Tom Backman, BMIL - RSES.org

Tom Backman, BMIL

Vane Anemometers The raw data is not accurate without some

correction. K-Factor, why and how to use it.

For a Pacer DA 400 against a coil we will use 0.80. Actual air velocity & standard air velocity.

AFPM and SFPM. Field measurement accuracy is +/- 10%.

The BMIL Base

Free your hands to hold

instruments and write numbers.

A System To Collect Useful Data With A Vane Anemometer

The 9 point data measuring point grid. Like reading a book.

Average the point data. From Velocity (FPM) to

Volumetric Flow Rate (CFM). From Actual Cubic Feet per

Minute (ACFM) to Standard Cubic Feet per Minute (SCFM).

Air Density Ratio (ADR).

1. 3. 2.

4. 6. 5.

7. 9. 8.

Using the air flow to calculate heating or cooling

Standard Cubic Feet Per Minute (SCFM). Formulas to make use of the data we can collect.

Sensible Heat Transfer Dry Bulb Temperature Tdb Qs = 1.083 x (ΔT) x SCFM = btu/hr

Latent Heat Transfer Wet Bulb Temperature Twb finds Enthalpy h. Keep your wick clean. QL = 4.5 x (Δh) x SCFM = btu/hr

The BMIL 1/3 Ton

CW Fan Coil

What about freezing wet bulb temps ?

Using cooling or heating capacity in Refrigeration Service

Equipment data from the manufacturer. Unit coolers (Evaporators) Air handlers Condensers

Is the coil underperforming or is the load higher than the coil rating?

Data trends over time.

Rules of Thumb Rules of Thumb are not for design,

but they are helpful in service.

400 to 500 sfpm is optimum Direct Expansion (DX) coil velocity.

350 sfpm minimum air velocity on DX coils. Chilled Water (CW )coils can go much lower.

550 sfpm maximum air velocity on DX or CW coils. Air can carry suspended water drops at 600 fpm. 1,500 sfpm air velocity is where noise begins. Air cooled Condenser coils 600 to 900 sfpm. DA 400 Vane anemometer

K factor is 0.80 before coils, after coils.