Chiller Efficiency Penalty from Approach Temperature

Rule-of-thumb estimate of chiller efficiency loss as condenser approach temperature rises due to fouling on heat-transfer surfaces (system dependent).

$$\Delta E\approx k\cdot \Delta T_{approach}$$

Variables

Symbol	Meaning	Unit
$\Delta E$	chiller efficiency loss	%
k	efficiency loss coefficient (about 1.5% per F of approach rise)	%/F
$\Delta T_{approach}$	rise in condenser approach temperature	F

Worked example

A 3 F rise in condenser approach temperature costs roughly 4.5% in chiller efficiency (3 F times about 1.5% per F).

---

Part of The Blueprint of Water