Mitsubishi Electric GUG-01SL-E, Technical Manual

Page: 54 / 76

51
CHAPTER
9
Model selection and capacity calculation
III: Calculation of Lossnay energy recovery effect
(A) Lossnay model
(B) Temperature exchange efficiency for winter (at 1000m
3 /h)
(C) Enthalpy exchange efficiency on heating (at 1000m
3
/h)
(D) Lossnay outlet air temperature
= ( (I) – (G) ) x (B) + (G) = (21˚C – 0˚C) x 0.80 + 0˚C
(E) Lossnay outlet air enthalpy
= ( (J) – (H) ) x (C) + (H) = (40.7 – 7.8) x 0.725 + 7.8
(F) Energy recovered by Lossnay
=((E) – (H)) x
ρ x Q
f
/3600 = (31.7 – 7.8) x 1.2 x 1000 / 3600
LGH-100RVX-E
13.2 kW
72.5 %
8.1 kW
80 %
5.1 kW
16.8 ˚C
31.7 kJ/kg(DA)
8.0 kW
Example 2-2 condition Outdoor air Return air
Dx-coil inlet air
(Lossnay outlet air)
Dry-bulb temperature [˚C]
(G)
0
(I)
21 16.8
Wet-bulb temperature [˚C] –1 14.6 11.1
Absolute humidity [kg/kg(DA)] 0.0031 0.0077 0.0058
Relative humidity [%] 83 50 49
Enthalpy [kJ/kg(DA)]
(H)
7.8
(J)
40.7
31.7
STEP2. Selection of Dx-coil unit system
Adequate Dx-coil unit model
GUG-02SL-E
Lossnay model
LGH-100RVX-E
Adequate outdoor unit model
PUHZ-ZRP71
Temperature control feature
Return air temperature control
Dx-coil unit and outdoor unit are selected as shown below.
STEP3-2. Calculation of Dx-coil unit heating capacity
I: Read out characteristics from the specification sheet
(1) Calculation conditions
- See the parameters used so far.
(2) Characteristics read out from specifications
(A) Heating capacity under specification condition
- Lossnay recovery
- Heating capacity of Dx-coil unit
In this Example 2-2, the floor is assumed same room with Example 2-1.
Required air volume is same with Example 2-1.
In this example, the outdoor and return air conditions are assumed that shown in table below.
STEP1. Calculation of required heating capacity
Example 2-2: Heating for a school classroom by RA temperature control
I: Calculation of required ventilation air volume and selection of Lossnay unit
II: Calculation of heating load to determine the required capacity
Dry Bulb Temp. Relative Humidity Wet Bulb Temp. Enthalpy Enthalpy Difference
Heating
Outdoor Air 0 °C 83% –1 °C 7.8 kJ/kg(DA)
32.9 kJ/kg(DA)
Return Air 21 °C 50% 14.6 °C 40.7 kJ/kg(DA)
Ventilation load per unit area under above condition can be calculated as following.
Ventilation load per unit area =
ρ [kg/m
3
] x n [person/m
2
] x V
f
[m
3
/h·person] x (h
R
- h
o
) [kJ/kg(DA)]
= 1.2 [kg/m
3
] x 0.5 [person/m
2
] x 40 [m
3 /h·person] x 32.9 [kJ/kg(DA)]
= 789.6 [kJ/h·m
2
]
= 219.3 [W/m 2 ]
Load type Load
Ventilation Load 219.4 W/m
2
lnternal Heat 56.1 W/m
2
Total 275.5 W/m
2
Required heating capacity to make up for above heating loads
= 275.5 [W/m
2
] × 50 [m
2
] = 13.8 [kW]