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(2) Heating during winter
Conditions:
Model LGH-50R type
(at 50Hz, high speed)
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
Air
temperature
conditioner
Absolute
humidity
Relative
humidity
Enthalpy
Calculation example
Lossnay
(Supply air diffuser temperature) t
(Supply air diffuser enthalpy)
Heat recovered (27.4 – 5.0) × 1.2 × 500
Outdoor air load (38.5 – 27.4) × 1.2 × 500
Sensible HRV
(Supply air diffuser temperature) t
(Supply air diffuser enthalpy)
Heat recovered (19.8 – 5.0) × 1.2 × 500
Outdoor air load (38.5 – 19.8) × 1.2 × 500
[Calculated enthulpy recovery efficiency 8,880 ÷ (8,880 + 11,200) × 100 = 44.2]
Conventional ventilator
If a conventional ventilator is used, the supply air diffuser is the same
as the outdoor air and the exhaust is the same as the room air.
Thus the heat recovered is 0 kJ/h and the outdoor air load is
(38.5 – 5.0) × 1.2 × 500 = 20,100 kJ/h = 5.6 kW
3
/h
3
)
Supply air
Lossnay
Sensible HRV
(°C)
15.4
(g/kg')
4.6
(%)
43
(kJ/kg)
27.4
(kW)
3.7
(kW)
1.9
(%)
33
Room air
20°C
7.2 g/kg'
50%
38.5 kJ/kg
= (20°C – 0°C) × 0.77 + 0°C = 15.4°C
SA
i
= (38.5 – 5.0) × 0.67 + 5.0
SA
= 27.4 kJ/kg
= 13,440 kJ/h = 3.7 kW
= 6,660 kJ/h = 1.9 kW
= (20°C – 0°C) × 0.77 + 0°C = 15.4°C
SA
i
= 19.8 kJ/kg
SA
(from psychrometric chart)
= 8,880 kJ/h = 2.5 kW
= 11,200 kJ/h = 3.1 kW
CHAPTER 3
General Technical Considerations
Heat recovery efficiency table (%)
(For winter)
Lossnay
Temperature
77
(sensible heat)
Enthalpy
67
(total heat)
* Calculated volume under below conditions.
Conventional
ventilator
15.4
0
1.8
1.8
17
50
19.8
5.0
2.4
0
3.2
5.6
57
100
Winter conditions
5.6
i
OA
Sensible HRV
77
44.2*
Outdoor air
Dry bulb
temperature
Absolute
humidity
Relative
humidity
Enthalpy
38.5
i
RA
27.4
i
SA
O
t
OA
0
Dry bulb temperature (°C)
Conventional
ventilator
–
–
Exhaust air
0°C
1.8 g/kg'
50%
5.0 kJ/kg
R
X
RA 0.0072
X
SA 0.0046
S
X
OA 0.0018
A
t
t
SA
RA
15.4
20
23
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