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INTRODUCTION
Boy’s gas calorimeter is a simple apparatus that is suitable for
determining caloric alue of gaseous fuels! This apparatus "as named
after an #nglish physicist and inentor $%ir Charles &ernon boys’ '()(*+!
,rom this- "e can calculate both the lo"er caloric alue as "ell
as the higher caloric alue of gases!
Calorimetry is the science of measuring heat! Caloric alue isdened as the amount of energy released after burning (.g of fuel!
There are t"o types of caloric alues as I stated earlier!
(! /igher caloric alue'/C&+0 It is the total heat liberated by the complete
combustion of (.g of fuel! This is determined by
bringing all the products of combustion bac. to pre
combustion temperature! '1eans condensing any
"ater apor produced!+ In higher caloric alue "e
assume that "ater is in a li2uid state after
combustion and it absorbs some amount of heat to
ma.e that li2uid "ater into apor "ater! This heat
is .no"n as the latent heat of apori3ation!4! 5o"er caloric alue '5C&+
0 It is the di6erence of higher caloric alue and heat
absorbed by "ater apors! This treats as any /4O
formed as apor! The energy re2uired to apori3e
"ater is therefore not released as heat!
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If the condensation part of the boy’s gas colorimeter "or.s properly "e
can nd the higher caloric alue! If "ater remains in the apor phase
then the lo"er caloric alue is sought!
Apparatus
Calorimeter Rotameter
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1anometer ,lo" control deice
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Procedure
7pparatus "as set up and necessary properties and constants "ere
noted do"n! 7fter setting rotameter alue for ('for steady combustion+ "e open
the gas 8o" and ignite the burner
Calorimeter "as placed properly and "ater circulation process "as
started! 9e .ept the apparatus for about :; minutes to ensure steady
conditions! 7fter that inlet temperature- outlet temperature and e<haust gas
temperature "as noted do"n! =as pressure "as read by the manometer!
9ater circulated "as collected to buc.et for > minutes and
measured!
Repeat this procedure for : minutes!
Equations for calculation
&olume of gas ? =as 8o" rate × time × (;0@ m:
7bsolute pressure ? =auge pressure A 7tmospheric pressure '(;(:4>
pa+
Conerting gas olume into standard conditions
P1V
1
T 1= P
2V
2
T 2
Temperature di6erence ? outlet temperature inlet temperature
m×C p×temperature difference=calorific value×standard volume
Calorificvalue=m×C p×temperaturedifference
standard volume
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Calculations
C p Of "ater !(*@ Eg.
Conersion of gas olume into standard conditions
Fgauge ? G < (;0: < ;!*4@ < (;;; < )!*( ? >@!G4 pa
Fabsolute ? (;(:4> A >@!G4 ? (;(:*(!G4 pa
,uel olume ? (!(4> < > < (;0@
P1V
1
T 1= P
2V
2
T 2
101381.72×1.125×5 x10−6
31+273=
1.023 X 105×V 2
300
&4 ? >!>;(4 < (;0@
%imilarly-
Pabsolute 101381.72 101406 101446
Volue!standard"
>!>;(4 < (;0@ *!:>:) < (;0@ ((!@*)> < (;0@
Calculation of caloric alue
()G; Hg < !(*@ HEg. <:. ?C v <>!>;(4 < (;0@Hm:
C ? )G 1Em:
%imilarly
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#ei$%t of
&ater!$"
'eperatur
e
di(erence!)
"
*tandard
+olue!3"
Calori,c
+alue!-/3
"
170 : >!>;(4 < (;0@ )G
1740 @ *!:>:) < (;0@ >4:(!:(
2140 >((!@*)> < (;0
@ :*:(!@
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iscussion
Fractical errors
9hen "e are calculating the caloric alue- "e assumed thatenergy released by burning fuel is all absorbed by the "ater to increase
its temperature! But it is not the case here! If the di6erence bet"een
the e<haust temperature and room temperature is so high- the amount
of heat loss through e<haust is not negligible! 9e can only assume that
e<haust gas temperature is almost e2ual to ambient temperature! If it is
the case since e<haust and atmosphere are in thermal e2uilibrium- "e
can state that there is no heat loss! But this is not the case in our
practical! But "e neglect e<haust heat loss! It "as an error in our
practical!
#en though "e did our calculations assuming fuel is burning
completely it is not true! 9hile "e’re doing the practical "e sa" blac.
smo.es or fumes coming out of the e<haust- indicating that it is an
incomplete burning process! This is also a practical error!
7s I stated in the introduction- in order to state that the alue "e
obtain is the higher caloric alue- "e need to ma.e sure that all the
"ater apor is condensed inside! But in our apparatus the condensing
part "as bro.en and "e cannot guarantee full condensation- "hichresults our data deiate from theoretical alues!
Other methods of nding caloric alue
(! ,or solid or li2uid fuel
Caloric alues of solid and li2uid fuels are generally
determined using a Bomb calorimeter! It resembles the shapeof bomb and thus .no"n as the bomb calorimeter!
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/ere fuel is burnt in a strong steel chamber "hich is
immersed in a .no"n mass of "ater! The fuel sample is ignited
by an electrically heated platinum "ire! Then temperature
readings should be ta.en for eery (; seconds!
The heat released by combustion is absorbed by
surrounding "ater! Thus by balancing energy "e can nd the
caloric alue!
7nother apparatus to nd the caloric alue of solid fuel isthe Thompson calorimeter!
4! ,or gaseous fuel
Caloric alue of gaseous fuel is determined by $Jun.er’s or
boy’s’ calorimeter!
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The metered gaseous fuel is continuously supply to the
calorimeter at constant pressure "here it burns in the
presence of air! Circulating "ater through the apparatus
absorbs the heat generated by burning fuel! Thus by energy
balance caloric alue of fuel is obtained!
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Ener$ balance for t%e sste
Kfuel ? /eat from burned fuel
K"ater ? heat absorbed by circulating "ater
Kloss through "alls ? heat transferred through the "alls of calorimeter by
conduction- conection and radiation
Kloss-e<haust ? /eat loss to atmosphere through e<haust gas
Kfuel ? K"ater A Kloss through "alls A Kloss-e<haust
Ener$ 1 2 3
eat ener$added !"
:GG:;!:> >G4)>!* *;(G:!4>
eat ener$
absorbed b
coolin$ &ater !"
4G:) :G;( G);
osses (4))(!:> (:>)!* :>:*:!4>
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