towerPlant

towerplant user inputs

Name Type Variability Description/Comments
ctN SI_GZ Start of phase Number of towers. Niles' ctNo. default 1.
tpStg choice:TPSTG Start of phase
  • staging choice, default TOGETHER. Niles' stgOp.
  • TOGETHER Towers are identical and all towers will operate at once
  • at the same load (fan speed or cycling fan duty cycle).
  • LEAD A "lead tower" will modulate, and as many additional one-speed
  • tower fans as necessary to meet the load will run at full power.
  • The water will continue to flow through the towers whose fans are off.
tpTsSp TEMP_GZ Start of hour Towers delivered water setpoint temperature (Niles' twoSp). degrees F, hourly, default 85F.
tpMtr TI input time
  • subscript of [METER][meter] object to which tower fan energy input will be posted,
  • category "Aux" (Per Bruce, 8-92). Cooling towers as modelled have no pumps
  • and use no energy except to drive their fans. default none.
  • If towStg is LEAD, the following two apply only to the lead tower; any additional towers are assumed to have ONESPEED fans.
ctTy choice:CTTY Start of phase Cooling tower fan control type choice: ONESPEED (default), TWOSPEED, or VARIABLE.
ctLoSpd FRAC_GZ Start of phase
  • Low speed for a TWOSPEED fan, as a fraction of full cfm. default 0.5.
  • The rest of the [TOWERPLANT][towerplant] input variables apply to each tower in the group;
  • the towers are assumed identical except for the single-speed fan on non-lead towers.
  • The following two inputs permit computation of the tower fan electrical energy
  • consumption (we only need bhp/eff, but Bruce/Steve say use two inputs):
ctShaftPwr BHP_GZ Start of phase
  • Shaft power of one tower fan motor. RQD. User name 'shaftBhp'.
  • Btuh internally, brake horsepower entered, units stuff converts.
ctMotEff FRAC_GZ Start of phase
  • Motor (and drive, if any) efficiency, default 0.88
  • [TOWERPLANT][towerplant] fan curve coefficients. Constant-speed (cycling) fan consumption is linear fcn of
  • avg speed (===frac of time on for one-speed); constant represents start-stop overhead.
ctFcOne ONESPEED tower fan curve coefficients, also for nonLead towers if ctStg = LEAD. default 0, 1
PYLINEAR
Name Type Variability Description/Comments
ctFcOne.k[index] number Array [3] Start of run FLOAT k[3]. One extra member needed as terminator by cul.cpp array input logic.
ctFcLo TWOSPEED low speed fan curve coeffs, default 0, ctLoSpd^2
PYLINEAR
Name Type Variability Description/Comments
ctFcLo.k[index] number Array [3] Start of run FLOAT k[3]. One extra member needed as terminator by cul.cpp array input logic.
ctFcHi TWOSPEED high speed fan curve coeffs, default -ctLoSpd*(ctLoSpd+1), ctLoSpd^2+ctLoSpd+1
PYLINEAR
Name Type Variability Description/Comments
ctFcHi.k[index] number Array [3] Start of run FLOAT k[3]. One extra member needed as terminator by cul.cpp array input logic.
ctFcVar
  • VARIABLE speed fan cubic curve coefficients, default 0,0,0,1
  • The next 6 [TOWERPLANT][towerplant] members specify one-tower performance under a one set of conditions (the "design conditions").
  • The conditions should be chosen to be representative of full load operating conditions.
  • verify next 3 per tower?? <--- issues2.txt memo sent to Bruce 10-92. *****
PYCUBIC
Name Type Variability Description/Comments
ctFcVar.k[index] number Array [5] Start of run
  • FLOAT k[5]. One extra member needed as terminator by cul.cpp array input logic, 5-92.
  • possible future setup optimizations: 1) select ptr to fcn that does not compute terms whose k is 0;
  • 2) precalculate constants to compute in form ((x*k[3] + k[2])*x + k[1])*x + k[0]
ctCapDs POWER_NZ Start of run
  • Design capacity, Btuh. (replaces Niles' design water inlet temperature.)
  • Default is sum of connected loads / [ctN][ctn], using largest stage in each coolPlant,
  • design Btu capacity of each HPLOOP heat exchanger. Made negative if entered positive.
ctVfDs AFLOW_GZ Start of phase Design air flow volume rate through tower / full speed fan flow??, cfm, RQD.
ctGpmDs H2OFLOW_GZ Start of run Design water flow rate, gpm. default: sum of connected heat rejection pump capacities / ctN.
ctTDbODs TEMP_GZ Start of phase Design outdoor drybulb temperature, F, RQD. (only needed to convert ctVfDs from cfm to lb/hr).
ctTWbODs TEMP_GZ Start of phase Design outdoor wetbulb temperature, F, RQD.
ctTwoDs TEMP_GZ Start of phase
  • Design leaving water temperature, F, default 85.
  • The following 6 [TOWERPLANT][towerplant] members give another one-tower performance point, the "Off-design" point.
  • Either give either all that don't have defaults, (and not [ctK][ctk]), or none ([ctK][ctk] may then be given).
  • verify next 3 per tower?? <--- issues2.txt memo sent to Bruce 10-92. ******
ctCapOd POWER_NZ Start of run
  • Off-design capacity, Btuh. (replaces Niles' design water inlet temperature.)
  • Default is sum of connected loads / [ctN][ctn], using largest stage in each coolPlant,
  • design Btu capacity of each HPLOOP heat exchanger. Made negative if entered positive.
ctVfOd AFLOW_GZ Start of phase Off-design air flow volume rate through one tower, cfm, must != ctVfDs.
ctGpmOd H2OFLOW_GZ Start of run
  • Off-design water flow rate, gpm. default: sum of connected heat rejection pump capacities/ [ctN][ctn].
  • must differ from [ctGpmDs][ctgpmds] (can't default both).
ctTDbOOd TEMP_GZ Start of phase Off-design outdoor drybulb temperature, F. (only needed to convert ctVfOd from cfm to lb/hr).
ctTWbOOd TEMP_GZ Start of phase Off-design outdoor wetbulb temperature, F.
ctTwoOd TEMP_GZ Start of phase
  • Off-design leaving water temperature, F, default 85.
  • [TOWERPLANT][towerplant] inputs...
ctK FRAC_GZ Start of run
  • exponent in formula ntuA = const * (mw/ma)^[ctK][ctk], as alternative to "off design" inputs.
  • default: derived from "Od" inputs if given, else .4.
ctStkFlFr number Start of phase
  • stack effect flow: air flow that occurs thru tower when fan is off, as a fraction of [ctVfDs][ctvfds].
  • Additional flow, when fan runs, is proportional to fan speed. default .18.
  • [TOWERPLANT][towerplant] inputs re makeup water
ctBldn number Start of phase Blowdown rate: frac inflowing water bled down drain, to reduce impurities buildup. default .01.
ctDrft number Start of phase Drift rate: frac inflowing water blown out of tower as droplets, w/o evaporating. default 0.
ctTWm TEMP_GZ Start of phase
  • Temperature of water in mains, for makeup water. default 60.
  • Auxiliaries desired? assume not 10-92.

TOWERPLANT setup time members

Name Type Variability Description/Comments
cp1 TI Start of run subscript of 1st COOLPLANT served by this TOWERPLANT. Next is COOLPLANT.nxCp4tp.
hl1 TI Start of run subscript of 1st HPLOOP with hx served by this TOWERPLANT. Next is HPLOOP.nxHl4tp.
oneFanP DBL Start of run
  • POWER
  • full-speed motor input power for one fan (Btuh): ctShaftPwr / [ctMotEff][ctmoteff].
maDs DBL Start of run
  • MFLOW
  • design air flow into 1 tower, [ctVfDs][ctvfds] converted from cfm to lb/hr
maOd DBL Start of run
  • MFLOW
  • off-design air flow into 1 tower, [ctVfOd][ctvfod] converted from cfm to lb/hr
mwDs DBL Start of run
  • H2OFLOW
  • design water flow into 1 tower, [ctGpmDs][ctgpmds] converted from gpm to lb/hr
mwOd DBL Start of run
  • H2OFLOW
  • off-design water flow into 1 tower, [ctGpmOd][ctgpmod] converted from gpm to lb/hr
maOverMwDs DBL Start of run maDs/mwDs, precomputed in setup.
ntuADs DBL Start of run number of transfer units for air side at design conditions (Niles ntuAd)
ntuAOd DBL Start of run .. at off-design conditions, if given. member only as debug aid.

TOWERPLANT runtime output member

Name Type Variability Description/Comments
tpTs DBL End of subhour
  • TEMP
  • temperature of leaving water, F. For use by chillers and hploop hx's. Niles twoDel.
  • set by tpEstimate and tpCompute. tp- to protect against confusion with AH::ts.

TOWERPLANT runtime mostly-internal members

Name Type Variability Description/Comments
tpClf BOO End of subhour call-flag: set nz if must call tpCompute so it can test tr, etc to see if computation needed.
tpPtf BOO End of subhour
  • compute-flag: set if must call tpCompute and it should unconditionally recompute.
  • tpCompute next inputs, calculated at entry to tpCompute before commitment to new calculation
trNx DBL End of subhour
  • TEMP
  • return water temp, F
mwAllNx DBL End of subhour
  • MFLOW
  • return water flow===total water flow entering towers, sum of loads, lb/hr.
qLoadNx DBL End of subhour
  • POWER
  • heat added to water by loads. Positive. Believe need in record only for debugging/reporting.
  • tpCompute current inputs, as used for current tpTs. -Nx's copied to next 3 after decision to calculate anew.
tr DBL End of subhour
  • TEMP
  • return water temp
mwAll DBL End of subhour
  • MFLOW
  • return water flow (sum of loads)===total water flow into all towers, lb/hr.
qLoad DBL End of subhour
  • POWER
  • heat added to water by loads. Positive. Believe need in record only for debugging/reporting.
  • tpCompute internal
mwi1 DBL End of subhour
  • MFLOW
  • flow into 1 tower (less flows out due to evaporation & drift): mwAll / [ctN][ctn].
qNeed DBL End of subhour
  • POWER
  • power needed from tower plant to deliver water at setpoint: ([tpTsSp][tptssp] - tr) * mwAll. negative.
qMax1 DBL End of subhour
  • POWER
  • max power of 1 tower under current conditions
qMin1 DBL End of subhour
  • POWER
  • power of 1 tower, fan off (stack effect only) under current conditions
towldCase TOWLOADCASE End of subhour
  • tower load case, tpCompute to endSubhr: facilitates deferring fan power calc
  • tldMIN: fans off; tpTs <= setpoint
  • tldSP: tpTs is at setpoint, must determine power
  • tldMAX: full power, tpTs >= setpoint
qMaxGuess number End of subhour for internal values for towModel initial guess at next call for various towModel calls.
qMinGuess number End of subhour ..
qLoGuess number End of subhour ..
qVarGuess number End of subhour .., used via varSpeedF
qVarTem DBL End of subhour
  • POWER
  • varSpeedF temporary that should be saved between calls (last q, used re initial f)
puteTs DBL End of subhour
  • TEMP
  • tpTs from tpCompute, not set by tpEstimate. debug aid.

TOWERPLANT runtime internal, set at end subhr. Variables believed local, here for probes/results/debugging

Name Type Variability Description/Comments
nCtOp number End of subhour number of tower fans operating
f DBL End of subhour fraction of full speed (fraction on for one speed fan), for lead tower only if LEAD.
fanP number End of subhour plant's fan input pwr this subhour (Btuh!)
q number End of subhour power imparted to water, for change detection/probes/reports 10-19-92

TOWERPLANT runtime prior values for change detection

Name Type Variability Description/Comments
tpTsSpPr TEMP End of subhour for tpEstimate
tpTsEstPr TEMP End of subhour for tpEstimate
tpTsPr TEMP End of subhour leaving water temp at last tpCompute, F (unused?)
tDbOShPr TEMP End of subhour outdoor drybulb temp at last tpCompute, F
wOShPr HUMRAT End of subhour outdoor humidity ratio at last tpCompute, F