Variable-speed
drives are used in a huge number of electric motor-driven industrial and
commercial applications around the world. By accurately controlling electric
motor speed, drives enable users to tightly regulate energy consumption in
processes such as pumps, mixers, grinders and conveyors to name just a few. In
addition, they’re an invaluable device in HVAC cooling towers. Read on as we
explain.
What is a cooling
tower?
A cooling tower is a heat rejection device that extracts
waste heat to the atmosphere, normally by using air to reduce the temperature
of circulating cooling water. When air and heated water come into contact, some
of the water evaporates which lowers the water temperature. The cooled water is
then pumped back into circulation where it absorbs more heat, and the process
is repeated.
Where are cooling
towers used?
Cooling towers are used in many heavy industrial
applications including petrochemical plants, oil refineries and thermal power
stations. They are also used as part of heating, ventilation and air-conditioning
(HVAC) systems in office buildings, shopping centres and hospitals.
How do HVAC cooling
towers work?
HVAC
systems pump refrigerant round an evaporator coil, where it absorbs warm
air. The now warm refrigerant returns to a condenser where heat is expelled via
a fan through an outdoor cooling tower. The refrigerant is now cool again and
the cycle is repeated.
Why are
variable-speed drives so useful in HVAC cooling towers?
Although electric
motors can only run at their rated speed, the HVAC systems they drive rarely
need to operate at 100 per cent capacity. This means that most of the time,
HVAC equipment is wasting energy as the electric motor runs constantly.
Traditionally, additional measures are used to control airflow such as cycling
fans on and off or varying the pitch of fan blades. However, this is extremely
inefficient and places strain on components.
Variable-speed drives enable users to control electric motor
speed according to changing conditions, making them ideal for HVAC
applications. For example, VSDs allow fan speed to be precisely adjusted, with
just a 20 per cent reduction in speed cutting energy consumption by 50 per cent
in many cases.
A VSD can also sense
unwanted fan rotation, such as reverse movement due to windmilling. The drive
will recognise that this is happening and slow the fan to a stop before
rotating it again in the correct direction.
VSDs can be installed in new cooling towers as well as being
retrofitted to existing applications, and along with saving users energy, they
reduce wear and tear on the motor and HVAC system components.
Gibbons Engineering Group are the preferred supplier,
installer and maintenance specialist for HVAC
drives due to our considerable expertise in both fields. Not only do we
have a dedicated HVAC Services division, with vast experience operating in the
commercial and industrial sectors, we’re also an ABB Authorized Value Provider
for variable-speed drives.
This exclusive position gives us access to a global network
of products and expertise for ABB drives,
allowing us to deliver state-of-the-art equipment within the shortest possible time,
with a wealth of support available.
To find out more about the benefits of variable-speed drives
for HVAC cooling towers, call Andrew Knight on 07850 204915 or email andrew.knight@gibbonsgroup.co.uk
0 comments:
Post a Comment