Retrotec USACE - Manual (Page 372)

I4 ENERGY & PROCESS ASSESSMENT PROTOCOL
Fan load, kW = L/s × e.
∆
P (Pa)/630,000
Fan load, hp = CFM ×
∆
P (in. w.g.)/4,000
Duct pressure drop f.
∆
P (Pa) per meter = 1.23 Pa/m.
Duct pressure drop
∆
P (in. w.g.) per 100 ft = 0.15 in. w.g.
Fan laws: L/s (CFM), SP (static pressure), kW (hp) (power). g.
(1) L/s
2
/ L/s
1
= RPM
2
/RPM
1
(2) SP
2
/ SP
1
= (RPM
2
/RPM
1
) 2
(3) kW
2
/kW
1
= (RPM
2
/RPM
1
) 3
3.3 Increase CHW temp: For each 1
°
F (0.55
°
C) increase in CHW supply
setpoint, the chiller compression motor load will decrease 1.5%. This is
a zero-cost ECO.
3.4 Decrease condenser CTW temperature: For each 0.56 °C (1
°
F) decrease
in CTW (cooling tower water) to the chiller condenser, the chiller com-
pressor load will decrease 1%. Zero-cost ECO.
3.5 CTW to centrifugal chiller: Centrifugal SMC chillers use 1 GPM (0.063
L/s) of condenser CTW per ton (3.5 kW) with a 10 °F (5.6 °C)
∆
T.
3.6 CTW to single-stage absorber: Single-stage absorption refrigeration
machines use 4.5 GPM (0.28 L/s) of CTW per ton (3.5 kW) with an 18
°F (10 °C)
∆
T. This is more than twice the cooling load of a centrifugal
unit.
3.7 Steam to single-stage absorber: A single-stage absorption chiller con-
sumes 17 lb/hr (0.002 kg/s) of 15 psig (103.4 kPa) steam per ton (3.5 kW)
CHW produced.
3.8 Steam to two-stage absorber: Two-stage absorption chillers consumes 10
lb/hr (0.0013 kg/s) of 125 psig (861.8 kPa) steam per ton (3.5 kW) CHW
produced.
I.4 Compressed Air Systems
4.1 Organize for success: Form a small, part-time compressed air (CA)
team responsible for implementing CA ECOs.
4.2 CA audit: Initiate a formal audit of CA generation, distribution, and
use.
4.3 Unit cost of CA: Incremental, electricity only, unit cost of CA is $0.18/
KCF ($.00636/m 3 ) at $0.05/kWh, 24 BHP, 100 SCFM (or 91 W,
47L/s), and 20% for auxiliary.
4.4 Total unit cost of CA: Total, variable, and fi xed unit cost of CA is $0.33/
KCF ($0.0117/m 3 ): $0.18 electricity, $0.038 debt service, $0.025 operating
and maintenance. Labor = $0.025 in materials and supplies and $0.012
in taxes, insurance, and miscellany. CBoS for CA is $0.18/kWh.