Applications
Steam/nett heat (quantity)
Application areas
Calculation of the mass flow and the heat quantity it contains that can be gained from a heat
exchanger, provided that only the energy contained in the steam (up to the condensate) is used.
The heat energy contained in the condensate remains unused.
Measurements
Measurement of: operating volume, temperature and pressure in a steam circuit directly before
a heat exchanger.
Inputs
• Steam circuit: Super-heated steam: Flow (q), pressure (p), temperature (T
D
)
Saturated steam: Flow (q), pressure (p) or
Flow (q), temperature (T
D
)
• Condensation circuit: Temperature (T
W
)
Calculated values
• Calculation of: mass flow, heat differential (heat contents of steam minus heat contents of
the condensate at saturated steam temperature), density, sp. Enthalpy (IAPWS–IF97
Standard).
In the simplified case it is supposed that the condensate (water) has a saturated steam
temperature which is equal to the pressure in front of the heat exchanger.
• Only 2 inputs are required for saturated steam calculations (flow, pressure/temperature), the
missing input is calculated using the internally memorised saturated steam curves.
Note!
For higher accuracy or for control purposes, it is recommended to calculate the steam condition using 3 inputs
(super heated steam). This is recommended because in this operating mode the wet steam alarm function (see
outputs) can be used.
Output values /display at unit
• Heat flow, mass flow, flow (Operating volume), temperature 1, temperature 2, pressure,
density, specific Enthalpy.
• Heat quantity sum, mass sum, flow sum.
Outputs
• All output values can be transmitted using the output terminals, this means both unchanged
inputs as well as calculated values. Please note that the number of outputs available is
dependent on the unit type.
• If a relay is set up for the “wet steam alarm”, this will operate as soon as the super-heated
steam reaches 2% of the saturated steam curve. An alarm message also appears in the
display.
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