30
HEAT MEASUREMENT
The integrated heat measurement function enables you
to determine the heat and cooling flow in your application
using QMF-PT100 or QMP-PT100 temperature sensors.
Introduction
The temperature sensor no.1 is installed in the warmer
section, while temperature sensor no. 2 is installed in
the cooler section of the circuit (The QMF-PT100 are
numbered on the cable). You can position the ultrasonic
transducers at the warmer or cooler section. GPI recom-
mends installing the transducers in the cooler section,
as it is unlikely that they will be operated beyond their
permissible temperature limit in these sections.
QStar UFM displays the thermal output and the accu-
mulated heat quantity.
FIGURE 56:
Block Diagram of Heat Measurement
Feed temperature
Thermal Input /
Heat Quantity
Consumed
Thermal Output /
Heat quantity
Return
temperature
Ultrasonic
Transducers
Thermal Output
/ Heat quantity
Volume Flow /
Quantity
Q Flow Rate
Temperature
Sensor T2
Temperature
Sensor T1
QStar UFM shows heat (kWh) and thermal output (kW)
Calculating Thermal Output
The cross-sectional area of the pipe’s inner diameter [A]
is multiplied by the flow velocity [v] and specific thermal
capacity of the medium [c], as well as the differential
temperature of both sensors, [T_hot- T_cold]. The product
defines thermal output [Q] in W units.
Calculating heat (quantity)
The heat quantity is derived as a function of thermal
output over time.
INSTALLING THE TEMPERATURE
SENSOR
Temperature sensors can be mounted on piping using
a metal belt (photo) or fabric-reinforced tape. Install the
temperture sensor on the pipe as follows.
FIGURE 57:
Mounted Temperature Sensor
i
The measuring method used is a relative
measurement. This means that the measured
temperature values with absolute reference may
deviate from this measuring equipment (for ex
-
ample, compared to submersion thermometers).
It is important to set up a relation between both
sensors. The ideal differential temperature be-
tween the temperature sensors should amount
to zero degrees prior to installation on the piping.
Zero Setup of Temperature Sensors
From main menu “Flow 1”: Press button SETUP ->
COMPL SETUP ->
à
CALIBRATION SETUP -> Select
“QMF-PT100 T2-T1”
i
The differential temperature between both
temperature sensors should amount to approxi-
mately zero degrees prior to installation of the
transducers on the piping. Avoid touching the
transducers in the preliminary phases. To equal
both temperature sensors put them in a glass
of water for a couple of minutes. To check the
temperature of both sensors, use the values
displayed in the “Heat quantity” measuring win
-
dow that is described in the following section.