Endress+Hauser Proline Prowirl 73 - Page 145

Proline Prowirl 73 Description of device functions
Endress+Hauser 145
SELECT FLUID
(contd.)
Selected fluid: WATER
Applications:
For calculating the quantity of heat in a flow of water, e.g. for determining the residual
heat in the return line of a heat exchanger.
!
Note!
The process pressure (p) in the process pipe is required to calculate the process variables
and the measuring range limit values. The process pressure can be read in from an
external pressure measuring device (e.g. Cerabar-M, for details on wiring ä 27) via
the HART INPUT (ä 167), or can be entered as a fixed value in the OPERATING
PRESSURE function (ä 150).
Calculated variables:
The mass flow, heat flow, density and the specific enthalpy are calculated from the
measured volume flow, the measured temperature and the specified process pressure
using water data as per the international IAPWS-IF97 standard (ASME water data).
Formulae for calculation:
• Mass flow: m = q ·  (T, p)
• Quantity of heat: E = q ·  (T, p) · h (T)
• Corrected volume flow: q
ref
= q · ( (T, p) ÷ 
ref
)
m = Mass flow
E = Quantity of heat
q = Volume flow (measured)
q
ref
= Corrected volume flow
h = Specific enthalpy
T = Operating temperature (measured)
p = Process pressure (ä 150)
 = Density*

ref
= Reference density (ä 152)
* from water data as per IAPWS-IF97 (ASME), for the measured temperature and the
specified pressure.
Selected fluid: USER DEFINED LIQUID
Applications:
For calculating the mass flow of a user-defined liquid, e.g. a thermal oil.
Calculated variables:
The mass flow, the density of the corrected volume flow and the quantity of heat are
calculated from the measured volume flow and the measured temperature. Either the
specific heat capacity or the gross calorific value has to be entered to calculate the
quantity of heat.
Formulae for calculation:
• Mass flow: m = q ·  (T)
•Density:  = 
1
(T
1
) ÷ (1 + 
p
· [ T – T
1
])
• Corrected volume flow: q
ref
= q · ( (T) ÷ 
ref
)
• Quantity of heat: E= q ·  (T) · c
p
· T for delta heat
Quantity of heat: E= q ·  (T) · h at combustion
m = Mass flow
q = Volume flow (measured)
q
ref
= Corrected volume flow
T = Operating temperature (measured)
T
1
= Temperature at which the value for 
1
applies (ä 149)*
 = Density

ref
= Reference density (ä 152)

1
= Density at which the value for T
1
applies (ä 150)*

p
= Expansion coefficient of the liquid at T
1
(ä 150)*
* Possible combinations of these values ä 158
(Continued on next page)
Function description, FLOW COMPUTER group