Lossnay Energy Recovery Effect - Mitsubishi Electric Lossnay series Technical Manual

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CHAPTER 3 General Technical Considerations

1. Lossnay Energy Recovery Effect

1.1 Comparing Ventilation Load of Various Ventilators
Examples of formulas that compare the energy recovered and ventilation load when ventilating with the Lossnay (total energy
recovery unit), a sensible energy recovery ventilation unit (sensible HRV), and a conventional ventilator unit are shown below.
(1) Cooling During Summer
Conditions
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Model LGH-F600RX
(at 60Hz, high speed)
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Ventilation rate: 600 CFM
(specific gravity of air ρ = 0.0749 Ib/ft
Dry bulb temperature
Absolute humidity
Relative humidity
Enthalpy
Total energy recovered
Ventilation load
Ventilation load ratio
Dry bulb
temperature
Indoor Unit
Absolute
of
humidity
Air Conditioner
Relative
humidity
Enthalpy
Calculation Example
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Lossnay Unit
(Supply air diffuser temperature) t
(Supply air diffuser enthalpy)
Heat recovered (36.4 – 29.6) × 0.0749 × 600 = 304.4 Btu/min = 5.4 kW
Ventilation load (29.6 – 22.7) × 0.0749 × 600 = 310.1 Btu/min = 5.5 kW
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Sensible HRV Unit
(Supply air diffuser temperature) t
(Supply air diffuser enthalpy)
Heat recovered (36.4 – 34.5) × 0.0749 × 600 = 85.4 Btu/min = 1.5 kW
Ventilation load (34.5 – 22.7) × 0.0749 × 600 = 530.3 Btu/min = 9.3 kW
[Calculated enthalpy recovery efficiency 85.4 ÷ (85.4 + 530.3) × 100 = 14%]
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Conventional Ventilator Unit
If a conventional ventilator unit is used, the energy recovered will be 0 as the supply
air diffuser is equal to the outdoor air.
The ventilation load is:
(36.4 – 22.7) × 0.0749 × 600 = 620.2 Btu/min = 10.9 kW
U-22
-E
5
3
)
Supply air
Lossnay Sensible HRV
Unit
(°F) 82.7
(Ib/Ib') 0.0159 0.0203
(%) 66.0
29.6
(Btu/Ib)
(kW) 4.7
(kW) 5.5
(%) 50
Room air
78.8°F
0.0105 Ib/Ib'
50%
22.7 Btu/Ib
= 91.4°F – (91.4°F – 78.8°F) × 0.69 = 82.7°F
SA
h = 36.4 – (36.4 – 22.7) × 0.50 = 29.6 Btu/Ib
SA
= 91.4°F – (91.4°F – 78.8°F) × 0.69 = 82.7°F
SA
h = 34.5 Btu/Ib (from psychrometric chart)
SA
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Energy recovery efficiency table (%)
(For summer)
Lossnay
Unit
Temperature
69
(Sensible Heat)
Enthalpy
50
(Total Heat)
* Calculated volume under conditions below.
Conventional
Unit Ventilator Unit
82.7 91.4
0.0203
84 63
34.5 36.4
1.6 0
9.3 10.9
86 100
Sensible HRV Conventional
Unit Ventilator Unit
69 –
14* –
Exhaust air
Outdoor air
Dry bulb
91.4°F
temperature
Absolute
0.0203 Ib/Ib'
humidity
Relative
63%
humidity
Enthalpy 36.4 Btu/Ib
Summer Conditions
36.4
i
OA
A O
29.6
i
SA
22.7
i
RA
S
R
t t t
RA SA OA
78.8 82.7 91.4
Dry bulb temperature (°F)
X
OA
0.0203
X
SA
0.0159
X
RA
0.0105