York country club in 2009. A portable
Siemens Sitrans FUE1010 unit was used
to assess the problematic ground water
loops of this 180-vertical-well system,
which was the sole source of year-round
cooling and heating for the property’s
condominium and hotel facility.
In this system, an underground
loop exchanges heat between the
ground and the water, resulting in the
return water being warmer or colder
(depending on the season) than the supply water. This water is then fed to 450
water-sourced heat pumps. From its
inception, this system had never been
operating properly, and, as a result, the
country club received constant complaints from guests that the system
did not provide enough heating and/
or cooling. It was, however, not only
the guests who were affected by the
problems: The plant’s maintenance staff
experienced several pump shutdowns at
irregular intervals. Resetting the entire
system appeared to be the only way to
restore operation.
The Problem
Using the flow meter, a balancing
company soon identified two major
problems with the ground source heating system. Using the temperature sensor part of the flow meter, engineers
measured the temperature of the supply
and return water and discovered that
the delta T was less than 4 F. This suggested that there was not enough heat
exchange through the vertical ground
loop buried approximately 300 feet
underground. The water was too hot in
summer and too cold in winter.
Measuring the flow of the ground
supply and return water, the company
found that the flow was at 50 percent of
the geothermal heat pump manufacturer’s specifications. The lack of sufficient
delta T indicated that the water flow in
the underground pipes was laminar (or
streamline). Laminar flows can create
a thermally resistant, static ‘boundary
layer’ of fluid that is in contact with the
pipe surface. This layer acts as an insulator, inhibiting efficient heat transfer.
The flow rate was simply too low to
encourage heat exchange.
The Solution
To prevent the insulating fluid layer
from forming, the flow rate needed to
be increased. This would ensure the
creation of turbulent flow in the pipes,
allowing optimal heat transfer conditions. The solution entailed making
overall changes to the system, including
upgrading the secondary water pump
used for the underground piping to
provide extra thrust. The results were
astounding: Delta T was tripled during
heating as well as cooling conditions;
a significant drop in electricity used to
run the pumps was recorded; 35,000-
40,000 fewer gallons of fuel oil were
used for the supplemental heating system; and the country club guests were
more comfortable.
Corrections made to the system
saved the country club more than
$100,000 a year in utility bills – from
eliminating both the supplemental fuel
oil used during the heating season and
the electricity used to cool the rooms
during the air conditioning season.
Whether tapping geothermal heat or
other energy sources, district energy systems will find clamp-on ultrasonic flow
meters a useful tool for verifying the
performance of energy-generating equipment and optimizing energy load and
usage. The portability and non-intrusive
nature of this technology allow this to be
done without interrupting existing operations. Ultrasonic flow meters enable
systems to ‘clamp-on’ to their energy
and make decisions that can improve
efficiency and save money.
Martin Dingman is a product
manager for Siemens Industry,
Inc.’s U.S. Clamp-on Ultrasonic
Flow Meter line. He has more
than 19 years’ experience in the
flow instrumentation field, where
he has served in a variety of manufacturing,
engineering project management and sales
roles. Dingman has completed numerous
engineering-related flow measurement
courses and has conducted training sessions
on ultrasonic flow measurement. His expertise
includes flow applications in various industries
including HVAC, oil and gas, water and
wastewater, and power. He can be reached at
martin.dingman@siemens.com.
