How To Calculate Cooling / Heating Capacity - Daikin VRV Service Manual

How to Calculate Cooling / Heating Capacity

3. How to Calculate Cooling / Heating Capacity
Measure the temperatures of suction air and discharge air of indoor unit. Then, calculate the
capacity by using the psychrometric chart.
How to calculate the cooling capacity
Cooling capacity = (Enthalpy of suction air – Enthalpy of discharge air) ×
(kW)
Example for cooling capacity calculation
Suction air. . . . . . Dry-bulb temperature: 30°C
Discharge air. . . . Dry-bulb temperature: 20°C
Air flow rate. . . . . 800 m
According to the psychrometric chart, following values are obtained.
Enthalpy of suction air: 72.7 kJ/kg
Enthalpy of discharge air: 52.9 kJ/kg
Specific volume of discharge air: 0.85 m
Cooling capacity is obtained by substituting those values to the above calculation formula.
Cooling capacity = (72.7 – 52.9) ×
How to calculate the heating capacity
Heating capacity = 1.00 × Discharge air temperature – Suction air temperature × Air flow rate ×
(kW) (kJ/kg · k)
Example for heating capacity calculation
Suction air temperature . . . . . 15°C
Discharge air temperature . . . 45°C
Air flow rate. . . . . . . . . . . . . . . 800 m
According to the psychrometric chart, following value is obtained.
Specific volume ... 0.91 m
Heating capacity is obtained by substituting those values to the above calculation formula.
Heating capacity = 1.00 × (45 –15) × 800 ×
198
(kJ/kg)
3
/h
3
/kg
1
× 800 ×
0.85
(˚C)
3
/h
3
/kg
1
×
0.91
Specific volume of discharge air
(kJ/kg)
Wet-bulb temperature: 24°C
Wet-bulb temperature: 18.5°C
1
·
= 5.18kW
·
3600
(˚C)
1
= 7.33kW
3600
1
× Air flow rate ×
3
3 (m /h)
(kg/m )
1
Specific volume
3
(m /h) 3
(kg/m )
Si30-408
1
3600
1
×
3600
Appendix