Chapter hvac engineering Fundamentals: Part 1 Introduction

10.5.4
Combustion efficiency
The
combustion efficiency
is the ratio of fuel heat input minus the
stack loss (through the chimney or vent), divided by the fuel heat
input. Typical efficiencies for mechanically fired boilers range from 75
to 83 percent for new installations at full-load conditions. Firing at
reduced capacity may reduce the combustion efficiency. Therefore it is
desirable to match the boiler to the load as closely as possible or to
use multiple boilers.
The
overall thermal efficiency
is the gross output in Btu / h divided
by the fuel heat input in Btu / h. This rating takes into account the
noncombustion losses from the boiler, such as radiation (see Fig. 10.2).
Equipment: Part 2
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