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