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Lossnay Heat Recovery Effect - Mitsubishi Electric Lossnay LGH-15RX3 Technical Manual

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CHAPTER 3 G General Technical Considerations

1. Lossnay Heat Recovery Effect

1.1 Comparison of outdoor air load of various ventilators
Examples of formulas to compare the heat recovered and outdoor air load when ventilating with the Lossnay (total heat
recovery unit), sensible heat recovery ventilation (sensible HRV) and conventional ventilators are shown below.
(1) Cooling during summer
Conditions
G
Model LGH-50R type
(at 50Hz, high speed)
G
Ventilation rate: 500 m
(specific gravity of air ρ = 1.2 kg/m
Dry bulb temperature
Absolute humidity
Relative humidity
Enthalpy
Total heat recovered
Outdoor air load
Outdoor air load ratio
Dry bulb
temperature
Air
conditioner
Absolute
humidity
Relative
humidity
Enthalpy
Calculation example
G
Lossnay
(Supply air diffuser temperature) t
(Supply air diffuser enthalpy)
Heat recovered
Outdoor air load
G
Sensible HRV
(Supply air diffuser temperature) t
(Supply air diffuser enthalpy)
Heat recovered
Outdoor air load
[Calculated enthulpy recovery efficiency 3,480 ÷ (3,480 + 15,600) × 100 = 18.2]
G
Conventional ventilator
If a conventional ventilator is used, the heat recovered will be 0 as the supply air
diffuser is equal to the outdoor air.
The outdoor air load is:
(85.0 – 53.2) × 1.2 × 500 = 19,080 kJ/h = 5.3 kW (4558 kcal/h)
22
3
/h
3
)
Supply air
Lossnay
Sensible HRV
(°C)
27.6
(g/kg')
14.8
(%)
63
(kJ/kg)
65.4
(kcal/kg')
(15.6)
(kW)
3.3
(kcal/h)
(2,809)
(kW)
2.0
(kcal/h)
(1,749)
(%)
38.5
Room air
26°C
10.5 g/kg'
50%
53.2 kJ/kg
(12.7 kcal/kg')
= 33°C – (33°C – 26°C) × 0.77 = 27.6°C
SA
= 85.0 – (85.0 – 53.2) × 0.615 = 65.4 kJ/kg
h
SA
(85.0 – 65.4) × 1.2 × 500 = 11,760 kJ/h = 3.3 kW (2,809 kcal/h)
(65.4 – 53.2) × 1.2 × 500 = 7,320 kJ/h = 2.0 kW (1,749 kcal/h)
= 33°C – (33°C – 26°C) × 0.77 = 27.6°C
SA
h
= 79.2 kJ/kg (18.9 kcal/kg) (from psychrometric chart)
SA
(85.0 – 79.2) × 1.2 × 500 = 3,480 kJ/kg = 1.0kW (831 kcal/h)
(79.2 – 53.2) × 1.2 × 500 = 15,600 kJ/H = 4.3 kW (3,727 kcal/h)
G
Heat recovery efficiency table (%)
(For summer)
Lossnay
Temperature
77
(sensible heat)
Enthalpy
61.5
(total heat)
* Calculated volume under below conditions.
Conventional
ventilator
27.6
33
20.3
20.3
86
63
79.2
85.0
(18.9)
(20.3)
1.0
0
(831)
4.3
5.3
(3,727)
(4,558)
82
100
Conventional
Sensible HRV
ventilator
77
18.2*
Exhaust air
Outdoor air
Dry bulb
33°C
temperature
Absolute
20.3 g/kg'
humidity
Relative
63%
humidity
85.0 kJ/kg
Enthalpy
(20.3 kcal/kg')
Summer conditions
85.0
h
OA
A
65.4
h
SA
53.2
h
RA
S
R
t
t
RA
SA
26
27.6
Dry bulb temperature (°C)
O
X
OA
0.0203
X
SA
0.0148
X
RA
0.0105
t
OA
33

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