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Assistance in establishing the thermal efficiency of combustion in a condensing boiler or high yield A professional use. By Rémi Guillet.


The establishment of the performance of heat generators is a delicate operation that requires heavy equipment. This is even more so with the Condensing!

We present a simple method to use, undemanding able material and particularly suited to cases of so-called generators condensing or high efficiency.

It is assumed that the combustion is complete (control CO performed!). This is an indirect approach of thermal performance, therefore based on the
knowledge of the "fuel" energy entering the generator and that conveyed by the combustion products (gas phase and possibly liquid) discharged to the outlet nozzle. The losses "at the walls" and the energy consumed by auxiliary devices are therefore not taken into account (in the case of recent generators, these elements are generally negligible compared to their nominal thermal power).

In any case, we are talking here about the "thermal efficiency of combustion" and we will call it Rt.

The reference conditions for the expression of the enthalpies of the different flows "H" being specified (in temperature and humidity), the value of Rt is written "Rt = 100 + Ha + Hc - Hpc"

Expression where Rt sizes, Ha (enthalpy of the air stream entering the generator), Hc (enthalpy of the flow of fuel entering) Hpc (enthalpy of combustion products discharged) are expressed in% of the calorific value.

Since this is primarily condensation generators, while the calorific value chosen a priori is the gross calorific value (Ro), that is to say, one that takes into account the water formed during condensation heat combustion.

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