[labnetwork] Flow Meters and/or Flow Computers for tracking distributed nitrogen usage?

[Lynn Rathbun]

John
At Cornell , we have just within the last year installed meters in 
about 5 zones.  The cleanroom is basically two zones, and one zone 
for each other floor and to one other major user.  And we have a 
total flow meter.  We will soon begin charging by the meters, with 
the use on each floor prorated out by floor to the users.  So a room 
on the third floor may pay more than a room on the 2nd floor, 
depending on use of neighbors.  Metering individual rooms is not practical.

there are some difficulties however.  Average flows are a ctually 
pretty steady, even instantaneous flows dont vary much. But the level 
of use in the zones is dramatically different so the meters have to 
be drastically different sizes.   Each meter only works well over  a 
limited range of flows, and the   errors and offsets are not 
small.....to the point where the  errors and offsets of the big 
flowmeters are larger than the flows of the little meters.    So the 
zone flows never add up to the total flow....Typically off by 
10%.   Not to bad except that that 10% respresents most of the flow 
to the rest of the building.    So , we get a ballpark reading of the 
percentages to each zone, I would not call it an accurate 
measurement.   And 10% of 200K/yr is real money.

Good luck






**************************************************************
Dr. Lynn Rathbun                                        Rathbun at cnf.cornell.edu
NNIN  Program Manager                   (607)-254-4872
CNF Laboratory Manager
Duffield Hall                                                (607)-255-8601 Fax
Cornell 
University                                       (607)-592-1549 Work Cell
Ithaca, New York 14853                     (607)-342-1880 Personal Cell




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