General Formulae:
Face Area Square Feet = (FH x FL) / 144
View face area charts for tube size
Cooling/Heating:
Total Capacity (BTU/hr) = 4.5 x CFM x (Hewb – H₁wb)
Sensible Capacity (Btu/hr) = 1.08 x CFM x (T1db – Tedb)
Latent Capacity (Btu/hr) = 0.68 x CFM x (Grains H2O removed per lb. air)
Sensible Heat Ratio = Sensible Heat / Total Heat
Lb per hr H20 Removed = 4.5 x CFM x Grains H20 removed per lb. air7000
Water Coils:
Fluid Velocity (feet per second) = (TC x GPM) / (Number of Feeds)
| Tube OD | Tube Wall | TC |
|---|---|---|
| 5/8″ | 0.020″0.025″0.035″0.049″ | 1.0951.1321.2111.337 |
| 1/2″ | 0.016″0.025″ | 1.6891.819 |
| 3/8″ | 0.014″0.022″ | 2.9543.255 |
*Cooling: Total Capacity (Btu/hr) = 500 x GPM x (T1w-Tew)
*Heating: Total Capacity (Btu/hr) = 500 x GPM x (Tew-T1w)
*Assumes use of water (no glycol solution)
Steam Coils:
Lbs condensate per hour = BTU per hr of coil / *Latent heat of steam
*Assumes saturated steam
| Steam pressure (psig) | Latent Heat |
|---|---|
| 2 | 966 |
| 5 | 961 |
| 10 | 953 |
| 50 | 912 |
| 100 | 881 |
| Symbol | Description |
|---|---|
| FH | Fin height (inches) |
| FL | Fin length (inches) |
| CFM | Cubic feet per minute airflow |
| Hewb | Enthalpy (total heat content) of air at entering wet bulb |
| Hwb | Enthalpy of air at leaving wet bulb |
| T1db | Leaving air dry bulb temperature |
| Tedb | Entering air dry bulb temperature |
| GPM | Gallons per minute of cooling or heating water |
| Tew | Entering water temperature |
| T1w | Leaving water temperature |
Useful Coil Conversion Factors
| To Obtain | Multiply | By |
|---|---|---|
| BTU | Kilo Calories | 3.9683 |
| BTU | Watts | 3.41214 |
| BTU/lb | kJ/Kg | 0.43 |
| Centimeters | Inches | 2.54 |
| CFM | Cubic Meters Per Hour | 0.5886 |
| Cubic Feet | 1 Liter | 0.035 |
| Cubic Feet Per Minute | Liters Per Second | 2.1189 |
| Cubic Feet Per Minute | Cubic Meters Per Minute | 35.31 |
| Cubic Meters | 1 Cubic Foot | 0.0283 |
| Cubic Meters Per Hour | CFM | 1.699 |
| Cubic Meters Per Hour | Liters Per Second | 3.57 |
| Degrees Celsius | Degrees Fahrenheit | (F-32)/1.8 |
| Feet | Meters | 3.281 |
| Feet Per Minute | Meters Per Hour | 0.05468 |
| Feet Per Minute | Meters Per Second | 196.85 |
| Feet Per Second | Meters Per Second | 3.28 |
| Fins Per Millimeter | Fins Per Inch Spacing | 25.4 |
| Gallons (U.K.) (IMP) | 1 Gallon (U.S.) | 0.8327 |
| Gallons (U.K.) (IMP) | 1 Liter | 0.21997 |
| Gallons (U.K.)/Minute | Liters Per Second | 13.198 |
| Gallons (U.S.) | 1 Gallon (U.K.) (IMP) | 1.2 |
| Gallons (U.S.) | 1 Liter | 0.2642 |
| Gallons (U.S.)/Minute | Liters Per Second | 15.85 |
| GPM (U.S.) | GPM Water Flow (U.K.) (IMP) | 1.2 |
| Horse Power | Kilowatts (kW) | 1.341 |
| Inches | Meters | 39.37 |
| Inches Mercury | Pa or N/m² | 0.004 |
| Inches of Mercury | kPa | 0.296 |
| Inches of Water Gauge | Feet of Water Gauge (Water Pressure Drop) | 12 |
| Inches WG | Kilo Pascals (kPa) | 4.015 |
| Kilo Calories Per Hour | BTU Per Hour | 0.251034 |
| Kilo Calories Per Hour | Watts | 0.8598 |
| Kilo Pascal | Feet of Water Gauge (Water Pressure Drop) | 2.99 |
| Kilo Pascal | PSI (Pounds Per Square Inch) | 6.895 |
| Kilo Pascals (kPa) | Inches of Water Gauge (Air Pressure) | 0.24908 |
| Kilo Pascals (kPa) | 1 Meter Water Gauge | 9.804 |