9 points every architect, engineer,
contractor and their clients should know about circulator theory
and selection - sample slides.
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integrated design program has
over 2100 slides illustrating architectural, interior design
and HVAC engineering principles which contribute to
indoor environmental quality and
energy allocation for
conditioning the occupants and building.
The following course materials on circulator
theory and selection are samples from the lecture and based on a Steven Covey principle of "Begin
with the End in Mind". They are a very small but important sample of the Covey
principle and are provided here to give you an idea of what
kind of materials we'll be discussing during the program.
The course is also registered with AIA and participants can
earn up to 21 Learning Units.
For more sample slides visit our list of training modules.
Energy converters...that's what circulators are - they
convert electrical energy to kinetic energy which
develops the required differential pressure known as
"head pressure" to rotate the fluid molecules around the
system. Often called a "pump" they do not actually
"pump" as in a well pump...nope - they circulate that's
why they are called...circulators - go figure.
Circulators can be one of the least inefficient
components of a system and the inefficiencies are
exasperated when the circulators are incorrectly
selected - which is often a result of poor to no
engineering in establishing flows and head losses.
Inefficiencies show up as noise, heat and vibrations. On
a good day...a small wet rotor circulator might achieve
20% efficiency which means 80% of the input electrical
energy did not go to circulating molecules. There are
"smart" circulators available but even these have to be
selected properly for optimum performance. Message - you
don't pick circulators based on connection size nor your
favourite color...you have to analyze the system
hydraulics and select a circulator so that it achieves
maximum efficiency through the year.
Figure 3: Unlike in years gone by, the
circulator technology of today offers several options in
selecting the right product for the application. There
are pro's and con's to each type and we'll discuss these
Figure 4: Since fluid based system are
always in a transient state, i.e. they are dynamic in
that the loads change as the weather changes - it's
important to control the circulator so overflow and
under flow is not created as valves open and close.
There are several control methods available for
addressing the changing flows in a system as shown
Figure 5: As with all elements of design,
there are laws which describe the relationships between
energy and performance. Circulators, pumps and fans all
follow the affinity laws - we'll demonstrate these
during the lecturer.
Figure 6: Since circulators consume
electrical energy based on head and flow, it's important
to correctly prepare the hydraulic analysis so energy
consumption is minimized. Using the affinity laws,
simply by doubling the delta T (∆T)
in the flow calculation the design flow will be reduced
by 50%, the system pressure reduced to 25% and the power
input to 12.5%...it's easy to say - but cutting the flow
in half has its own issues - we show you when and where
you can apply such principles to ensure your clients are
not over paying for circulator power.
Figure 7: One very useful way to analyze
energy effectiveness in HVAC systems is to compare the
electrical energy to the thermal energy. What does
this mean? It means you should always look at the ratio
of heat being moved by electricity. We frequently find
inexperienced designers using far too much electrical
energy when designing system in comparison to those
system designed by experienced engineers. This is not a
trivial matter as the client becomes energy penalized
for the life of the system when optimization is not
done...we will give several examples of what to do and
not to do to improve this ratio.
Figure 8: From the hour long lecturer
we'll conclude with several message as shown above and
in Figure 9 below.
Figure 9: Circulators are an
essential component and they have several relationships
though the system but like all items they can be easily
misapplied and this contributes to inefficiencies and
instabilities in the system...something no client wants
to hear about.
So there you have it, a few sample slides
from our circulator theory lecturer...just a hors d'oeu·vre
from our library of over 2100 slides addressing a small
but important element of integrated design and radiant
based HVAC systems. In the
program we will get into this and a whole lot
more? How much more? Well just follow the links to the
other parts of our website and you’ll get a feel for the
scope of materials that we’ll be covering.
See you soon.
Registered Engineering Technologist - Building
construction (ASET #8167)
Professional Licensee (Engineering) - HVAC (APEGA
Building Sciences / Industry Development
ASHRAE Committees: T.C.61. (CM), T.C.6.5 (VM), T.C. 7.04
(VM), SSPC 55 (VM)
ASHRAE SSPC 55 - User Manual Task Leader
Note: The author
participates on several ASHRAE and other industry
related committees but be advised the materials and
comments presented do not necessarily represent the
views of these societies, only the president of the
society or nominated representative may speak on behalf
of the organization.