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Energy Saving in Makeup Air Units Using Two-Fluid
Humidification and Two-Temperature Chilled Water Systems
Yun Chun Tung, National Taipei
University of Technology
The function of makeup air unit (MAU) systems is to provide the
conditioned fresh makeup air to cleanrooms. The makeup air aims
to offset the large quantities of process exhaust. It is also used
to provide the cleanroom pressurization to prevent the infiltration
of external contamination. The primary latent heat load source in
cleanrooms is the makeup air system: therefore, the other important
function of MAUs is to maintain the room relative humidity value
in a specific range. In winter, processes of humidification and
cooling in MAUs should be provided in Taiwan. Energy saving in MAUs
using two-fluid (air and water) humidification and two-temperature
chilled water systems were analyzed and studied. At the thin-film
transistor liquid-crystal displayer fabrication (TFT-LCD fab) plants,
two-fluid humidifiers installed in the return air duct reduce the
capacity of dry cooling coils and decrease the flow rate of steam
(0.0009 kg/kg dry air). Compared with single temperature chilled
water system, two-temperature chilled water supplied to cooling
coils in MAUs has energy saving of 10.78 percent and 6.6 percent
for piping layouts of parallel and series, respectively.
Labs21 Connection:
Precise levels of cleanroom temperature and humidity are required
and that cost a lot of energy in simultaneous cooling and heating
of air. Conventionally, air washers and steam humidifiers installed
in MAUs were respectively used in semiconductor and TFT-LCD fabs.
Two-fluid humidifiers installed in the return air duct benefit the
reduction of the capacity of chillers due to the room heat load
partially absorbed by the evaporation of water, and the flow rate
of steam. The effect of humidification for two-fluid humidifiers
is modulated by the amount of water and compressed air. In addition,
two-temperature chilled water systems used in MAUs benefit energy
savings. Series piping layout of two-temperature chilled water system
results from 6 degrees chilled water supplied into the second cooling
coil, heated to 12 degrees, and then flowing into the first cooling
coil directly. Chilled water of 6 degrees and 12 degrees flowing
into the second and the first cooling coils, respectively, results
in parallel piping layout of two-temperature chilled water system.
Biography:
Yun-Chun Tung (Master, National Taipei University of Technology,
Taiwan, ROC) is a member of American Society of Heating, Refrigerating,
and Air-conditioning Engineers and a certificated professional engineer
of refrigerating and air-conditioning engineering. He participated
in Sinotech, a noted engineering consultant company in Taiwan, as
a mechanical engineer in 1989, and has focused on the study of clean
room regarding topics of particle trajectory and AMC absorption
since 2000.
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