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CombustionGasesinReciprocatingGasEngines
17
The
η
canbedescribedwiththeformulaepresentedabovefortwotypes
offurnaceconstruction:
a)withoutarecuperator
b)witharecuperator.
Theequationswillbeasfollows:
a)forthefurnacewithoutarecuperator
η
=
H
g
+
H
H
a
9
g
i
–
H
f
9
j
b)forthefurnacewitharecuperator:
η
=
H
g
+
H
H
a
g
–
H
f
9
j
.
(9)
(10)
ThevaluesofenthalpyHglHaandHfintheaboveformulaecanbecalcu-
latedwithformula(5).
Numerouspublications,especiallythoseindustrially-oriented,suchasthe
bookwrittenbyoneoftheleadingdesignersofgasburnersJ.Wuennig[6],
definethedegreeofheatenergyrecuperationinthefurnace.Itisdetermined
bytheratio
ε
oftheenergyfedintotheairintherecuperatortotheamountof
energycontainedintheexhaustgasesoramaximumofenergytransferable
intotherecuperatororregenerator:
ε
=
energytra
nsformed
into
preheated
air
in
recuperato
r
energywhi
ch
is
possible
to
transform
ε
=
T
T
f
a
9
j
–
–
T
T
a
a
9
i
9
i
(11)
Theformulaisderivedfromformulaedescribingthewholeenergybal-
anceofthefurnaceundertheassumptionsthat:
a)themassofexhaustfumesequalsthatoftheairflowingintothefur-
nace
b)thespecificheatoftheexhaustfumesisequaltothespecificheatof
theair
Fortemperaturestypicaloftheinvestigationscarriedoutinourlaboratory
thecalculatedvaluesweresimilartothosepresentedinTable3.
