Total cooling energy costs in a customer’s facility are a combination of
chilled-water rates from the utility and
the electricity consumed by operating
pumps and fans in the buildings. Figure
4 shows the performance improvement
that can be achieved when decoupled
building is converted to a direct-connect
building with pressure-independent modulating control valves at the cooling coils.
Conclusions
Return-water temperature control is
one example of a design strategy that
increases Delta T across the building to
reduce chilled-water flow at the plant
and in the main distribution. Unfortunately,
the benefit to the central plant and distribution can compromise building performance. With the growing use of high-quality pressure-independent modulating control valves, there is no longer a
need to decouple buildings just to
address low Delta T issues at coils.
Despite unavoidable system pressure
fluctuations or the evolution in the
hydraulic profile over time, these valves
help generate the maximum possible
Delta T to minimize flow requirements
at any load.
If the district cooling industry hopes
to further develop the advantages it
offers over self-generated building cooling systems, it is vital that operators
choose components that maximize
chilled-water Delta T performance at
cooling coils. Incentive chilled-water
rates help foster investments in equipment to optimize performance. High
Delta T in the distribution and at the
central plant improves diversity and
increases available system capacity, permitting the cooling of more customers
with less equipment and less energy.
This should translate into more cost-effective service.
With directly connected buildings
and pressure-independent modulating
control valves, customers can expect less
fan energy consumption, less building
equipment, simpler system operation,
reduced capital and operating expenses,
and better humidity control.
Eric M. Moe, director of business development for Flow Control
Industries Inc., is an engineer with
more than 16 years’ experience in
mechanical systems design and
integration in multiple industries,
including aerospace, energy and HVAC. His
technical expertise lies in energy analysis, fluid
flow and heat transfer. Moe is an active member of both IDEA and the Association of Energy
Engineers. He has a bachelor of science degree
in mechanical engineering and master’s degrees
in both business and engineering from the
University of Washington. He can be reached
by email at ericm@flowcontrol.com.
