Mitsubishi Electric GUG-01SL-E, Technical Manual

Page: 49 / 76

46
CHAPTER
9
Model selection and capacity calculation
(3) Corrected refrigerant pipe length factor
(4) Adjusted Dx-coil unit capacity
Specification condition
Designing condition
For the quick reference of air condition difference factor C
2
, see the page 63.
(A) Refrigerant pipe length factor C
3
Same condition with Example 1-1.
(A) Dx-coil unit heating capacity on the specification
(B) Adjusted Dx-coil unit heating capacity
= (A) x C
1
x C
2
x C
3
= 8.1 x 1.0 x 0.71 x 1.0 = 5.75 5.8
(A) Outdoor air wet-bulb temperature
(B) Dx-coil inlet air dry-bulb temperature
(C) Air condition difference factor C
2-1
All of cooling specification for each Dx-coil unit are designed under above condition.
Therefore C
2-1
( = 1.02) is fixed value for all unit.
(D) Outdoor air wet-bulb temperature
(E) Dx-coil inlet air dry-bulb temperature
(F) Air condition difference factor C
2-2
(Find C
2-2
from the graph on page 62. )
(G) Total air condition difference factor C
2
= C
2-2
/C
2-1
= (F) / (C) = 0.72 / 1.02
6
˚C
WB
–
3˚CWB
8.1 kW
17.4˚CDB
16.0˚CDB
5.8 kW
1.02
0.72
0.71
1.0
IV: Calculate the supply air conditions from Dx-coil unit
Enthalpy of supply air from Dx-coil : h
o
= C
a
/ (
ρ
x Q
f
/ 3600) + h
i
[kJ/kg(DA)]
Enthalpy of supply air from Dx-coil :
Absolute humidity, the ratio of water weight against the unit weight of dry air, is unchanged during heating.
By calculations from STEP 1 to 3, the capacity of L Dx-coil unit is summate as shown below.
5.8 kW
29.1 kJ/kg(DA)
46.4 kJ/kg(DA)
h
i
: Enthalpy of Dx-coil inlet air
(equal to Lossnay outlet air) [kJ/kg(DA)]
C
a
: Adjusted capacity of Dx-coil unit [kW]
h
o
= C
a
/ ( ρ x Q
f
/ 3600) + h
i
[kJ/kg(DA)]
= 5.75 / ( 1.2 x 1000 / 3600 ) + 29.2
STEP4. Comparison of L Dx-coil unit capacity with required capacity
Capacity calculation result
(A) Required cooling capacity
(B) Lossnay energy recovery
(C) Dx-coil heating capacity
(D) L DX-coil unit system cooling capacity
= (B) + (C)
8.1 kW
5.8 kW
26.7 kW
13.9 kW
As a result, (D) is smaller than (A). Therefore, consider to add other heating equipment.
(In this example, air-conditioning equipment whose capacity is 12.8 kW ( 26.7 - 13.9 ) is necessary.)
Supply air from Dx-coil unit
Dry-bulb temperature [°C] 33.2
Wet-bulb temperature [°C] 16.7
Absolute humidity [kg/kg(DA)] 0.0051
Relative humidity [%] 16
Enthalpy [kJkg(DA)] 46.4
Supply air condition from Dx-coil can be read out by psychrometric chart.