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Engineering Calculators

Condensate Rate Calculator

Instructions:

  1. Review the methodology to ensure it aligns with your project's requirements.

  2. Select US or Metric Units

  3. Select whether to enter the Temperature as the Dry Bulb Temperature (TDB) or the Dew Point Temperature (TDP).

  4. Enter the Initial and final conditions of the TDB or TDP based on your entry for item #2 above. 

  5. If you selected TDB in #2 above, select whether you will next enter the TWB or Relative Humidity [RH%]. If you selected TDP in #2 above, you will enter the RH%.

  6. Enter the initial and final conditions of the TWB or RH%

  7. Enter the air flow rate, CFM [l/s]

  8. Enter the altitude of the project, ft [m]

  9. Click the Calculate button

  10. The results and all the psychrometric parameters are shown in the Results Table.​

Condensate generated

lb/hr

Low temperature warning

Also calculated
Entering temperature, DB °F (°C)
Leaving temperature, DB °F (°C)
Entering temperature, WB °F (°C)
Leaving temperature, WB °F (°C)
Entering temperature, DP °F (°C)
Leaving temperature, DP °F (°C)
Entering relative humidity %
Leaving relative humidity %
Entering specific volume, v ft³/lb,da (m³/kg)
Leaving specific volume, v ft³/lb,da (m³/kg)
Entering specific enthalpy, h btu/lb (kJ/kg)
Leaving specific enthalpy, h btu/lb (kJ/kg)
Entering atmospheric pressure in. Hg (mbar)
Leaving atmospheric pressure in. Hg (mbar)
Entering saturation vapour pressure in. Hg (mbar)
Leaving saturation vapour pressure in. Hg (mbar)
Entering partial vapour pressure in. Hg (mbar)
Leaving partial vapour pressure in. Hg (mbar)

Condensate generated

kg/hrgal/hr (l/hr)pints/dayBTU/hkW Condensate generated Condensate generated, kg/hr Condensate generated, gal/hr (l/hr) Condensate generated, pints/day Condensate generated, BTU/h Condensate generated, kW
lb/lb (g/kg)grains/lb Entering humidity ratio, w Entering humidity ratio, w, lb/lb (g/kg) Entering humidity ratio, w, grains/lb Leaving humidity ratio, w Leaving humidity ratio, w, lb/lb (g/kg) Leaving humidity ratio, w, grains/lb

Condensate is the moisture the coil strips out of the air: lb/hr = airflow ÷ specific volume × 60 × the drop in humidity ratio between the entering and leaving conditions. The psychrometrics on both sides come from the 2021 ASHRAE Fundamentals saturation-pressure correlation, over ice below freezing and over water above it, at the total pressure the altitude implies.

Each side of the coil is fixed by two conditions. Pick dry bulb or dew point for the first; when the first is dry bulb the second is wet bulb or relative humidity, and when it is dew point the second is the relative humidity box.

Every unit pair reads US first and metric in parentheses, following the units dropdown: 80 means 80 °F under US Units and 80 °C under Metric Units. Airflow is CFM or l/s and altitude is feet or metres.

The other condensate units are conversions of the pints per day, using 1.04 lb per pint and 1055 BTU per lb of water, the same two constants the Condensate Converter uses. kW is BTU/h ÷ 3412.142.

The warning appears when the entering first condition is below freezing, where the correlation is least reliable. It reads "-" otherwise.

The results are blank when the airflow or the entering specific volume makes the rate unreadable, rather than printing a zero that was never computed.

Methodology and Equations:

This calculator can be used in US or Metric Units.  The user inputs leaving and entering coil conditions as Dry Bulb or Dew Point Temperature, Wet Bulb Temperature or Relative Humidity, coil Airflow rate, and project altitude.  The formulas to calculate the psychometric of the initial and final conditions are based on the methodology outlined in the ASHRAE 2021 Handbook.  The change in the humidity ratio is used to calculate the Condensate Generated.

lb,moisture/hr = Q / v x w x C

    where:       Q = air flow rate, CFM

v= Specific Volume, ft^3/lb,dry air

w= Humidity Ratio lb,moisture/lb,dry air

C= 60 min/ hr

The following conversions are used to calculate the various units of condensate generated :

BTU/h = Pints/day x 1.04 lb/pint  / 24 hrs/day x 1055 BTU/lb

1 kW = 3412.142 BTU/hr

1 kW = 1000 W

1 Gallon = 8 pints = 3.78541 liters

1 Gallon of water = 8.34 lbs

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