Pipe length
High notch air volume at 60 Hz
3
Low notch air volume at 60 Hz
Heat recovery efficiency correction curve
Heat recovery
Air volume ratio =
efficiency
(%)
0.5
90
80
70
60
50
40
50
2
Exhaust air volume
Supply air volume
0.6
0.7
0.8
0.9
60
70
80
Corrected heat recovery efficiency (%)
1.2 1.3
1.0 1.1
1.4
90
100
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