Application Principle
This principle drawing introduces a space air conditioning system
with some main HVAC (Heating Ventilation and Air Conditioning)
applications where variable speed AC drives can be used. This
simplified diagram is for space cooling but the cooling can be
replaced by space heating instead. The variable speed AC
drives are not always used in all these applications but in the
modern buildings at least some of these applications are usually
controlled by AC drives. |
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Air conditioning system with variable speed
drives |
The purpose of the air conditioning system is to maintain the air
quality for working and living in the room or space. These
"Comfort Zone" requirements are:
- Temperature 22-26 oC
- Relative humidity 30-70%
- Air change 35 m3/hour/person
- Air speed 0.15 - 0.25 m/s
- CO2 content less than 0.1%
Detailed Description
This system for space cooling of the room (9.) has both exhausts fan
(1.) and supply fan (2.). The air volume is controlled with AC
drives (8.) according to the temperature and pressure requirements to
keep the comfort in the room. The supply air is flowing through a
heat exchanger (10.), which is cooled with water circulated by the
chilled water pump (3.). The chilled water flow is controlled by an AC
drive. The chilled water is cooled in the head exchanger (7.) and
the primary side of hte heat exchanger is the evaporator of the chiller
compressor (4.). Chiller compressor capacity is controlled by an AC
drives and the water circulated by the cooling tower pump (5.) cools its
condenser. The pump flow is controlled by an ABB AC drive. Cooling
tower fan (6.) makes the cooling water cooling and the fan capacity is
controlled by an ABB AC drive.
Performance in Creating Comfort Zone
The use of variable speed AC drives improves the controllability
of the whole heating, cooling and air conditioning system, enabling
good possibilities to maintain the Comfort Zone. THe use of
variable speed drives usually increases the first-cost of investment
but through savings in electrical energy in motors along the
investment in VSD has pay-back time between 0.2 - 3 years. In
addition to savings in electrical energy, there are several
important customer benefits speaking for VSD:
- Fast control to maintain the comfort zone conditions
- Accurate control to keep the desired air quality
- Reduced consumption of heating and cooling energy
- Reduced consumption of electrical energy
- Simple to keep the noise level down
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Air conditioning is an important system in
high rise office buildings (Guangzhou, China) |
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