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″
  • 1.095
  • 1.132
  • 1.211
  • 1.337
1/2″
  • 0.016″
  • 0.025″
  • 1.689
  • 1.819
3/8″
  • 0.014″
  • 0.022″
  • 2.954
  • 3.255

*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