Eurotherm 6100, Руководство пользователя

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100/180MM DISTRIBUTED GRAPHIC RECORDER: USER GUIDE
HA029324
Issue 11 Oct 14 Page 113
4.3.11 FUNCTION (Cont.)
SATURATED STEAM HEAT CONSUMED
Note: The following assumptions are made with regard to this implementation:
1. The condensate return is 100% wet saturated water. No fl ash steam component is included.
2. The same mass leaves the system as enters it.
Note: The overall accuracy of a fl ow measurement installation depends on a number of factors
outside the control of the recorder manufacturer. For this reason, the recorder manufacturer takes
no responsibility for the accuracy of the results obtained using the mass fl ow equations imple-
mented in the maths pack.
The equations solved is:
Inlet pressure
or temperature
Inlet
flow
Steam supply
Condensate
Steam
Trap
Heat
exchanger
Process 2
Steam
Trap
Heat
exchanger
Process 1
Condensate
temperature
Figure 4.3.11k Measurement transducer - typical locations
Notes:
1 The units of kg/sec and m
3
/sec are used above for simplicity. In fact any time unit can be used.
For example if the measured fl ow is in m
3
/hour, then the Mass fl ow will be in kg/hour.
2. ASME Steam tables 1999, from IAPWF IF97.
where, QE
t
= Heat energy consumed (in kJ/sec), at time ‘t’ (Note 1)
Flow
t
= Measured fl ow in m 3 /sec (Note 1)
V
LT1
= Volume of liquid per kg of steam (m 3 /kg) at temperature T1 ˚C
ΔV
T1
= V
VT1
- V
LT1
, where V
VT1
is the volume of vapour per kg of steam at temperature T1 ˚C
d = Dryness factor between 0 (no vapour) and 100 (no liquid)
h
LT1
= Enthalpy of the liquid in kJ/kg at temperature T1 ˚C
Δh
T1
= h
VT1
- h
LT1
, where h
VT1
is the enthalpy of vapour in kJ/kg vapour at temperature T1 ˚C
h
LT2
= Enthalpy of the condensate liquid in kJ/kg at temperature T2 ˚C
V
LT1
and ΔV
T1
; h
LT1
, Δh
LT2
and Δh
T1
are available from published tables (note 2), but the recorder user needs
only to enter ‘values’ for measured fl ow, either the temperature or the pressure of the steam and the tem-
perature of the condensate. These ‘values’ can be constants, input channels or maths channels. Figure
4.3.11l and accompanying parameter descriptions give full details.
Figure 4.3.11k is a simplifi ed sketch of a typical installation, showing where fl ow rate, pressure and tem-
perature readings are taken.
QE
t

Flow
t
V
LT1
 
V
T1
d
100
 








h
LT1
 
h
T1
d
100
 

h
LT 2
 