How to choose a precision air conditioner (TCU/ECU)
How to choose a precision air conditioner (TCU/ECU)
How to calculate the required capacity of precision air conditioner (TCU/ECU) (all-fresh type)
① Cooler (evaporator)
②Heating device
③Humidifier
④Mixing box
⑤Blower fan
A. Air conditioner intake air (OA)
B. Blowout air (SA)
The basic air conditioning processes of precision air conditioner (TCU/ECU) are "cooling," "heating," "humidification," and "dehumidification." Unlike general air conditioners, it is necessary to calculate the required capacity for each process and select the model. However, since the concept of "dehumidification" is mainly used, it is often calculated together with "cooling."
Required cooling/dehumidification capacity calculation formula
Required cooling/dehumidification capacity [W] = air volume [m³/min] x 60 x enthalpy difference [kcal/kg (DA)] x air density (1.2 kg (DA)/m³) ÷ 0.86
◆What is the required cooling and dehumidifying capacity when the airflow is 5m³/min, OA①: 25℃, 60% SA: 23℃, 55%?
OA ①: 25℃, 60%: Specific enthalpy value → 13.24kcal/kg (DA)
SA: 23°C, 55%: Specific enthalpy value → 11.38kcal/kg (DA), dew point 13.5°C
SA dew point 13.5℃, 100%: Specific enthalpy value → 9.06kcal/kg (DA)
Please refer to the psychrometric chart below.
Required cooling and dehumidifying capacity calculation: 5 x 60 x (13.24 - 9.06) x 1.2 ÷ 0.86 = 1750 [W]
Required heating capacity calculation formula
Required heating capacity [W] = air volume [m³/min] x 60 x enthalpy difference [kcal/kg (DA)] x air density (1.2 kg (DA)/m³) ÷ 0.86
Required heating capacity [W] = Air volume [m³/min] x 60 x (Set temperature - Intake temperature) x (Air density x Specific heat) (0.29 kcal/m³・℃) ÷ 0.86
◆What is the required heating capacity when the airflow is 5m³/min, OA②: 20℃, 40% SA: 23℃, 55%?
From the required heating capacity calculation formula: 5 x 60 x (23 - 20) x 0.29 ÷ 0.86 = 304 [W]
Required humidification capacity calculation formula
Required humidification capacity [kg/h] = air volume [m³/min] x 60 x absolute humidity difference [kg/kg (DA)] x air density (1.2 kg (DA)/m³)
◆What is the required humidification capacity when the airflow is 5m³/min, OA②: 20℃, 40% SA: 23℃, 55%?
OA ②: 20℃, 40%: Absolute humidity → 0.0058kg/kg (DA)
SA: 23°C, 55%: Absolute humidity → 0.0096 kg/kg (DA)
Please refer to the psychrometric chart below.
From the required humidification capacity calculation formula: 5 x 60 x (0.0096 - 0.0058) x 1.2 = 1.368 [kg/h]
Humid air hx diagram (total pressure P = 760 mmHg)
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