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ANNEX E
Optional measures list:
MEASURE DEFINITION
λ, n Air index (defined as λ, sometimes also indicated as n).
e
Air excess. Expressed as a percentage according to the formula in the appendix B, is the
ratio between the volume of air actually entering the combustion chamber and the one
theoretically needed.
ΔT
Differential temperature:
It is the difference between the smoke temperature and the air combustion temperature.
Qs (LHV)
Stack losses in relation to the Lower Heating Value:
It is the percentage of dissipated heat through the stack referred to the lower heating val-
ue (LHV)
Qs (HHV)
Stack losses in relation to the Higher Heating Value:
It is the percentage of dissipated heat through the stack referred to the higher heating
value (HHV)
ηs (LHV)
Sensible efficiency in relation to the Lower Heating Value:
It is the burner efficiency calculated according to the UNI 10389-1 standard, as the ratio
between conventional heating power and the burner heating power. Among the combus-
tion losses, only the sensible heat lost with flue gasses is taken into account, thus ne-
glecting the radiation losses and incomplete combustion losses. This value is referred to
the Lower Heating Value (LHV) of the fuel and cannot exceed 100%.
The sensible efficiency value is to be compared against minimum efficiency stated for the
heating system performances.
ηs (HHV)
Sensible efficiency in relation to the Higher Heating Value:
It is the burner efficiency calculated according to the UNI 10389-1 standard, as the ratio
between conventional heating power and the burner heating power. Among the combus-
tion losses, only the sensible heat lost with flue gasses is taken into account, thus ne-
glecting the radiation losses and incomplete combustion losses. This value is referred to
the Higher Heating Value (HHV) of the fuel and cannot exceed 100%.
The sensible efficiency value is to be compared against minimum efficiency stated for the
heating system performances.
ηc (LHV)
Condensation efficiency in relation to the Lower Heating Value:
Efficiency deriving from the condensation of water vapour contained in flue gases, calcu-
lated according to the UNI 10389-1 standard, and it is referred to the LHV.
ηc (HHV)
Condensation efficiency in relation to the Higher Heating Value:
Efficiency deriving from the condensation of water vapour contained in flue gases, calcu-
lated according to the UNI 10389-1 standard, and it is referred to the HHV.
ηt (LHV)
ηt = ηs + ηc
Total efficiency in relation to the Lower Heating Value:
Total efficiency. It is the sum of sensible efficiency and condensation efficiency. It is re-
ferred to LHV (Lower Heating Value) and can exceed 100%.
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