Heat Exchanger Fouling Factor Explained

A fouling factor (or fouling resistance) is an extra thermal resistance added to a heat exchanger design to account for deposits — scale, biofilm, dirt or corrosion products — that build up on the heat transfer surface over time. It is expressed in m²·K/W and reflects how much the surface will degrade between cleanings.

Without a fouling allowance, a heat exchanger would meet duty only when perfectly clean and would fall short as soon as deposits form. The fouling factor adds extra surface area so the unit still meets its duty when partially fouled, giving a realistic service interval between cleanings.

Clean closed-loop water might use a small fouling factor, while river water, cooling-tower water or process fluids with suspended solids need larger allowances. Published tables (TEMA and others) give typical values by fluid, but plant experience is the best guide where it exists.

Too large a fouling factor produces an over-sized, low-velocity unit that actually fouls faster because deposits settle in slow flow. The goal is a margin matched to the service — enough to keep duty between cleanings, not so much that it harms performance.

Shanghai Jiangxing's engineers select an appropriate fouling factor for your fluid and cleaning schedule as part of every thermal design. Send your service details to Evan, jxmike@shheatex.com, or WhatsApp +86 173 1725 8304.