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# Coil Selection Calculator

Coil Selection

Instructions:

BTUH Capacity & Leaving Air Temperature

1. Select US or Metric Units

2. Sensible Cooling:

1. Select the parameter for which to solve: Sensible Cooling, Volume Flow Rate, Leaving air Temperature, or Entering Air Temperature.

2. Enter all of the required inputs.

3. Click the Calculate button, and the Result will show below the table.

3.   Total Cooling:

1. Select the parameter for which to solve: Total Cooling, Volume Flow Rate, Leave air Enthalpy, or Entering Air Enthalpy (note there is a  Calculate Enthalpy button to take you to our Psychrometric Calculator to solve for Enthalpy).​

2. Enter all of the required inputs.

3. Click the Calculate button, and the Result will show below the table.

4. Latent Cooling

1. Select the parameter for which to solve: Latent Cooling, Volume Flow Rate, Leave air Humidity Ratio, or Entering Air Humidity Ratio (note there is a  Calculate Humidity Ratio button which will take you to our Psychrometric Calculator to solve for Humidity Ratio).​

2. Enter all of the required inputs.

3. Click the Calculate button, and the Result will show below the table.

Area & Velocity

1. Select US or Metric Units

2. Enter the fin length and height

3. Enter the flow rate

4. Click the calculate button, and the Results will show below the table.

Water and Glycol Flow

1. Select US or Metric Units

2. Select the parameter for which to solve: Fluid Capacity, Volume Flow Rate, Entering Temperature, or Leaving Temperature.

3. Enter all of the required inputs.

4. Click the calculate button, and the Result will show below the table.

Water Velocity

1. Select US or Metric Units

2. Enter flow rate, tube diameter, and number of tubes.

3. Click the calculate button, and the Result will show below the table.

Methodology and Equations :

BTUH Capacity & Leaving Air Temperature

The following equations are used in this calculator:

Sensible Cooling [BTU/h] = CFM x 1.0746 x (T1 – T2)

Latent Cooling [Btu/h] = CFM x 0.69143 x (G1 – G2)

Total Cooling [Btu/h] = CFM x 4.5 (H1 – H2)

where

CFM = volume flow rate [cfm]

G1= Entering humidity ratio [grains,moisture/lb,dry air]

G2 = Leaving humidity ratio [grains,moisture/lb,dry air]

H1 = Entering enthalpy [BTU/lb, dry air]

H2 = Leaving enthalpy [BTU/lb, dry air]

T1 = Entering air temperature [oF]

T2 = Leaving air temperature [oF]

Area & Velocity

The following equations are used in this calculator:

Coil area [ft] = Fin height x Fin length / 144 in^2/ft^2

Air Velocity = CFM / FPM

where

CFM = volume flow rate of air [cfm]

FPM = velocity of air [fpm]

Water and Glycol Flow

The following equation is used in this calculator:

Fluid capacity [BTU/h] = rho x cp x (T1 - T2) x [GPM] x 60 min/hr

where

rho = fluid density [lb/gallon]

cp = specific heat of fluid [Btu/lb-oF]

T1 = Entering fluid temperature [oF]

T2 = Leaving fluid temperature [oF]

GPM = Volume flow rate [GPM]

Water Velocity

The following equations are used in this calculator:

V = Q x C / ID^2 / No. of Tubes

where

C = English Unit Conversion Constant = 0.408498

ID = Tubing Inner Diameter [in]

Q = flow rate [GPM]

V = velocity [f/s]

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