How do you calculate coil pressure drop?

Multiply the baseline pressure drop by the flow or fouling correction factor. With a 100 psi baseline and a 1.2 factor, the adjusted total load is 120 psi. Over an 8-hour test that's 15 psi per test hour.

What is a good pressure drop for a heat exchanger coil?

It's set by the coil's design spec and pump curve, not a universal number, but most liquid coils target a few psi to low tens of psi at rated flow. The acceptance window is what matters — the corrected drop must land inside the drawing's min and max.

What does the correction factor account for?

It normalizes the measured drop to a reference condition — adjusting for test flow that differs from rated flow, or layering in expected fouling. A 1.2 factor raises the 100 psi baseline by 20% to 120 psi.

Why does fouling increase pressure drop?

Scale, sediment, and biofilm narrow the tube bore and roughen the wall, raising friction. The correction factor lets you project the in-service drop a clean coil will reach once fouled, so you can size pumps with margin.

What is pressure drop per test hour used for?

It normalizes the load over the bench duration so you can compare runs of different length or track a slope. At 15 psi per hour over an 8-hour test you have a per-hour figure to trend against other coils.

Pressure drop vs flow rate — how are they related?

For turbulent flow, pressure drop rises roughly with the square of flow rate, so a small flow increase raises drop sharply. That's why the linear correction factor here is only valid close to the reference flow it was calibrated at.

Heat Exchanger, Coil & Radiator Manufacturing calculator

Coil Pressure Drop Calculator

Coil pressure drop is the pressure a fluid loses passing through a heat-exchanger coil or radiator core, and it's the headline acceptance metric on most coil test benches. Test engineers and quality teams in heat exchanger and radiator manufacturing track it because too high a drop means restricted tubes, tight bends, or fouling, while too low can signal a leak or bypass — both fail the part. It matters because pressure drop directly sets pumping power and thermal performance in the field, so a coil that's out of spec on the bench will underperform or oversize the pump downstream. Applying a flow or fouling correction factor to a baseline drop lets the bench normalize results to a reference condition for clean pass/fail comparison.

What this calculator does

Estimate adjusted coil pressure drop from a measured or specified baseline pressure drop, a flow or fouling correction factor, and test duration.
Use it when an HVAC coil, radiator, oil cooler, or heat exchanger needs a quick pressure drop planning check before a water, glycol, air, or refrigerant test.
It adjusts a baseline coil pressure drop by a flow or fouling correction factor, then divides the result over the test or operating duration to give pressure drop per hour.

Formula used

Adjusted pressure drop = baseline pressure drop × flow or fouling correction factor
Pressure drop per test hour = adjusted pressure drop ÷ test or operating duration

Inputs explained

Baseline pressure drop: undefined
Flow or fouling correction factor: undefined
Test or operating duration: undefined

How to use the result

Use it on the test bench to normalize a measured drop to reference flow, or to project fouling-corrected drop for an in-service coil.
It scales drop with a single linear correction factor; real pressure drop varies with the square of flow, so the factor only holds near the reference flow rate it was derived at.

Current U.S. benchmarks

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Common questions

How do you calculate coil pressure drop? Multiply the baseline pressure drop by the flow or fouling correction factor. With a 100 psi baseline and a 1.2 factor, the adjusted total load is 120 psi. Over an 8-hour test that's 15 psi per test hour.
What is a good pressure drop for a heat exchanger coil? It's set by the coil's design spec and pump curve, not a universal number, but most liquid coils target a few psi to low tens of psi at rated flow. The acceptance window is what matters — the corrected drop must land inside the drawing's min and max.
What does the correction factor account for? It normalizes the measured drop to a reference condition — adjusting for test flow that differs from rated flow, or layering in expected fouling. A 1.2 factor raises the 100 psi baseline by 20% to 120 psi.
Why does fouling increase pressure drop? Scale, sediment, and biofilm narrow the tube bore and roughen the wall, raising friction. The correction factor lets you project the in-service drop a clean coil will reach once fouled, so you can size pumps with margin.
What is pressure drop per test hour used for? It normalizes the load over the bench duration so you can compare runs of different length or track a slope. At 15 psi per hour over an 8-hour test you have a per-hour figure to trend against other coils.

Last reviewed 2026-05-12.