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Description:
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Empirical models of airflow output and power consumption were developed for
series and parallel fan powered variable air volume terminal units at typical design
pressure conditions . A testing procedure and experimental setup were developed to test
sets of terminal units from three different manufacturers . Each set consisted of two
series and two parallel units , each with 8 in . (203 mm ) and 12 in . (304 mm ) primary air
inlets , for a total of four units in each set . Generalized models were developed for the
series and parallel units , with coefficients varying by size and manufacturer . Statistical
modeling utilized SAS software (2002 ) .
Fan power and airflow data were collected at downstream static pressures over a
range from 0 .1 to 0 .5 in . w .g . (25 to 125 Pa ) for the parallel terminal units . Downstream
static pressure was held constant at 0 .25 in . w .g . (62 Pa ) for the series units . Upstream
static pressures of all variable air volume (VAV ) terminal units ranged from 0 .1 to 2 .0
in . w .g . (25 to 498 Pa ) . Data were collected at four different primary air damper
positions . Data were also collected at four different terminal unit fan speeds , controlled
by a silicon controlled rectifier (SCR ) . The models utilized the RMS voltage entering
the terminal unit fan , the 'rake' sensor velocity pressure , and the downstream static
pressure . In addition to the terminal unit airflow and power models , a model was
developed to quantify air leakage in parallel terminal units , when the unit fan was off .
In all but two of the VAV terminal units , the resulting models of airflow and
power had R2 values greater than 0 .90 . In the two exceptions , there appeared to be
manufacturing defects : either excessive air leakage or a faulty SCR that limited the
effectiveness of the airflow and power models to capture the variation in the data . |