Hi there-
Curious if anyone out there knows anything about the chiller EIR-fPLR
curve that is inserted by default in eQuest, when a user selects a
variable frequency drive compressor? Most of the time, the EIR-fPLR
curve is a quadratic curve based only on the PLR, but this curve is
biquadratic, with another term called dt. Can anyone enlighten me on
which dt they are talking about here? I can't find it in the
documentation.
Sincerely,
Chien Si Harriman
http://doe2.com/download/DOE-22/DOE22Vol6-NewFeatures_44e2.pdf, printed
page 74 (PDF page 79).
It's the differential between the entering condenser water temperature and
the leaving chilled water temperature.
Savings for chillers with VFDs are dependent on the pressure rise the
impellor must overcome. Maximum savings accrue if the dT is low when the
load is low. If the cooling tower is running warm when the load is low,
then the impellor may have to run at close to full speed to produce the
required pressure rise and avoid surge. The dT term takes that effect into
account.