# How to Calculate Heat Loss Due to Moisture Present in Air?

Calculating % heat loss due to moisture present in air to determine the boiler efficiency.

## % Loss Due to Mositure Present in Air

The percentage heat loss due to moisture present in air is one of the factor to determine the boiler efficiency. The vapour present in the incoming air is in the form of humidity which is super heated when it passes through the boiler. As, the heat passes through the stack it causes a loss. Below given the formula to calculate the % heat loss due to moisture present in air.

**Formula:**

**L**_{4} = (AAS x Humidity Factor x C_{p} (T_{f} - T_{a}) / GCV of Fuel) x 100

**Where,**

AAS = Actual mass of air supplied per kg of fuel

Humidity Factor = Kg of water / kg of dry air

C_{p} = Specific heat of superheated steam in kCal/kg^{o}C

T_{f} = Flue gas temperature in ^{o}C

T_{a} = Ambient temperature in ^{o}C (dry bulb)

GCV of Fuel = Gross Calorific Value of Fuel

Let us consider an example on how to calculate the heat loss due to moisture present in air with the given values.

**Step 1:** Given that,

Actual mass of air supplied per kg of fuel = 20 kg

Humidity Factor kg of dry air = 0.015

Specific heat of superheated steam = 0.45 kCal/kg^{o}C

Flue gas temperature = 250 ^{o}C

Ambient temperature = 30 ^{o}C (dry bulb)

GCV of Fuel = 13000 kJ/kg

**Step 2:** Applying the values in the formula

L_{4} = (AAS x Humidity Factor x C_{p} (T_{f} - T_{a}) / GCV of Fuel) x 100

L_{4} = (20 x 0.015 x 0.45_{} (250_{} - 30_{}) / 13000) x 100

L_{4} = 0.228 %

**Result:** % Heat Loss Due to Moisture Present in Air = 0.228%

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