Boiler Combustion Efficiency & Stack Loss Calculator

Determine industrial boiler thermal efficiency using the ASME PTC 4 indirect loss method, including dry gas loss, hydrogen moisture loss, and economizer savings.

Fuel & Combustion Temperatures

Fuel Type & Properties:

Stack Flue Gas Temp (°F):

Ambient Air Temp (°F):

Flue Gas Emissions & Casing Loss

Flue Gas Dry O2 (%):

Carbon Monoxide CO (ppm):

Boiler Shell Radiation / Casing Loss (%):

Combustion Efficiency Breakdown

Gross Thermal Efficiency (HHV)

-- %

--% Net LHV Efficiency

Dry Gas Stack Loss

-- %

Sensible heat vented

Hydrogen Moisture Loss

-- %

Latent heat in water vapor

Operating Excess Air: -- %

Net Stack Rise (Tstack - Tamb): -- °F

Economizer Savings Potential: --% efficiency gain

ASME PTC 4 heat loss calculation reveals exact thermal losses and energy saving opportunities.

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Frequently Asked Questions

Why does natural gas have higher latent hydrogen heat loss than oil or coal?

Natural gas (methane, CH4) contains 24% hydrogen by weight, forming two water molecules for every carbon burned. This water vapor carries away approximately 10% of the fuel’s gross heat value as latent heat of vaporization up the stack, compared to only 5% for fuel oil.

What is the rule of thumb for economizer stack temperature fuel savings?

Every 40°F (22°C) reduction in flue gas stack exit temperature achieved by a feedwater economizer or air preheater increases overall boiler thermal efficiency by approximately 1.0%.

What is the difference between Gross (HHV) and Net (LHV) boiler efficiency?

Higher Heating Value (HHV) assumes all water formed during combustion condenses to liquid and releases its latent heat. Lower Heating Value (LHV) assumes all water vapor leaves uncondensed. In North America, boilers are rated on HHV, while in Europe they are typically rated on LHV.