Boiler efficiency formula

[SexSeaEngineer]

Does anyone know how to calculate the efficiency of a boiler? I know how to calculate the efficiency of turbines and compressors, but I can't find a formula for boiler efficiency? Thank you.

 

[desertfox]

HI SeaSexEngineer

The formula for boiler efficiency is:-

boiler eff= energy gained by fluid/energy in to boiler


regards desertfox

 

[davefitz]

The official means of calculation is defined in the ASME power test code PTC 4.0. It can be calculated either on basis of HHV ( higher heating value of fuel) or LHV ( lower heating value of fuel) , and via input/output or loss methods

 

[aobjr]

SexSeaEngineer,

There are two methods to calculate the boiler efficiency.
You may refer to ASME PTC 4-1998.

AOBJR

 

[chicopee]

The formula presented by DesertFox is concise and accurate but it is not easy to measure efficiency of a running boiler that is why the ASME power test code was developed.

 

[mur]

For a simple method, try

eff.= Heat energy transfered to water & Steam
--------------------------------------
Heat energy supplied by fuel


eff. = mass of steam(kg/hr)* (h(s)enthalpy of Steam -
h(w)enthalpy of feed water)
---------------------------------------------------
mass of fuel (kg/hr) * calorific Value Mj/kg

N.B. Enthalpy obtained from steam tables

 

[kenvlach]

Cleaver-Brooks has a 21-page file on Boiler Efficiency:

http://www.speci-fire.com/EmmisEffic/boiler_efficiency_facts.pdf

It covers the different methods of calculating efficiency as well as the factors (excess air, type of fuel and H/C ratio, no. of passes, ambient temperature) affecting the efficiency.
Tables give stack losses as f(flue gas T) and fuel consumption as f(efficiency).

An example is given of their preferred Fuel-to-Steam efficiency calculation. It uses actual measurements of flue gas T, CO₂ or O₂ concentration, ambient T, and tabulated “Hays charts” of flue losses by fuel type and “Radiation and Convection” losses.