Dynasonics TFXP Series Transit Time Ultrasonic Flow Meter - Manual (Page 97)

Rev. 5/09 -A.1- TFXP
The TFX flow meter with the optional RTD (heat flow) Module
installed is designed to measure the rate and quantity of heat
delivered to a given building, area or heat exchanger. The
instrument measures the volumetric flow rate of the heat exchanger
liquid (water, water/glycol mixture, brine, etc.), the temperature at
the inlet pipe and the temperature at the outlet pipe. Heat delivery
is calculated by the following equation:
Rate of heat delivery = Q × (T
in
– T
out
) × c
Where
Q = volumetric flow rate
T
in
= temperature at the inlet
T
out
= temperature at the outlet
c = specific heat of the liquid
The RTD module installed in the TFX measures the differential
temperature of two 1,000 Ohm three-wire platinum RTDs. The
three-wire configuration allows the temperature sensors to be
located several hundred feet away from the TFX meter without
influencing system temperature measuring accuracy or stability.
The RTDs included with the TFX heat flow option have been factory
calibrated and are marked with an identification as to which input
number, 1 or 2, the RTD has been calibrated. The RTDs are 1,000
Ohm platinum and are designed to be mounted on the exterior
surface of the pipe. The RTDs are rated for a temperature range of
-40 to +200 °C in three steps:
0 to + 50 °C
0 to +100 °C
-40 to +200 °C
The RTD temperature range should be chosen referencing the
maximum temperature of the liquid to be measured. By using the
narrowest temperature range, the resolution of the temperature
measurement will be maximized.
General
HEAT FLOW ADDENDUM