Fouling Energy Penalty Rule

Field rule estimating extra chiller energy from fouling: each 1 degree F rise in condenser approach raises chiller energy consumption by about 1.5 to 2 percent. Translates fouling into operating cost.

$$\Delta P_{\%}\approx (1.5\text{to}2)\%\times \Delta T_{\text{approach}}$$

Variables

Symbol	Meaning	Unit
\Delta P_%	Percent increase in chiller energy consumption	percent
$\Delta T_{a}pproach$	Rise in condenser approach temperature	degrees F

Worked example

A 1,000-ton chiller at 0.60 kW/ton draws 600 kW. Baseline at 4,000 hr/yr and $0.10/kWh=$240,000/yr. A 5 degree F approach rise at 2 percent per degree adds 600 x (5 x 0.02) = 60 kW, so 660 kW gives $264,000/yr,about$24,000 more per year.

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Part of The Blueprint of Water