How condensing boilers work

How the condensing boiler works:this type of boiler was introduced on the market in 1989 by the manufacturer Junkers.

Therecondensing boilerit is a heat generator characterized by the recovery of thermal energy from condensation, therefore it offers good yields.

This kind ofboilerusually it is aforced draftwith combustion achieved by pre-mixing the air with the fuel. After this brief introduction, let's see in detailhow a condensing boiler works.

Condensing boiler, operation diagram

The following image shows the typical operation diagram of condensing boilers. As is clear, the air and the fuel (gas) enter together to make combustion possible in a sealed chamber.boilerit is equipped with an electric fan with the function of drawing external air and to force the expulsion of the combustion products towards the "chimney" which will disperse them.

1- Gas entry
2- Air entry
3- Smoke outlet
4- Return from the radiators
5- To the radiators
6- Condensed water

With thisoperation, thecondensing boilerallows athermal efficiencymore than 90% of the fuel used thanks to lateral heat recovery ofcondensationof the water vapor contained in the combustion fumes.

The higher thermal efficiency of thecondensing boilersis due to the fact that these heat generators are able to exploit the energy produced by the thermodynamic transformation necessary during combustion.

Why thecondensing boilersare they more efficient?

  • Thedifferenceswith the classicsboilers

The normal onesboilers, even those labeled as"high-performance”Use only part of the heat that can be obtained from the combustion fumes because they avoid itcondensation as this phenomenon, in the normalboilers, it would be corrosive.

All the water vapor generated by combustion, in normal boilers, is dispersed and with it also the thermal energy defined as "lateral heat". In theimplants a condensationthis potential is exploited.

How does it work?
In thecondensing boilersthe fumes produced with combustion are cooled down to bring them back to the liquid state (in fact, condensation is created from the steam generated with combustion) thus recovering the heat used to preheat the return water.

With this technology, the temperature of the outlet fumes is lowered to about 40 ° C and is close to the water delivery temperature (incondensing boilersmore efficient, the flue gas temperature can even be lower than the water delivery temperature). The temperature of the outgoing fumes in theboilersnon-condensing, generally it is:
- below 140 - 160 ° C inboilershigh-performance
- below 200 - 250 ° C inboilerstraditional

Condensing boilers are able to exploit the thermal energy of the fumes because they are made of materials resistant to the acidity of condensate. In particular, they use ad hoc heat exchangers, resistant to the acidity (pH 4-5) that is formedcondensingthe combustion vapor.

How does the condensing boiler work,all a matter of temperatures
When the temperature of the fumes falls below the "dew point" (about 56 ° C for the fumes produced by the combustion of methane), the vapor begins to condense and, returning to the liquid state, releases the so-called "latent heat", exploited by the heat exchangers heat from condensing boilers.

In the boilers “Normal”, whether traditional or high-performance, the temperature of the combustion fumes is always kept above the dew point. Just think about the temperature of the exhaust fumes boilers not at condensation to understand how much heat has been lost.

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Video: Designing for Condensing Boiler Performance (June 2021).