안녕하세요?
Fan 선정의 어떤 룰(규정)이란 습공기선도상의 fan의 온도 상승을 말하나요?
그렇다면, 다음의 ASHRAE 의 규정을 참조하시길 바랍니다.
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2009 ASHRAE Handbook—Fundamentals Chapter 18
Nonresidential Cooling and Heating Load Calculations 18.33
Heat Gain from Fans
Fans that circulate air through HVAC systems add energy to the system through the following processes:
• Increasing velocity and static pressure adds kinetic and potential energy
• Fan inefficiency in producing airflow and static pressure adds sensible heat (fan heat) to the airflow
• Inefficiency of motor and drive dissipates sensible heat
The power required to provide airflow and static pressure can be determined from the first law of thermodynamics with the following equation:
PA = 0.009804Vp
where
PA = air power, kW
V = flow rate, ㎥/s
p = pressure, kPa
at standard air conditions with air density = 1.2 kg/㎥ built into the multiplier 0.009804. The power necessary at the fan shaft must account for fan inefficiencies, which may vary from 50 to 70%. This may be determined from
PF = PA /ηF
where
PF = power required at fan shaft, kW
ηF = fan efficiency, dimensionless
The power necessary at the input to the fan motor must account for fan motor inefficiencies and drive losses. Fan motor efficiencies generally vary from 80 to 95%, and drive losses for a belt drive are 3% of the fan power. This may be determined from
PM = (1 + DL) PF /EM ED
where
PM = power required at input to motor, kW
ED = belt drive efficiency, dimensionless
EM = fan motor efficiency, dimensionless
PF = power required at fan shaft, kW
DL = drive loss, dimensionless
Almost all the energy required to generate airflow and static pressure is ultimately dissipated as heat within the building and HVAC system; a small portion is discharged with any exhaust air. Generally, it is assumed that all the heat is released at the fan rather than dispersed to the remainder of the system. The portion of fan heat released to the airstream depends on the location of the fan motor and drive: if they are within the airstream, all the energy input to the fan motor is released to the airstream. If the fan motor and drive are
outside the airstream, the energy is split between the airstream and the room housing the motor and drive. Therefore, the following equations may be used to calculate heat generated by fans and motors:
If motor and drive are outside the airstream,
qfs = PF
qfr = (PM – PF )
If motor and drive are inside the airstream,
q s = PM
qfr = 0.0
where
PF = power required at fan shaft, kW
PM = power required at input to motor, kW
qfs = heat release to airstream, kW
qfr = heat release to room housing motor and drive, kW
Supply airstream temperature rise may be determined from psychrometric formulas or Equation (9). Variable- or adjustable-frequency drives (VFDs or AFDs) often drive fan motors in VAV air-handling units. These devices release heat to the surrounding space. Refer to manufacturers’ data for heat released or efficiencies. The disposition of heat released is determined by the drive’s location: in the conditioned space, in the return air path, or in a nonconditioned equipment room. These drives, and other electronic equipment such as building control, data processing, and communications devices, are temperature sensitive, so the rooms in which they are housed require cooling, frequently yearround.
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RTS-SAREK 에서는 상기의 식을 적용하였습니다.
:::: 김정원의 글 ::::
다름이 아니라. 부하를 계산하고 Fan 선정까지 되는걸로 알고 있습니다.
부하는 ASHRAE의 계산법 적용한것으로 아는데 Fan 선정은 어떤 룰(규정)을 적용하였는지 궁금하군요..
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